Fig. 8. The GA-DELLA signalling system regulates floral development by modulation of miR159/GAMYB and SOC1. Schematic representation of the regulation of the floral transition in SD photoperiods via the GA-DELLA signalling pathway. GA relieves the DELLA repression of GAMYB (e.g. MYB33) and SOC1 and enhances activity of the downstream floral meristem identity gene LEAFY. This activation is moderated by the GA activation of miR159, a post-transcriptional regulator of GAMYB transcript levels. This GA-dependent homeostatic mechanism provides sensitive regulation of the floral transition in SDs and anther development via the regulation of GAMYB levels.