Effect of high hydrostatic pressure on seeds Carica papaya
The breaking of seed dormancy induced by stress [1] is extremely important with regard to the acceleration of germination process [1,2]. Abiotic stress processes, just like high hydrostatic pressure (HHP), are applied in several biotechnological studies, mainly because HHP induces changes in physiological and biochemical processes [3]. Pretreatment with a stress induction tool can be lethal or induce the synthesis of protective factors. When the stress does not kill the organism, it is called sublethal stress, and it can even increase the resistance to other stresses. High hydrostatic pressure is an important model in stress response study, for it has the ability to change the plasma membrane fluidity so as to keep the organism alive, which allows studies on the metabolic changes. Water is used as the medium of fluid pressure transmission since it has lower compressibility and greater compatibility, resulting in less risk of contamination. In our experiment, Carica Papaya seeds were put into a polyethylene tube containing water, the system is then closed in a capsule of high resistance steel, and suffers pressures between 10 and 400 MPa. The seeds were set to germinate in vitro, while the pressure transfer fluid present in the capsule was used to analyze abscisic acid per HPLC. The HHP generated positive effects due the seed hydration, which reflected in the percentage and speed of germination [4]. The begin of the seeds germination subjected to HHP was anticipated to 70 hours due to greater water retention, characterized by the increasing of weight (about 2.8 times greater when compared to dry weight), followed by germination values between 70-90%, while the seeds subjected to ambient pressure (control group) showed hydration of about 2.4 times and germination around 55-65%. The ambient pressure (0.1 MPa) showed lower water retention, resulting in lower mean percentage and germination speed when compared to HHP treatments. The abscisic acid (ABA) is closely related to tolerance to stress conditions (HHP) and its relation to gibberellin (GA) is crucial in the process of germination. The pressure transfer fluid has proven useful for the detection of abscisic acid, characterized by the presence of chromatograph peak with retention time equals to analyses of samples fortified with industrial ABA. The analyses of the HPLC chromatograms demonstrate changes in the composition of the water used as medium of pressure transfer. The seeds undergoing HHP pressure showed through gas chromatogram, differences between the concentrations of protein, peptides and phenol, when compared to the seeds subjected to hydrostatic control group. The balance between the concentrations of abscisic acid and gibberelin is related to germination. The presence of ABA in fluid of pressure transfer indicates a factor of germination capacity of seeds subjected to HHP stress. HHP stress is an effective biotechnological tool in the search for new mechanisms of stimulation of Carica Papaya seeds in order to provide improved germination and breaking of dormancy. Some data obtained in this experiment were omitted because due to patent submission.
Germinação e desenvolvimento inicial de plântulas de soja convencional e sua derivada transgênica RR em condições de estresse salino
Brazil stands out as the largest worldwide producer of transgenic soybeans and has extended its production mainly to regions with saline soils, where there is accumulation of salts that interferes in seed germination and seedling development. The object of this research was to evaluate the effect of saline stress on the germination and initial development of soybean conventional seedling and its transgenic derivatives Roundup Ready (RR) submitted to different salinity conditions. For that purpose two lots of soybean seeds were used (CD 206 and CD 206 RR), the treatments consisted of the following levels of NaCl: 0, 5, 15, 30, 60 and 120mmol L-1. The evaluation of physiological seed quality was obtained by germination test, root and seedling length, seedling dry mass and volume of roots. The salt stress reduced germination of seeds of both genotypes, and the development of seedling of genotype transgenic RR is less sensitive in conditions of greater salinity (60 to 120mmol L-1 of NaCl).
Characterization of a novel tyrosine permease of lager brewing yeast shared by Saccharomyces cerevisiae strain RM11-1a.
In Saccharomyces cerevisiae yeast, the uptake of aromatic amino acids is mediated by the relatively specific permeases Tat1p, Tat2p, Bap2p, and Bap3p, as well as by two other permeases with broader specificities: Gap1p and Agp1p. Here, a novel permease gene TAT3 (Tyrosine Amino acid Transporter) identified in the S. cerevisiae-type subset genome of the lager brewing yeast strain Weihenstephan Nr.34 (34/70) is reported. The TAT3 sequence was also found in the genome of S. cerevisiae strain RM11-1a, but not in S. cerevisiae strain S288C. Tat3p showed a significant similarity to Penicillium chrysogenum ArlP permease, which has transport activity for aromatic amino acids and leucine. When overexpressed in ssy1Delta gap1Delta mutant cells, Tat3p exhibited a tyrosine transport activity with an apparent K(m) of 160 microM. TAT3 transcription in lager brewing yeast was subjected to nitrogen catabolite repression in a manner similar to that of GAP1. Furthermore, the subcellular localization of Tat3p-green fluorescent protein (GFP) fusion protein was dependent on the quality of the nitrogen source, indicating a post-translational control of Tat3p function.