Comparative analysis of detoxification-related gene superfamilies across five hemipteran species

New Insights into Expanding the Insecticidal Spectrum of dsRNA Mediated by the High Sequence Identity between dsRNA and Nontarget mRNA

RNA interference (RNAi) is being used to develop methods to control pests, yet its widespread application is limited by the high comprehensive application cost of dsRNAs. Here, we utilized the high identity matching between double-stranded RNA (dsRNA) and nontarget genes to achieve expanding the dsRNA insecticidal spectrum. First, we found that dsRNA was more likely to induce off-target effects in genes with higher transcript levels and higher sequence identity; the existence of either a completely contiguous matching sequence exceeding 15 nt or a partially contiguous matching sequence of 24 nt between genes can lead to off-target effects in Tribolium castaneum. Accordingly, we successfully interfered with T. castaneum and Laodelphax striatellus using dsRNA targeted against Nilaparvata lugens. Additionally, the use of dsRNA targeting L. striatellus effectively interfered with N. lugens, both instances resulting in lethal effects. Moreover, the dsRNA spray method proved to be more efficient than the rice seedling soaking method to deliver dsRNA. Our research offers new insights into expanding the insecticidal spectrum of dsRNA mediated by a high degree of sequence identity between genes.

Transcriptomic resources for Bagrada hilaris (Burmeister), a widespread invasive pest of Brassicales

The bagrada bug, Bagrada hilaris (Burmeister), is an emerging agricultural pest in the Americas, threatening agricultural production in the southwestern United States, Mexico and Chile, as well as in the Old World (including Africa, South Asia and, more recently, Mediterranean areas of Europe). Substantive transcriptomic sequence resources for this damaging species would be beneficial towards understanding its capacity for developing insecticide resistance, identifying viruses that may be present throughout its population and identifying genes differentially expressed across life stages that could be exploited for biomolecular pesticide formulations. This study establishes B. hilaris transcriptomic resources for eggs, 2nd and 4th larval instars, as well as male and female adults. Three gene families involved in xenobiotic detoxification-glutathione S-transferases, carboxylesterases and cytochrome P450 monooxygenases-were phylogenetically characterized. These data were also qualitatively compared with previously published results for two closely related pentatomid species-the brown marmorated stink bug, Halyomorpha halys (Stål), and the harlequin bug, Murgantia histrionica (Hahn)-to elucidate shared enzymatic components of terpene-based sex pheromone biosynthetic pathways. Lastly, the sequence data were screened for potential RNAi- and virus-related content and for genes implicated in insect growth and development.

Biological Characteristics of the Cytochrome P 450 Family and the Mechanism of Terpinolene Metabolism in Hyalomma asiaticum (Acari: Ixodidae)

The CYP450 enzyme is a superfamily enzyme ubiquitously found in nearly all organisms, playing a vital role in the metabolism of both endogenous and exogenous compounds, and in biosynthesis. Unfortunately, an understanding of its classification, functions, expression characteristics, and other biological traits in Hyalomma asiaticum, a vector for Crimean-Congo Hemorrhagic Fever, as well as of the genes implicated in its natural product metabolism, is lacking. Towards this end, this study has identified 120 H. asiaticum CYP450 genes via transcriptome data in the face of a joint genome threat from terpinolene. The proteins these genes encode are of higher molecular weight, devoid of a signal peptide, and composed of unstable hydrophobic proteins principally containing 1-3 variable transmembrane regions. Phylogenetic evolution classifies these H. asiaticum CYP450 genes into four subfamilies. These genes all encompass complete CYP450 conserved domains, and five specific conserved motifs, albeit with different expression levels. GO and KEGG annotation findings suggest a widespread distribution of these CYP450 genes in many physiological systems, predominantly facilitating lipid metabolism, terpenoid compound metabolism, and polyketone compound metabolism, as well as cofactor and vitamin metabolism at a cellular level. Molecular docking results reveal a hydrophobic interaction between the ARG-103, ARG-104, LEU-106, PHE-109, and ILE-119 amino acid residues in CYP3A8, which is primarily expressed in the fat body, and terpinolene, with a notably up-regulated expression, with affinity = -5.6 kcal/mol. The conservation of these five key amino acid residues varies across 12 tick species, implying differences in terpinolene metabolism efficacy among various tick species. This study thereby fills an existing knowledge gap regarding the biological characteristics of H. asiaticum CYP450 genes and paves the way for further research into the functions of these particular genes.

Comparative genomics reveals evolutionary drivers of the dietary shift in Hemiptera

Hemiptera insects exhibit a close relationship to plants and demonstrate a diverse range of dietary preferences, encompassing phytophagy as the predominant feeding habit while a minority engages in carnivorous or haematophagous behaviour. To counteract the challenges posed by phytophagous insects, plants have developed an array of toxic compounds, causing significant evolutionary selection pressure on these insects. In this study, we employed a comparative genomics approach to analyse the expansion and contraction of gene families specific to phytophagous insect lineages, along with their adaptive evolutionary traits, utilising representative species from the Hemiptera order. Our investigation revealed substantial expansions of gene families within the phytophagous lineages, especially in the Pentatomomorpha branch represented by Oncopeltus fasciatus and Riptortus pedestris. Notably, these expansions of gene families encoding enzymes are potentially involved in hemipteran-plant interactions. Moreover, the adaptive evolutionary analysis of these lineages revealed a higher prevalence of adaptively evolved genes in the Pentatomomorpha branch. The observed branch-specific gene expansions and adaptive evolution likely contribute significantly to the diversification of species within Hemiptera. These results help enhance our understanding of the genomic characteristics of the evolution of different feeding habits in hemipteran insects.

Malpighian tubules of Rhodnius prolixus: More than post-prandial diuresis

Rhodnius prolixus, a major vector of Chagas disease, may be considered the model upon which the foundations of insect physiology and biochemistry were built. It is an obligate blood feeder in which the blood meal triggers growth, development and reproduction. The blood meal also triggers a post-prandial diuresis to maintain osmotic homeostasis. In R. prolixus, as with other insects, the Malpighian tubules play a critical role in this diuresis, and much has been learned about diuresis in R. prolixus, and in other model insects. But the post-genomic era has brought new insights, identifying functions quite apart from diuresis for Malpighian tubules. Indeed, microarrays, transcriptomes, and proteomics have revealed the major roles that Malpighian tubules play in immunity, detoxification, pesticide resistance, and in tolerance to overall stress. This is particularly relevant to R. prolixus since gorging on blood creates several challenges in addition to osmotic balance. Xenobiotics may be present in the blood or toxins may be produced by metabolism of blood; and these must be neutralized and excreted. These processes have not been well described at the molecular level for Malpighian tubules of R. prolixus. This paper will review the involvement of Malpighian tubules in immunity and detoxification, identifying new aspects for Malpighian tubule physiology of R. prolixus by virtue of a transcriptome analysis. The transcriptome analysis indicates the potential of Malpighian tubules of R. prolixus to mount a robust innate immune response, and to contribute to antioxidant production and heme detoxification.