GAR1, a DNA Binding Gibberellin Receptor, Directly Activates Gene Expression to Regulate Rice Height and Fertility

Contrary to the prevailing paradigm that all GA responses require GID1, we demonstrated that a rice GID1-like 2 protein (designated GA Receptor 1, GAR1) is a GA receptor that functions independently of GID1. Isothermal titration calorimetry revealed that GAR1 can bind bioactive GAs, and multiple assays confirmed that GAR1 physically interacts with the promoter of GAMYB, a central regulator of GA responses, whereas GID1 does not.

Using a transgenic rice line containing the GA biosensor GIBBERELLIN PERCEPTION SENSOR 1 (GPS1), we demonstrated that the subcellular distributions of GAR1 and its homologs GAR3 and GAR4 overlapped with strong GA signals in specific cells of rice leaves, anthers, and filaments. gar1 gar2 double mutants exhibited a semi-dwarf phenotype with slightly shorter anthers, whereas gar3 gar4 mutants displayed normal plant height with elongated filaments; both double mutants showed slightly reduced male fertility.