Mechanisms of Impact of Alnus ferdinandi-coburgii Odor Substances on Host Location of Tomicus yunnanensis

In the chemosensory system of insects, odorant-binding proteins (OBPs) and odorant-degrading enzymes (ODEs) play a role in the host location process. This study identified and analyzed chemosensory-related genes from the transcriptomes of different tissues of male and female adults of <i>Tomicus yunnanensis</i>. Subsequently, host odorants from <i>Pinus yunnanensis</i> and non-host odorants from <i>Alnus ferdinandi-coburgii</i> were used to treat the adults of <i>T. yunnanensis</i> to clarify the gene expression changes in the insects and, combined with molecular docking, to explore the mechanism of the non-host odor interfering with the host localisation of <i>T. yunnanensis</i>. A total of 137 chemosensory-related genes were obtained, among which <i>TyunOBP6</i> was specifically highly expressed in the antennae of <i>T. yunnanensis</i>; <i>TyunCYP4G2</i> and <i>TyunCYP6DF1</i> were highly expressed in the remnants of <i>T. yunnanensis</i>, selected as key genes for further research. The odor interference experiment results show that both host and non-host odorants caused up-regulation of <i>TyunOBP6</i> in antennal expression, and significant changes in the expression of <i>TyunCYP4G2</i> and <i>TyunCYP6DF1</i> in the remnants were also observed. The molecular docking results indicate that non-host compounds could compete with host compounds for protein binding sites. The non-host odor of <i>A. ferdinandi-coburgii</i> can interfere with TyunOBPs and TyunCYPs in <i>T. yunnanensis</i> and affect their host localization.