Archives of Insect Biochemistry and Physiology最新文献

Cover image: The cover image is based on the article Functional expression and characterization of CAPA receptor in the digestive tract and life stages of Drosophila suzukii, and differential activities with insect PRXamide peptides by Briana E. Price et al., https://doi.org/10.1002/arch.22080.

T2 RNases are transferase-type enzymes distributed across phyla, crucial for breaking down single-stranded RNA molecules. In addition to their canonical function, several T2 enzymes exhibit pleiotropic roles, contributing to various biological processes, such as the immune response in invertebrates and vertebrates. This study aims at characterizing RNASET2 in the larvae of black soldier fly (BSF), Hermetia illucens, which are used for organic waste reduction and the production of valuable insect biomolecules for feed formulation and other applications. Given the exposure of BSF larvae to pathogens present in the feeding substrate, it is likely that the mechanisms of their immune response have undergone significant evolution and increased complexity. After in silico characterization of HiRNASET2, demonstrating the high conservation of this T2 homolog, we investigated the expression pattern of the enzyme in the fat body and hemocytes, two districts mainly involved in the insect immune response, in larvae challenged with bacterial infection. While no variation in HiRNASET2 expression was observed in the fat body following infection, a significant upregulation of HiRNASET2 synthesis occurred in hemocytes shortly after the injection of bacteria in the larva. The intracellular localization of HiRNASET2 in lysosomes of plasmatocytes, its extracellular association with bacteria, and the presence of a putative antimicrobial domain in the molecule, suggest its potential role in RNA clean-up and as an alarm molecule promoting phagocytosis activation by hemocytes. These insights contribute to the characterization of the immune response of Hermetia illucens larvae and may facilitate the development of animal feedstuff enriched with highly valuable BSF bioactive compounds.

Heat shock proteins (Hsp) function as crucial molecular chaperones, playing pivotal roles in insects' response to stress stimuli. Apolygus lucorum, known for its broad spectrum of host plants and significant crop damage potential, presents a compelling subject for understanding stress response mechanisms. Hsp is important for A. lucorum to tolerate temperature and insecticide stress and may be involved in the formation of resistance to the interactive effects of temperature and insecticide. Here, we employed comprehensive genomic approaches to identify Hsp superfamily members in its genome. In total, we identified 42 Hsp genes, including 3 Hsp90, 16 Hsp70, 13 Hsp60, and 10 Hsp20. Notably, we conducted motif analysis and gene structures for Hsp members, which suggested the same families are relatively conserved. Furthermore, leveraging the weighted gene coexpression network analysis, we observed diverse expression patterns of different Hsp types across various tissues, with certain Hsp70 showing tissue-specific bias. Noteworthy among the highly expressed Hsp genes was testis-specific, which may serve as a pivotal hub gene regulating the gene network. Our findings shed light on the molecular evolutionary dynamics and temperature stress response mechanisms of Hsp genes in A. lucorum, offering insights into its adaptive strategies and potential targets for pest management.

The invasive species Aedes albopictus is a major vector of several arboviruses. The global spread of this species seriously threatens human health. Insecticide resistance is an increasing problem worldwide that limits the efficacy of mosquito control. As the major structural component of cuticles, chitin is indispensable to insects. Chitin synthase (CHS) is the enzyme that catalyzes the biosynthesis of chitin at the final step. In this study, two CHS genes of Aedes albopictus (AaCHS1 and AaCHS2) were identified and their basic characteristics were evaluated via bioinformatics analysis. The highest abundance of AaCHS1 transcripts was detected in pupae, whereas that of AaCHS2 transcripts was detected in females; the highest expression levels of AaCHS1 and AaCHS2 were found in the epidermis and the midgut of pupae, respectively. The survival and emergence rates of pupae were significantly reduced after the injection of double-stranded RNA of AaCHS1 or AaCHS2, indicating that both AaCHS1 and AaCHS2 play crucial roles in the pupal development. In addition, the chitin content of pupae was obviously decreased after the suppression of AaCHS1 expression by RNA interference (RNAi) treatment. This influence of the RNAi treatment was further supported by the reduced chitin thickness and weakened chitin fluorescence signal in the new cuticle. The midgut of pupae presented a reduced intensity of the chitin fluorescence signal along with RNAi treatment specific to AaCHS2 expression. The results of this study indicate that CHS genes may be suitable as molecular targets used for controlling mosquitoes.

Tenvermectin B (TVM-B) and five TVM-B analogs were produced by fermentation of a genetically engineered strain Streptomyces avermitilis HU02, and TVM-B is being developed as a new insecticide. Through 11 generations of resistance selection against TVM-B in the diamondback moth, Plutella xylostella, the median lethal concentration (LC₅₀) was increased from 14.84 to 1213.73 mg L⁻¹. The resistance to TVM-B in P. xylostella developed fast and its realized heritability was high (h² = 0.2901 (F7), h² = 0.4070 (F11)). However, the relative fitness was 0.6916 suggesting a fitness cost in the resistant strains. The fitness cost was partially explained by the upregulation of the detoxification enzyme activity by 2.15 folds in carboxylate esterase (CarE) and the gene expressions of ATP-binding cassette transporter gene (ABCC2) and the alpha subunit of the glutamate-gated chloride channel (GluCl) by 1.70- and 2.32 folds, respectively. The resistance was also explained by two points of mutations at the alpha subunit of the glutamate-gated chloride channel in the P. xylostella (PxGluClα) subunit in F11. However, there was little change in the binding affinity. These results provided helpful information for the mechanism study of TVM-B resistance and will be conducive to designing rational resistance management strategies in P. xylostella.

JH and ecdysone signaling regulate insect metamorphosis through the master transcription factors, Krüppel homolog 1 (kr-h1), Broad-Complex (BR-C), and E93. Ecdysone signaling activates successively expressed ecdysone responsive transcription factors (ERTFs), and the interaction between ERTFs determines the expression profiles of ERTFs themselves. Through the construction of expressed sequence tag (EST) database of Bombyx mori from many tissues, the existence of a large number of cuticular protein (CP) genes was identified in wing disc cDNA library of the 3 days after the start of wandering (W3). From the genomic analysis, 12 types of CP clusters of CP genes were identified. DNA sequences of CP genes revealed the duplication of CP genes, which suggests to reflect the insect evolution. These CP genes responded to ecdysone and ecdysone pulse; therefore, CP genes were applied for the analysis of transcriptional regulation by ERTF. The binding sites of ERTF have been reported to exist upstream of CP genes in several insects, and the activation of CP genes occurred by the binding of ERTFs. Through the analysis, the following were speculated; the successive appearance of ERTFs and the activation of target genes resulted in the successively produced CPs and cuticular layer. The sequence of the ERTF and CP gene expression was the same at larval to pupal and pupal to adult transformation. The involvement of several ERTFs in one CP gene expression was also clarified; BmorCPG12 belongs to group showing expression peak at W3 and was regulated by two ERTFs; BHR3 and ßFTZ-F1, BmorCPH2 belongs to group showing expression peak at P0 and was regulated by two ERTFs; ßFTZ-F1 and E74A. The involvement of BHR39 as a negative regulator of CP gene expression was found. Larval, pupal, and adult cuticular layers were supposed to be constructed by the combination of different and similar types of CPs, through the expressed timing of CP genes.

High temperature stress has long-term negative effects on the growth and development of silkworm (Bombyx mori). Different silkworm varieties show the different tolerance to high temperature. The induction of autophagy is linked to increased thermotolerance in diverse ectothermic organisms. However, the function of autophagy in the thermotolerant and thermosensitive silkworm strains under high-temperature conditions remains unclear. The thermotolerant Liangguang NO.2 and thermosensitive Jingsong × Haoyue strains were used to explore the role of autophagy in thermotolerance. Here, we first found that the larval body weight gain was increased in the thermosensitive Jingsong × Haoyue strain, but there was no difference in the thermotolerant Liangguang NO.2 strain under high temperature conditions. High temperature stress had a negative influence on the cocoon performance in both the Liangguang NO.2 and Jingsong × Haoyue strains. Additionally, the autophagy-related gene Atg5 mRNA expression in the Liangguang NO.2 strain was upregulated by high temperature, while the expression of Atg12 mRNA was reduced in the Jingsong × Haoyue strain. Titers of 20-Hydroxyecdysone and the ultraspiracle 1 mRNA expression in the Liangguang NO.2 strain were upregulated by high temperature, which might be associated with the induction of autophagy. These results demonstrate the potentially regulatory mechanism of autophagy in silkworms' tolerance to high temperature, providing a theoretical basis for exploring the physiological mechanism of thermotolerance in insects.