Abstract
SPINDLY (SPY) encodes an o-GlcNAc transferase, which has been considered to be a negative regulator in gibberellin (GA) signaling by modification and regulation of DELLA proteins through unknown mechanism. We have studied GA signaling using GA related mutants of rice. In the absence of GA, a rice DELLA protein, SLR1, represses GA actions. When a soluble receptor, GID1, binds GA, GID1 interacts with SLR1, resulting in the degradation of SLR1 through the SCFGID2 proteasome pathway. In order to understand the function of SPY in the GA signal pathway, we produced transgenic rice plants, in which SPY expression is reduced, in the gid1 and gid2 mutant backgrounds. Transgenic lines showed taller phenotype than the control plants not only in the background of gid1 but also in gid2. These results suggest that SPY functions to activate the suppression activity of SLR1 rather than to regulate SLR1 degradation though GID2 function.
