Project description:cDNA library sequencing in the midgut, mixed segment and first proctodeal segment of worker termites in Nasutitermes takasagoensis by 454 GS Junior pyrosequencing
Project description:Termites produce the most diverse array of terpenoids among metazoans, comprising over 200 structures involved in chemical communication and defense described to date, some of which are exclusive to termites. However, their biosynthesis has not yet been elucidated, and the responsible terpene synthases remain unknown. Here, we draw lessons from discoveries in other insects which showed that terpene synthases can originate through duplications and neofunctionalizations of isoprenyl diphosphate synthase genes, occurring independently in individual clades. We identify a novel gene family which arose through the duplication of geranylgeranyl pyrophosphate synthase (GGPPS) in the common ancestor of Neoisoptera, the modern terpene-producing termite lineage. This family subsequently expanded into multiple paralogs and has been retained in neoisopteran genomes throughout 100 million years of diversification. We functionally characterized several GGPPS-like enzymes from two neoisopteran species and demonstrated that they indeed act as terpene synthases generating biologically relevant sesqui- and diterpenes. In Embiratermes neotenicus, EneoC produces enantiomerically pure (3R,6E)-nerolidol, known as the queen pheromone, and EneoE produces (E,E,E)-neocembrene, another queen-specific compound. In Nasutitermes takasagoensis, NtGGPPS6 synthesizes (E,E,E)-neocembrene, the precursor of polycyclic diterpenes characteristic of this genus. We explore the evolutionary transition from isoprenyl diphosphate synthase to terpene synthase activity in these enzymes in terms of structural features and selection pressures, and highlight the potential role of transposable elements in the evolution of the GGPPS-like family. We conclude that we have identified an enzyme family underlying the remarkable richness of termite terpenoids, which likely contributed to the ecological success of Neoisoptera
