Archives of Insect Biochemistry and Physiology最新文献

Hygienic behavior (HB) is a crucial biological mechanism in honeybees that is associated with disease resistance. This study aimed to investigate the effect of the SNP18 sequence and environmental factors on the HB of honey bees, using a total of 14 colonies and 148 bee samples from seven different bee breeds. Association analysis revealed that colonies with Italian hybrids (IH) or young queens statistically (p < 0.01) exhibited high hygienic behavior (HHB). HB increased by 71.6% when the number of frames in the colony, representing colony power (CP), increased by one (p < 0.05). In restriction fragment length polymorphism (RFLP) analysis, novel mutations in the MlyI polymorphism of the SNP18 sequence were firstly found in Apis mellifera. In addition, the restriction fragments of the novel variants of the SNP18 HHB and SNP18 low hygienic behavior (LHB) lines were determined by sequencing. In this study, several important findings emerged: Due to one-base differences in the restriction fragment, this sequence could not be genotyped by RFLP. Honeybees could be homozygous (HHB or LHB) or heterozygous (HHB and LHB) for the SNP18. SNP18 sequence could be located in different regions of the chromosome and could only be determined by genome sequencing. Finally, since genotypes cannot be clearly determined, no specific allele or genotype can be recommended for HB selection in beekeeping. Therefore, additional research is required to assess discovered novel variants for genetic selection of HHB for ecological beekeeping, healthy products and sustainability.

The damage caused by Megalurothrips usitatus, a common pest, has significantly affected the Chinese vegetable industry. The inappropriate application of chemical pesticides has caused M. usitatus to become highly resistant to conventional insecticides. Glutathione S-transferase (GST), known for its multifunctional properties, contributes to detoxification and antioxidation. It enhances insects' adaptability to pesticides by facilitating the elimination of lipid peroxidation products resulting from pyrethroid insecticides. This research employed RT-qPCR to identify GST genes that exhibited significant expression in response to lambda-cyhalothrin stress. It also quantified changes in antioxidant and apoptosis markers within the M. usitatus under lambda-cyhalothrin exposure. The functional significance of GST was validated by assessing alterations in the antioxidant defense system and resistance to lambda-cyhalothrin following the inhibition of GST activity. The study's outcomes indicated that MuGSTs1 was markedly upregulated in response to lambda-cyhalothrin stress (p < 0.0001). The GST activity was effectively suppressed by the specific inhibitor, diethyl maleate, achieving an inhibition rate of 64.05%. Following the inhibition of GST, the overall antioxidant capacity was reduced by 3.1-fold compared with the control, and the M. usitatus exhibited a 7.91-fold increase in sensitivity to lambda-cyhalothrin. These findings confirm the pivotal role of GST in the oxidative stress response of the M. usitatus and their contribution to the development of resistance to lambda-cyhalothrin through enhanced antioxidant defenses. This research offers valuable perspectives on the adaptive reactions of insects to chemical stressors, facilitating the management of resistance and the formulation of effective pest control strategies.

Glucose-regulated protein 78 (Grp78), a crucial molecular chaperone in the endoplasmic reticulum, has been extensively investigated in vertebrates. However, its functional exploration in insects remains limited. This study cloned the full-length cDNA sequence of Grp78 in Plutella xylostella (L.), which is 2583 bp long. The open reading frame (ORF) is 2004 bp in length and encodes a total of 667 amino acids, including three conserved characteristic sequences of the HSP70 family. PxGrp78 is expressed in various developmental stages of P. xylostella, with the highest expression observed in third instar larvae and higher expression in female adults compared to male adults. The interference with PxGrp78 in female adults was found to significantly reduce the quantity of egg laying and the hatching rate, as well as shorten the oviposition period and down-regulate the expression of the PxVg gene. These results suggested an important role for PxGrp78 in the reproduction of P. xylostella.

In multicellular organisms, the indole melatonin synthesized by aralkylamine N-acetyltransferase (AANATI) serves as an antioxidant. To test this, sex-mixed 3-day-old mated fly adults bw¹ and AANAT1 homozygous recessive loss-of-function mutant (bw AANAT1^lo) of Drosophila melanogaster were fed by a standard diet or by one containing paraquat (PQ, 1,1′-dimethyl-4,4′-bipyridilium dichloride hydrate) at a final concentration of 15.5 mM. Experiment lasted 8 h and began at 11 a.m. In bw¹ flies the paraquat treatment resulted in a significant (evaluated by Student's t-tests) decrease of the superoxide dismutase (SOD) activity and an increase the catalase (CAT) and glutathione S-transferase (GST) activities. Meanwhile, in these flies, total Antioxidative capacity (TAC) was significantly curbed by the paraquat presence. Importantly, these changes were not observed in the AANAT1-mutants. Thus, melatonin seems to play an important defence role against the oxidative stress elicited by paraquat.

Insects have important symbiotic relationships with their intestinal microbiota. The intestinal microbiota is involved in or influences various processes in insects such as development, metabolism, immunity, and reproduction. Currently, research on the intestinal microbiota of parasitic insects is still in its early stages. The tachinid parasitoid Exorista sorbillans is a dipteran parasitic insect, with the silkworm (Bombyx mori) being its main host. Silkworms parasitized by E. sorbillans can suffer from severe silkworm maggot disease, which also poses a serious threat to sericulture. In this study, the intestinal microbiota of larval E. sorbillans at three instar stages was analyzed using 16S rRNA amplicon sequencing to explore the community composition of the intestinal microbiota. Additionally, using conventional culture methods, six cultivable strains were isolated and identified from the larval E. sorbillans on an antibiotic-free LB medium, and four cultivable strains were isolated and identified from the hemolymph of parasitized silkworms. This study investigated the E. sorbillans from the perspective of intestinal microbiota, elucidating the composition and structural characteristics of the intestinal microbiota of the tachinid parasitoid, and preliminarily discussing the functional roles of several major microorganisms, which helps to further clarify the potential mechanisms of interaction between the parasitoid and the silkworm.

Prostaglandin E₂ (PGE₂) is an eicosanoid that mediates a range of physiological actions in vertebrates and invertebrates, including reproduction and immunity. The PGE₂ receptor was identified and functionally assessed in two lepidopteran insects, Manduca sexta and Spodoptera exigua. However, its binding affinity to the receptor has not been reported. The PGE₂ receptor is a G-protein coupled receptor (GPCR) although its corresponding G-protein is not identified. PGE₂ binding assays were performed with membrane preparations from hemocytes of M. sexta larvae. We recorded an optimal binding in 4 h reactions conducted at pH 7.5 with 12 nM tritium-labeled PGE₂. We found that hemocytes express a single population of PGE₂ binding sites with a high affinity (Kd = 35 pmol/mg protein), which are specific and saturable. The outcomes of experiments on the influence of purine nucleotides suggested these are functional GPCRs. A bioinformatics analysis led to a proposed trimeric G-protein in the S. exigua transcriptome, in which the Gα subunit is classified into five different types: Gα(o), Gα(q), Gα(s), Gα(12), and Gα(f). After confirming expressions of these five types in S. exigua, individual RNA interference (RNAi) treatments were applied to the larvae using gene-specific double-stranded RNAs. RNAi treatments specific to Gα(s) or Gα(12) gene expression significantly suppressed the cellular immune responses although the RNAi treatments specific to other three Gα components did not. While PGE₂ treatments led to elevated hemocyte cAMP or Ca²⁺ levels, the RNAi treatments specific to Gα(s) or Gα(12) genes led to significantly reduced second messenger levels under PGE_2, although the RNAi treatments specific to the other three Gα components did not. These results showed that the PGE₂ receptor has high PGE₂ affinity in the nanomolar range and binds G-proteins containing a Gα(s) or Gα(12) trimeric component in S. exigua and M. sexta, and likely, all lepidopteran insects.

Furanocoumarins are a class of chemical compounds with phototoxic properties. For herbivores, efficient detoxification of such defense compounds is the prerequisite to feed successfully on furanocoumarin-containing plants. The cotton bollworm Helicoverpa armigera is a very important polyphagous pest in agriculture, but how it copes with toxic furanocoumarins in some of its host plants is not well understood. Given that cytochrome P450s are well known for their capacity in xenobiotic metabolism, this study attempted to explore the potential roles of cytochrome P450s in furanocoumarin transformation in this pest. Our data showed that two linear structures (psoralen and xanthotoxin) could be metabolized by three recombinant CYP9A enzymes, but no detectable depletion was observed for the linear one with the 8-dimethylallyloxy substituent on the coumarin moiety (imperatorin) and the angular furanocoumarin (angelicin). Initial epoxidation of the double bond connecting C2' and C3' of the furano ring following by cleavage of the epoxidated furan ring, leading to the formation of more soluble, less reactive and nonphotosensitizing metabolites, was identified as a common mechanism of linear furanocoumarin metabolism using a quadrupole/time-of-flight (Q-TOF) mass spectrometry interfaced with a high performance liquid chromatography (HPLC) system. Our data demonstrated that multiple P450s were involved in the detoxification of linear furanocoumarins in the cotton bollworm. These findings contribute to a better understanding of the biochemical basis of adaptation to plant defense chemicals in this economically important pest.

Presently, the European Commission is moving forward with a plan to reduce the use of chemical pesticides and increase the percentage of organic farming by 2030; this plan demands increased availability of biopesticides for organic farming. Glycoalkaloids are a class of molecules found in certain plants, including tomatoes and potatoes, which contain sugar and an alkaloid group. These compounds are known to have insecticidal properties, as they can act as natural defenses against insect pests. This study examined how a biological substance, glycoalkaloids, affects mortality and the retrocerebral complex of two beetle species, Tenebrio molitor and Zophobas atratus. More specifically, we focused on two glycoalkaloids, α-solanine and α-tomatine. Although these two insects belong to the same taxonomic family, they were not equally susceptible to these substances. In the mortality test, we observed that the T. molitor beetle seemed more susceptible, whereas the changes in the retrocerebral complex were more significant in the case of Z. atratus. In general, the effects vary between substances and insects, and changes in the retrocerebral complex may impair the reproduction of insects.

Short-wavelength blue light is ubiquitous in daily life and has a lasting destructive influence. Its potential harm to biological health is significant. This study used Drosophila as a model organism to investigate the protective effects of kaempferol, a flavonoid, against the toxicity of blue light. It also examined its physiological effects on Drosophila under blue light irradiation. In this experiment, fruit flies were fed with three different concentrations of kaempferol solutions (0.1, 0.01, and 0.001 mol/L) dissolved in food. The survival rate and physiological indexes of Drosophila were investigated under blue light irradiation of 2500 lux. The results showed that 0.1 mol/L kaempferol increased the activity of male flies during the day and significantly extended the male survival time under blue light irradiation. However, the study found that kaempferol did not significantly prolong the survival time of Drosophila in the oxidative stress experiment, and no significant difference was observed in the feeding experiment. In summary, our research found that kaempferol, at the concentration of 0.1 mol/L, has a protective effect on Drosophila under blue light irradiation, potentially achieved through alterations in circadian rhythm.

Phosphine fumigation is essential for controlling storage pests like Tribolium castaneum, but its frequent application has resulted in resistance, primarily due to mutations in the Dihydrolipoamide dehydrogenase (DLD) gene associated with the rph2 allele. This study demonstrates that the Patiala population exhibits homozygous resistance variations across populations, contrasting with the susceptibility observed in laboratory cultures. Our assessment of mitochondrial DLD and Cytochrome c oxidase (COX) activities showed significantly elevated levels in the Patiala population, with increases of approximately sevenfold for DLD and 6.92-fold for COX, indicating mitochondrial adaptations for enhanced energy production. Kinetic analyses of DLD in the resistant Patiala population showed a higher V_max (0.005 mmol/min) and a significantly increased Km (16.66 mM), indicating variations in maximal enzyme activity and substrate affinity. Furthermore, resistant T. castaneum populations displayed substantial upregulation of DLD and COX gene expression, with DLD expression increasing by 10.53-fold and COX expression peaking at 102.57-fold in Patiala. Pearson correlation analysis indicated strong positive correlations (r > 0.8) between enzymatic activity and gene expression for both DLD and COX, suggesting a coordinated role in resistance mechanisms. The PCA biplot illustrated distribution patterns of enzymatic activity and gene expression among field-resistant populations, highlighting the association between increased resistance and elevated enzymatic activity and gene expression levels. Therefore, the upregulation of DLD and COX activities in resistant populations underscores their critical roles in counteracting phosphine, reflecting metabolic reprogramming for improved energy production under stress.