RNAi-mediated pest control targeting the Troponin I (wupA) gene in sweet potato weevil, Cylas formicarius.

The sweet potato weevil (Cylas formicarius) is a critical pest producing enormous global losses in sweet potato crops. Traditional pest management approaches for sweet potato weevil, primarily using chemical pesticides, causes pollution, food safety issues, and harming natural enemies. While RNA interference (RNAi) is a promising environmentally friendly approach to pest control, its efficacy in controlling the sweet potato weevil has not been extensively studied. In this study, we selected a potential target for controlling C. formicarius, the Troponin I gene (wupA), which is essential for musculature composition and crucial for fundamental life activities. We determined that wupA is abundantly expressed throughout all developmental stages of the sweet potato weevil. We evaluated the efficiency of double-stranded RNAs in silencing the wupA gene via microinjection and oral feeding of sweet potato weevil larvae at different ages. Our findings demonstrate that both approaches significantly reduced the expression of wupA and produced high mortality. Moreover, the 1st instar larvae administered dswupA exhibited significant growth inhibition. We assessed the toxicity of dswupA on the no-target insect silkworm and assessed its safety. Our study indicates that wupA knockdown can inhibit the growth and development of C. formicarius and offer a potential target gene for environmentally friendly control.

A female-specific odorant receptor mediates oviposition deterrence in the moth Helicoverpa armigera.

Finding ideal oviposition sites is a task of vital importance for all female insects. To ensure optimal conditions for their progeny, females of herbivorous insects detect not only the odors of a relevant host plant but also chemicals released by eggs, named oviposition-deterring pheromones (ODPs). It is reported that such chemicals play critical roles in suppressing female oviposition behavior; however, the molecular mechanism underlying the detection of egg-derived ODPs remains elusive. Here, we have identified three specific fatty acid methyl esters from the surface of eggs of Helicoverpa armigera serving as ODPs-methyl oleate (C18:1ME), methyl palmitate (C16:0ME), and methyl stearate (C18:0ME). We demonstrated that these ODPs are detected by the receptor, HarmOR56, exclusively expressed in sensilla trichodea on female antennae. To assess the significance of this receptor, we disrupted HarmOR56 in H. armigera using CRISPR-Cas9 and found that mutant females did not respond to the ODPs, neither in behavioral nor in electrophysiological tests. We therefore conclude that HarmOR56 is indispensable for identifying the ODPs. This study explores, for the first time, how a female-specific odorant receptor detects chemicals from conspecific eggs. Our data elucidate the intriguing biological phenomenon of repulsion to conspecific eggs during oviposition and contribute new insight into a female-specific olfactory pathway linked to reproduction.

Ionotropic receptor 8a is involved in the attraction of Helicoverpa armigera to acetic acid.

Ionotropic receptors (IRs) were first found in Drosophila melanogaster, and derive from ionotropic glutamate receptors (iGluRs), which are implicated in detecting acids, ammonia, amine, temperature and humidity. Although IRs are involved in sensing acid odors in a few insects, such as D. melanogaster, Aedes aegypti, and Manduca sexta, the function of IRs in Helicoverpa armigera is still unknown. IR8a was confirmed to be a co-receptor associated with acid detection. From the results of phylogenetic analysis, HarmIR8a displayed high similarity compared to homologs in D. melanogaster, M. sexta, and A. aegypti, suggesting that HarmIR8a might have a consistent function as a co-receptor for acid detection. In this study, clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR-associated protein 9 (Cas9)-mediated genome editing was implemented to knockout HarmIR8a for in vivo functional analysis. Electrophysiological and behavioral assays were performed to compare the differences between HarmIR8a knockout mutants and wild type individuals. From electroantennogram (EAG) analysis, we found that wild type H. armigera adults could detect short-chain carboxylic acids. In addition, wind tunnel experiments showed that 1% acetic acid attracted wild type H. armigera adults. However, acid sensing and attraction were reduced or abolished in the HarmIR8a knockout mutants. Our data suggest that HarmIR8a is important for H. armigera to detect short-chain carboxylic acids and mediate attraction behavior to acetic acid.

Apolygus lucorum genome provides insights into omnivorousness and mesophyll feeding.

Apolygus lucorum (Miridae) is an omnivorous pest that occurs worldwide and is notorious for the serious damage it causes to various crops and substantial economic losses. Although some studies have examined the biological characteristics of the mirid bug, no reference genome is available in Miridae, limiting in-depth studies of this pest. Here, we present a chromosome-scale reference genome of A. lucorum, the first sequenced Miridae species. The assembled genome size was 1.02 Gb with a contig N50 of 785 kb. With Hi-C scaffolding, 1,016 Mb contig sequences were clustered, ordered and assembled into 17 large scaffolds with scaffold N50 length 68 Mb, each corresponding to a natural chromosome. Numerous transposable elements occur in this genome and contribute to the large genome size. Expansions of genes associated with omnivorousness and mesophyll feeding such as those related to digestion, chemosensory perception, and detoxification were observed in A. lucorum, suggesting that gene expansion contributed to its strong environmental adaptability and severe harm to crops. We clarified that a salivary enzyme polygalacturonase is unique in mirid bugs and has significantly expanded in A. lucorum, which may contribute to leaf damage from this pest. The reference genome of A. lucorum not only facilitates biological studies of Hemiptera as well as an understanding of the damage mechanism of mesophyll feeding, but also provides a basis on which to develop efficient control technologies for mirid bugs.

Odorant Receptors for Detecting Flowering Plant Cues Are Functionally Conserved across Moths and Butterflies.

Odorant receptors (ORs) are essential for plant-insect interactions. However, despite the global impacts of Lepidoptera (moths and butterflies) as major herbivores and pollinators, little functional data are available about Lepidoptera ORs involved in plant-volatile detection. Here, we initially characterized the plant-volatile-sensing function(s) of 44 ORs from the cotton bollworm Helicoverpa armigera, and subsequently conducted a large-scale comparative analysis that establishes how most orthologous ORs have functionally diverged among closely related species whereas some rare ORs are functionally conserved. Specifically, our systematic analysis of H. armigera ORs cataloged the wide functional scope of the H. armigera OR repertoire, and also showed that HarmOR42 and its Spodoptera littoralis ortholog are functionally conserved. Pursuing this, we characterized the HarmOR42-orthologous ORs from 11 species across the Glossata suborder and confirmed the HarmOR42 orthologs form a unique OR lineage that has undergone strong purifying selection in Glossata species and whose members are tuned with strong specificity to phenylacetaldehyde, a floral scent component common to most angiosperms. In vivo studies via HarmOR42 knockout support that HarmOR42-related ORs are essential for host-detection by sensing phenylacetaldehyde. Our work also supports that these ORs coevolved with the tube-like proboscis, and has maintained functional stability throughout the long-term coexistence of Lepidoptera with angiosperms. Thus, beyond providing a rich empirical resource for delineating the precise functions of H. armigera ORs, our results enable a comparative analysis of insect ORs that have apparently facilitated and currently sustain the intimate adaptations and ecological interactions among nectar feeding insects and flowering plants.

[Analysis of microsatellite loci from Bactrocera dorsalis based on transcriptome dataset].

The transcriptome database of the oriental fruit fly, Bactrocera dorsalis (Hendel), was used to identify the functional gene-microsatellite (EST-SSR) markers and to analyze the SSR loci information. In total, 1890 EST-SSR loci were identified, of which, 1296 SSR sequences could be used for primer design. The average distribution frequency of the transcriptomic SSRs was 1/10. 21 kb. However, these distribution frequencies varied considerably among different types of repeat SSRs. The tri-nucleotide repeat SSRs were found to have the highest frequency among the different types of repeat SSRs in the EST-SSR of B. dorsalis. Combining with other literatures, we inferred that the tri-nucleotide repeat SSRs were the most abundant EST-SSR in all of insects. In this study, 42 pairs of EST-SSR primers were designed and 18 pairs produced amplification bands of expected sizes. According to the results of other related literatures, the practices and challenges of strategy for SSR isolation from insect transcriptome databases were discussed, and the problems which should be considered in the screening of insect transcriptomic EST-SSR were put forward.