Identification and Fine Mapping of Osdsm3, a Drought-Sensitive Gene in Rice (Oryza sativa L.)

Abstract

Drought poses a significant constraint on rice production, and, in this study, we have discovered a novel drought-sensitive mutant, designated as dsm3, arising from the progenies of indica rice variety Zhonghui8015 treated with ethyl methane sulphonate (EMS). Under drought stress conditions, dsm3 exhibited characteristic withered leaf tips, accompanied by increased levels of malondialdehyde (MDA) and H2O2, a reduced net photosynthetic rate (Pn), and decreased activity of peroxidase (POD) and superoxide dismutase (SOD). Genetic analysis revealed that the withered leaf tip phenotype was governed by a single recessive gene, designated as Osdsm3. To begin with, Osdsm3 was initially mapped to the short arm of chromosome 1 through a cross involving dsm3 and 02428. Subsequently, utilizing a population of 2591 F2 individuals, we narrowed down the location of Osdsm3 to a 78 Kb interval, encompassing 13 open reading frames (ORFs). Sequencing analysis unveiled a mutation (1275G → A) in the exon of the candidate gene (LOC_Os01g10680), leading to premature translation termination. Moreover, a quantitative RT-PCR assay demonstrated a high expression of OsDSM3 in the panicle and sheath, with a significant upregulation of drought-stress-related genes under drought conditions. Phylogenetic analyses indicated that Osdsm3 shares evolutionary homology with UNE1, an intracellular transport protein found in Arabidopsis thaliana. Subcellular studies further confirmed that OsDSM3 resides in the cytoplasm. In conclusion, the forthcoming cloning of Osdsm3 holds promise for delving deeper into the molecular mechanisms governing rice drought resistance.