UNIFLORA, a pivotal gene that regulates floral transition and meristem identity in tomato (Lycopersicon esculentum).

•  Flowering of uniflora (uf), a tomato (Lycopersicon esculentum) mutant which consistently produces solitary flowers instead of inflorescences, is late and highly asynchronous in winter. This puzzling behaviour prompted us to further investigate flowering regulation in this mutant to improve our understanding of UNIFLORA gene function. •  Growing plants under different daylengths and light intensities revealed that flowering time in uf is dependent on daily light energy integral. Transferring plants from low to high light energy integrals at different times after sowing showed that the light-conditions effect was stage dependent, suggesting that interactions between light energy integrals and endogenous regulatory pathways affect meristem sensitivity to flowering signals. •  Carbohydrate analyses suggested that one of these signals could be sucrose, but other interacting factors are probably generated by the root system, as indicated by grafting experiments. •  The UNIFLORA gene thus appears to have a dual role in tomato: floral transition regulation and the maintenance of inflorescence meristem identity.