ISOLATION OF THE GA-RESPONSE MUTANT SLY1 AS A SUPPRESSOR OF ABI1-1 INARABIDOPSIS-THALIANA

Seed dormancy and germination in higher plants are partially controlle d by the plant hormones abscisic acid (ABA) and gibberellic acid (GA). ABA establishes dormancy during embryo maturation, whereas GA breaks dormancy and induces germination. Previous attempts to identify GA res ponse genes were con founded because GA mutants are not expected to ge rminate and, unlike GA auxotrophs, should fail to be rescued by exogen ous GA. Here, we describe a screen for suppressors of the ABA-insensit ive mutant ABI1-1 that enriches for GA auxotrophs and GA-insensitive m utants. The vast majority (76%) of the suppressors of ABI1-1 strongly resemble GA auxotrophs in that they are severely dwarfed and have dark green foliage and flowers with underdeveloped petals and stamen. Thre e isolates were alleles of the GA auxotroph gal. The remaining severe dwarves were not rescued by GA and belong to a single complementation group that we designate sly1 (Sleepy 1). The alleles of sly1 identifie d are the first recessive GA-insensitive mutations to reflect the full spectrum of GA-associated phenotypes, including the failure to germin ate in the absence of the ABI1-1 lesion. Thus, we postulate that SLY1 is a key factor in GA reception.