Abstract
We isolated a rice brassinosteroid-related mutant, which displayed dwarfism, erect leaves and stunted leaf sheath. Application of brassinolide rescued the mutant phenotype, indicating that the mutant was defective in BR biosynthesis. Mutated gene was located on the Chr. 10 and this locus contains a homologous gene to Arabidopsis DIMINUTO. The putative amino acid sequence of this gene (OsDIM) shared 80% identity with AtDIM. Sequencing analysis revealed that the mutant produced a premature stop codon in the OsDIM gene. We could not found any OsDIM homologous genes in the rice genome. Although the phenotype of the Osdim was typical for BR-deficient mutants, the severeness of its phenotype was much milder than that of the brd1-1 plants, which is defected in BR-6 oxidase. This suggests a possibility that there is an alternative BR biosynthesis pathway not involved DIM in contrast to Arabidopsis, in which defect in DIM induces a severe phenotype.
