Identification of an Alarm Pheromone-Binding Chemosensory Protein From the Invasive Sycamore Lace Bug Corythucha ciliata (Say)

An Antennae-Enriched Odorant-Binding Protein EonuOBP43 Mediate the Behavioral Response of the Tea Green Leafhopper, Empoasca onukii Matsuda to the Host and Nonhost Volatiles

Olfaction is crucial for Empoasca onukii Matsuda to recognize odors from the host and nonhost plants, and it has been proposed that odorant binding proteins are directly required for odorant discrimination and represent potential targets of interest for pest control. Here, we cloned EonuOBP43 and expressed the recombinant EonuOBP43 protein. Furthermore, competitive fluorescence binding assays with 19 ligands indicated that terpenoids and alkanes showed a relatively higher than for other classes of chemicals. Additionally, ligand docking and site-directed mutagenesis results revealed that seven hydrophobic residues, including Val-86, Met-89, Phe-90, Ile-104, Ile-105, Leu-130, and Val-134, played a key role in the binding of EonuOBP43 to plant volatiles. In olfactometer tests, E. onukii were significantly attracted to α-farnesene and repelled to β-caryophyllene, and dsOBP43 treated adult lost response to α-farnesene and β-caryophyllene. In summary, our results demonstrated that EonuOBP43 may function as a carrier in the process of sensing plant compounds of E. onukii.

Functional characterization of chemosensory proteins in response to artificial light treatment in Thalassodes immissaria

BACKGROUND

Chemosensory proteins (CSPs) play a vital role in the response to environmental stimuli in insects. However, the involvement of insect CSPs in the stress response to night-time environmental changes has not been examined.

RESULTS

In the current study, four TiCSP genes were first cloned from Thalassodes immissaria by transcriptome and RACE-PCR techniques. TiCSPs had typical characteristics of insect CSPs, including a highly conserved four-cysteine motif and olfactory-specific protein D (OS-D) or OS-D superfamily domains. TiCSP1-4 were clustered classified within different clades in a phylogenetic analysis and were differentially expressed at all developmental stages. Under night-time artificial light stress, the expression levels of TiCSP1 in males were significantly decreased at 24 h, and those of TiCSP2 were decreased in both adult sexes at 48 h. In a molecular docking analysis, TiCSPs showed relatively higher binding affinities with sex pheromone components than with host plant volatile molecules.

CONCLUSION

Taking the reduced expression levels of TiCSPs and binding affinities into account, TiCSP1 and TiCSP2 are involved in the stress response processes of T. immissaria under light treatment. Our study supplies basic data for the evaluation of the effects of light interference control technology - an emerging physical control measure on nontarget pests of lychee orchards. © 2023 Society of Chemical Industry.

Exploration of Candidate Genes Involved in the Biosynthesis, Regulation and Recognition of the Male-Produced Aggregation Pheromone of Halyomorpha halys

The aggregation pheromone of the brown marmorated stink bug, Halyomorpha halys (Stål), is produced by adult males, and plays an important role in the behavioral regulation of H. halys. However, information on the molecular mechanisms underlying this pheromone's biosynthesis is limited. In this study, HhTPS1, a key candidate synthase gene in the aggregation pheromone biosynthesis pathway of H. halys, was identified. Then, through weighted gene co-expression network analysis, the candidate P450 enzyme genes in the biosynthetic downstream of this pheromone and the related candidate transcription factor in this pathway were also identified. In addition, two olfactory-related genes, HhCSP5 and HhOr85b, involved in the recognition of the aggregation pheromone of H. halys, were detected. We further identified the key amino acid sites of HhTPS1 and HhCSP5 that interact with substrates by using molecular docking analysis. This study provides basic information for further investigations into the biosynthesis pathways and recognition mechanisms of aggregation pheromones in H. halys. It also provides key candidate genes for bioengineering bioactive aggregation pheromones necessary for the development of technologies for the monitoring and control of H. halys.

Antennae-abundant expression of candidate cytochrome P450 genes associated with odorant degradation in the asian citrus psyllid, Diaphorina citri

The Asian citrus psyllid, Diaphorina citri, is a notorious pest that is an efficient vector for Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus huanglongbing (HLB). The olfactory system of insects is crucial for foraging and mating behavior. Antennae-abundant odorant degrading enzymes (ODEs), including cytochrome P450 (CYPs), are important in degrading redundant odorant molecules to recover the insect olfactory. In this study, to isolate the antennal CYP genes of D. citri, we generated four transcriptomes from female/male antennae and body through deep sequencing of RNA libraries. Seven DcCYP genes preferentially expressed in antennae were first identified by comparing the antennal and body transcriptomes. Phylogenetic analysis grouped four DcCYPs (DcCYP6a13, DcCYP6j1, DcCYP6k1, and DcCYP6a2) into the CYP3 class, whereas DcCYP4d2, DcCYP4c62, and DcCYP4d8 were clustered in the CYP4 clade. qRT-PCR analyses across developmental stages and tissues showed they were antennae-abundant in both genders and constantly expressed from the first instar nymph to the adult. The results presented here highlight the isolation and expression of CYP genes in D. citri antennae, providing valuable insights into their putative role in odorant degradation.

Functional Characterization of Chemosensory Protein AmalCSP5 From Apple Buprestid Beetle, Agrilus mali (Coleoptera: Buprestidae)

In the sensitive and complex chemo-sensation system of insects, chemosensory proteins (CSPs) can facilitate the transfer of chemical information and play important roles for variable behaviors of insects. We cloned the chemosensory protein AmalCSP5 from antennae of the apple buprestid beetle (Agrilus mali Matsumura), a serious invasive pest of wild apple trees. Expression profiling showed that AmalCSP5 was expressed in various tissues, suggesting its significance in multiple physiological activities and behaviors of A. mali. AmalCSP5 was preferentially expressed in female antennae and male abdomens. AmalCSP5 was able to bind a variety of test volatiles, especially alcohols and esters. AmalCSP5 exhibited good binding affinity for all five test secondary compounds (i.e., procyanidin, phlorizin, kaemferol, chlorogenic acid, and rutin), suggesting its preferential binding abilities to nonvolatile host plant secondary metabolites and critical roles in gustatory perception of nonvolatiles. Tyr27 and Ser69 of AmalCSP5 could form hydrogen bonds with hexyl benzoate and hexyl hexanoate, respectively. Procyanidin, the best ligand among all test compounds, could form hydrogen bonds with three amino acid residues (i.e., Arg7, Leu8, and Lys41) of AmalCSP5. Thus, high ligand binding affinity for AmalCSP5 seemed to be dependent mainly on the formation of hydrogen bonds. The putative key amino acid residues of AmalCSP5 can be used as molecular targets for designing and screening new attractants and repellents for A. mali. Our results provide insights into binding interactions of AmalCSP5 with volatile and nonvolatile ligands, and a firm basis for developing eco-friendly management strategies of A. mali.

Transcriptome sequencing, molecular markers, and transcription factor discovery of Platanus acerifolia in the presence of Corythucha ciliata

The London Planetree (Platanus acerifolia) are present throughout the world. The tree is considered a greening plant and is commonly planted in streets, parks, and courtyards. The Sycamore lace bug (Corythucha ciliata) is a serious pest of this tree. To determine the molecular mechanism behind the interaction between the London Planetree and the Sycamore lace bug, we generated a comprehensive RNA-seq dataset (630,835,762 clean reads) for P. acerifolia by sequencing both infected and non-infected leaves of C. ciliata using the Illumina Hiseq 4000 system. We assembled the transcriptomes using the Trinity De Novo assembly followed by annotation. In total, 121,136 unigenes were obtained, and 80,559 unigenes were successfully annotated. From the 121,136 unigenes, we identified 3,010,256 SNPs, 39,097 microsatellites locus, and 1,916 transcription factors. The transcriptomic dataset we present are the first reports of transcriptome information in Platanus species and will be incredibly useful in future studies with P. acerifolia and other Platanus species, especially in the areas of genomics, molecular biology, physiology, and population genetics.

Changes in Gene Expression and Metabolite Profiles in Platanus acerifolia Leaves in Response to Feeding Damage Caused by Corythucha ciliata

The sycamore lace bug, Corythucha ciliata (Say) is a highly invasive pest insect that feeds on sycamore trees (Platanus spp.) worldwide. The interaction between Platanus species and this insect pest has not yet been studied at the molecular level. Therefore, a recent study was conducted to compare the gene expression and metabolite profiles of Platanus acerifolia leaves in response to C. ciliata feeding damage after 24 and 48 h. We employed high throughput RNA sequencing (RNA- seq) to identify a total of 2,828 significantly differentially expressed genes (DEGs) after C. ciliata feeding. In addition, 303 unigenes were found to be up-regulated at both time points. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that monoterpenoid biosynthesis, the linoleic acid metabolism pathway, and alpha- linolenic acid metabolism were the most prominent pathways among the DEGs. Further analysis of the metabolite profiles showed that nine metabolites were significantly different before and after C. ciliata damage. In addition, we analyzed DEGs detected in the P. acerifolia and C. ciliata interaction using Mapman. The terpene synthase gene family was also identified. We suggest that the results obtained from DEGs and metabolite analysis can provide important information for the identification of genes involved in the P. acerifolia–C. ciliata interaction, which might be necessary for controlling C. ciliata efficiently.