Glucose repression of alpha-amylase in barley embryos is independent of GAMYB transcription

The induction of alpha -amylase triggered by gibberellic acid in barley embryos is repressed by sugars. We investigated the effects of glucose on the gibberellin signal transduction pathway to localize the site of interaction of the sugar/hormone signalling pathways. Our results indicate that glucose represses gibberellin signalling late along this hormone transduction pathway, downstream of transcription of the gibberellin-modulated transcriptional activator (GAMYB) needed for alpha -amylase induction. This result suggests either that glucose repression is transduced by a pathway independent of gibberellin signalling or that repression occurs at the level of GAMYB translation.