REFERENCE TO SEQUENCE LISTING SUBMITTED VIA EFS-WEB

This application is being filed electronically via EFS-Web and includes an electronically submitted sequence listing in .txt format. The .txt file contains a sequence listing entitled “2018-06-12_5992-0208PUS1_ST25.txt” created on Jun. 12, 2018 and is 29,245 bytes in size. The sequence listing contained in this .txt file is part of the specification and is hereby incorporated by reference herein in its entirety.

TECHNOLOGY FIELD

The present invention relates to use of a Repetitive Proline-rich Protein (RePRP) for modifying features of transgenic plants overly expressing it.

BACKGROUND

Environmental abiotic stresses such as drought, extreme temperatures, and flooding have caused significant crop losses in agricultural output as global climate change has worsened in recent years. It has been estimated that as much as two thirds of the yield of major crops are routinely lost due to adverse/stressful environments (see Boyer, 1982). Intense study is under way to understand how plants survive and how to minimize the impact of abiotic stresses on crop yield.

Most of the tolerance mechanisms associated with water-deficit stresses are related to osmotic adjustments, maintenance of ionic homeostasis, and removal of damaging reactive oxygen species (see Kar, 2011). The basic architectural features of plants are also known to be adjusted under stress, such as increased waxes on the surface, sunken stomata, and facilitation of leaf rolling.

Abscisic acid (ABA) is the most commonly recognized stress hormone during water-deficit stress. ABA can (i) cause stomata in leaves to close in order to reduce transpiration, and (ii) enhance the expression of other genes needed for the establishment of stress tolerance.

Rice plant growth and development readjusts to avoid unnecessary growth in the shoot, thereby reducing water loss under the stress of severe water deficit or upon treatment with high concentrations of ABA. Rice roots become shorter, thicker, and heavier, resulting from the accumulation of biomass synthesized from surplus nutrients transported from the shoots.

A group of highly proline rich glycoproteins (“OsRePRPs”) is highly induced in rice roots by ABA, salinity, and drought (see Tseng et al., 2013). OsRePRPs, which are localized to the plasma membrane where they interact with cell wall polysaccharides, are necessary and sufficient for making roots shorter and thicker. No reports demonstrate their effects in stress tolerance and growth of plants.

Some approaches have been developed to improve plant stress tolerance. However, plants survival under stress often exhibit growth retardation which is negative to productivity and cannot satisfy the need in agriculture. The need still exists to provide an approach to breed plants with tolerance to multiple stresses that still maintain growth and productivity.

SUMMARY

The present disclosure is based, at least in part, on the unexpected findings that expression of a Repetitive Proline-rich Protein (RePRP) results in improved stress tolerance, especially causes no substantial effects in growth retardation in transgenic plants overly expressing such. Compared with a control (wild type) plant without transformation with a RePRP gene, the transgenic plants of the invention exhibit significant increase in survival rate without substantial reduction of growth under stress conditions. The transgenic plants of the invention also exhibits a less level of yield reduction under stress conditions compared with a control (wild type) plant.

Therefore, the present invention provides a method of improving stress tolerance and/or preventing growth reduction of a plant, comprising:

(a) transforming plant cells with a vector comprising a nucleic acid operably linked to a promoter to obtain recombinant plant cells expressing a RePRP protein, wherein the nucleic acid encodes the RePRP protein;

(b) growing the recombinant plant cells obtained in (a) to generate a plurality of transgenic plants; and

(c) selecting a transgenic plant from the plurality of transgenic plants generated in (b) that exhibits an improved tolerance to stress or substantially no growth reduction or a combination thereof, as compared with a non-transgenic plant counterpart growing under the same conditions.

In some embodiments, the transgenic plant exhibits less yield reduction as compared with the non-transgenic plant counterpart.

In some embodiments, the RePRP protein comprises the amino acid sequence of SEQ ID NO: 1, 2, 3 or 4.

In some embodiments, the promoter is heterologous to a naturally occurring gene encoding the RePRP protein.

In some embodiments, the promoter is a constitutive promoter or an inducible promoter.

In some embodiments, the promoter is a constitutive promoter selected from the group consisting of a maize ubiquitin (Ubi) promoter, a rice actin (Actl) promoter, and a cauliflower mosaic virus 35S (CaMV35S) promoter.

In some embodiments, the promoter is an inducible promoter selected from the group consisting of anArabidopsiscorl SA promoter, anArabidopsiskinl promoter, anArabidopsisheat-shock factor (HSF) promoter, anArabidopsiskinl promoter, anArabidopsisrd29A promoter, an alpha-amylase promoter and a synthetic ABRC321 promoter.

In some embodiments, the promoter is 3XABRC321.

In some embodiments, the transgenic plant is a monocot plant. Examples of a monocot plant include rice, barley, wheat, rye, oat, corn, bamboo, sugarcane, onion, leek and ginger.

In some embodiments, the transgenic plant is a dicot plant. Examples of a dicot plant includeArabidopsis, soybean, peanut, sunflower, safflower, cotton, tobacco, tomato, pea, chickpea, pigeon pea or potato.

In some embodiments, the stress is biotic stress or abiotic stress.

In some embodiments, the stress is abiotic stress including osmotic stress, drought stress, salt stress, or a combination thereof.

The details of one or more embodiments of the invention are set forth in the description, in the drawings, and in the examples below. Other features, objects, and advantages of the invention will be apparent from the detailed description of several embodiments and also from the claims. All publications and patent documents cited herein are incorporated by reference in their entirety.

