Abstract
SummaryDrought is one of the major abiotic stresses that directly implicate plant growth and crop productivity. Although many genes in response to drought stress have been identified, genetic improvement to drought resistance especially in food crops is showing relatively slow progress worldwide. Here, we reported the isolation of abscisic acid, stress and ripening (ASR) genes from upland rice variety, IRAT109 (Oryza sativa L. ssp. japonica), and demonstrated that overexpression of OsASR5 enhanced osmotic tolerance in Escherichia coli and drought tolerance in Arabidopsis and rice by regulating leaf water status under drought stress conditions. Moreover, overexpression of OsASR5 in rice increased endogenous ABA level and showed hypersensitive to exogenous ABA treatment at both germination and postgermination stages. The production of H2O2, a second messenger for the induction of stomatal closure in response to ABA, was activated in overexpression plants under drought stress conditions, consequently, increased stomatal closure and decreased stomatal conductance. In contrast, the loss‐of‐function mutant, osasr5, showed sensitivity to drought stress with lower relative water content under drought stress conditions. Further studies demonstrated that OsASR5 functioned as chaperone‐like protein and interacted with stress‐related HSP40 and 2OG‐Fe (II) oxygenase domain containing proteins in yeast and plants. Taken together, we suggest that OsASR5 plays multiple roles in response to drought stress by regulating ABA biosynthesis, promoting stomatal closure, as well as acting as chaperone‐like protein that possibly prevents drought stress‐related proteins from inactivation.
Highlights
Drought is a major environmental stress affecting plant growth and reducing crop productivity
The expression changes in the ASR genes in response to drought were analysed between Upland rice (UR) variety, IRAT109, and lowland rice (LR) variety, Nipponbare (O. sativa L. ssp. japonica)
Rice contains six ASR paralogous genes (Philippe et al, 2010); among them, OsASR3 was up-regulated in IRAT109, and OsASR5 and OsASR6 were induced and upregulated by drought in IRAT109 relative to Nipponbare (Figure S1)
Summary
Drought is a major environmental stress affecting plant growth and reducing crop productivity. Multiple strategies are adapted by plants in response to drought stress; among them, drought avoidance and drought tolerance are the two major mechanisms for improving drought resistance (Luo, 2010; Price et al, 2002). Abscisic acid (ABA), a key plant hormone, increases dramatically, which in turn leads to a number of molecular and cellular responses, among which the best known are inducing stress-related genes and triggering stomatal closure (Daszkowska-Golec and Szarejko, 2013; Lee and Luan, 2012; Ye et al, 2012). The genes that regulate stomatal movement through ABA-dependent and H2O2-mediated pathway in crops have not been identified, and the mechanism of stomataregulated drought tolerance in crops is largely unknown
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