We cloned a rice (Oryza sativa) ASR gene, OsASR1, and characterized its function in rice plants. OsASR1 expression was induced by abscisic acid (ABA), salt, and drought treatments. Transgenic rice plants overexpressing OsASR1 displayed improved water regulation under salt and drought stresses, which was associated with osmolyte accumulation, improved modulation of stomatal closure, and reduced transpiration rates. OsASR1-overexpressing plants were hypersensitive to exogenous ABA and accumulated higher endogenous ABA levels under salt and drought stresses, indicating that OsASR1 is a positive regulator of the ABA signaling pathway. The growth of OsASR1-overexpressing plants was superior to that of wild-type (WT) plants under paddy field conditions when irrigation was withheld, likely due to improved modulation of stomatal closure via modified ABA signaling. The transgenic plants had higher grain yields than WT plants for four consecutive generations. We conclude that OsASR1 has a crucial role in ABA-mediated regulation of stomatal closure to conserve water under salt- and drought-stress conditions, and OsASR1 overexpression can enhance salinity and drought tolerance, resulting in improved crop yields.
Figure 7: Grain yields from consecutive generations of transgenic plants in paddy fields under drought conditions. (A) The phenotype of transgenic plants at the reproductive stage in 2015 (T3), 2016 (T4), 2017 (T5), and 2018 (T6). (B) Panicle phenotype of transgenic plants at the reproductive stage. (C) qRT-PCR analysis of grain yield-related genes from transgenic and WT plants grown in paddy fields for 6 weeks. Asterisks indicate significant differences between treatments determined by Student's t-test (P < 0.05).