Characterization of the Mutant in Rice and Its Impact on Plant Height Reduction and Water Use Efficiency.

Rice ( L.), a fundamental global staple, nourishes over half of the world's population. The identification of the mutant in rice through EMS mutagenesis of the cultivar Shuhui527 revealed a dwarf phenotype, characterized by reduced plant height, smaller grain size, and decreased grain weight. Detailed phenotypic analysis and map-based cloning pinpointed the mutation to a single-base transversion in the gene, encoding a cytochrome P450 enzyme, which results in a premature termination of the protein. Functional complementation tests confirmed as the gene responsible for the observed phenotype. We further demonstrated that the mutation leads to significant alterations in gibberellic acid (GA) metabolism and signal transduction, evidenced by the differential expression of key GA-related genes such as , , and . The mutant also displayed enhanced drought tolerance, as indicated by higher survival rates, reduced water loss, and rapid stomatal closure under drought conditions. This increased drought resistance was linked to the mutant's improved antioxidant capacity, with elevated activities of antioxidant enzymes and higher expression levels of related genes. Our findings suggest that plays a crucial role in regulating both plant height and drought stress responses. The potential for using gene editing of to mitigate the dwarf phenotype while retaining improved drought resistance offers promising avenues for rice improvement.