Mechanism mediating the biosynthesis of the anti-insect volatile (Z)-3-hexenyl acetate in Acacia confusa Merr., an intercropping plant in tea plantations.

Abstract

Intercropping tea plants with Acacia confusa Merr. offers an environmentally sustainable approach to insect population control in tea plantations. However, the primary compounds in A. confusa responsible for this effect and their biosynthetic mechanisms remain undetermined. This study identified (Z)-3-hexenyl acetate, (Z)-3-hexenol, and 1-hexanol as the major volatiles in A. confusa. Field experiments demonstrated that all three compounds affected the tea leafhopper, a significant pest. (Z)-3-Hexenyl acetate repelled leafhoppers, while the other two compounds attracted them. Leafhopper feeding on tea leaves significantly decreased after fumigation with (Z)-3-hexenyl acetate, potentially altering the metabolism of defensive substances in tea leaves. These findings suggest (Z)-3-hexenyl acetate as a crucial component for pest control in tea plantations intercropped with A. confusa. Furthermore, the study identified the nucleus- and cytoplasm-localized AcAAT4 in A. confusa as responsible for (Z)-3-hexenyl acetate biosynthesis. Notably, AcAAT4 expression and the production of the upstream transcription factor AcMYC2b corresponded to the (Z)-3-hexenyl acetate emission pattern. The research also elucidated the positive regulatory effects of nucleus-localized AcMYC2b on AcAAT4 expression. These findings elucidate the molecular basis of (Z)-3-hexenyl acetate emission from A. confusa and provide a theoretical foundation for enhancing intercropping practices in tea plantations.