Gibberellin hormone signal perception: down‐regulating DELLA repressors of plant growth and development

The gibberellin (GA) hormone signal is perceived by a receptor with homology to hormone-sensitive lipases, GID1 (GA-INSENSITIVE DWARF1). This leads to GA-stimulated responses, including stem elongation, seed germination and the transition to flowering. GA-binding enables GID1 to interact with and block the function of the DELLA repressors of GA responses. DELLA repression can be blocked both by proteolytic and non-proteolytic mechanisms triggered by the formation of a GID1-GA-DELLA complex. DELLA is down-regulated by the SLEEPY1/GID2 F-box proteins via the ubiquitin-proteasome pathway, and can be regulated by other post-translational modifications. This chapter reviews the structural requirements for GA-binding by GID1 and for GID1-GA-DELLA protein complex formation, and reviews the current understanding of the mechanisms regulating DELLA repressors.