The tomato terpene synthase gene family

Compounds of the terpenoid class play many roles in the interactions of plants with their environment, such as attracting pollinators and defending the plant against pests. We show here that the genome of Solanum lycopersicum (cultivated tomato) contains 40 terpene synthase (TPS) genes, including 28 which are functional or potentially functional. Of these 28 TPS genes, 25 were expressed in at least some parts of the plant. The enzymatic functions of eight of the TPS proteins were previously reported, and here we report the specific in vitro catalytic activity of nine additional tomato terpene synthases. Many of the tomato TPS genes are found in clusters, notably on chromosomes 1, 2, 6 and 8. All TPS family clades previously identified in angiosperms are also found in tomato. The largest clade of functional TPS genes found in tomato, 13 members, belong to the TPS-a clade and appear to encode only sesquiterpene synthases. Some of these sesquiterpenes use z,z-farnesyl diphosphate in vitro as well or more efficiently than the e,e-FPP substrate. Genes encoding monoterpene synthases are also prevalent and they fall into three clades: TPS-b and TPS-g and TPS-e/f. With the exception of two enzymes involved in the synthesis of ent-kaurene, the precursor of gibberellins, no other tomato TPS genes could be demonstrated to encode diterpene synthases so far. Analysis of the number, arrangement, and sequence divergence of tomato TPS genes suggests recent changes, including gene duplications, gene loss, and mutations, in this family in the lineage leading to present-day S. lycopersicum.