Identification and odor exposure regulation of odorant-binding proteins in Picromerus lewisi

The highly developed sensitive olfactory system is essential for <i>Picromerus lewisi</i> Scott (Hemiptera: Pentatomidae) adults, an widely distributed natural predatory enemy, to locate host plants. During this process, odorant-binding proteins (OBPs) are thought to have significant involvement in the olfactory recognition. However, the roles of OBPs in the olfactory perception of <i>P. lewisi</i> are not frequently reported. Here, we conducted odor exposure and transcriptome sequencing experiments using healthy and <i>Spodoptera litura</i>-infested tobacco plants as odor sources. The transcriptomic data revealed that the alteration in the expression of mRNA levels upon exposure to odor was sex-dependent. As the expression profiles differed significantly between male and female adults of <i>P. lewisi</i>. A total of 15 <i>P. lewisi</i> OBPs (PlewOBPs) were identified from the <i>P. lewisi</i> transcriptome. Sequence and phylogenetic analysis indicated that PlewOBPs can be classified into two subfamilies (classic OBP and plus-C OBP). The qRT-PCR results showed that the transcript abundance of 8 <i>PlewOBPs</i> substantially altered following exposure to <i>S. litura</i>-infested tobacco plants, compared to the blank control or healthy plants. This implies that these <i>PlewOBPs</i> may have an olfactory function in detecting <i>S. litura</i>-infested tobacco plants. This study establishes the foundation for further understanding of the olfactory recognition mechanism of <i>P</i>. <i>lewisi</i> and helps discover novel targets for functional characterization in future research.