Three Arabidopsis GID1 Genes Encode Gibberellin Receptors with Overlapping Functions

Arabidopsis contains a family of three genes (GID1a, GID1b, and GID1c) that encode putative gibberellin (GA) receptors. Griffiths et al. (pages 3399–3414) present a thorough genetic characterization of single, double, and triple gid1 mutants of Arabidopsis that provides strong evidence that the proteins encoded by all three genes are bona fide GA receptors. The triple gid1 mutant, which lacks all three receptors, is severely dwarfed and does not exhibit any of the known GA responses examined. Although the three GID1s were found to be largely functionally redundant, gene expression and mutant analysis showed that they likely have some degree of functional specificity. For example, in contrast with the triple mutant, all of the single and double mutants flowered at the same time as wild-type plants, indicating that the GID1 genes possess functionally redundant roles in promoting floral initiation in long-day photoperiods. However, some specificity was evident in their regulation of stem, filament, and silique elongation. Severe defects in floral organ morphology of the gid1 triple mutant. Severe defects in floral organ morphology of the gid1 triple mutant.