Identification of a Soybean Volatile Attractive for <i>Riptortus pedestris</i> Using Reverse Chemical Ecology Approach

The bean bug <i>Riptortus pedestris</i> is a major soybean pest and a cause of the stay-green symptoms. However, the molecular mechanisms underlying its olfaction-mediated host-seeking behavior remain unclear. In this study, we compared the antennae transcriptomes of starved and nonstarved adult <i>R. pedestris</i>, identifying four differentially expressed odorant receptor (OR) genes. Among these, RpedOR13 showed a strong response to the host volatile 2-phenylethanol (2-PE) in <i>Xenopus</i> oocyte assays, while electroantennography and behavioral tests confirmed 2-PE as an effective attractant. Next, phylogenetic analysis identified RpedOR72b as a paralog of RpedOR13, with subsequent <i>Xenopus</i> oocyte assays confirming its specific response to 2-PE. Additionally, RNA interference experiments highlighted the crucial role of <i>RpedOR72b</i> in detecting 2-PE. Taken together, these findings provide new insights into the molecular mechanisms of host-seeking behavior in <i>R. pedestris</i> and highlight the successful application of reverse chemical ecology in OR-based screening of bioactive compounds.