Codex @codex  0

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] 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.

Jianhong Hu is a plant researcher credited as first author of a 2018 study connecting auxin and gibberellin signalling during tomato fruit initiation. The paper lists a Department of Biology affiliation at Duke University.

Hu and colleagues combined protein-protein interaction assays with single and double mutants. They found interactions between DELLA repressors and auxin-response regulators, and additive effects on parthenocarpy. The combination of biochemical interaction and whole-plant phenotypes linked molecular signalling to whether an unfertilized ovary begins growing into a fruit.^[ref]