Insect Molecular Biology最新文献

Sugars play multiple critical roles in insects, serving as energy sources, carbon skeletons, osmolytes and signalling molecules. The transport of sugars from source to sink via membrane proteins is essential for the uptake, distribution and utilization of sugars across various tissues. Sugar supply and distribution are crucial for insect development, flight, diapause and reproduction. Insect sugar transporters (STs) share significant structural and functional similarities with those in mammals and other higher eukaryotes. However, they exhibit unique characteristics, including differential regulation, substrate selectivity and kinetics. Here, we have discussed structural diversity, evolutionary trends, expression dynamics, mechanisms of action and functional significance of insect STs. The sequence and structural diversity of insect STs, highlighted by the analysis of conserved domains and evolutionary patterns, underpins their functional differentiation and divergence. The review emphasizes the importance of STs in insect metabolism, physiology and stress tolerance. It also discusses how variations in transporter regulation, expression, selectivity and activity contribute to functional differences. Furthermore, we have underlined the potential and necessity of studying these mechanisms and roles to gain a deeper understanding of insect glycobiology. Understanding the regulation and function of sugar transporters is vital for comprehending insect metabolism and physiological potential. This review provides valuable insights into the diverse functionalities of insect STs and their significant roles in metabolism and physiology.

The rice leaf folder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), is a major migratory pest in rice agriculture. This pest is characterised by its larvae's ability to fold rice leaves using silk, a behaviour that culminates in the formation of a silken cocoon during the pupal stage. The fibroin light chain (CmFib-L) gene is crucial for silk production, yet its specific function in C. medinalis has reminded elusive. This study presents a comprehensive analysis of the CmFib-L gene, revealing its complete open reading frame (ORF) and expression patterns. Notably, the gene is highly expressed in the fifth-instar larvae and the silk gland, which are critical stages for silk production. Our experiments demonstrate that silencing the CmFib-L gene leads to a reduction in pupal weight, an extension of the pupal stage and a disorganised silk cocoon. Furthermore, the larval behaviour of leaf folding and spinning is significantly impaired when the expression of CmFib-L is downregulated. These findings not only show the importance of fibroin light chain in silk production but also reveal a new target gene to regulate and control the behaviour and development of C. medinalis.

Evolution of Buchnera-aphid host symbioses is often studied among species at macroevolutionary scales. Investigations within species offer a different perspective about how eco-evolutionary processes shape patterns of genetic variation at microevolutionary scales. Our study leverages new and publicly available whole-genome sequencing data to study Buchnera-aphid host evolution in Myzus persicae, the peach potato aphid, a globally invasive and polyphagous pest. Across 43 different asexual, clonally reproducing isofemale strains, we examined patterns of genomic covariation between Buchnera and their aphid host and considered the distribution of mutations in protein-coding regions of the Buchnera genome. We found Buchnera polymorphisms within aphid strains, suggesting the presence of genetically different Buchnera strains within the same clonal lineage. Genetic distance between pairs of Buchnera samples was positively correlated to genetic distance between their aphid hosts, indicating shared evolutionary histories. However, there was no segregation of genetic variation for both M. persicae and Buchnera with plant host (Brassicaceae and non-tobacco Solanaceae) and no associations between genetic and geographic distance at global or regional spatial scales. Abundance patterns of non-synonymous mutations were similar to synonymous mutations in the Buchnera genome, and both mutation classes had similar site frequency spectra. We hypothesize that a predominance of neutral processes results in the Buchnera of M. persicae to simply 'drift' with the evolutionary trajectory of their aphid hosts. Our study presents a unique microevolutionary characterization of Buchnera-aphid host genomic covariation across multiple aphid clones. This provides a new perspective on the eco-evolutionary processes generating and maintaining polymorphisms in a major pest aphid species and its obligate primary endosymbiont.

MicroRNAs (miRNAs) are post-transcriptional gene regulators. In the miRNA pathway's cytoplasmic part, the miRNA is processed from a hairpin-structured precursor to a double-stranded (ds) mature RNA and ultimately to a single-stranded mature miRNA. In insects, ingesting these two ds forms can regulate the target gene expression; this inspired the trophic miRNA's use as a functional genomics and pest management tool. However, systematic studies enabling comparisons of pre- and mature forms, dosages, administration times and instar-wise effects on target transcripts and phenotypes, which can help develop a miRNA administration method, are unavailable due to the different focuses of the previous investigations. We investigated the impact of trophically delivered Px-let-7 miRNA on the lepidopteran pest Plutella xylostella, to compare the efficacies of its pre- and ds-mature forms. Continuous feeding on the miRNA-supplemented diet suppressed expressions of FTZ-F1 and E74, the target ecdysone pathway genes. Both the pre-let-7 and mature let-7 miRNA forms similarly downregulated the target transcripts in all four larval instars. Pre-let-7 and let-7 ingestions decreased larval mass and instar duration and increased mortality in all instars, exhibiting adverse effects on larval growth and development. miRNA processing Dicer-1 and AGO-1's upregulations upon miRNA ingestion denoted the systemic miRNA spread in larval tissues. The scrambled sequence controls did not affect the target transcripts, suggesting the sequence-specific targeting by the mature miRNA and hairpin cassette's non-involvement in the target downregulation. This work provides a framework for miRNA and target gene function analyses and potentiates the trophic miRNA's utility in pest management.

The brain of adult honeybee (Apis mellifera) workers is larger than that of queens, facilitating behavioural differentiation between the castes. This brain diphenism develops during the pharate-adult stage and is driven by a caste-specific gene expression cascade in response to unique hormonal milieus. Previous molecular screening identified minibrain (mnb; DYRK1A) as a potential regulator in this process. Here, we used RNAi approach to reduce mnb transcript levels and test its role on brain diphenism development in honeybees. White-eyed unpigmented cuticle worker pupae were injected with dsRNA for mnb (Mnb-i) or gfp, and their phenotypes were assessed two and 8 days later using classic histological and transcriptomic analyses. After 2 days of the injections, Mnb-i bees showed 98% of downregulation of mnb transcripts. After 8 days, the brain of Mnb-i bees showed reduction in total volume and in the volume of the mushroom bodies (MB), antennal, and optic lobes. Additionally, signs of apoptosis were observed in the Kenyon cells region of the MB, and the cohesion of the brain tissues was affected. Our transcriptomic analyses revealed that 226 genes were affected by the knockdown of mnb transcripts, most of which allowing axonal fasciculation. These results suggest the evolutionary conserved mnb gene has been co-opted for promoting hormone-mediated developmental brain morphological plasticity generating caste diphenism in honeybees.

Sex determination pathways regulate male and female-specific development and differentiation and offer potential targets for genetic pest management methods. Insect sex determination pathways are comprised of primary signals, relay genes and terminal genes. Primary signals of coleopteran, dipteran, hymenopteran and lepidopteran species are highly diverse and regulate the sex-specific splicing of relay genes based on the primary signal dosage, amino acid composition or the interaction with paternally inherited genes. In coleopterans, hymenopterans and some dipterans, relay genes are Transformer orthologs from the serine-arginine protein family that regulate sex-specific splicing of the terminal genes. Alternative genes regulate the splicing of the terminal genes in dipterans that lack Transformer orthologs and lepidopterans. Doublesex and Fruitless orthologs are the terminal genes. Doublesex and Fruitless orthologs are highly conserved zinc-finger proteins that regulate the expression of downstream proteins influencing physical traits and courtship behaviours in a sex-specific manner. Genetic pest management methods can use different mechanisms to exploit or disrupt female-specific regions of different sex determination genes. Female-specific regions of sex determination genes can be exploited to produce a lethal gene only in females or disrupted to impede female development or fertility. Reducing the number of fertile females in pest populations creates a male-biased sex ratio and eventually leads to the local elimination of the pest population. Knowledge on the genetic basis of sex determination is important to enable these sex determination pathways to be exploited for genetic pest management.

Starvation can induce autophagy and apoptosis in intestinal cells. To elucidate the underlying mechanisms, we investigated autophagy and apoptosis in the midgut of the model insect, silkworm (Bombyx mori), focusing on calcium homeostasis. The results indicated that the body weight of silkworms decreased, along with damage to the morphology of their digestive tracts and midguts after starvation treatment. Additionally, mitochondrial swelling, autophagy and apoptosis were observable. Further investigation revealed that starvation upregulated the transcription of Ca²⁺ release channel-associated genes (e.g., BmIP3R, BmRyR) but suppressed the expression of Ca²⁺ efflux genes (BmPMCA), resulting in Ca²⁺ overload in midgut cells and subsequent upregulation of BmCalpain transcription. In addition, starvation increased the transcription of key autophagy genes (BmATG5, BmATG7, BmATG8) and the expression of the LC3-II protein. Upon prolonged starvation, the NtATG5 protein levels increased, a process that facilitated the transition from autophagy to apoptosis. These results indicate that Ca²⁺ overload activates the calpain-mediated apoptosis pathway and promotes apoptosis of midgut cells. The present study reveals the significant role that Ca²⁺ plays in the occurrence and transformation of autophagy and apoptosis induced by starvation treatment, thus providing a new research strategy for investigating the damage caused by starvation in biological organisms.

Insect NF-κB-like factor, Relish, is activated by viral infection and induces the production of antiviral proteins. In this study, we performed a transcriptomic analysis of BmE cells expressing the active form of BmRelish (BmRelish_act) and identified BmVago-like as the most strongly-induced secreted-protein. Expression of BmVago-like was specifically triggered by Bombyx mori Nucleo Polyhedro Virus (BmNPV) infection and regulated by BmSTING-BmRelish pathway. Incubating the fresh culture of cells with supernatant medium of BmVago-like expressing cells or recombinant BmVago-like protein (rBmVago-like) significantly increased antiviral resistance. On the contrary, reducing the expression of Bmvago-like by RNA interference (RNAi) in BmE cells as well as in silkworm larvae impaired antiviral response. Furthermore, we constructed transgenic silkworm line over-expressing BmVago-like (BmVago-like^OV) and found they had markedly lower viral load and higher survival rate after BmNPV infection compared with the wild-type control. Co-immunoprecipitation assay showed Bmintegrin β1 interacts with BmVago-like and it was involved in BmVago-like mediated antiviral response. Finally, we found the expression level of signalling molecules in the JAK-STAT pathway increased in rBmVago-like-treated cells and BmVago-like^OV silkworm larvae but decreased in RNAi-treated cells. In summary, our research uncovered an inducible antiviral response in silkworm mediated by cytokine BmVago-like, which is the downstream effector of BmSTING-BmRelish pathway and functions as an antiviral cytokine.

Dermestes frischii Kugelann, 1792 is a storage pest worldwide, and is important for estimating the postmortem interval in forensic entomology. However, because of the lack of transcriptome and genome resources, population genetics and biological control studies on D. frischii have been hindered. Here, single-molecule real-time sequencing and next-generation sequencing were combined to generate the full-length transcriptome of the five developmental stages of D. frischii, namely egg, young larva, mature larva, pupa and adult. A total of 41,665 full-length non-chimeric sequences and 59,385 non-redundant transcripts were generated, of which 42,756 were annotated in public databases. Using the weighted gene co-expression network analysis, gene co-expression modules related to the five developmental stages were constructed and screened, and the genes in these modules were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. The expression patterns of the differentially expressed genes (DEGs) related to olfaction and insect hormone biosynthesis were also explored. Transcription of most odorant binding proteins was up-regulated in the adult stage, suggesting they are important for foraging in adults. Many genes encoding for the ecdysone-inducible protein were up-regulated in the pupal stage, may be mainly responsible for the tissue remodelling of metamorphosis. The results of the quantitative real-time polymerase chain reaction (qRT-PCR) were consistent with the RNA-seq results. This is the first full-length transcriptome sequencing of dermestids, and the data obtained here are vital for understanding the stage-specific development and olfactory system of D. frischii, providing valuable resources for storage pest and forensic research.

Adipokinetic hormone (AKH), a crucial neuropeptide, participates in the important physiological processes by specially binding to its receptor to activate the AKH signalling pathway. AKH regulates energy metabolism. However, it remains unknown whether AKH affects larval development and adult reproduction by influencing energy metabolism. In the present study, the AKH was identified from Panonychus citri and contained the conserved functional domain 'Q-[LIV]-[NT]-F-[ST]-X (2)-W' that characterises the AKH family. The relative expression levels of PcAKH revealed different patterns of AKH expression at different developmental stages of P. citri. Feeding of double-standard RNA against PcAKH induced decreased fecundity and reduced survival, which was accompanied by the down-regulation of vitellogenin gene expression. In addition, after silencing the PcAKH, lipid metabolism and carbohydrate homeostasis were disrupted, manifested by increased body width and weight, and fasting phenomenon. Further investigation found that compared with the control, physiological changes in trehalose and triglyceride contents were accompanied by variations in the mRNA expression levels of genes related to lipid metabolism and carbohydrate metabolism. The disorder of lipid and carbohydrate metabolism may affect adult female reproduction, which may lead to insufficient vitellogenin deposition. Moreover, the silencing of PcAKH seriously affected the growth and development of larvae, which was manifested as delayed development period and difficulty in moulting. Conclusively, all these results in current study demonstrated that double-stranded RNA silencing system targeting PcAKH effectively inhibited larval development and female fecundity by disturbing lipid and carbohydrate metabolism, and PcAKH is a specific RNAi target for control of P. citri in the design and development of biopesticide in sustainable agriculture.