Mutation of IDR1 enhances drought tolerance by reducing ROS production and activating ROS scavenging in rice

To discover new mutant alleles conferring enhanced tolerance to drought stress, we screened a mutagenized rice population (cv. IAPAR9) and identified a mutant, named idr1-1 (for increased drought resistance 1-1), with obviously increased drought tolerance under upland field conditions. The idr1-1 mutant possessed a significantly enhanced ability to tolerate high-drought stress in different trials. Map-based cloning revealed that the gene LOC_Os05g26890 (corresponding to D1 or RGA1 gene), residing in the mapping region of IDR1 locus, carried a single-base deletion in the idr1-1 mutant, which caused a frameshift and premature translation termination. Complementation tests indicated that such a mutation was indeed responsible for the elevated drought tolerance in idr1-1 mutant. IDR1 protein was localized in nucleus and to plasma membrane or cell periphery. Further investigations indicated that the significantly increased drought tolerance in idr1-1 mutant stemmed from a range of physiological and morphological changes occurring in such a mutant, including greater leaf potentials, increased proline contents, heightened leaf thickness, and upregulation of antioxidant-synthesizing and drought-induced genes, etc., under drought-stressed conditions. Especially, ROS production from NADPH oxidases and chloroplasts might be remarkably impaired, while ROS-scavenging ability appeared to be markedly enhanced as a result of significantly elevated expression of a dozen ROS-scavenging enzyme genes in idr1-1 mutant under drought-stressed conditions. Besides, IDR1 physically interacted with TUD1, and idr1-1 mutant showed impaired EBR responsiveness. Altogether, these results suggest that mutation of IDR1 leads to alterations of multiple layers of regulations, which ultimately confers obviously enhanced drought tolerance to the idr1-1 mutant. One-sentence summaryMutation of IDR1 significantly enhances drought tolerance in an upland cultivar IAPAR9 by decreasing apoplastic and chloroplastic ROS production and increasing ROS-scavenging ability