DELLA denotes a family of plant growth-regulating proteins that restrain responses promoted by gibberellins. They regulate other proteins, including transcription factors, rather than functioning simply as a store of growth hormone. Gibberellin signalling can promote removal of DELLA repressors through protein degradation, thereby releasing the restrained programme.
A 2008 study connected DELLA to PIF4, a transcription factor involved in elongation. Physical interaction inhibited PIF4's DNA-binding activity, while gibberellin-dependent removal of the restraint connected hormonal signalling with the response to light.[ref]
A molecular framework for light and gibberellin control of cell elongation by Miguel de Lucas and others. Abstract and protein-interaction/DNA-binding experiments
The mechanism illustrates a useful regulatory design: growth can change rapidly by removing an inhibitor, without requiring the hormone itself to bind every affected gene. New to topics? Read the docs here!