Insect Molecular Biology最新文献

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.

Metamorphosis plays an important role in the evolutionary success of insects. Accumulating evidence indicated that microRNAs (miRNAs) are involved in the regulation of processes associated with insect metamorphosis. However, the miRNAs coordinated with juvenile hormone (JH)-regulated metamorphosis remain poorly reported. In the present study, using high-throughput miRNA sequencing combined with Drosophila genetic approaches, we demonstrated that miR-iab-8, which primarily targets homeotic genes to modulate haltere-wing transformation and sterility was up-regulated by JH and involved in JH-mediated metamorphosis. Overexpression of miR-iab-8 in the fat body resulted in delayed development and failure of larval-pupal transition. Furthermore, metabolomic analysis results revealed that overexpression of miR-iab-8 caused severe energy metabolism defects especially the lipid metabolism, resulting in significantly reduced triacylglycerol (TG) content and glycerophospholipids but enhanced accumulation of phosphatidylcholine (PC) and phosphatidylethanolamine (PE). In line with this, Nile red staining demonstrated that during the third larval development, the TG content in the miR-iab-8 overexpression larvae was continuously decreased, which is opposite to the control. Additionally, the transcription levels of genes committed to TG synthesis and breakdown were found to be significantly increased and the expression of genes responsible for glycerophospholipids metabolism were also altered. Overall, we proposed that JH induced miR-iab-8 expression to perturb the lipid metabolism homeostasis especially the TG storage in the fat body, which in turn affected larval growth and metamorphosis.

Insects use seasonal diapause as an alternative strategy to endure adverse seasons. This developmental trajectory is induced by environmental cues like short-day lengths in late summer and early fall, but how insects measure day length is unknown. The circadian clock has been implicated in regulating photoperiodic or seasonal responses in many insects, including the Northern house mosquito, Culex pipiens, which enters adult diapause. To investigate the potential control of diapause by circadian control, we employed ChIP-sequencing to identify the downstream targets of a circadian transcription factor, PAR domain protein 1 (PDP1), that contribute to the hallmark features of diapause. We identified the nearest genes in a 10 kb region of the anticipated PDP1 binding sites, listed prospective targets and searched for PDP1-specific binding sites. By examining the functional relevance to diapause-specific behaviours and modifications such as metabolic pathways, lifespan extension, cell cycle regulation and stress tolerance, eight genes were selected as targets and validated using ChIP-qPCR. In addition, qRT-PCR demonstrated that the mRNA abundance of PDP1 targets increased in the heads of diapausing females during the middle of the scotophase (ZT17) compared with the early photophase (ZT1), in agreement with the peak and trough of PDP1 abundance. Thus, our investigation uncovered the mechanism by which PDP1 might generate a diapause phenotype in insects.

The cabbage stem flea beetle (CSFB, Psylliodes chrysocephala) is a key pest of oilseed rape. The ban on neonicotinoids in the European Union due to environmental concerns and the emergence of pyrethroid-resistant populations have made the control of CSFB extremely challenging. In search of a solution, we have recently shown that RNA interference (RNAi) has potential in the management of CSFB. However, the previously tested target genes for RNAi-mediated pest control (subsequently called target genes) exhibited moderate and slow-acting lethal effects. In this study, 27 double-stranded RNAs (dsRNAs) were orally delivered to identify highly effective target genes in CSFB adults by leveraging the findings of a genome-wide RNAi screen in Tribolium castaneum. Our screen using 500 ng of dsRNA identified 10 moderately effective (> 50% mortality) and 4 highly effective target genes (100% mortality in 8-13 days). The latter mainly included proteasome subunits. Gene expression measurements confirmed target gene silencing and dose-response studies revealed LD₅₀ values as low as ~20 ng in 14 days following a single exposure to dsRNA. Four highly effective dsRNAs also inhibited leaf damage (up to ~75%) and one affected locomotion. The sequences of promising target genes were subjected to in silico target prediction in non-target organisms, for example, beneficials such as honeybees, to design environmentally friendly dsRNAs. Overall, the study provides valuable insights for the development of dsRNA-based insecticides against CSFB.

Insect reproductive capacity can affect effective pest control and infertility studies and has become an important focus in recent molecular genetic research. Nucleosome assembly protein (Nap) is highly conserved across multiple species and is involved in forming the sperm nucleus in many species. We used clustered regularly interspaced palindromic repeats/Cas9 technology to knockout BmNap in Bombyx mori and observed that the mutations caused female infertility, whereas male fertility was not affected. BmNap mutants grew and mated normally; however, female mutants laid smaller eggs that could not be fertilised and did not hatch. In addition, female sterility produced by the mutation could be inherited stably via male mutants; therefore, Nap could be used as a potential target for lepidopteran pest control through population regulation. In the current study, we elucidated a new function of BmNap, increased the understanding of the oogenesis regulation network in Lepidoptera and promoted the development of insect sterility technologies.

The black soldier fly (BSF), Hermetia illucens, has the ability to efficiently bioremediate organic waste into usable bio-compounds. Understanding the impact of domestication and mass rearing on fitness and production traits is therefore important for sustainable production. This study aimed to assess patterns of genomic diversity and its association to phenotypic development across early generations of mass rearing under two selection strategies: selection for greater larval mass (SEL lines) and no direct artificial selection (NS lines). Genome-wide single nucleotide polymorphism (SNP) data were generated using 2bRAD sequencing, while phenotypic traits relating to production and population fitness were measured. Declining patterns of genomic diversity were observed across three generations of captive breeding, with the lowest diversity recorded for the F3 generation of both selection lines, most likely due to founder effects. The SEL cohort displayed statistically significantly greater larval weight com the NS lines with pronounced genetic and phenotypic directional changes across generations. Furthermore, lower genetic and phenotypic diversity, particularly for fitness traits, were evident for SEL lines, illustrating the trade-off between selecting for mass and the resulting decline in population fitness. SNP-based heritability was significant for growth, but was low or non-significant for fitness traits. Genotype–phenotype correlations were observed for traits, but individual locus effect sizes where small and very few of these loci demonstrated a signature for selection. Pronounced genetic drift, due to small effective population sizes, is likely overshadowing the impacts of selection on genomic diversity and consequently phenotypic development. The results hold particular relevance for genetic management and selective breeding for BSF in future.

We highlight the recent 5 years of research that contributed to our understanding of the mechanisms of RNA interference (RNAi) in insects. Since its first discovery, RNAi has contributed enormously as a reverse genetic tool for functional genomic studies. RNAi is also being used in therapeutics, as well as agricultural crop and livestock production and protection. Yet, for the wider application of RNAi, improvement of its potency and delivery technologies is needed. A mechanistic understanding of every step of RNAi, from cellular uptake of RNAi trigger molecules to targeted mRNA degradation, is key for developing an efficient strategy to improve RNAi technology. Insects provide an excellent model for studying the mechanism of RNAi due to species-specific variations in RNAi efficiency. This allows us to perform comparative studies in insect species with different RNAi sensitivity. Understanding the mechanisms of RNAi in different insects can lead to the development of better strategies to improve RNAi and its application to manage agriculturally and medically important insects.

Animal silk is economically important, while silk secretion is a complex and subtle mechanism regulated by many genes. We identified the poly (ADP-ribose) polymerase (PARP1) gene of the silkworm and successfully cloned its coding sequence (CDS) sequence. Using clustered regularly interspaced short palindromic repeat (CRISPR/Cas9) technology, we screened single guide RNA (sgRNA) with high knockout efficiency by cellular experiments and obtained PARP1 mutants by knocking out the PARP1 gene of the silkworm at the individual level. We found that the mutants mainly exhibited phenotypes such as smaller cocoon size and reduced cocoon shell rate than the wild type. We also detected the expression of silk protein genes in the mutant by quantitative real-time PCR (qPCR) and found that the expression of some silk protein genes was slightly down-regulated. Meanwhile, together with the results of transcriptomic analysis, we hypothesized that PARP1 may affect the synthesis of silk proteins, resulting in their failure to function properly. Our study may provide an important reference for future in-depth refinement of the molecular mechanism of silk protein expression in silk-producing animals, as well as a potential idea for future development of molecular breeding lines of silkworms to improve silk production.

Uridine diphosphate (UDP)-glycosyltransferases (UGTs) are important metabolizing enzymes functioning by adding a sugar moiety to a small lipophilic substrate molecule and play critical roles in drug/toxin metabolism for all realms of life. In this study, the silkworm Bombyx mori UGT33D1 gene was characterized in detail. UGT33D1 was found localized in the endoplasmic reticulum (ER) compartment just like other animal UGTs and was mainly expressed in the silkworm midgut. We first reported that UGT33D1 was important to BmNPV infection, as silencing UGT33D1 inhibited the BmNPV infection in silkworm BmN cells, while overexpressing the gene promoted viral infection. The molecular pathways regulated by UGT33D1 were analysed via transcriptome sequencing upon UGT33D1 knockdown, highlighting the important role of the gene in maintaining a balanced oxidoreductive state of the organism. In addition, proteins that physically interact with UGT33D1 were identified through immunoprecipitation and mass spectrometry analysis, which includes tubulin, elongation factor, certain ribosomal proteins, histone proteins and zinc finger proteins that had been previously reported for human UGT-interacting proteins. This study provided preliminary but important functional information on UGT33D1 and is hoped to trigger deeper investigations into silkworm UGTs and their functional mechanisms.