Transcriptome analysis and identification of chemosensory genes in the larvae of Plagiodera versicolora.

Background: In insects, the chemosensory system is crucial in guiding their behaviors for survival. Plagiodera versicolora (Coleoptera: Chrysomelidae), is a worldwide leaf-eating forest pest in salicaceous trees. There is little known about the chemosensory genes in P. versicolora. Here, we conducted a transcriptome analysis of larvae heads in P. versicolora.

Results: In this study, 29 odorant binding proteins (OBPs), 6 chemosensory proteins (CSPs), 14 odorant receptors (ORs), 13 gustatory receptors (GRs), 8 ionotropic receptors (IRs) and 4 sensory neuron membrane proteins (SNMPs) were identified by transcriptome analysis. Compared to the previous antennae and foreleg transcriptome data in adults, 12 OBPs, 2 CSPs, 5 ORs, 4 IRs, and 7 GRs were newly identified in the larvae. Phylogenetic analyses were conducted and found a new candidate CO receptor (PverGR18) and a new sugar receptor (PverGR23) in the tree of GRs. Subsequently, the dynamic expression profiles of various genes were analyzed by quantitative real-time PCR. The results showed that PverOBP31, OBP34, OBP35, OBP38, and OBP40 were highly expressed in larvae, PverOBP33 and OBP37 were highly expressed in pupae, and PverCSP13 was highly expressed in eggs, respectively.

Conclusions: We identified a total of 74 putative chemosensory genes based on a transcriptome analysis of larvae heads in P. versicolora. This work provides new information for functional studies on the chemoreception mechanism in P. versicolora.