Active infection results in several outward signs in humans, including visible symptoms, changes in behavior and possible alterations in skin color and gait. A potential adaptive function of these indicators is to signal distress and elicit care from close others. We hypothesized that sickness behavior, a suite of stereotypical changes in mood and behavior, also serves to communicate health status to others. We further hypothesized that such outward signals/cues of health status would vary based on context and sociocultural norms.n = 1259) using multinomial probit regressions.We explored self-reported, recalled sickness behavior, communication style, demographics and theoretically relevant cultural factors in a large national US sample (In accordance with predictions, relatively few participants were willing to talk or complain about sickness to strangers. Self-reported, recalled sickness behavior was associated with some communication styles but attention received from others was more consistently associated with potential signaling. Several cultural factors, including stoicism and traditional machismo, were also associated with different sickness signaling styles.These preliminary, self-reported data lend some tentative support to the sickness behavior signaling hypothesis, though experimental or observational support is needed. The role of cultural norms in shaping how such signals are transmitted and received also deserves further attention as they may have important implications for disease transmission.Evolutionary medicine hypothesizes that signs and symptoms of infectious disease—including sickness behavior—have adaptive functions, one of which might be to reliably signal one’s health status to others. Our results suggest that evolved signals like these are likely shaped by cultural factors.  Signs and symptoms are one of the hallmarks of infectious disease, are critical for differential diagnosis and disease tracking, and are the target of many therapeutic treatments. A major contribution of evolutionary medicine is the recognition that signs and symptoms often benefit hosts and pathogens, rather than being the inconvenient byproducts of infection . For inset al. [in vitro interleukin-6 (IL-6) release from lipopolysaccharide (LPS) stimulated white blood cells when compared to individuals who had seen neutral or non-disease related threat images.Symptoms may also function to communicate sickness and infectivity on a group level. This is a key premise of the putative behavioral immune system, whereby salient indications of infectious disease lead to avoidance behavior, or, intriguingly, elevated immunological responses in healthy individuals . For inset al.  found thSneezing, coughing, rhinorrhea, red eyes and other such symptoms are undoubtedly obvious indicators of sickness and generally occur later in the course of the illness. Experiments have shown that even the activation of the inflammatory response—absent any replicating pathogen—has observable effects on behavior and physiology within a brief timespan (i.e. 1–2 h). Following LPS administration, facial skin became lighter and less red in a sample of non-Hispanic Whites, which is consistent with other studies showing that paler, less red skin indicates poor health in individuals with white skin . ExperimIn addition to these changes in physiological characteristics, sickness behavior may also communicate infection. Sickness behavior occurs early after infection and is tightly linked with inflammation through several pro-inflammatory cytokines . Some ofAny relationship between sickness behavior and elicitation of caregiving must strike a fine balance between the benefits of that care for the sick individual and potential costs associated with exposing a caregiver to a pathogen. Additionally, while sickness behavior is thought to improve recovery and survival, it is not without its own costs. In nonhuman animals, lost opportunities for reproduction or offspring care are likely among the most salient opportunity costs . In humaThere is experimental evidence showing that inflammation is associated with stronger desires to be around supportive others through increased activity in the ventral striatum, an area of the brain strongly implicated in reward processing . These rFinally, sickness behavior and its expression are expected to be at least somewhat culturally constructed . PreviouFamilism, a set of values rooted in familial support and obligation, has also been associated with the adoption of a sick role . It is pWe included questions exploring the communication function of sickness behavior in a large nationwide survey addressing multiple elements of sickness behavior. Based on the hypothesis that sickness behavior serves a signaling function, we predicted that participants would be more likely to express or otherwise communicate sickness around friends and family than around strangers and that self-reported, recalled sickness behavior would be associated with communication to friends and family, as would the amount of perceived attention received by the participant when sick (i.e. operant conditioning). Given the role of cultural norms and values in shaping self-reported sickness behavior, interpretations of symptoms and disclosure of health status, we also include several theoretically relevant sociocultural factors as covariates to determine their incremental effects on sickness communication. Specifically, we examine the potential effects of stoicism, traditional machismo, gender role, individualism and collectivism, active coping and familism . While tData come from an online survey distributed through Qualtrics in November of 2018. Participation was open to all non-Hispanic White, non-Hispanic Black or Hispanic US adults between the ages of 18–55 who self-identified as having been sick within the past year. All ethical approvals were obtained (IRB #19-020E), as was informed consent. Qualtrics distributed the survey and recruited and screened all participants. Further details about screening and the survey response rate can be found in our previous publication . EthniciScales measuring norms and beliefs used in this analysis are described in Finally, to explore possible signaling behaviors during sickness, participants were asked several true/false questions related to their behavior and sensations around friends/family and strangers. These were, ‘I am more likely to feel worse physically when around (friends or family/strangers) than when I am alone’, ‘I am more likely to exaggerate the severity of my symptoms or complain about them when around (friends or family/strangers) than when I am alone’, and ‘I often talk about or mention my symptoms when around (friends or family/strangers)’. For each possible signaling ‘domain’ , participants were coded as not signaling to both friends/family and strangers (‘taciturn’), signaling to only friends/family, signaling to only strangers, and signaling to both friends/family and strangers (‘gregarious’). These categories were theoretically informed by research suggesting that sickness behavior expression  is dependent on social contexts , 20.All analyses were conducted in STATA 14 . MultinoFull results of the baseline models  can be found in the P < 0.05. Stoic endurance of pain and illness was uniformly associated with a decreased likelihood of talking about sickness with others . Consistent with this, we found that self-reported, recalled sickness behavior was positively associated with feeling subjectively worse around close others, though this effect disappeared when adding sociocultural variables to our model. Contrary to predictions, we found stable relationships between sickness behavior and signaling to strangers or adopting a gregarious communication style. Specifically, sickness behavior was associated with exaggerating/complaining to strangers only and with worse subjective sensations when around others, whether family and friends or strangers. One possible explanation for sickness behavior’s association with such gregariousness is that the time and energy spent on social interactions when sick simply leads to feeling worse, a reversal of our proposed causality.On the other hand, the largely consistent associations between signaling and attention received suggest that there is a positive benefit to these behaviors for the sick person. It seems likely that received attention reinforces the sickness signaling strategy; signals that do not result in a net benefit for the signaler are not likely to be maintained or selected for. Note that this measure of attention is only a single item and does not specify what type of attention is received, whether it be caregiving, simple expressions of concern and so on.We also found a role for sociocultural norms/values in sickness signaling. When adding these variables to our models, the relationship between SicknessQ scores and feeling subjectively worse around close others disappeared, suggesting that this association is entirely explained by sociocultural factors. One dimension of stoicism, enduring pain and illness, was associated with a reduced likelihood of talking about sickness with others, particularly friends and family, a result in line with other research on stoicism and help-seeking . AdditioContrary to our tentative predictions, we found that traditional machismo was positively associated with signaling in multiple domains, particularly in exaggerating sickness. Like stoicism, machismo is sometimes associated with reduced preventative health behaviors, including screening exams . HoweverP-value criterion to minimize the risk of Type 1 errors in our models. For instance, active coping and traditional machismo were also associated with additional aspects of signaling at the 0.05 significance level, consistent with the above descriptions.Individualism was associated with talking about sickness to friends/family and gregariously. Those high in individualism tend to have more universal or abstract prosocial values, which may translate into helping in-group and out-group members equally, such as notifying someone that they feel sick and perhaps avoiding shaking hands or other close contact . FamilisCertain demographic factors were also associated with communication style. Increased age was associated with less likelihood of talking about sickness or exaggerating/complaining. This may reflect greater self-sufficiency at older ages or perhaps some degree of generational differences in norms surrounding discussing or otherwise communicating sickness. Women were less likely to report increased subjective symptom severity or exaggerate their symptoms around all others. This is in agreement with experimental results showing that men tend to overexaggerate common cold symptoms and that men have a lower threshold for expressing discomfort following an LPS injection, suggesting that men communicate about sickness more readily than women . InteresIn sum, our analyses found some tentative support for a signaling function for sickness behavior, although results contradicted to our predictions of greater signaling to close others only. Signaling behavior is perhaps reinforced by successfully receiving attention in the past. We also find evidence that some demographic and sociocultural factors affect signaling styles and moderate at least one relationship between sickness behavior and signaling. There are several limitations to the study, including its self-reported nature and the use of a recalled measure of sickness behavior. Further, while many compelling effects emerged, many effect sizes were modest, particularly for relationships with SicknessQ. Asking more detailed questions about the exact type of attention or assistance given to individuals when they are sick would be helpful. Experimental studies will be able to manipulate social interactions to better test predictions about signaling and will be able to collect data when participants are actively experiencing sickness behavior, rather than relying on recall. Additionally, experimental studies that vary the dose of LPS received can determine whether the nature of a sickness signal varies based on the severity of the illness . TheoretTo our knowledge, this is one of the first attempts to explicitly connect sickness behavior and signaling in humans. Given the fundamental nature of energy use by the immune system, it seems likely that any signaling function of sickness behavior is an exaptation . This does not mean that such a signaling function is inconsequential. Indeed, communicating sickness—and acting upon that signal—have been a central social interaction throughout the history of our species and contributed to our substantial success . These signals are no less important today, though their meaning may be bolstered or obscured through complex cultural lenses.EMPH online.eoab017_Supplementary_DataClick here for additional data file.


Differences in technical efficiency across farms are one of the major factors explaining differences in farm survival and growth and changes in farm industry structure. This study employs Data Envelopment Analysis (DEA) to compute technical inefficiency scores for output, energy, materials, pesticides and fertiliser of a sample of Dutch indoor vegetable farms within the period 2006–2016. A bootstrap truncated regression model is used to determine statistical associations between producer-specific characteristics and technical inefficiency scores for the specified inputs. For the sample of indoor growers, the average technical inefficiency was about 14% for energy, 23% for materials, 24% for pesticides and 22% for fertilisers. The bootstrap truncated regression suggested that the degree of specialisation exerts adverse effects on the technical inefficiency of variable inputs. While age, short-term, long-term debt and subsidy were statistically significant, the coefficients were not economically significant. Building the capacity of farmers to reduce input inefficiency will enable farmers to be competitive and reduce the adverse effects of input overuse on the environment. The horticulture sector comprising greenhouse and open ground production of vegetables and flower is the highest value sector in Dutch agriculture, followed by grassland-based livestock keeping . In 2017Since the 1950s, Dutch horticulture has followed a model of increased intensification with increasing inputs of fertilisers, pesticides and energy. To consolidate and strengthen the Dutch position as the second agricultural exporter in the world, the process is continuing. Dutch horticulture is one of the most intensive production systems globally, with high output levels using the latest technologies , 4. Ther2 emissions and energy focused on glasshouse horticulture but excluding insights into the efficiency of other inputs such as fertilisers, materials and pesticides, which also occupy an important place in Dutch horticulture. Other studies that focussed on vegetable production analysed overall technical efficiencies without references to specific inputs [Although the Dutch government in recent decades has committed to sustainable agriculture, several studies –8 have rc inputs –13. In tEstimating inefficiency levels and drivers of inefficiency for specific inputs employed in the production process provides further insight for farm managers to improve their use of these inputs enabling better decision making. Information on input-specific inefficiency levels is also useful for policymakers in terms of specifying the policy instruments that promote greater levels of efficiency of inputs use and assessing the effectiveness of policies that have already been implemented .As input inefficiencies are directly linked to the decisions of farm managers, it is worth investigating farm characteristics that could explain inefficiency differences between farms. Many studies have explained differences in technical inefficiency scores by farm characteristics such as age, years of farm managerial experience, received subsidies and capital structure –18. ExplThis study aims to measure input-specific technical inefficiency of Dutch specialist indoor vegetable farms and identify farm-specific characteristics associated with inefficiency. This study makes two distinct contributions to the literature. First, we measure the technical inefficiency scores separately for energy, materials, pesticides and fertilisers for specialist indoor vegetable growers. This allows for more refined insight into the potential for reducing the use of specific inputs. Secondly, this study reveals farm characteristics that explain differences in the inefficiency of each input across farms. To achieve these, our study adopts a two-stage approach. First, data envelopment analysis (DEA) analysis is employed to measure technical inefficiency scores of the specified inputs used in the production of vegetables in the Netherlands. Second, a bootstrap truncated regression model is used to identify farm characteristics associated with technical inefficiency.i =  decision making units (DMUs) which use F fixed inputs S variable inputs Consider for instance T(y) can also be expressed non-parametrically asY is the (N × 1) vector of observed outputs; yi is the observed output level of firm i; X is the (N × S) matrix of observed variable inputs; xi is the vector of variable inputs used by firm i; Xf is the matrix (N x F) of observed fixed inputs; i; λ is a (N × 1) vector of intensity variables (firm weights). The technology set is considered non-empty and convex. Under the production technology set, we assume outputs, fixed inputs and variable inputs are freely disposable, implying their reduction is not costly [The production technology t costly .gy and gx until it reaches the frontier [To estimate inefficiency scores for the output and inputs, a directional distance function was used. The directional distance function measures the amount that a given observation can be projected in the directions frontier . The outgx and gy, refer to the directional vectors associated with variable inputs and outputs, respectively. β denotes technical inefficiency measuring the equal maximum contraction of all variable inputs and maximum expansion of all outputs. To account for differences in environmental conditions across time, x1, x2, x3 and x4 are scalar values of specific variable inputs used by farm i. βy refer to the technical inefficiency concerning the separate variable inputs and output y, respectively. The inefficiency scores (β) take values between 0 and 1, except for βy (can be greater than 1) where a value of 0 indicates no improvement potential. The vector of firm weights (λ) identifies the firms with the relevant reference points for a given observation, i.e. these are the firms that are located on the frontier. The constraint N1′ λ = 1 (with N1 being an N × 1 vector of ones) allows the sampled farmers to exhibit increasing, constant and decreasing return to scale  technology). To approximate the technology under constant returns to scale (CRS), we omitted the constraint N1′ λ = 1. To compute scale inefficiency, the difference between the VRS and CRS scores was computed.In βk is the estimated technical inefficiency score of input k. Following Schneider, Skevas, and Oude Lansink [Ζ denotes farm-specific characteristics (explanatory variables). δ denotes the vector of coefficients, and ε the error term. The distribution of the error term was assumed to be truncated normal, with zero mean, unknown variance, and left truncated at point 0- δΖ [ε denotes the standard deviation of the error term. Next, linear predictions of the inefficiency scores were generated based on the estimated coefficients and the producer-specific characteristics. For 2,000 iterations, errors were sampled out of a truncated distribution using the computed variance β is the estimated technical inefficiency score of input k. Z is the mean of a particular explanatory variable. δ* is the bootstrapped coefficient for the explanatory variable, ϕ(·) is the standard normal distribution and Φ(·) is the standard normal cumulative distribution function.To identify determinants of inefficiency, this study added a two-stage approach to account for nondiscretionary factors associated with the estimated inefficiency scores. Unfortunately, scores obtained from DEA are serially correlated by construction . Thus, t Lansink , inefficnt 0- δΖ . The max Lansink .∂Eβk∣Z,Data on specialised vegetable farms for the period 2006–2016 were obtained from Wageningen Economic Research (WeCR). WeCR uses stratified sampling for specialist indoor Dutch vegetable farms, which are collected for the European Farm Accounting Data Network (FADN). The panel is unbalanced, and on average, farms stay in the sample for 6–7 years. After removing farms with missing information, the dataset used for estimation comprised 1090 observations from 222 indoor vegetable farms. For the second stage bootstrap truncated regression, producer-specific characteristics such as capital structure is categorised into short- and long-term debt ratios. Short- and long-term debt were separated to investigate their differential association with technical inefficiencies. Farmer’s age plays a dual role in explaining inefficiency. Older farmers are associated with lower inefficiency resulting from the experience gathered over the years in farming leading to better managerial skills . On the According to the results, pesticides were the most technically inefficient variable input used by Dutch indoor vegetable farmers. This may suggest that the farmers are not keen on improving pesticide efficiency as it contributes the least to the total variable cost. As agricultural production activities are accompanied by a significant amount of risks, farmers may use pesticides as an insurance policy. Particularly for indoor cultivation, the high cost of investments and input cost results in increased production costs and consequently increased financial risks. Farmers at this point have a natural tendency to protect these investments through increased use of pesticides . The proEnergy had the lowest technical inefficiency score. This is supported by the findings of Oude Lansink and Silva , who repTechnical inefficiency scores of materials and fertilisers also indicate an efficiency gap in the use of these resources. Given that land and other fixed production factors are limited, the efficiency of materials such as quality seeds, planting materials and fertiliser are important as they have a direct link with output volumes . MateriaResults from the second stage bootstrap regression  suggest The farmers’ age, short-term and long-term debt ratios and subsidises were also found to have significant statistical associations with technical inefficiency of at least one of the inputs. One must, however, note that the economic importance of these marginal effects is not significant as substantial variations in these variables have only minimal effects on inefficiencies of the inputs. The direction of the statistical associations provides insights as it suggests precisely how changes in the explanatory variables may potentially impact inefficiency.The negative marginal effect of age suggests that older growers may be statistically associated with lower inefficiency of pesticide use. This is supported by the study of Schneider, Skevas and Oude Lansink , who expContrary to short term debt, the negative association between long-term debt ratio and inefficiency of energy may indicate investment in efficient innovations and technology resulting in improved energy and farm efficiency in general . It may This study suggests that the motivation for reducing inefficiency of the inputs  may be higher when the farmers receive subsidies. This is evidenced by the negative statistical association between subsidy and inefficiency. The impact of subsidy on farm’s efficiency can be double-sided. On one hand, it could lead to improvement in the efficiency of farms when subsidies are invested in improving the technology of production . On the As inefficiency scores are a relative measure of performance, the number of DMUs can influence inefficiency scores. A low number of DMUs can result in a relatively higher number of efficient farms (farms with zero inefficiencies). The available dataset also limited our study on farm characteristics that could have potentially significant associations with technical inefficiency; that is, more farm and farmer-specific variables such as education level, family composition and the location of the farm may explain differences in technical inefficiency levels between farms.The study estimated the input-specific technical inefficiency among Dutch indoor vegetable farms for the period 2006–2016 and identified the sources of inefficiencies for the specified inputs.Results from the study suggest considerable inefficiencies in the use of variable inputs among Dutch indoor vegetable farms. This implies that there is substantial scope for reducing inefficiency in the use of the inputs analysed. The results indicate that the sample of farmers, on average have fully exploited the potential to expand output. Meanwhile, they could reduce energy inefficiency by 14%, materials by 23%, pesticide by 24% and fertilisers by 22% while maintaining optimal output levels. Pesticides were identified to have the highest technical inefficiency score and energy the most efficiently used variable input. Results also show that scale improvements could lead to a 5–7% further reduction in the inputs’ use. The bootstrap truncated regression suggested that a higher degree of specialisation is significantly associated with a higher technical inefficiency of variable inputs. Age, short-term, long-term debt and subsidy were significant but devoid of economically significant effects.The empirical results have implications for both policymakers and farm managers. The noticeable inefficiencies observed for the separate inputs necessitate policy actions to build farmers’ capacity to improve on the use efficiency of these inputs. Legislations should target the reduction of inputs such as energy, pesticides and fertilisers. This would consequently have positive impact in the environment through for example lower greenhouse gas emissions and lower runoff of minerals and pesticides, reducing at least costs. Alternatively, policies could be aimed at introducing levies on specific variable inputs when market incentives to improve efficiency fails.


Damage to sensory input is an underlying pathology of chronic ankle instability (CAI). Therefore, it is necessary to evaluate the sensory function of patients with CAI. The present study quantitatively evaluated sensory nerve function in patients with CAI and healthy controls using current perception threshold (CPT) measurements, as well as the influence of sex, age, and body mass index (BMI) on CPT values and the relations between CPT frequencies.Fifty-nine subjects with CAI and 30 healthy controls participated in this study. CPT values at the anterior talofibular ligament region were recorded on the injured and uninjured sides in CAI patients and on both sides in the healthy control group. Between group differences were compared. The influence of sex, age and BMI on CPT values was evaluated. Correlations between different frequencies were also studied.p < 0.01), and the effect size were large. No significant difference was observed under 2000-Hz stimuli. There were correlations between CPT values at different frequencies (p < 0.01), especially 250 Hz and 5 Hz.There were no significant differences in age, sex, height, weight or BMI between the CAI and healthy control groups. The CPT values did not show a significant difference by sex. The CPT values did not significantly correlate with age or BMI. Compared to the control group, the CAI group had significantly higher CPT values on the injured and uninjured sides under 250-Hz and 5-Hz electrical stimuli; the difference between the groups was significant (The present study revealed increased sensory thresholds in 250-Hz- and 5-Hz-related sensory nerve fibres in the injured and uninjured ankles of patients with CAI. This increase may indicate dysfunction of A-delta and C fibres. Sex, age and BMI did not significantly impact CPT values. There were correlations between CPT values at different frequencies, especially 250 Hz and 5 Hz.Level III, case-control study. Ankle sprain is one of the most common injuries in daily life and sports. Up to 70% of individuals who sustain an acute ankle sprain may develop residual physical disability . PerceivPostural control is dependent on integrated sensory input, central information processing in the central nervous system, and motor output . Errors Sensory function may be evaluated subjectively and objectively . SubjectCurrent perception threshold (CPT) testing selectively evaluates the A-beta, A-delta, and C fibres in sensory nerves. A-beta fibres are large myelinated fibres that are activated by 2000-Hz electrical stimuli and transmit vibration and tactile messages. A-delta fibres are thinly myelinated fibres that are activated by 250-Hz electrical stimuli and transmit fast pain signals. C fibres are unmyelinated fibres that are activated by 5-Hz electrical stimuli and transmit slow pain signals , 11. ThePrevious studies have shown inconsistent results regarding sex and age differences , 20, 21.Therefore, in the present study, we quantitatively evaluated CPT values at the anterior talofibular ligament region using CPT measurements, compared CPT values according to sex, and calculated correlations between age, BMI and CPT values. We hypothesized that patients would exhibit higher CPT values due to sensory dysfunction than the controls. Sex, age, and BMI may influence CPT values. There may be internal correlations between different frequencies.This study was designed as a case-control study.Fifty-nine subjects with CAI  and 30 healthy controls  were recruited from a regional hospital from April 2017 to November 2018. Healthy controls were staff and medical students in the hospital. The inclusion and exclusion criteria for patients with CAI were selected according to criteria from the International Ankle Consortium . The incThis study was performed in accordance with the Declaration of Helsinki. Participants read and signed an informed consent form, which was approved by the ethics committee of our hospital, prior to the study.CPT measurements were performed using a neurometer . A CPT value of 1 is equal to an output intensity of 0.01 mA with an available maximum of 9.99 mA. The stimuli were applied to the skin of the anterior talofibular ligament region  of the injured and uninjured ankles in participants with CAI and both ankles in control participants by a well-trained doctor with experience in CPT testing administration. The order of the CPT testing in CAI participants and controls was randomly assigned using random number software. Values in the CAI group were recorded on the injured side and the uninjured side. Values in the control group were recorded on the random side and the control side, which were randomly assigned by the software, since the injured side may be the left or right side. The electrical stimuli were delivered via two 10-mm-diameter gold-plated electrodes at frequencies of 2000 Hz, 250 Hz and 5 Hz to the tested site. A doctor, who was blinded to participants’ group assignment, manually increased the electrical stimuli slowly until the participants reported a sensation of stimulation. The current was rapidly decreased and increased until the same threshold measurement was obtained on at least three consecutive trials . To prev2) were calculated, with 0.01 indicating a small effect size, 0.06 indicating a medium effect size and 0.14 indicating a large effect size [p < 0.05.Statistical analyses were performed using SPSS 26.0 . The normality of the variable distribution was evaluated using the Kolmogorov-Smirnov test. Continuous data are expressed as the mean ± standard deviation (SD). Independent t-tests were used to compare demographic data between the two groups, except by sex. The chi-squared test was used to compare sex differences between the CAI and control groups. Comparisons of CPT values between CAI patients and the control group were performed by 2 × 2 (group x side) repeated-measures ANOVA, and effect sizes ; the eta squared values were 0.176 (250 Hz) and 0.266 (5 Hz), which were large. No significant differences were found between the injured and uninjured sides of patients in the CAI group.CPT values are reported in Table No significant differences were found between male and female patients with CAI Table .Table 3There was no significant correlation between the CPT value and age. No significant correlation between the CPT value and BMI was observed Table .Table 4There were significant correlations between CPT values at different frequencies. The correlation between 250 Hz and 5 Hz was stronger than that between 2000 Hz and 250 Hz and that between 2000 Hz and 5 Hz (Table The pathogenesis of CAI is very complicated. We tested the CPT values in the anterior talofibular ligament area of injured and uninjured ankles. The results showed that patients with CAI had higher CPT values under 250-Hz and 5-Hz electrical stimuli than healthy controls, which were related to fast pain-related small myelinated A-delta and slow pain-related unmyelinated C fibres of the sensory nerves, respectively.The injured ankle showed a trend of higher CPT values than the uninjured ankle in the CAI group under 250-Hz and 5-Hz stimuli. Both ankles in the CAI group showed higher CPT values than those in the control group. These differences may indicate inherent differences or changes after injury via chronic pain. Decreased sensitivity contralateral to sites of peripheral nerve injury has been reported and might result from peripheral lesions involving afferent fibres that alter central processing and reorganization at the spinal, subcortical, or cortical level . AccordiSensory disorder is one of the pathophysiological changes in CAI. Sensory function becomes impaired due to injury to the receptors in the ligaments, capsule, and tendons of the ankle . ReceptoPrevious researchers have primarily reported on proprioception deficits in CAI –7 and leNotably, the injured and uninjured sides showed increased CPT values under 250-Hz and 5-Hz stimuli in our study, and these bilateral changes may reflect inherent differences or changes after injury via central modulation. Previous studies have reported bilateral changes after unilateral ankle sprain and CAI , 23. SouPrevious studies have shown inconsistent results regarding the effects of sex, age and BMI. Uddin et al.  reportedOur study revealed correlations between CPT values at different frequencies. Participants with higher CPT values at one frequency showed trends of higher CPT values at other frequencies. This result may be due to individual variability. The correlations may reflect the consistency of the sensory threshold test using CPT measurements. The correlation between 250 Hz and 5 Hz was stronger than that between other frequencies, which may be because the 250-Hz and 5-Hz stimuli activated small fibres, while the 2000-Hz stimuli activated large fibres. These may reflect CPT neuroselectivity. The findings are consistent with those reported by Pitei .The results of the present study support the use of CPT testing as a quantitative sensory detection method for CAI. Further studies are needed to evaluate the recovery and prognosis values of this method.However, there are some disadvantages to CPT tests. These testing procedures require participant reaction and feedback, similar to the hearing test. Therefore, they are not entirely objective methods. Nerve conduction velocity as measured using electromyography is an objective measurement, but there were reports of lower motor nerve conduction velocity , only seThere are some limitations to this study. First, this report was a case-control study performed at a tertiary referral centre, and unknown selection bias may have affected the study results. Second, only CPT values at the anterior talofibular ligament region were measured, and future studies are needed to investigate the CPT values at more sites in the lower extremities in CAI subjects. Third, participants in the control group were staff and medical students. Further studies may include a hypermobile group of patients who do not suffer CAI. Studies of the relationships between CPT tests and other sensory tests are also needed.The present study revealed increased sensory thresholds in the injured and uninjured limbs of 250-Hz- and 5-Hz-related sensory nerve fibres in patients with CAI. These results suggest dysfunction of A-delta and C fibres. Bilateral changes may be caused by inherent differences or neuromodulation. Sex, age and BMI did not significantly impact CPT values. There were correlations between CPT values at different frequencies, especially 250 Hz and 5 Hz. CPT testing has potential as a tool to quantitatively assess the function of sensory nerve fibres in CAI and monitor dynamic changes after treatment.


B lymphocytes produce antibodies under the stimulation of specific antigens, thereby exerting an immune effect. B cells identify antigens by their surface B cell receptor (BCR), which upon stimulation, directs the cell to activate and differentiate into antibody generating plasma cells. Activation of B cells via their BCRs involves signaling pathways that are tightly controlled by various regulators. In this review, we will discuss three major BCR mediated signaling pathways  and related regulators, which were roughly divided into positive, negative and mutual-balanced regulators, and the specific regulators of the specific signaling pathway based on regulatory effects. It has three main functions: producing antibodies, presenting antigens, and secreting cytokines involved in immune regulation.In the bone marrow, B cell development undergoes the stages of progenitor B cell, pre-B cell, immature B cell, and mature B cell. Two major changes in the various stages of B cell development in the bone marrow are rearrangement of immunoglobulin genes and the expression of membrane surface marks.1The pre-B cells are differentiated from pro-B cells and have undergone rearrangement of Ig heavy chain genes. In the cytoplasm of pre-B cells, IgM heavy chain molecules, namely μ chains, can be detected. But due to the absence of light chain (L chain) gene rearrangement, no membrane Ig expression occurs. Instead a surrogate L chain can be combined with the μ chain and act as a surrogate BCR complex on the plasma membrane, and this surrogate BCR takes a significant role in the further development of the pre-B cell. Due to lack of a complete BCR, pre-B cells cannot respond to antigenic stimulation and thus do not have any immune function.2During the immature B cell stage, L chain gene rearrangement occurs, resulting in the formation of completed IgM molecules which express antigen specific receptors on the membrane surface (mIgM). Further differentiation of immature B cells, leads to development to mature B cells that leave the bone marrow to enter immune organs. At this time, IgM and IgD are expressed together on the membrane, and their specificity of antigen recognition are the same.3In the peripheral lymphatic organs, mature B cells are stimulated by antigen, and activated to proliferate and differentiate into short lived plasma cells, which can synthesize and secrete antibodies. Each plasma cell produces only one type of Ig molecule, which has a unique antigen binding specificity. During antibody production, the type of Ig produced is transformed from the IgM isotype to IgG, IgA, or IgE isotypes.Following antigenic stimulation and B cell activation, some B cells transform into small lymphocytes and stop proliferation as well as differentiation, their IgD disappears, and their life expectancy increases to months or years. When contacting the same antigen again, these B cells quickly become activated and differentiate to plasma cells. Therefore, they are termed “memory B cells,” which play an important role in the secondary immune response.4 A B cell identifies a pathogen by the homologous BCR on its membrane surface. BCR signaling is essential for normal B cell development and maturation. Mutations in the component genes downstream of the BCR precursor signal block the development of B cells in the bone marrow, leading to antibody defects.5 Mutations in BCR co-receptors impair affinity maturation and antibody responses, thereby affecting humoral immune responses7 Mutations in the TLR signaling component and defects in BAFF-R can also impair B cell development and antigen responses.1The BCR is the most numerous surface receptor on the B cell, having 100,000 to 200,000 per cell.8 On the other hand, mutations in related components of the BCR signaling pathway can also induce B-cell lymphomas and autoimmune diseases. About 70% of the newly generated B cells in the body are autoreactive.9 The body's self-protection function silences these autoreactive cells through receptor editing,10 clone deletion,11 and conversion to non-reactive B cells.12 Therefore, BCR signaling pathway inhibitors and potent autoimmune checkpoint activators within a short period of time are becoming important targets for the treatment of B-cell malignancies and B-cell dependent autoimmune diseases.15Additionally, BCR signaling is also a key pathway for B-cell malignancy. On the one hand, BCR can induce B cell lymphoma by the chronic activation of foreign microorganisms or viral antigens, such as Helicobacter pylori-induced mucosal lymphoid tissue lymphoma and Hepatitis C virus-induced splenic marginal lymphoma.Here, we will discuss the BCR mediated signaling pathways and related regulators.24BCR is the specific surface marker of B cells, consisting of an extracellular region, transmembrane (TM) region, and intracellular region. According to the latest research, most of membrane BCRs exist as oligomers rather than individual monomeric receptors. This finding suggests that B cell activation is related to the BCR oligomer opening for binding regulatory molecules to transduce BCR signaling.The monomeric form of the BCR is made of a membrane-bound form of immunoglobulin (mIg) which is combined with an Igα/Igβ heterodimer non-covalently linked. The mIg of mature B cells is mainly mIgM and mIgD that belong to the immunoglobulin superfamily prototype, which contains the structure of a tetramer chain with two heavy chains (IgH) and two light chains (IgL) connected by a disulfide bond. The intracellular regions of mIg are very short, and the intracellular regions of IgM and IgD contain only three amino acids (KVK). This structural feature prevents mIg from transmitting the signal of antigen stimulation without the participation of other molecules.mb-1 and B29 genes, and belong to the immunoglobulin superfamily.16 They both have an Ig domain on the cell membrane surface, an evolutionarily conserved TM region, and a cytoplasmic tail with an immune receptor tyrosine-based activation motif (ITAM), which is about 26 amino acid residues long.4The two molecules are covalently bound together through a disulfide bond at the extracellular and TM regions. There are two main functions of Igα and Igβ: to serve as the main signal transduction molecules during antigen binding BCR and to participate in the expression and transposition of mIg.Igα and Igβ are also named CD79a and CD79b, which are 47 and 37 kDa glycoproteins, encoded by the 34  results in increased synthesis of PIP2.18 Syk and Btk activate PLC-γ2 via tyrosine phosphorylation, and catalyzes PIP2 to second messengers DAG and IP3.In the PLC-γ2 pathway, the B cell linker (BLNK) is a key adaptor protein that recruits Syk and Btk. After BCR antigen stimulation, Y204, an evolutionarily conserved non-ITAM tyrosine residue, near the ITAM of Igα recruits BLNK through SH2 domain binding to phosphorylated Igα. Syk is grouped to phosphorylated ITAM of Igα/Igβ, then activated, and phosphorylates BLNK, which combines with PLC-γ2, Grb2 and Btk to form a multimolecular protein complex.2+ release, IP3 binds to its receptor IP3R, a ligand-gated Ca2+ channel on the ER membrane, resulting in an increase in Ca2+ release from the ER. Due to the small number of Ca2+ in the endoplasmic reticulum, its reduction is immediately detected by the STIM1 protein which becomes separated from Ca2+ and accumulates in ER regions related to the cell membrane. STIM1 then combines with Orai channels and activates Ca2+ release-activated Ca2+channels (CRAC) in the cell membrane directly, allowing the extracellular Ca2+ to enter the cytosol. This second stage of Ca2+ transference is known as store-operated Ca2+ entry (SOCE), which maintains a continually increasing level of the intracellular Ca2+, and is necessary for continued Ca2+ signaling.18In the first stage of Ca2+ concentrations activate Ca2+ dependent protein, calmodulin. Calmodulin activates calcineurin, which dephosphorylates NFAT, resulting in nuclear translocation and transcriptional activation of nuclear factor of activated T cell (NFAT). Thus, Ca2+ concentrations regulate NFAT nuclear localization, since any decrease in Ca2+ will deactivate calmodulin, resulting in phosphorylation of NFAT and exiting the nucleus.19Elevated Ca20 TAK1 and IKK are recruited to phosphorylated CARMA1 through CBM. In resting B cells, the NF-κB dimer is stored in the cytoplasm and binds to IκB protein, but when TAK1 contacts IKK, TAK1 phosphorylates IKK, then activates the IκB kinase (IKK) complex, resulting in IκB phosphorylation and proteasomal degradation. This free NF-κB dimer (p50/cRel) translocates into the nucleus to transcribe targeted genes, which leads to expression of BCL-2, cyclin D, CDK4 and other important molecules. In addition, PKCβ activates MAPK family members to induce cell survival as well as proliferation.21Second messenger DAG is confined to the plasma membrane and connects to RasGRP, this mediates PKCβ activation, which can phosphorylate CARMA1 and induce the conformational change of CARMA1 to combine with BCL10-MALT1 and become CARMA1-BCL10-MALT1 complex (CBM).22 The possible reason is that the cSH2 structure of PLC-γ2 can stabilize the early signaling complex of BCR cross-linking. If it is lacking, it will lead to the imbalance of B cell surface actin polymerization, which will reduce the BCR recruitment, insufficient phosphorylation of Syk, Btk, and BLNK, and the co-localization of the BCR signaling complex is reduced and the Ca2+ response is insufficient. The inhibitory factor Cbl of Ca2+ signaling is co-localized with BCR, which further inhibits the activity of PLC-γ2.23 At the same time, impaired Ca2+ signaling can also cause various immunodeficiency-related diseases, such as X-linked gamma globulinemia (XLA)24 and common variant immunodeficiency (CVID).25In the PLC-γ2 pathway, if PLC-γ2 lacks the autoinhibitory C-terminal Src homology 2 (cSH2) domain, PLC-γ2 associated antibody deficiency and immune dysregulation (PLAID) will occur.3.226In B cells, PI3Kδ plays a role in signals from BCR, CXCR4, CXCR5, BAFF, and CD19. It is made up of the regulatory subunit p85 and the catalytic subunit p110δ. Regulatory subunit p85 includes an SH2 domain that recruits PI3K to tyrosine kinase linked receptors and their substrates.Both phosphorylated CD19 and BCAP recruit and activate PI3K. Following BCR stimulation by antigen, Lyn phosphorylates the SH2 domain in the p85α subunit of PI3K that is located on the intracellular domain of the BCR regulatory membrane receptor, CD19. BCAP, an adaptor molecule of PI3K, is coupled to the BCR by the adaptor protein Nck. After coupling with the BCR, Syk as well as Btk phosphorylate BCAP and then BCAP binds with PI3K.The enzymatic activity of PI3K is enhanced by the GTPase, Rac1. Activation of Rac1(Rac1-GTP) is through the guanine nucleotide exchange factor Vav, which is recruited to the BLNK-Grb2 complex and then phosphorylated.P110 subunit of PI3K activation results in phosphorylation of membrane PIP2 to generate PIP3. Akt and Btk bind through their PH domains to PIP3. Akt is recruited to the cell membrane by binding to PIP3, here it is phosphorylated by 3-phosphoinositide-dependent kinase-1 (PDK1) and enters the cytoplasm to activate transcription factors involved in cell survival such as FOXO1. BTK recruitment to the cell membrane through PIP3 interaction results in recruitment and activation of Wiskott Aldrich Syndrome protein (WASP), an actin nucleation promoting factor. WASP binds BTK through its SH3 domain and is then phosphorylated by CDC42, which was activated by Vav.27Overactivation of the PI3K pathway leads to phosphoinositide 3–kinase d syndrome (APDS), a type of immunodeficiency disease with major clinical symptoms including recurrent sinus infection, conjunctivitis, bacterial lymphadenitis and herpes virus infection, and benign lymphocyte proliferation, malignant tumors and autoimmune manifestations. Insufficient activation of the PI3K pathway also causes immunodeficiency, which usually manifests as infections in the lungs and intestines. These patients have a low number of B cells and exhibit panhypogammaglobulinemia or agammaglobulinemia from an early age.3.328Ras GTPase activation, which in turn activates the Ras-Raf-MEK-ERK pathway, is the most clearly discussed MAPK cascade. In B cells stimulated by antigens, DAGs bind and activate RasGRP, which activates the molecular switch protein Ras which is fixed on the cell membrane, transforming it from Ras-GDP to Ras-GTP state. GTP bound Ras recruits Raf to the cell membrane. The membrane localized Raf protein is activated by enzymatic transphosphorylation through forming dimers, which then phosphorylates and activates MAPKK, MEK1, and MEK2, the specific MAPKKs in the ERK cascade. ERK1 and ERK2 are activated by MEK-dependent dual phosphorylation in the participation of enzymes, transmitting the signal of MEK1 and MEK2. The activated ERK is transported to the nucleus. ERKs phosphorylate nuclear transcription factors, c-Myc, Myb, Elk, and downstream kinases, RSKs, MNKs, MSKs, to further spread the signal and increase the number of ERK cascade regulated targets.29 At the same time, loss-of-function (LOF) variants can also occur in children with combinatorial immunodeficiency induced by components used in CBM.30CARD protein–BCL-10–MALT1 (CBM) signalosomes plays an important role in the MAPK pathway and mediates B/T cell proliferation and differentiation, metabolic reprogramming and survival after antigen recognition. Its genetic alterations also cause a variety of immunodeficiencies, autoimmune diseases and lymphomas. For example, in MALT lymphoma, somatic gain-of-function (GOF) mutations of CARD11, BCL-10, and MALT1 cause overexpression of BCL-10 or MALT1, causing abnormal NF-κB activation and formation of malignant tumors.44.14.1.131 In the PLC-γ2 pathway, BCAP contains 3 proline-rich sequences that serve as binding sites for PLC-γ2. The cooperation of BCAP and BLNK recruits PLC-γ2 for its activation in membrane rafts. The lack of BCAP in B cells reduces PLC-γ2 activation and Ca2+ flux. In addition, BCAP also regulates the expression of c-Rel. BCAP deficiency decreases c-Rel expression and the effector molecules CDK4, Bcl-2 and cyclin D, which are for B cell survival and proliferation.32BCAP is a positive regulator of BCR signaling. In the PI3K pathway, BCAP associates with PI3K and regulates its localization.33 For instance, CD19 is a positive regulator of BCR signaling.34 BCR cross-linking with CD19 reduces the BCR activation threshold by reducing the internalization of BCR, thus extending the residence of BCR in lipid rafts.35The co-receptor CD21/35 on the surface of B cells maintains B cell self-tolerance by regulating the turnover rate of CD19 on the cell membrane, inducing internalization of CD19 and inhibiting Ca2+ release.36 CD21/35 can also inhibit BCR signaling by isolating CD19 from BCRs.37 Moreover, the co-receptor CD81 may promote BCR signaling by linking and immobilizing CD19.38BCR-induced signaling can be affected by coregulatory molecules.40 In the PI3K pathway and MAPK pathway, CD40 and BAFF-R promote BCR downstream signaling through similar mechanisms.45Conversely, non-receptor tyrosine phosphatase PTP1B and hematopoietic protein tyrosine phosphatase inhibit this pathway to down-regulate BCR signaling.47CD40 and BAFF-R are positive regulators of BCR signaling. Both belong to the tumor necrosis factor receptor (TNFR) family. In the NF-κB pathway downstream of PLC-γ2, clAP1/2 is an E3 ubiquitin ligase group recruited by tumor necrosis factor receptor-associated factor 2 (TRAF2). CD40 or BAFF-R can prevent NIK from being ubiquitinated and degraded by recruiting TRAF3, which binds to the TRAF2-clAP1/2 complex. When TRAF3 is present, clAP1/2 is activated and ubiquitinates TRAF3 for degradation, while NIK is spared and continues to bind to the downstream kinase IKK to ensure that the NF-κB pathway is not constitutively inhibited.2+-dependent ROI generation.48 In the catalytically active sites of tyrosine phosphatases , it is possible for H2O2 to oxidize conserved cysteine residues by a plasma membrane-associated NADPH oxidase so that it does not active.49 Thus, BCR proximal phosphatases are inactivated, facilitating BCR-induced signal transduction.33Reactive oxygen intermediates (ROI), such as H2O2 are positive regulators of BCR signaling. Crosslinked BCRs lead to Ca50 MicroRNA can affect B cell proliferation, apoptosis, and sensitivity to BCR stimulation by regulating B cell transcriptional gene expression, thereby regulating BCR signaling.51 Conversely, BCR signaling can affect the expression of certain microRNAs. Among them, the relatively clear miR-155 is considered to be a positive regulator of BCR signaling. It can upregulate BCR signaling by targeting the up-regulation of transcription factor PU.1, down-regulating the expression of SHIP-1, and increasing the sensitivity of B cells to BCR stimulation.52 Other micro-RNA regulation of BCR signaling are still under study.Recent studies have shown that there is an interaction between microRNA and BCR signaling.53Additionally, new signaling molecules are being discovered to enhance positive BCR signaling. Leucine-rich repeat kinase 1 (LRRK1) is a member of the ROCO family of proteins that cooperates with CARMA1 to regulate NF-κB activation and BCR-induced B cell proliferation.4.1.254 In the Ras pathway, Grb2 recruits Sos to the membrane, resulting in activated Ras.55 The competitive binding of Cbl and Sos to Grb2 is exclusive mutually because their proline-rich regions compete for the same binding site in the Grb2 SH3 domain.56 Therefore, Cbl negatively regulates the Ras pathway through prohibiting Sos recruitment to the membrane.The Cbl protein is a negative regulator of BCR signaling. In the PLC-γ2 pathway, Cbl competitively inhibits PLC-γ2 through binding of its SH2 domain to phosphorylated BLNK, resulting in the inhibition of PLC-γ2 phosphorylation.2+ mobilization by phosphorylating a short stretch of highly conserved S180 serine residues in the TH domain of Btk.17PKCβ is a negative regulator of BCR signaling. PKCβ, which is a feedback inhibitor of Btk activation, inhibits BCR signaling and Ca2+ signaling downstream of BCR signaling.57 Lyn phosphorylates the adaptor downstream of tyrosine kinase 3 (Dok3) after BCR cross-linking, allowing the SH2 domain of Grb2 to interact with Dok3. Then, they translocate to PIP3 regions in the cell membrane through the Dok3 PH domain, inhibiting Btk activation by competitively binding to PIP3, thereby inhibiting Btk-dependent PLC-γ2 phosphorylation.18 In addition, Grb2 also interacts with SHIP, which binds to CD22 and FcγRIIB1, suggesting that Grb2 may integrate a coreceptor that inhibits BCR-mediated Ca2+ mobilization.57Growth factor receptor binding protein 2 (Grb2) is a negative regulator of Ca58 Possible mechanisms are:The transcription factor interferon regulatory factor 4 (IRF4) is a negative regulator of BCR signaling.60;1. inhibiting BCR-induced calcium signaling by increasing expression of SHIP2. increasing phosphorylation of Syk and BLNK by decreasing BCAP expression and decreasing PI3K/Akt pathway activity;613. promoting actin polymerization by inhibiting the interaction between BCR and co-receptor CD19, increasing the BCR signaling threshold, and down-regulating BCR signaling.4.1.362 Its main component is the cortical actin network. The cortico-actin network is part of the actin cytoskeleton made of actin filaments that are linked by actin-binding proteins and are bound to transmembrane proteins with the help of ezrin/radixin/moesin (ERM) proteins.64 F-actin is anchored to the plasma membrane through ERM proteins to form distinct compartments on the membrane that limit the lateral movement of membrane proteins. The cytoplasmic domain of ERM proteins extend into the cortical actin network. Thus, a cortical actin network can inhibit BCR aggregation by limiting BCR lateral flow. To initiate BCR signaling, the cortical actin network must first be disassociated. On one hand, the actin cytoskeleton positively regulates BCR signaling. There are three possible mechanisms:1.65B-cell proliferation is triggered by actin recombination, and the area of contact between B cells and antigen on the membrane is increased, thereby increasing the number of antigens that interact with BCRs.2.67Amplify the BCR signal by enhancing the formation of BCR microclusters.3.71Act as a scaffold for BCRs to recruit relevant signaling molecules, therefore promoting BCR signaling.The actin cytoskeleton of B cells is a bidirectional regulator of BCR signaling.1.73 resulting in BCRs collapsing into a central cluster, and also contraction of the B cell. This halts BCR signaling and decreases the signaling,66 which is crucial for maintaining B cell tolerance.Activated BCRs induce actin polymerization for B cell spreading and accumulation of BCR signaling microclusters. Approximately 5 min into these events, SHIP-1 is activated to reduce the F-actin within the BCR microclusters,2.75 Abp-1 recruits actin to clathrin-coated pits and creates forces on the neck of dynamin to help the vesicles detach from the plasma membrane, thereby accelerating antigen uptake and BCR internalization and down-regulating BCR signaling.79After BCR activation, recruitment and phosphorylation of actin binding protein (Abp-1) can be induced.3.80Abp-1 also promotes BCR microcluster polymerization and B cell contraction and recruits inhibitory molecules SHIP-1 and HPK1 to BCR microclusters to attenuate BCR signaling.On the other hand, the actin cytoskeleton also negatively regulates BCR signaling. The possible mechanisms are:81Hematopoietic progenitor kinase 1 (HPK1) can inhibit BCR signaling by promoting phosphorylation and ubiquitination of BLNK.76 translocating it to the cell surface. Activated WASP stimulates actin polymerization through binding to Arp2/3,84 promoting lateral migration of BCRs and B cell proliferation.85 At this point, BCR signaling reaches a maximum level and subsequently, SHIP-1 is activated to dephosphorylate PIP3, the binding site of Btk on the plasma membrane,86 thereby inhibiting WASP activity and in turn activating N-WASP.66 This mechanism may also be related to the signal transducing protein, Grb2.90 Activated N-WASP promotes the reorganization of F-actin and internalization of BCRs by vesicles,93 inducing the conversion of B cells from diffusion to contraction, and causing BCR microclusters to accumulate into a central cluster. Thus, the BCR signaling is down-regulated, and B-cell self-tolerance is enhanced.94WASP and N-WASP are a pair of bidirectional regulators for BCR signals. Wiskott–Aldrich Syndrome Protein (WASP) is a cytoskeleton-regulatory protein unique to hematopoietic cells, and N-WASP has 50% homology with it. After activation of BCRs, Btk is activated and stimulates PIP2 production by activating Vav, the guanine nucleotide exchange factor of Cdc42, thereby inducing WASP to be phosphorylated and activated,95The complement system and Toll-like receptors are bidirectional regulators of BCR signaling and play an important role in B cell self-tolerance.98In B cells the complement system includes complement proteins and complement receptors, and the combination of them can trigger the complement cascade, which in turn regulates BCR signaling. The common complement protein is C3, and common complement receptors include C3a receptors that bind to C3a, the complement receptor type 1  that binds to C3b and C4b, and complement receptor type 2  that bind to C3d and CR3 (CD11b/CD18), as well as CR4 (CD11c/CD18) that bind to iC3. In human B cells, CR1 and CR2 have mutual antagonistic effects.100 so the TLR content in plasma cells and memory B cells is higher than naive B cells, which makes them more sensitive to antigenic stimulation.101 The TLR on the plasma membrane and the TLR on the endosome has an antagonistic effect. Existing studies have shown that TLR9 on the plasma membrane has an inhibitory effect on endosomal TLR9. When BCR activates and produces a signal response in response to endosomal TLR9, the plasma membrane TLR9 can inhibit and down-regulate BCR signaling through binding to different ligands, thereby increasing B cell tolerance.The major TLRs in human B cells are TLR1/2, TLR6, TLR7, TLR9, and TLR10. When BCR or CD40 is activated, TLR expression is increased,95 In addition, under the conditions of autoimmune disease, both the complement system and TRL can enhance the recognition rate of B cells against autoantigens, thereby improving the tolerance of B cells.106When cells are damaged or stimulated by self-molecules , the B-cell complement system and TLR signal are activated, and there exists a combination of TLR and CR and BCR. Studies have shown that cross-linking of CR1 with TLR9 can down-regulate BCR signaling.55Transmembrane tyrosine phosphatase, CD45, and tyrosine-protein kinase, Csk, are a pair of antagonistic regulators that regulate Lyn activation. CD45 promotes Lyn activation, whereas Csk inhibits its activation. Lyn receptor-induced tyrosine phosphorylation increases significantly with reduction in Csk and decreases significantly with reduction in CD45. BCR signaling is balanced by CD45 and Csk activity, thereby further regulating the Src-PTKs carboxy-terminal tyrosine phosphorylated state.4.2108 Some of the domains have a tyrosine-based activation motif (ITAM) and others have a tyrosine-based inhibition motif (ITIM). When the antigen-antibody complex binds to them, Src family kinases phosphorylate the tyrosines on ITIM or ITAM, thereby mediating binding to its downstream SH2 domain containing molecule, including Igα/β heterodimers, Lyn, Syk, Slp65, CD19, Btk, BLNK, and Vav1, and promote or suppress corresponding BCR signaling.109There are many membrane molecules on the B cell membrane, such as FcγRIIB, FCRL, CD22, Siglec-10, CD31, mouse PIR-B/human LIRB1 and LIRB2PD-1, BTLA, CD5, and CD72.2+ mobilization and proliferation.110 FCRL2-5 has an ITIM motif that inhibits Ca2+ mobilization and down-regulates BCR signaling by recruiting and activating SHP-1which has SH2 domains.115 SHP-1 inhibits the phosphorylation of Syk, thereby inhibiting the BCR signaling pathway.116Among them, FCRL1 contains two ITAM motifs, which can up-regulate BCR signaling by enhancing BCR-induced Ca33 SHP-1 inhibits BCR-induced signaling by removing tyrosine phosphorylation of signaling molecules mentioned above.117 Paired immunoglobulin receptor B (PIR-B) and Siglec-G negatively regulate BCR signaling by the same mechanism. In addition, CD22 interacts physically with PMCA4, causing plasma membrane calcium-ATPase 4 (PMCA4) to weaken the BCR signaling in a SHP-1-dependent manner by excreting Ca2+ from the cytosol.118Transmembrane protein CD22 is a negative regulator of BCR signaling. Random activation of Src kinases related to BCR activation phosphorylates the tyrosines of the CD22 ITIM. These phosphotyrosines recruit SHP-1 through their SH2 domain.120 and SHIP.121 Inositol 5-phosphatase 1 (SHIP1), which contains a SH2 domain, catalyzes the dephosphorylation of PIP3, inhibiting the PH domain-dependent recruitment of BTK to the membrane. This eliminates PLC-γ2 activation and Ca2+ flux, thus inhibiting signals produced by antigen bound to BCR.86 Additionally, phosphatase and tensin homologues (PTEN) negatively regulate BCR signaling through the same mechanism.17FcγRIIB is a low affinity Fc receptor of IgG. Phosphorylation of the ITIM within the FcγRIIB cytoplasmic domain also inhibits BCR signaling. Once Lyn phosphorylates FcγRIIB, FcγRIIB recruits SHP-1122SH2-domain-containing protein tyrosine phosphatase2 (SHP-2) acts synergistically with FcγRIIB to dephosphorylate the adaptor protein Gab1, thereby blocking the PI3K pathway.123Also, PTPN22 inhibits the activity of Syk, PLC-γ2 and Akt and thus inhibits the BCR signal through the PI3K pathway.2+ influx.124 Binding of Vav to Grb2 and BLNK results in potent Rac1 activation following BCR stimulation. Rac1-GTP, in turn, activates PI3K.125 Furthermore, Grb2 and BLNK localize Vav to lipid rafts to promote the most efficient activation of B cells.126 Through this mechanism, Vav can promote the continuous production of PIP3 and calcium influx, positively regulating the response of B cells.127Vav is the positive regulator of the PI3K pathway. The Vav family proteins  are guanine nucleotide exchange factors (GEFs) in cytoplasm of the GTPases of the Rho family and are essential for BCR-induced Ca55The Scr family PTK, Lyn, is a bidirectional regulator of BCR signaling. Activation of Lyn results in the phosphorylation of ITIM, and the decrease of Lyn reduces the phosphorylation of ITIM, thereby inhibiting the suppression signals of FcγRIIB and CD22, causing BCR hyper-responsiveness.4.3In the SOCE pathway, the oligomerization and assemblage of STIM1-Orai are regulated by many regulating proteins.2+ concentration is low, CRACR2A connects to STIM1 and Orai1, forming a ternary complex in the cytoplasm that stabilizes the CRAC active complex.128 After the rise of cytoplasmic Ca2+, CRACR2A can unbind STIM1 and Orai1 and inhibit the influx of extracellular Ca2+, thus regulating Ca2+ mobilization bidirectionally.18When the cytoplasmic Ca2+-binding integrated ER membrane protein junctate, a connecting protein between STIM1 and Orai1,129 mediates the transport of STIM1 clusters at the ER-PM junction and promotes Ca2+ influx.130The Ca2+ release, and subsequently inhibiting expression of CD69 and CD86 under antigen-specific induction.131LPA5 is a receptor for lysophosphatidic acid (LPA) and may inhibit BCR signaling by inhibiting the activity of IP3R to down-regulate Ca133 Septin repositions in plasma membrane during ER Ca2+ storage depletion, promoting binding of STIM1 to ER-PM junction and recruitment of Orai1.Septin, one of the GTP binding proteins, is involved in the organization of membrane microdomains of STIM1 and Orai1 by forming hetero-oligomeric complexes.Surfeit locus protein 4 (Surf4) can bind to STIM1 then interact with the ER region of STIM1, this inhibits the transport of STIM1 to the junction of SOCE and ER-PM, thus inhibiting the SOCE pathway.18Moreover, inositol 1,4,5-triphosphate 3-kinase B (Itpkb) is also a negative regulator of the SOCE pathway which inhibits SOCE by phosphorylating IP3 to form IP4.4.4134In the Ras-MAPK pathway, GEFs, such as RasGRP, RasGRF, and SOS, are important positive regulators of Ras that control and induce the transference between the GDP-binding state to activated GTP-bound state. The conversion is moved backward by GTPase-activated proteins (GAPs), for example NF1 and RasGAP, which act as negative regulators, thereby promoting Ras's inner GTPase activity, leading to the transformation from GTP to GDP. Therefore, the Ras activation circulation is controlled by the balance of GEFs and GAP activities.28In addition, the regulation mechanisms of ERK in mature B cells is via the negative regulation of DAG signaling mediated by phosphorylation of DAG by DAG kinase (DGK) and conversion to the phosphatidic acid (PA), thus inhibiting the activity of ERK in mature follicular B cells.5135 In GC, B cells continue to proliferate and undergo somatic hypermutation (SHM) and in IgH constant region, Cμ is replaced by Cγ, Cα or Cε, resulting in class switched recombination (CSR)3 in the immunoglobulin V region under the action of activation-induced cytosine deaminase (AID) to differentiate into memory B cells or plasma cells.137 CSR is achieved by excision and reconnection of DNA. By recombining the DNA sequence between the two switch (S) regions, the VDJ fragment of the rearrangement completed gene is placed upstream of a new constant region fragment. Thereby, an Ig having the same variable region and different isotype of the constant region is generated.138 Among them, low-affinity GC cells with broadly reactive BCRs differentiate into memory B cells, which is beneficial to increase the breadth of antibody responses, whereas high-affinity and intermediate-affinity GC B cells tend to differentiate into plasma cells and continue to maintain GC cells.139The naïve B cells that secrete IgM are the main body of the primary immune response and, when activated by antigenic stimulation, rapidly proliferate and form a germinal center (GC) with the help of follicular helper T cells (Tfh).2Different types of memory B cells secrete different immunoglobulins, including IgM, IgD, IgG, IgE, and IgA, and they migrate to corresponding sites with the help of chemokine receptors  to exert an immune function. Among them, the signal pathways of IgM and IgD are similar.140 Because the cytoplasmic regions of mlgG and mIgE contain immunoglobulin tail tyrosine (ITT), ITT can be phosphorylated by Syk,131 which can provide binding sites for growth factor receptor binding protein 2 (Grb2) via the SH2 domain then enhance the phosphorylation of BCR downstream effector proteins and enhance Ca2+ mobilization.140 In mIgM-expressing B cells, Grb2 is a negative regulator that interacts with the inhibitory surface receptor CD22, cytoplasmic adaptor proteins Dok3 and SHIP, and inhibits BCR signaling.143 However, in B cells expressing mIgG and mIgE, the binding of Grb2 to CD22 or Dok3 is blocked by the binding of ITT with Grb2, thereby blocking the negative regulatory pathway. On the other hand, Grb2 interacts with Btk to promote phosphorylation of PLC-γ2 by Btk, thereby reducing the activation threshold of mIgG- and mIgE-containing memory B cells.131 In addition, IgG enhances BCR oligomerization after antigen stimulation, promoting Syk recruitment and Ca2+ mobilization.144Memory B cells expressing IgG and IgE are more responsive to BCR signaling.145IgE is an antibody involved in allergic reactions. Its expression on the cell surface is much lower than that of BCR containing mIgG and mIgM. By reducing the survival life of IgE-type B cells, the body suppresses the excessive production of IgE, thereby reducing B-cell self-reactions and allergic reactions.146 Since mIgA does not contain ITT, the BCR signal is not enhanced.140IgA mainly exists on the exposed skin surface and mucosal secretions and belongs to the body's first line of defense.147 AID can be used to decarboxylate cytidine into uridine in the immunoglobulin V region, causing base mismatches and excision repair. In addition, DNA double-strand breaks (DSBs) are also generated between two S regions in the heavy chain gene cluster, resulting in rearrangement of the CH locus as well as loss of the insertion sequence,149 and rejoining two fracture areas by non-homologous end joining (NHEJ), CSR was completed.151 Under the action of LPS and IL-4, PTEN expression was reduced, AKT and FOXO1 were hyperphosphorylated, inhibited AID expression in GC of IgM-BCR, and at the same time downregulated the chemokine receptor CXCR4, thereby reducing the conversion to IgG class.153 By integrating signals from the non-classical and classical NF-κB pathways, BCRs and TLRs synergistically induce AID and T cell independence.154 TLR ligands, such as LPS and CpG, can promote T cell-dependent specific antibody responses and have been used extensively as vaccine adjuvants.157 CD38,158 CD40,159 CD180,160 TACI,161 and IL-10R162 can enhance TLR-dependent CSR. In addition, in the differentiation of memory B cells and plasma cells, IRF4 can promote GC formation and plasma cell differentiation,163 MITF is a corresponding antagonist factor.164 B lymphocyte induced mature protein 1 (Blimp-1) can promote plasma cell differentiation,136 and BTB and CNC homolog 2 (Bach2) is the corresponding antagonist factor.165AID is a B cell-specific factor that is specifically expressed in the GC of peripheral lymphoid organs after antigen stimulation.6169 In contrast, signal molecules that originally functioned as normal signaling functions can be ubiquitinated and degraded by molecules that have E3 ubiquitin ligase activity, such as Cbl-b, and thereby inhibit BCR signaling.172 In the future, drug therapy studies for autoimmune diseases and lymphomas can be based on the signaling regulators summarized in this article and to control and treat BCR signaling related diseases through siRNA and other means.173BCR signaling is a series of signals generated by B cells under the stimulation of antigens. It stimulates the differentiation of B cells to produce an immune response, helping the body to fight against pathogens. However, excessively strong BCR signal responses can make B cells highly reactive, which is the cause of autoimmune diseases. In addition, an abnormal increase in BCR signaling can also lead to B-lymphocyte malignancy. Under normal conditions, when the BCR is activated by antigenic stimulation, B cells will start up their own inhibitory pathway to down-regulate BCR signaling, which is the basis of B cell tolerance. Among them, in the BCR signaling pathway, there are many phosphorylation of receptors and key molecules, so BCR signaling can be down-regulated by dephosphorylation. In the downstream NF-κB pathway, there are many key molecules that require ubiquitination, so deubiquitinating enzymes (DUB), such as CYLD, A20, OTUD7B, etc, can also down-regulate BCR signaling by deubiquitinating related molecules.This review focused on mature B cells containing mIgM, and discussed the regulatory mechanisms and regulators of the three main signaling pathways mediated by BCR. Compared with previous literature, this paper summarizes the positive and negative regulators that affect BCR signal transduction, and hopes to provide researchers with a macro view to further study the details of the BCR signaling pathway, or to conduct research on the related diseases through experimental control. However, cells are small, but all-embracing, and the regulatory mechanisms and regulators of signaling pathways are complex and trivial. Because of the short writing time and limited personal knowledge, this review is difficult to cover, and it would be a great honor for me if it was helpful.


Plants continually monitor their innate developmental status and external environment and make adjustments to balance growth, differentiation and stress responses using a complex and highly interconnected regulatory network composed of various signaling molecules and regulatory proteins. Phytohormones are an essential group of signaling molecules that work through a variety of different pathways conferring plasticity to adapt to the everchanging developmental and environmental cues. Of these, jasmonic acid (JA), a lipid-derived molecule, plays an essential function in controlling many different plant developmental and stress responses. In the past decades, significant progress has been made in our understanding of the molecular mechanisms that underlie JA metabolism, perception, signal transduction and its crosstalk with other phytohormone signaling pathways. In this review, we discuss the JA signaling pathways starting from its biosynthesis to JA-responsive gene expression, highlighting recent advances made in defining the key transcription factors and transcriptional regulatory proteins involved. We also discuss the nature and degree of crosstalk between JA and other phytohormone signaling pathways, highlighting recent breakthroughs that broaden our knowledge of the molecular bases underlying JA-regulated processes during plant development and biotic stress responses. During growth and development, plants are constantly battling against a challenging environment. These adverse or unfavorable environmental conditions are often categorized as: (i) abiotic stresses, such as ultraviolet (UV) radiation, flood, drought, heat, cold, heavy metal toxicity and nutrient deficiency, and (ii) biotic stresses, such as pathogen infection and animal herbivory . Within Jasmonic acid (JA) and its metabolic derivatives, such as jasmonic acid isoleucine (JA-Ile) and methyl jasmonate (MeJA), collectively known as jasmonates (JAs), are a class of lipid-derived, natural and widely distributed phytohormones in higher plants. JAs have been studied for decades as key signaling compounds involved in many aspects of plant development and stress responses ,16,17,18Studies in recent decades have remarkably expanded our knowledge on the molecular basis underlying JA biosynthesis, transportation, signal transduction and the crosstalk with other signaling pathways. The history of JA research ever since the first isolation of MeJA in 1962 has been well documented . The impIn this review, we focus on recent updates on JA biosynthesis and signal transduction mainly in Arabidopsis, the crosstalk complexity between JA and other phytohormone signaling during plant development and stress responses, as well as the roles of the involved transcription factors (TFs) and other regulatory proteins.Thanks to modern technologies and dedicated researchers in biochemistry, cell biology and genetics, the molecular mechanisms underlying JA biosynthesis and signal transduction have been progressively uncovered in both monocotyledon and dicotyledon plants, especially in Arabidopsis ,16,18,22To date, three JA biosynthetic pathways have been identified in Arabidopsis: (1) the octadecane pathway starting from α-linolenic acid , (2) the hexadecane pathway starting from hexadecatrienoic acid (16:3), and (3) the 12-oxo-phytodienoic acid (OPDA) reductase 3 (OPR3)-independent pathway . All thriso-JA] (iso-JA-Ile (JA-Ile)  . dnOPDA :3 hydrol(JA-Ile) . When tr(JA-Ile) ,35,36,37opr3-3 [The OPR3-independent pathway was recently identified by studying a total loss-of-function OPR3 mutant, opr3-3 . In the opr3-3 .The biosynthesis of JA involves the translocation of the JA-precursor, OPDA, from the chloroplast into the peroxisome. For a long time, the component(s) responsible for the export of OPDA from the chloroplast remained elusive. However, recently, a Bet v1-like family protein, termed JASSY, was identified as the exporter of OPDA from the chloroplast . JASSY iabcd1 mutant Arabidopsis [In Arabidopsis, the peroxisomal localized D-type ATP-binding cassette (ABC) transporter CTS , and peroxisomal defective 3 (PED3)) was found to be involved in the peroxisomal import of JA precursors . In addibidopsis . The idebidopsis ,42. ThisOf note, the fatty acid β-oxidations, which take place exclusively in the peroxisome of plants, contribute to the biosynthesis of not only JA but several other major phytohormones, such as indole-3-acetic acid (IAA) and SA. To our knowledge, CTS/AtABCD1/AtPXA1 is the sole peroxisomal transporter to have been identified that is responsible for the import of, presumably esterified, precursors of JA (OPDA), IAA (indole-3-butyric acid (IBA)) and SA (cinnamic acid (CA)), suggesting a core function of CTS for peroxisome-mediated biosynthesis of phytohormones ,44,45.Recent studies have found that several members of the G-subfamily of ABC transporters (ABCGs) also function as JA transporters that mediate both intracellular and long-distance JA movement ,47,48,49abcg16/jat1 exhibits phenotypes that are consistent with compromised JA signaling [A member of the G-subfamily of ABC transporters, AtJAT1/AtABCG16, has recently been identified and characterized as a dual function transporter of JA and JA-Ile in Arabidopsis  Figure . AtJA1 iignaling . Whetherignaling .2+) fluxes, presumably also through cell–cell transportation. It is hypothesized that AtJAT3- and AtJAT4-mediated loading of locally produced JA drives de novo JA synthesis successively during cell–cell transportation along the phloem passage [More recently, two plasma membrane localized transporters, AtJAT3/AtABCG6 and AtJAT4/AtABCG20, have been identified as potential JA importers that mediate long distance cell–cell translocation of wound-induced JA along the phloem  Figure . It has  passage ,50,51,52 passage  and anot passage , are inv passage .It has been proposed that the peroxisome-localized AtJAT2/AtABCG1 may mediate the peroxisomal export of JA while AtJAT5 mediates the cellular export of JA  Figure . As defiOther candidate JA transporters have also been implicated in various studies, including several members of the NITRATE TRANSPORTER1/PEPTIDE TRANSPORTER FAMILY (NPFs) such as NPF2.10/GLUCOSINOLATE TRANSPORTER 1 (GTR1) and NPF4.1/ABA-IMPORTING TRANSPORTER 3 (AIT3) ,55,56. HCOI1, JASMONATE ZIM DOMAIN (JAZ) proteins and inositol pentakisphosphate (InsP5) [The generally accepted “relief of repression” model for JA perception is built upon decades of research beginning with the identification of the core co-receptor complex for JA-Ile, that is composed of the F-box protein CORONATINE INSENSITIVE 1 (COI1) containing SKP1-CULLIN1-F-box-type (SCF) E3 ubiquitin ligase complex SCF (InsP5) ,58,59,60Under normal conditions, where little or no nuclear JA-Ile is present, certain TFs, such as MYC2 (a basic helix-loop-helix (bHLH) family TF and key activator of JA responses), are repressed by a series of JASMONATE ZIM DOMAIN (JAZ) proteins through direct interaction. MYC2 binds to the G-box motif at the promoter regions of the JA-responsive genes and activates their expression  Figure . Most JACOI1-JAZ co-receptor complex, resulting in the ubiquitination of JAZ and its subsequent degradation via the 26S proteasome [ETHYLENE RESPONSE FACTOR1 (ERF1) and OCTADECANOID-RESPONSIVE ARABIDOPSIS59 (ORA59), and defense-related responsive genes, such as VEGETATIVE STORAGE PROTEIN2 (VSP2). When certain developmental or environmental cues cause a cellular burst of JA, the active derivative JA-Ile is transferred into the nucleus by JAT1 and promotes the formation of the SCFoteasome ,35,36,37Among the 13 Arabidopsis JAZ proteins identified, five  contain the ETHYLENE RESPONSIVE FACTOR-associated amphiphilic repression (EAR) motif responsible for the direct interaction of the protein with TPL co-repressors. Therefore, these JAZs can directly recruit TPLs in the absence of NINJA ,68. In aCOI1-JAZ co-receptor complex, leading to the weakened interaction between COI1 and MED25, as well as subsequent JAZ degradation. This conformational change also strengthens the interaction between MYC2 and MED25 due to the release of the competitive/interfering effect by JAZ. MED25 then recruits the rest of the Mediator complex and RNA Pol II, as well as other coactivators, such as HISTONE ACETYLTRANSFERASE1 (HAC1) and LEUNIG_HOMOLOG (LUH), to the promoter region of MYC2 target genes for transcriptional activation [Over the last decade, another key player in JA signaling, MEDIATOR25 (MED25), has been added to the picture ,73,74. Mtivation ,79,80 -dependent phosphorylation of JAV1 and its subsequent degradation. The disintegration of the JJW complex results in the activation of JA biosynthesis gene expression [2+/CaM is independent of JA-Ile elicitation [2+ vs. JA-Ile) can be simultaneously perceived by the promoters of JA biosynthesis genes  that are also directly regulated by MYC2 [Recently, a WRKY TF and VQ domain protein involved mechanism of herbivory- and wound-induced JA biosynthesis has been reported . The WRK regions . The herpression   and SIB2 while potentially being able to interact with JAZ4 and JAZ8, although further study is needed to elucidate the details of the molecular context ,86.Argonaute18 (AGO18) gene, which encodes a core RNA silencing component that promotes AGO1-mediated antiviral RNAi [AGO18. Elevated accumulation of AGO18 ultimately leads to enhanced antiviral defense in rice [In addition to MYC2 serving as the main transcriptional regulator of JA-induced gene activation, other members of the MYC TF family as well as members of other TF families have also been shown to be directly involved in controlling JA-regulated gene expression . MYC3 anral RNAi . The tra in rice ,94. It iINDUCER OF CBF EXPRESSION1 (ICE1) and ICE2 are two MYC-like bHLH transcriptional activators playing critical roles in modulating cold stress responses . Both arPLANT DEFENSIN1.2 (PDF1.2) [Several members in the APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) TF family, such as ETHYLENE INSENSITIVE3 (EIN3), EIN3-LIKE 1 (EIL1), ERF1 and ORA59 comprise the classical ERF branch of JA signaling, which is marked by the activation of the downstream defense gene (PDF1.2) . Transcr(PDF1.2) . EIN3 an(PDF1.2)  and thusSENESCENCE4 (SEN4) and SENESCENCE-ASSOCIATED GENE12 (SAG12), as well as another two JAZ repressor genes (JAZ1 and JAZ5) to regulate their expression (WRKY57 enhances JA-mediated leaf senescence and resistance against Botrytis cinerea (B. cinerea) infection, suggesting it a negative regulator of JA signaling [WRKY57, a WRKY TF involved in both JA-induced leaf senescence and necrotrophic pathogen response in Arabidopsis, is repressed by JAZ4 and JAZ8 through physical interaction ,86. WRKYpression . Intriguignaling ,86.A YABBY (YAB) TF family member FILAMENTOUS FLOWER (FIL)/YAB1 has been found as a direct target of JAZ3 . Via JA-Whether these JAZ-regulated TFs also share other components of the regulatory mechanism , and if they act synergistically or independently in response to different types of stimuli upstream of JA, are certainly questions for future research.Since JA is a stress signal that generally leads to growth inhibition, proper desensitization and termination of the JA signal is undoubtedly as important as its activation for overall plant growth and fitness. In fact, the JA signal is elaborately controlled at multiple levels to ensure that each response only lasts for an appropriate period at an appropriate amplitude ,80,103. Cytosolic JA-Ile dynamics are shaped by at least two JA-inducible catabolic pathways in Arabidopsis. The first pathway is the direct oxidation of JA-Ile by members of the cytochrome P450 subfamily 94 (CYP94) enzymes, CYP94B1, CYP94B3 and CYP94C1, which turn JA-Ile into bio-inactive 12OH-JA-Ile and 12COOH-JA-Ile ,105 Fig. The secJAZ gene expression while most JAZ genes in Arabidopsis can produce truncated JAZ splice variants that can still bind to the MYC proteins but have little capability of forming complexes with JA-Ile and COI1 for proteasomal degradation. Overexpression of certain JAZ splice variants, such as JAZ10, result in dominant repression of JA responses [JAZ loci by MED25. PRP39a and PRP40a, in turn, facilitate the full splicing of JAZ transcripts to produce the full-length JAZ proteins, thus preventing the excessive desensitization of JA responses caused by the overaccumulation of JAZ splice variants [JAZ genes is under exquisite modulation.JA-Ile stimulates rapid activation of esponses ,113. Cryesponses . These fvariants . These dSeveral bHLH family subgroup IIId members  in Arabidopsis and the MYC2-TARGETED BHLHs (MTBs) in tomato) have been identified as negative regulators of JA responses ,118,119.Taken together, these groundbreaking discoveries suggest that plant cells orchestrate a complex and autoregulatory negative feedback circuit to desensitize and terminate JA signals at multiple layers. F-box E3 ligase complex-mediated turnover of the repressive proteins to activate the master TFs appears to be a universal mechanism among several phytohormones [COI1 receptor recognition to release the repression on MYC TFs, the auxin-induced activation of auxin-responsive genes is achieved through the degradation of AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) repressors that interact with AUXIN RESPONSE FACTOR (ARF) transcription activators. The degradation of Aux/IAA repressors is mediated by the SCFTRANSPORT INHIBITOR RESPONSE1 (TIR1) receptor complex [SLEEPY1 (SLY1)-mediated degradation in response to GA [Data accumulated over years of research have revealed that several signaling pathways, including JA, auxin and GA, share a highly conserved mechanistic framework for gene regulation. The SCFhormones . For ins complex ,123. In se to GA . Ultimatse to GA ,64,125. Although participating in many developmental processes, JA is generally recognized as a stress hormone in response to various biotic and abiotic stresses. Within plants, numerous signal transduction pathways intertwine and interact in a complicated but highly arranged manner in response to stress(es) . AlthougThe antagonism between two phytohormones often involves the enhanced repression of one hormone caused by another. Examples of this antagonism can be seen in the crosstalk between JA and GA, two major phytohormones responsible for defense responses and growth processes, respectively. The crosstalk between the JA and GA pathways occurs partially through the interaction between their key repressors, the JAZ and DELLA proteins ,129. SimInterestingly, synergy between JA and GA has also been observed in some defense response. The WD-repeat/bHLH/MYB TF complexes are key controllers of anthocyanin biosynthesis and trichome formation, that contribute significantly to insect resistance in plants ,135. TheANTHRANILATE SYNTHASE α1 (ASA1) and YUCCA2 (YUC2), two genes encoding key enzymes in auxin biosynthesis, and promote their expression for auxin production required for lateral root formation [The interplay between JA and auxin signaling is also essential for plant development. It has been reported that JA induces lateral root formation by promoting auxin biosynthesis . Furtherormation ,139,140 PLETHORA1 (PLT1) and PLT2, two AP2-domain TF genes that are essential for auxin-induced root stem cell niche patterning [In contrast to its canonical role in activation, JA-activated MYC2 directly represses the expression of tterning . Therefotterning   and Aux/IAA (IAA29) proteins competitively interact with WRKY57, suggesting that WRKY57 serves as a point of converging for JA and auxin signaling in leaf senescence [JAZ1 and JAZ5, to negatively regulate plant defense against necrotrophic pathogen B. cinerea [JAZ1 and JAZ5 are direct targets of both WRKY33 and WRKY57. WRKY33, acting opposite to WRKY57, positively regulates plant necrotrophic resistance by transcriptional repression of JAZ1 and JAZ5 [The Arabidopsis WRKY57 also exhibits bifunctional attributes as a negative regulator of both leaf senescence and necrotrophic pathogen defense ,86. Durinescence . Subsequand JAZ5 ,143  and AGMATINE COUMARYL TRANSFERASE (ACT) [PDF1.2 [ET is another major phytohormone hallmarked as a regulator of plant development and defense against necrotrophic fungi. A large number of studies have shown that JA and ET act synergistically in plant defense responses through the activation of several AP2/ERF TFs, such as ERF1, ERF2, ERF14 and ORA59, which then transactivate a set of defense-related genes, including SE (ACT) ,146,147.SE (ACT) . EIN3 an [PDF1.2 ,148. Zhu [PDF1.2  demonstrRecent studies have shown that MYC TFs can inhibit ERF TFs within the JA signaling pathway to antagonize ET signaling. MYC2 and EIN3, the two master TFs of JA and ET signaling pathways, were also found to physically interact with each other and mutually inhibit each other’s transcriptional activity to coordinate plant development and defense responses ,150,151 The phytohormone ABA is well documented in its ability to mediate developmental processes and abiotic stress tolerance, particularly drought and salinity stress ,153. ABApyl4 and pyl5, exhibit JA-hypersensitive shoot growth and reduced anthocyanin accumulation in response to JA [AOC” pathway in rice has provided another clue to the ABA-promoted JA biosynthesis that results in the synergistical inhibition of seed germination [AOC expression by binding to the G-box element in AOC promoter, thus elevating the endogenous level of JA [In general, ABA and JA act synergistically in processes such as seed germination inhibition and herbivory defense, and antagonistically in several developmental processes . Early mse to JA . In addise to JA   functions as a negative regulator of ABA signaling by directly binding to ABI5, leading to its ubiquitination and degradation. KEG has also been shown to interact with JAZ12 and enhances its stability by interfering with its JA-triggered degradation . TherefoIt is well known that GA promotes seed germination by counteracting ABA action. This has been elucidated at the molecular level by experimental demonstrations that connect DELLA repressors to ABI5 . For exaDAD1, AOC1 and MYC2) and ABA  and NCED9) through binding to their promoters. Overexpression of ORA47 significantly increased ABA and JA accumulation in plants under stress conditions [Additionally, the bHLH TF ABA-INDUCIBLE BHLH-TYPE TRANSCRIPTION FACTOR (AIB)/JAM1, previously reported as an ABA-induced positive regulator of ABA signaling , was demnditions . By closnditions  suggestsIn addition to the crosstalk mentioned above, JA signaling also actively interacts with other hormone signaling pathways, such as cytokinin, brassinosteroid (BR) and SA ,168,169.We have just now begun to uncover the functionality and significance of JA signaling that is indispensable for plant development and stress tolerance. It remains to be determined whether different environmental cues trigger different compositions of systemic signals and whether different forms of JA and its precursors are differentially transmitted as different environmental signals. Why there are a plethora of JA derivatives is still unknown, as is whether these different forms of JA have other functions yet to be discovered. It also is unknown how bioactive JA is purged from the cell nucleus when the level of signal needs to be dampened or JA signaling is no longer needed.Plants have evolved sophisticated and efficient perception, signaling and regulatory networks to survive different stress conditions at the cost of reduced growth and yield. Therefore, fully understanding the integrated molecular mechanisms, including the hormone signaling crosstalk, at the genome-scale will greatly help increase plant resilience towards the changing global climate and further assist in the improvement of horticultural and agricultural productivity. Although the history of plant research has greatly increased our knowledge on how plants achieve their ultimate fitness through the implementation and coordination of different signaling pathways at a given developmental stage and in response to various abiotic and biotic stress conditions, it still remains a challenge to elucidate the dynamic interactions among various signaling pathways that occur during the life cycle of a plant under static environments and in the changing environments encountered in nature. This partially explains why only a small fraction of academic research discoveries are translated to and adopted as field applications. Nevertheless, science-based agricultural improvements continue to provide important advancements that benefit humankind today.