PLASTOCHRON1 regulates leaf inclination through Brassinolide pathway in Oryza sativa

Abstract Leaf inclination directly affects the lamina angle of rice ( Oryza sativa ), which in turn affects the photosynthetic efficiency of the leaves and grain yield. A mutant s544 characterized by enhanced leaf inclination as well as small aerial organs was identified from the progeny of ethyl‐methanesulfonate treated seeds of Indica rice ‘Xida 1B’. Genetic analysis indicated that the mutant traits were controlled by a single recessive nuclear gene. Using a F 2 population derived from ‘Jinhui 10’ and the mutant, the mutated gene was mapped on chromosome 10 between markers RM25367 and XJ‐1, with a physical distance of 246 kb, which included PLASTOCHRON1 ( PLA1 ). Sequencing revealed a C to A substitution at position 1489 of the coding region of PLA1 , which caused conversion of the encoded amino acid from proline to threonine. The s544 mutant showed increased sensitivity to exogenous brassinolide (24‐eBL) compared with the wild type. QPCR revealed that the genes of s544 positively regulated brassinolide signal transduction, especially for BU1 and ILI1 with up‐regulated expression over seventy times, and that MDP1 , a negative‐regulated gene, decreased significantly in the half of the wild type. Meanwhile, D4 and D11 involved into BR‐synthesis were up‐regulated in s544 . These results suggested that PLA1 may regulate BR signaling and biosynthetic pathways in rice organ development.