The leaf beetle Ambrostoma quadriimpressum (Coleoptera: Chrysomelidae) is a predominant forest pest that causes substantial damage to the lumber industry and city management. However, no effective and environmentally friendly chemical method has been discovered to control this pest. Until recently, the molecular basis of the olfactory system in A. quadriimpressum was completely unknown. In this study, antennae and leg transcriptomes were analyzed and compared using deep sequencing data to identify the olfactory genes in A. quadriimpressum. Moreover, the expression profiles of both male and female candidate olfactory genes were analyzed and validated by bioinformatics, motif analysis, homology analysis, semi-quantitative RT-PCR and RT-qPCR experiments in antennal and non-olfactory organs to explore the candidate olfactory genes that might play key roles in the life cycle of A. quadriimpressum. As a result, approximately 102.9 million and 97.3 million clean reads were obtained from the libraries created from the antennas and legs, respectively. Annotation led to 34344 Unigenes, which were matched to known proteins. Annotation data revealed that the number of genes in antenna with binding functions and receptor activity was greater than that of legs. Furthermore, many pathway genes were differentially expressed in the two organs. Sixteen candidate odorant binding proteins (OBPs), 10 chemosensory proteins (CSPs), 34 odorant receptors (ORs), 20 inotropic receptors [1] and 2 sensory neuron membrane proteins (SNMPs) and their isoforms were identified. Additionally, 15 OBPs, 9 CSPs, 18 ORs, 6 IRs and 2 SNMPs were predicted to be complete ORFs. Using RT-PCR, RT-qPCR and homology analysis, AquaOBP1/2/4/7/C1/C6, AquaCSP3/9, AquaOR8/9/10/14/15/18/20/26/29/33, AquaIR8a/13/25a showed olfactory-specific expression, indicating that these genes might play a key role in olfaction-related behaviors in A. quadriimpressum such as foraging and seeking. AquaOBP4/C5, AquaOBP4/C5, AquaCSP7/9/10, AquaOR17/24/32 and AquaIR4 were highly expressed in the antenna of males, suggesting that these genes were related to sex-specific behaviors, and expression trends that were male specific were observed for most candidate olfactory genes, which supported the existence of a female-produced sex pheromone in A. quadriimpressum. All of these results could provide valuable information and guidance for future functional studies on these genes and provide better molecular knowledge regarding the olfactory system in A. quadriimpressum.

Background: The fall webwormHyphantria cuneais an invasive and polyphagous defoliator pest that feeds on nearly any type of deciduous tree worldwide. The silk web ofH. cuneaaids its aggregating behavior, provides thermal regulation and is regarded as one of causes for its rapid spread. In addition, both chemosensory and detoxification genes are vital for host adaptation in insects.Results: Here, a high-quality genome ofH. cuneawas obtained. Silk-web-related genes were identified from the genome, and successful silencing of the silk protein geneHcunFib-Hresulted in a significant decrease in silk web shelter production. The CAFE analysis showed that some chemosensory and detoxification gene families, such asCSPs,CCEs,GSTsandUGTs, were expanded. A transcriptome analysis using the newly sequencedH. cuneagenome showed that most chemosensory genes were specifically expressed in the antennae, while most detoxification genes were highly expressed during the feeding peak. Moreover, we found that many nutrient-related genes and one detoxification gene,HcunP450(CYP306A1), were under significant positive selection, suggesting a crucial role of these genes in host adaptation inH. cunea. At the metagenomic level, several microbial communities inH. cuneagut and their metabolic pathways might be beneficial toH. cuneafor nutrient metabolism and detoxification, and might also contribute to its host adaptation.Conclusions: These findings explain the host and environmental adaptations ofH. cuneaat the genetic level and provide partial evidence for the cause of its rapid invasion and potential gene targets for innovative pest management strategies.

Using scanning electron microscope, eight types of sensilla were found on the antennae of all castes in eight Bombus species (Hymenoptera: Apidae) collected in Jilin Province, China. The numbers of various types of antennal sensilla were analyzed by rough set data analysis method to determine which sensillum type might be useful in species and caste discrimination. The results showed that the number of sensilla basiconica A, B (s. t. a, s. t. b), sensilla trichodea A, B, C/ D (s. t. a, s. t. b, s. t. c/ d) and sensilla placodea (s. p) can be used in species discrimination, whereas only types s. t. a, s. t. b, and s. t. b are relevant in caste discrimination. Other types of sensilla had a lower taxonomic value for species and caste discrimination. This study provides a mathematic reference for the function research of antennal sensilla of Bombus determined by single-cell recording at both peripheral and antennal lobe (central nervous system) levels.

Carbon dioxide (CO₂) released by plants can serve as a cue for regulating insect behaviors. Hyphantria cunea is a widely distributed forestry pest that may use CO₂ as a cue for foraging and oviposition. However, the molecular mechanism underlying its ability to sense CO₂ has not been elucidated. Our initial study showed that CO₂ is significantly attractive to H. cunea adults. Subsequently, 44 H. cunea gustatory receptors (GRs) were identified using transcriptome data, and 3 candidate CO₂ receptors that are specifically expressed in the labial palps were identified. In vivo electrophysiological assays revealed that the labial palp is the primary organ for CO₂ perception in H. cunea, which is similar to findings in other lepidopteran species. By using the Xenopus oocyte expression system, we showed that the HcunGR1 and HcunGR3 co-expressions produced a robust response to CO₂, but HcunGR2 had an inhibitory effect on CO₂ perception. Finally, immunohistochemical staining revealed sexual dimorphism in the CO₂-sensitive labial pit organ glomerulus (LPOG). Taken together, our results clarified the mechanism by which H. cunea sense CO₂, laying the foundation for further investigations into the role of CO₂ in the rapid spread of H. cunea.