Behavioral Evidence and Olfactory Reception of a Single Alarm Pheromone Component in Halyomorpha halys

Abstract

<i>Halyomorpha halys</i> is a major herbivore insect in the fruit orchards of China that has become a devastating invasive pest in North America and Europe since its accidental introductions in the 1990s and 2000s, respectively. Like other hemipteran insects, <i>H. halys</i> releases defensive chemicals against natural enemies, including (<i>E</i>)-2-decenal, which is an aldehyde associated with alarm pheromones. In this study, a series of electrophysiological and behavioral tests were conducted to characterize the alarm functions of (<i>E</i>)-2-decenal among <i>H. halys</i> adults and nymphs. An antennal transcriptome was obtained from a Chinese <i>H. halys</i> population, and 44 odorant-binding protein (<i>OBP</i>) genes were annotated. Among them, five putative alarm pheromone-binding proteins were screened and were extremely consistent with their homologs from US populations. These five OBPs were later expressed in a heterologous expression system, harvested, and then challenged with (<i>E</i>)-2-decenal in a binding assay. All five OBPs showed high binding activities to (<i>E</i>)-2-decenal, which demonstrated its behavioral significance as a defensive component in <i>H. halys</i>, as well as being the first report of its olfactory reception. These findings will help develop behavioral-mediating tools as part of integrated pest management approaches to control this invasive pest.