1. Introduction
The general odorant binding proteins (GOBPs), a group of odorant binding proteins (OBPs), play essential roles in host volatiles perception of lepidopteran insects by binding and transporting hydrophobic ligand across the aqueous sensilla lymph to the odorant receptors (ORs) on the dendritic membrane of olfactory neurons (Vogt and Riddiford, 1981; Krieger et al., 2004). GOBP1 and GOBP2 were subsequently defined as conserved non-sex-biased antennal OBPs from lepidopteran GOBPs by sequence comparison (Vogt et al., 1991). While the pheromone binding proteins (PBPs) as another subfamily of OBP has conserved sex-biased antennal OBPs, which bind and transport pheromone molecules to the cognate pheromone receptors (PRs) on the dendritic membrane of olfactory neurons (Liu et al., 2011; Zhang et al., 2016). Phylogenetic analyses show that GOBPs/PBPs from lepidoptera are a unique subfamily, having evolved independently within the order of lepidoptera (Vogt et al., 2015; Zhang et al., 2013; Yasukochi et al., 2018). Besides, the difference between the GOBPs/PBPs form distribution pattern antennae is distinct (Steinbrecht et al., 1995; Nardi et al., 2003). However, evolutionary facts are explained that the GOBPs might be evolved from PBP by gene duplication. This fact was reported in Manduca sexta , PBP and GOBP2 have a close relationship and play a crucial role in coordinated olfactory behaviors (Merritt et al., 1988; Vogt et al., 2002). More interestingly, GOBPs were reported could bind sex pheromones and are possibly responsible for their transportation by some searches, like in Spodoptera exigua ,Chilo suppressalis , Bombyx mori (Liu et al., 2015; Khuhro et al., 2017; Zhou et al., 2009; Nardi et al., 2003). While this function of GOBPs may remain controversial, and in vivofunctional studies will provide more convincing evidence. Furthermore, OBPs and chemosensory proteins (CSPs) as two different classes of polypeptides have been identified in the lymph of chemosensilla may have some connection. A significant amount of structural information has been accumulated on OBPs and CSPs in the attempt to elucidate their function, but so far, physiological studies have been scant and no convincing models for their action (Pelosi et al., 2006). The gradual application of CRISPR/Cas9 gene editing technique provides a new and more convincing perspective insight for functional verification of the above issues in lepidopteran insects (Wang et al., 2018; Zhang and Reed, 2016).
The yellow peach moth,Conogethes punctiferalis(Guenée), is a highly destructive fruit borer can attack more than 100 essential plant species, including peach, durian, chestnut, citrus, papaya, cardamom, ginger (Wan et al., 2016; Lu et al., 2010). Over the past decade, it has become a serious maize pest in China, causing more significant damage than Ostrinia furnacalis (Guenée) in some summer corn regions of China (Wang et al., 2006). Previously, our study reported that the GOBP1 of the yellow peach moth plays a crucial role in sex pheromones and plant volatiles recognition based on binding assay (Jing et al., 2019). In the present study, GOBPs (GOBP1 and GOBP2) were further evaluated for testing, using the CRISPR/Cas9 technique along with electrophysiological and behavioral assays. The results provide new insights into the functional role of GOBPs, as well as an essential reference for developing GOBP based behavioral interference control strategies for the yellow peach moth.