Phenotypic Analysis And Molecular Characterization Of An Allelic Mutant Of The D61Gene In Rice

Rice is one of the most important food crops in the world. It is very important to breedhigh-yielding rice varieties to feed the increasing population on the world. The research ofplant height, especially the research of dwarf properties of plant can afford a theory gist indeveloping rice varieties with high yielding potential. Plant height is mainly affected by theGibberellin (GA) and Brassinosteroid (BR), gene mutation related to GA and BRbiosynthesis and signal pathways can cause dwarf phenotype.Brassinosteroids (BRs) are aclass of plant-specific steroidal hormones that play important roles in multiple biologicalprocesses. In this paper, a classic rice mutant gsor300084showing erect leaves andsemi-dwarf stature was characterized. Morphological analysis in darkness showed thatmesocotyl of the gsor300084mutant did not elongate when grown in the dark condition. Ingsor300084the coleoptile elongation and root growth were less affected by the exogenousapplication of BL, the most active form of BRs, than in the wild-type rice varietyMatsumae. Lamina joint bending analysis also showed that gsor300084was less sensitiveto exogenous BL when compared with Matsumae. These result suggested that thegsor300084mutant was defective in BR sensitivity. Map-based cloning indicated thatgsor300084is a novel allelic mutant of the DWARF61(D61) gene, which encodes theputative BRs receptor OsBRI1. A single base mutation occurred in the LRRs domain ofOsBRI1, changing the444th amino acid from tryptophan (W) to arginine (R). Subcellularlocation analysis suggested that both the wild-type and mutant OsBRI1protein werelocalized at the cytoplasmic membrane. Structure modeling revealed that the W444Rsubstitution may affect the perception of BRs by the LRR domain.