Sensory neuron membrane proteins (SNMPs) play important roles in insect chemoreception and SNMP1s have been reported to be essential in detecting sex pheromones in Drosophila and some lepidopteran species. However, SNMPs for Cyrtotrachelus buqueti (Coleoptera: Curculionidae), a major insect pest of bamboo plantations, remain uncharacterized. In this study, a novel SNMP gene, CbuqSNMP1b, from C. buqueti was functionally characterized. The expression of CbuqSNMP1b was significantly higher in antennae than in other tissues of both sexes and the expression level was significantly male-biased. Additionally, CbuqSNMP1b showed significantly higher transcription levels in the adult stage and very low transcription levels in other stages, suggesting that CbuqSNMP1b is involved in the process of olfaction. Fluorescence binding assays indicated that CbuqSNMP1b displayed the strongest binding affinity to dibutyl phthalate (K_i = 9.03 μM) followed by benzothiazole (K_i = 11.59 μM) and phenol (K_i = 20.95 μM) among fourteen C. buqueti volatiles. Furthermore, molecular docking revealed key residues in CbuqSNMP1b that interact with dibutyl phthalate, benzothiazole, and phenol. In conclusion, these findings will lay a foundation to further understand the olfactory mechanisms of C. buqueti and promote the development of novel methods for controlling this pest.

Pheromone-binding proteins (PBPs) play important roles in binding and transporting sex pheromones. However, the PBP genes identified in coleopteran insects and their information sensing mechanism are largely unknown. Cyrtotrachelus buqueti (Coleoptera: Curculionidae) is a major insect pest of bamboo plantations. In this study, a novel PBP gene, CbuqPBP2, from C. buqueti was functionally characterized. CbuqPBP2 was more abundantly expressed in the antennae of both sexes than other body parts, and its expression level was significantly male-biased. Fluorescence competitive binding assays showed that CbuqPBP2 exhibited the strongest binding affinity to dibutyl phthalate (K_i = 6.32 μM), followed by styrene (K_i = 11.37 μM), among twelve C. buqueti volatiles. CbuqPBP2, on the other hand, showed high binding affinity to linalool (K_i = 10.55), the main volatile of host plant Neosinocalamus affinis. Furthermore, molecular docking also demonstrated the strong binding ability of CbuqPBP2 to dibutyl phthalate, styrene, and linalool, with binding energy values of −5.7, −6.6, and −6.0 kcal/mol, respectively, and hydrophobic interactions were the prevailing forces. The knockdown of CbuqPBP2 expression via RNA interference significantly reduced the electroantennography (EAG) responses of male adults to dibutyl phthalate and styrene. In conclusion, these results will be conducive to understanding the olfactory mechanisms of C. buqueti and promoting the development of novel strategies for controlling this insect pest.

The larch looper, Erannis ankeraria Staudinger (Lepidoptera: Geometridae), is one of the major insect pests of larch forests, widely distributed from southeastern Europe to East Asia. A naturally occurring baculovirus, Erannis ankeraria nucleopolyhedrovirus (EranNPV), was isolated from E. ankeraria larvae. This virus was characterized by electron microscopy and by sequencing the whole viral genome. The occlusion bodies (OBs) of EranNPV exhibited irregular polyhedral shapes containing multiple enveloped rod-shaped virions with a single nucleocapsid per virion. The EranNPV genome was 125,247 bp in length with a nucleotide distribution of 34.9% G+C. A total of 131 hypothetical open reading frames (ORFs) were identified, including the 38 baculovirus core genes and five multi-copy genes. Five homologous regions (hrs) were found in the EranNPV genome. Phylogeny and pairwise kimura 2-parameter analysis indicated that EranNPV was a novel group II alphabaculovirus and was most closely related to Apocheima cinerarium NPV (ApciNPV). Field trials showed that EranNPV was effective in controlling E. ankeraria in larch forests. The above results will be relevant to the functional research on EranNPV and promote the use of this virus as a biocontrol agent.

The gypsy moth, Lymantria dispar, is a polyphagous forest pest worldwide. The baculovirus, Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) is a natural pathogen of L. dispar. The Toll-like receptors (TLR) pathway plays a crucial role in both innate and adaptive immunity in animals. However, The TLR pathway and its underlying immune mechanism against baculovirus in L. dispar have not been explored. In this study, eleven TLRs and five downstream TLR pathway components were identified and characterized from L. dispar. Structural analysis indicated that intracellular Toll/interleukin-1 receptor (TIR) domains of LdTLRs and LdMyD88 contained three conserved motifs, and the 3D structures of TIR domains of LdTLRs possessed similar patterns in components arrangement and spatial conformation. The TLR proteins of L. dispar were placed into five monophyletic groups based on the phylogenetic analysis. LdTLR1, 2, 5, 6, 7, 8 and all identified downstream TLR pathway factors were highly induced upon LdMNPV infection, indicating that the TLR pathway of L. dispar was activated and might play a role in the immune response to LdMNPV infection. Collectively, these results help elucidate the crucial role of the TLR pathway in the immune response of L. dispar against LdMNPV, and offer a foundation for further understanding of innate immunity of the pest.

Nucleopolyhedrovirus (NPV) can alter its host behaviour such that infected larvae hang at the top of trees before their death. This phenomenon was firstly described by Hofmann in 1891 and named as “tree-top disease”. Subsequent studies have described effects during the infection proceedings as NPVs manipulate the host to avoid the immune response, cross defensive barriers and regulate hormones. In this study, we demonstrate that the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway is involved in host manipulation by Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV). Particularly at the late stage of infection, a multifunctional dephosphorylase in the PI3K/AKT signaling pathway is dynamically upregulated, namely, the phosphatidylinositol-3, 4, 5-trisphosphate 3-phosphatase and dual-specificity protein phosphatase (PTEN) gene. The biological assays of PTEN gene knockdown showed that an increase in PTEN gene expression was necessary for the infected Lymantria dispar larvae’s terminal climbing behavior, death postponement and virion production. The results imply that the PI3K/AKT signaling pathway and PTEN gene might play an essential role in “tree-top disease” induced by LdMNPV.

Sclerodermus sichuanensis Xiao is an important natural enemy of forest boring pests. We used a two-way selection test to investigate the behavioral mechanisms used by S. sichuanensis when searching for hosts. Y-tube olfactometers and electroantennogram recordings were used to study learning by S. sichuanensis exposed continuously or discontinuously to a mixture of longhorn beetle (Anoplophora chinensis Forster) fecula and wood meal, and to mixtures of A. chinensis fecula and wood meal from different trees, either successively or simultaneously. Following exposure of 4-day-old adult S. sichuanensis to a mixture of A. chinensis fecula and wood meal for 3 d, tropism toward this odor did not improve significantly. After discontinuous exposure to a mixture of A. chinensis fecula and wood meal, adult S. sichuanensis exhibited a habitual response and its tropism to this odor decreased markedly. Five-day-old female S. sichuanensis that previously experienced a mixture of A. chinensis fecula and wood meal from two different host trees (willows, Salix sp., and oriental parasol, Platanus orientalis) or a mixture of A. chinensis fecula and wood meal (willows) during the eclosion period and were then stimulated by the mixture of A. chinensis fecula and wood meal (oriental parasol) at 4 days old exhibited a relatively strong behavioral reaction to mixed stimulation by the two types of substrate information. These observations suggest that the learning behavior of S. sichuanensis is cumulative. The parasitoid can differentiate between two kinds of chemical information experienced simultaneously and recognize the two odors when they are experienced successively. This discovery is important for elucidating the behavioral mechanisms of learning in parasitoids and for the development and application of natural enemy insects for pest control.