Abstract
Recently, we isolated a soluble GA receptor, GID1, from rice. Under the condition of presence of GA, GID1/GA complex interacts with SLR1, a repressor in GA signaling, which results in the degradation of SLR1 and the following GA responses. Here, we report the results of the domain analysis of GID1 for GA binding and SLR1 interaction.
GA binding analyses using mutated recombinant GID1 proteins revealed that the central and C-terminal regions of GID1 are important for the binding. Because GID1 resembles the hormone sensitive lipase (HSL) and the amino acids which corresponding to "catalytic triad" of HSL are present in these regions, we inferred that the conformation of the HSL catalytic active center is conserved in GID1 and is necessary for its GA-binding. We also determined the GID1-interacting domain of SLR1 using yeast-two-hybrid assay. The DELLA and TVHYNP domains of SLR1 were essential for the interaction with GID1.
