Function analysis of a semi-dwarf sdg in rice with near isogenic lines

The physiological phenotype of the rice semi-dwarf mutant, sdg, was characterized in details using a pair of near isogenic lines. Neither gibberellin-deficient nor gibberellin-insensitive is characteristic of the sdg phenotype. By analyzing the secretion of α-amylase and the promotion of stem growth caused by exogenous gibberellin (GA), the sdg plant was found to have decreased sensitivity to the GA at the seedling stage. The dwarfism stature of the sdg mutant can be attributed to the shortened internodes. Increase of the cell number rather than lack of elongation in the sdg mutant is responsible for shoot elongation by the treatment of exogenous GA. These results indicate the protein encoded by the wild type gene of sdg may be a regulator for cell elongation.