A molecular framework for light and gibberellin control of cell elongation

Many developmental processes in plants are regulated jointly by light and by the gibberellins, yet the molecular basis of cross-talk between the two is not fully understood. Two groups now report results that reveal a signalling cascade that contributes to coordinated plant growth regulation by light and gibberellins. In the absence of gibberellins, DELLA proteins inhibit the binding of the transcription factor PIF3 (a phytochrome-interacting protein) to gene promoters. Gibberellins trigger the degradation of DELLA proteins, thereby allowing PIFs to bind to their target promoters and regulate gene expression. Light acts via a photoreceptor to destabilize PIF4. Thus the DELLA proteins, and competitive interactions between members of the PIF family, appear to key components linking light to the gibberellins.