Archives of Insect Biochemistry and Physiology最新文献

Mitochondrial genome is a powerful tool for studying evolutionary biology, because it is affected by niche adaptation, energy requirements and phenotypic plasticity of organisms. Generalizations about mitogenome evolution are tricky and lead to inconsistent results. The mitogenome can contain lesser mutations than expected and escape mutational meltdown only through the balance of mutation-selection-drift. The state of equilibrium can be achieved by not being significantly affected by any evolutionary process. The reduction of variation by selective sweeps or background selection due to selection and the results of negative purifying selection by the mechanism of genetic drafting exhibit the same effect: reduction of variation on rapidly adapting genes by positive selection and rapid removal of variation from the population due to important functional limitations. Apis mellifera represents a unique model for studying mitogenome evolution, thanks to the characters about adaptation related with life style and biochemistry related with energy requirement. The evolutionary drivers of A. mellifera mitogenomes were tested using 66 mitogenome data representing 21 subspecies. First, processes of mutations/variations were evaluated in nucleotide content and its attitudes. The genome-wide mutational processes were estimated via the abundance of rearrangements and ORF remnants. Selection forces acting on mitogenomes were tested in protein-coding genes. The direction of selection was predicted using a phylogenetic tree- based inferences, and the effects of differences on the possible 3D structures of the proteins were examined. In A. mellifera mitogenomes, the mutation-selection-drift balance was biased to deviation. The balance seems to be maintained by relaxed selection phenomenon, which affects mitogenome quite indirectly. It appears to affect the total mitogenome via copies or “remnants” of the gene, without affecting the mitogenome/mitochondrial gene at the protein level, or even without major changes in the “real” nucleotide sequences of the gene. It does this by inserting repetitive sequences into the d-loop, conserved and possibly functional gene remnants (atp8) into rRNA genes, and affecting the entire genome largely through selective sweeps. Additionally, nd3 gene was positively selected in A. mellifera mitogenomes.

ATP-binding cassette (ABC) transporters constitute a ubiquitous transmembrane protein family that are required for several physiological and metabolic processes in insects. While their structure and function have been discussed in Lepidopteran, Dipteran, Coleopteran, and various other insects, their role in Thysanoptera remains uncharacterized. Here, a genome-wide identification of ABC transporters in Megalurothrips usitatus (MusABCs) were performed using comparative genomics, structural validation, and phylogenetic analysis. Expression analysis and validation were conducted via transcriptomics and qRT-PCR. A total of 53 MusABCs were identified, which were classified into eight subfamilies (ABCA–ABCH), with notable clusters in ABCG (19 genes), ABCC (13 genes), and ABCH (7 genes). The expansion of MusABCC, MusABCG, and MusABCH subfamilies may suggest their critical roles in M. usitatus. Structural analysis suggested MusABCs containing motifs 3, 4, 6, 7, 8 and 10 may be associated with substrate transport and drug efflux. All MusABCs were expressed throughout the development of M. usitatus, with MusABCC3, MusABCG18, and MusABCH3 varying significantly across the stages. Furthermore, MusABCC3, MusABCH3, along with MusABCB1 and MusABCC10 exhibited distinct responses to different insecticides (spinetoram, thiamethoxam, and beta-cypermethrin). MusABCH3 exhibited the most prominent upregulation by 9.33-fold with LC₁₀ of spinetoram and 11.32-fold with LC₃₀ of thiamethoxam, and uniquely upregulated by beta-cypermethrin among the four genes. A total of 41 orthologous MusABCs were identified, and their potential function in the development and insecticide resistance has been discussed. This study provides a comprehensive genomic resource for MusABCs, offering potential targets for management strategies on thrips.

The prevailing view has always been that insects only have innate immune defenses and do not have acquired immune defenses. However, recent studies have shown that some insects exhibit immune priming, which means they can initiate an effective immune response upon secondary pathogen infection, thereby protecting themselves from reinfection. Interestingly, this immune protection effect can not only be generated in the parent generation but also be transmitted to the offspring, thus protecting the offspring from the same pathogen infection. This phenomenon is known as transgenerational immune priming (TGIP). However, research on TGIP in insects is still in its infancy, and many unknown questions do not have perfect answers. In this review, we will systematically review the factors that induce TGIP in insects, analyze the molecular mechanisms that induce TGIP, and ultimately expect to provide theoretical support and development directions for the study of TGIP in insects.

Fatty acid desaturase (FAD) serves as a pivotal enzyme in the lipid synthesis pathway, regulating fatty acid unsaturation levels in insects through catalytic activity. While FAR, another crucial enzyme in the same pathway, has been demonstrated to influence the integument architecture of the brown planthopper (BPH), the functional role of FAD in this biological process remains insufficiently explored. In the present investigation, we systematically identified 10 NlFAD family genes through bioinformatics analysis and subsequently characterized their expression patterns using real-time quantitative polymerase chain reaction (RT-qPCR). Through integrated approaches combining RNA interference (RNAi), transmission electron microscopy (TEM), and targeted fatty acid metabolomics, we elucidated the regulatory effects of NlFAD silencing on both integument ultrastructure and fatty acid biosynthesis in BPH. Key findings revealed that NlFAD3 knockdown induced: Silencing of NlFAD3 resulted in a significant increase in the mortality rate of BPH, the highest percentage of moulting deaths, the phenomenon of significant disruption of its integument structure, and a significant increase in the content of BPH stearic acid. This study provides a new research idea for the search of effective target genes to realize the effective control of BPH.

In insects, heat shock proteins (HSPs) are crucial for protecting against environmental stressors, particularly insecticides. However, in the important agricultural pest Agrotis ipsilon, the specific protective function provided by HSPs against different insecticides remains unclear. Herein, we identified a small HSP (sHSP) gene in A. ipsilon: AisHSP19.6. Peak AisHSP19.6 expression occurred during the sixth-instar larval stage in the larval midgut. Treatment with phoxim (PHO), lambda-cyhalothrin (LCT), and chlorantraniliprole (CAP) causes oxidative stress in A. ipsilon larvae. Furthermore, PHO, LCT, and CAP exposure, as well as H₂O₂ injection, significantly elevated AisHSP19.6 transcription. Although AisHSP19.6 did not metabolize PHO, LCT, and CAP, it protected the cells from oxidative stress. Moreover, A. ipsilon larvae in which AisHSP19.6 was silenced using RNA interference (RNAi), exhibited a significantly higher mortality rate in response to PHO, LCT, and CAP exposure relative to AisHSP19.6-expressing larvae. This study provides new insights into sHSP-mediated insecticide susceptibility in A. ipsilon. These findings also provide a potential RNAi-based strategy for the management of this agricultural pest.

Proteins are essential for insect development, with methionine (Met) being crucial for protein synthesis. However, the roles of methionine and the methionine-rich storage protein 1 (HaSP1) in Helicoverpa armigera larvae remain unclear. In this study, casein removal (-casein) from the larval diet was employed to simulate protein deficiency. Compared with the normal diet control, the -casein group displayed significant reductions in larval body weight and pupation rate, along with markedly increased mortality. Additionally, the methionine content in the fat body and the expression of HaSP1 were both significantly reduced. During larval development, both methionine levels and HaSP1 expression peaked in the late final instar stage. Both 20-hydroxyecdysone (20E) and juvenile hormone (JH) upregulated HaSP1 in midgut. Further RNA interference (RNAi) experiments indicated that knockdown of HaSP1 resulted in decreased larval body weight, increased mortality, and reduced Met content than the Green Fluorescent Protein (dsGFP) control. Furthermore, Methoprene-tolerant 1 (HaMet1) and Hormone Receptor 3 (HaHR3) expression was significantly downregulated upon HaSP1 knockdown. This study revealed that Met was indispensable for larval development and that HaSP1 governed systemic Met levels, thereby playing a pivotal role in larval growth. The findings provide experimental evidence and a theoretical basis for developing green pest-control pesticides that target key genes in nutrient metabolism.

Silkworms (Bombyx Mori) are traditionally reared on mulberry leaves; however, artificial diets have been developed to enable year-round rearing and automation. The physiological performance and cocoon yield of silkworms fed artificial diets remain inferior to those reared on mulberry leaves. We compared growth and nutrient composition in larvae reared on mulberry leaves (ML) and antibiotic-free artificial diet (ADS), and profiled gut microbiota in ML, ADS, and antibiotic-supplemented artificial diet (ADSA) to assess dietary effects on host physiology and microbial ecology. Proximate analysis revealed that protein accumulation was greater in ML-fed larvae, while ADS-fed larvae showed relatively higher fat content at the late fifth instar. Amino acid profiling showed consistently higher silk-related residues (Gly, Ala, Ser) and the derived Silk Amino Acid Index in ML-fed larvae, indicating enhanced fibroin synthesis potential. Microbiome analysis using 16S rRNA amplicon sequencing demonstrated dominance of Enterococcus mundtii in ADS groups, resulting in reduced alpha diversity and uneven community structure. In contrast, ML-fed larvae harbored diverse taxa, including Methylorubrum and Methylobacterium, while ADSA groups exhibited intermediate profiles with occasional dominance of Bacillus cereus. These findings highlight that artificial diet alters host nutrient metabolism and drives dysbiosis of gut microbiota, underscoring the need for optimized formulations and microbiome-stabilizing strategies, such as probiotics or prebiotics.

Spiromesifen is a nonsystemic insecticide that has been primarily recognized for its efficacy against immature stages of whiteflies and mites. However, its activity against adult and egg stages has been less well characterized. In this study, we evaluated its sublethal effects on the reproduction and egg development of the Mediterranean (MED) cryptic species of Bemisia tabaci (Hemiptera: Aleyrodidae). Leaf-dipping bioassays demonstrated that spiromesifen causes significantly higher mortality in nymphs than in eggs and adults. Beyond direct lethality, adult exposure to spiromesifen-treated tomato leaves reduced oviposition rates and disrupted egg development, inducing abnormal egg morphologies in 39.2% and 58.5% of the eggs, respectively, compared with the untreated control. In addition, as the exposure duration increased, egg hatchability declined proportionally, reaching 50.2% compared with the untreated control. These results indicate that spiromesifen has both lethal and sublethal impacts on B. tabaci, combining direct mortality with reproductive suppression. Such dual effects highlight spiromesifen as a promising tool for integrated pest management (IPM) programs, provided it is used judiciously within resistance management frameworks.