Engineering <scp> Nicotiana tabacum </scp> for the de novo biosynthesis of <scp>DMNT</scp> to regulate orientation behavior of the parasitoid wasps Microplitis mediator

Background (E)-4,8-dimethylnona-1,3,7-triene (DMNT), one of the homoterpenes, is thought to contribute to plant indirect defense against insect herbivores. DMNT-enriched plants have great application potential to regulate insect behavior in the 'push & pull' strategy of pest management. However, de novo biosynthesis of DMNT in plants without a homoterpene metabolic pathway in their wild type is still not achieved, and the role of DMNT played in these plants and their interacted insects remains unclear. Results Cytochrome P450s and terpene synthases involved in homoterpenes biosynthesis in cotton plants were employed to generate DMNT-releasing tobacco plants. Single GhTPS14 transgenic Nicotiana tabacum only emitted (E)-nerolidol, the precursor of DMNT. Transgenic tobaccos expressing single GhCYP82Ls were unable to produce DMNT or TMTT, while DMNT was detected when exogenous (E)-nerolidol was added. Compared to wild-type plants, only co-expression of GhCYP82Ls and GhTPS14 in transgenic tobaccos triggered the constitutive release of single-component DMNT. Furthermore, DMNT-emitting transgenic tobacco plants, whether infested with Helicoverpa armigera larvae or not, significantly incited orientation behavior of parasitoid wasps Microplitis mediator. Conclusion Wild type N. tabacum plants have no DMNT metabolic pathway. DMNT could be de novo biosynthesized via co-expression of GhCYP82Ls and GhTPS14. What is more, the parasitoid wasp M. mediator could be recruited by DMNT-releasing transgenic tobaccos, especially by H. armigera-infested transgenic tobaccos, suggesting the potential roles of engineered N. tabacum in regulating the behavioral preference of M. mediator.