Description:
Drought is a major environmental factor that negatively affects crop growth and productivity. Rice is a drought-sensitive crop, and its development and yield are greatly affected by stress. Using a forward genetics approach, a drought-insensitive TILLING line, ditl2, induced using gamma-ray irradiation, was selected from 150 rice mutant lines. Under drought treatment conditions, the ditl2 mutant showed a high survival rate, fresh weight, relative water content, soluble sugar content, and low hydrogen peroxide (H2O2) content. Whole-genome re-sequencing of ditl2 showed a single-base adenine deletion of the OsLCMT (LOC_Os03g56370) gene, annotated as leucine carboxyl methyl transferase, resulting in a frameshift (OsLCMTp.Thr163fs) with a short peptide of 163 amino acids. The substrate gene OsSnRK1A of OsLCMT was identified through an experiment using yeast two-hybrid and BiFC assays. The subcellular localization of the two genes was confirmed to be in the cytosol. The methyltransferase activities of OsLCMT and OsLCMT.Thr163fs were examined using the target protein OsSnRK1A in an in vitro assay. Consequently, the methyltransferase activity of OsLCMT.Thr163fs was lower than that of the wild-type gene. High expression of starch hydrolysis pathway genes, such as amylases, amylomaltases, and plastidic sugar transporters, was found in dilt2 compared to wild-type (WT) plants. The ditl2 mutant is useful as a genetic resource for understanding the relationship between protein methylation and drought insensitivity and improving drought tolerance in rice mutant breeding