Abstract
Gibberellin (GA), which is synthesized after germination, is involved in expression of a gene for a proteinase, EP-C1 in germinated seeds of common bean. It is known that DELLA proteins are involved in repression of GA-response genes. The genes are activated by degradation of the proteins induced by GA treatment. We isolated two types of cDNA clones for DELLA proteins designated PvGAI1 and PvGAI2, respectively. Because expression level of PvGAI2 was higher than that of PvGAI1 in germinated cotyledons, RNA blot analysis was carried out using cDNA for PvGAI2 as a probe. PvGAI2 mRNA was not detected in cotyledons of dry seeds, and appeared at 1 day after imbibition started (DAI), its level increasing until 3 DAI. In contrast, EP-C1 mRNA appeared at 3 DAI. These results suggest that GA synthesized after germination induces degradation of PvGAI2, which is required for activation of the EP-C1 gene.
