Abstract
GA receptor GID1, DELLA protein SLR1, and F-box protein GID2 are major components governing the early GA signaling events in rice. When GID1 binds to GA, GID1 becomes capable of interacting with SLR1, a repressor of GA action. It is thought that SCFGID2 complex specifically recognizes the SLR1 protein within the GID1-SLR1 complex via GID2, which leads to degradation of SLR1. To elucidate the precise molecular events on SLR1 degradation, interaction between GID1, SLR1 and GID2 was studied. Our results confirmed that interaction between GID2 and SLR1 is GA and GID1 dependent. Furthermore, we identified important regions of each protein in forming GID1-SLR1-GID2 complex. Our results suggest that when DELLA/TVHYNP domains of SLR1 interact with GID1 in the presence of GA, the GRAS domain of SLR1 becomes capable of interacting with GID1, and this interaction is indispensable for GID2 to recognize SLR1.
