Genetic analysis of reproductive development in tomato.

Besides being an important commercial crop, tomato (Solanum lycopersicum L.) constitutes a model species for the study of plant developmental processes. Current research tends to combine classic disciplines such as physiology and genetics with modern approaches coming from molecular biology and genomics with a view to elucidating the biological mechanisms underlying plant architecture, floral transition and development of flowers and fruits. Comparative and functional analyses of tomato regulatory genes such as LATERAL SUPPRESSOR (LS), SELF PRUNING (SP), SINGLE FLOWER TRUSS (SFT) and FALSIFLORA (FA) have revealed mechanisms involved in shoot development and flowering time which are conserved among Arabidopsis, tomato and other plant species. Furthermore, several regulatory genes encoding transcription factors have been characterized as responsible for singular features of vegetative and reproductive development of tomato. Thus, the sympodial growth habit seems to require a specific control of the developmental fate followed by shoot meristems. In this process, novel genetic and molecular interactions involving SP, SFT and FA genes would be essential. Also this latter, but mainly ANANTHA (AN) and COMPOUND INFLORESCENCE (S) have recently been found to regulate the inflorescence architecture of the tomato. Concerning fruit development, genetic and molecular analyses of new genes such as fw2.2, FASCIATED, OVATE and SUN have proved their contribution to the domestication process and most importantly, their function as key regulators of fruit size and shape variation. Tomato ripening is also being elucidated thanks to the characterization of regulatory genes such as RIPENING INHIBITOR (RIN), NON-RIPENING (NOR), TDR4 and COLORLESS NON-RIPENING (CNR), which have been found to control early stages of fruit development and maturation. At the same time, much research is dedicated to isolating the targets of the ripening regulators, as well as the key genes promoting the parthenocarpic development of tomato fruits. Hopefully, the ongoing sequencing project and the progress made by integrating several research fields will help to unravel the genetic and molecular pathways controlling tomato development.