Shedding light on gibberellic acid signalling.

Gibberellic acid (GA) promotes a range of developmental and growth processes in plants, the most well-known being germination, elongation growth and flowering time. DELLA repressors are the key players of the pathway. Their presence or their GA-dependent turnover via the 26S proteasome correlates to a large extent with the repression or derepression, respectively, of GA-dependent growth responses. Recent progress has revealed the role of DELLA repressors in several novel response pathways, and at the biochemical level, they have now been shown to function as repressors of the PHYTOCHROME INTERACTING FACTOR3 (PIF3) and PIF4 transcriptional activators in the context of light-regulated seedling development. Furthermore, the first insights have been gained into the evolution of the GA signalling pathway on the basis of comparative genomics between the moss Physcomitrella patens, the lycophyte Selaginella moellendorffii and seed plants.