Binding properties of odorant‐binding protein 4 from bean bug Riptortus pedestris to soybean volatiles

Abstract

The bean bug Riptortus pedestris is a notorious insect pest that can damage various crops, especially soybean, in East Asia. In insects, the olfactory system plays a crucial role in host finding and feeding behaviour in which the odorant‐binding proteins (OBPs) are believed to be involved in initial step in this system. In this study, we produced the R. pedestris adult antennae‐expressed RpedOBP4 protein using a recombinant expression system in E. coli. Fluorescence competitive binding confirmed that RpedOBP4 has binding affinities to 7 of 20 soybean volatiles (ligands), and that a neutral condition is the best environment for it. The binding property of RpedOBP4 to these ligands was further revealed by integrating data from molecular docking, site‐directed mutagenesis and ligand binding assays. This demonstrated that five amino acid residues (I30, L33, Y47, I57 and Y121) are involved in the binding process of RpedOBP4 to corresponding ligands. These findings will not only help us to more thoroughly explore the olfactory mechanism of R. pedestris during feeding on soybean, but also lead to the identification of key candidate targets for developing environmental and efficient behaviour inhibitors to prevent population expansion of R. pedestris in the future.

A Faboideae-Specific Floral Scent Betrays Seeds to an Important Granivore Pest

“…One likely mechanism is that the insect tracks similar odorous cues, produced by the different legume species when they are in the reproductive stage and "ready" to be infested. 25,26 To address the question of whether R. pedestris uses common odor cues from different legume species to locate food sources, we analyzed the floral scents of several host and non-host plant species of R. pedestris, representing three species-rich subfamilies of the Fabaceae, namely, the Cercidoideae, Faboideae, and Caesalpinioideae. The aim was to understand whether common patterns of floral scent (i.e., groups of unique volatile organic compounds) may serve R. pedestris adults to locate food sources throughout the season by switching hosts from one generation to another.…”

“…However, the underlying mechanisms allowing such synchronization remain unknown. One likely mechanism is that the insect tracks similar odorous cues, produced by the different legume species when they are in the reproductive stage and “ready” to be infested. , …”