Evolutionarily conserved odorant-binding proteins participate in establishing tritrophic interactions

Summary

Attracting herbivores and their natural enemies is a standard method where plant volatiles mediate tritrophic interactions. However, it remains unknown whether the shared attraction has a shared chemosensory basis. Here we focus on the odorant-binding proteins (OBPs), a gene family integral to peripheral detection of odoriferous chemicals. Previous evidence suggests that the herbivorous beetle Monochamus alternatus and its parasitoid beetle Dastarcus helophoroides are attracted to stressed pines. In this study, (+)-fenchone, emitted by stressed pines, is found to be attracted to M. alternatus and D. helophoroides in behavioral assays. Meanwhile, two orthologous OBPs with a slower evolutionary rate, respectively, from the two insects are shown to bind with (+)-fenchone, and the attraction is abolished after RNAi. These results show the ability of evolutionarily conserved OBPs from herbivores and their enemies to detect the same plant volatiles, providing an olfactory mechanism of chemical signals–mediated tritrophic relationships.

Graphical abstract

Highlights

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  Monochamus alternatus and Dastarcus helophoroides are attracted to (+)-fenchone from host pines

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  They harbor evolutionarily conserved odorant-binding proteins (OBPs)

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  One pair of the conserved OBPs can bind with (+)-fenchone

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  The behavioral preference is lost upon RNAi knockdown of the OBPs

Abstract

Biochemistry; Evolutionary biology; Phylogenetics