Altered expression of SPINDLY affects gibberellin response and plant development

Gibberellins (GAs) are plant hormones with diverse roles in plant growth an d development. SPINDLY (SPY) is one of several genes identified in Arabidop sis that are involved in GA response and it is thought to encode an O-GlcNA c transferase. Genetic analysis suggests that SPY negatively regulates GA r esponse. To test the hypothesis that SPY acts specifically as a negatively acting component of GA signal transduction, spy mutants and plants containi ng a 35S:SPY construct have been examined. A detailed investigation of the spy mutant phenotype suggests that SPY may play a role in plant development beyond its role in GA signaling. Consistent with this suggestion, the anal ysis of spy er plants suggests that the ERECTA (EX) gene, which has not bee n implicated as having a role in GA signaling, appears to enhance the non-G A spy mutant phenotypes. Arabidopsis plants containing a 35S:SPY construct possess reduced GA response at seed germination, but also possess phenotype s consistent with increased GA response although not identical to spy mutan ts, during later vegetative and reproductive development. Based on these re sults, the hypothesis that SPY is specific for GA signaling is rejected. In stead, it is proposed that SPY is a negative regulator of GA response that has additional roles in plant development.