The transition to flowering in tomato

Tomato (Solanum lycopersicum L.) is a very important commercial crop and also a useful model to study the transition to flowering in a sympodial perennial plant. Here we try and summarize past and recent progress in understanding the environmental cues that affect the initial transition to flowering in this species and the genes that are involved in this transition and additional transitions occurring on the sympodial shoot. Environmental cues discussed are daylength, light intensity and growth temperature. In the last eight years much progress has been made in identifying the genes and in analyzing genetic interactions of the different mutations. Most of the genes isolated so far seem to play similar roles in Arabidopsis flowering. For example, mutations in the tomato SINGLE FLOWER TRUSS gene cause late flowering and this gene was recently shown to encode a protein similar to that encoded by the Arabidopsis FT gene. FT-like proteins seem to act as major flower promoters in diverse species. We also discuss issues in tomato flowering that we believe still require further research.