Search

Helicoverpa armigera and Aphis gossypii are two important insect species that feed on cotton plants. These insects have distinct abilities to induce plant resistance and tolerate plant toxins, which results in interspecific competition imbalance that may be fatal to the low-tolerance A. gossypii and force these insects to develop avoidance behaviors and subsequently separate from their niche. We implemented ecological experiments to test the effects of H. armigera-induced plant resistance and behavioral avoidance in A. gossypii, and employed transcriptomics and metabolomics analyses to reveal changes in resistance genes and metabolites in plants.Our results demonstrate that cotton plants induced by H. armigera cause significant inhibitory and avoidance effects on A. gossypii insect populations. Electrical penetration graph (EPG) analysis showed changes in plant resistance induced by H. armigera leading to a decreased feeding efficiency of A. gossypii. In addition, genes associated with jasmonic acid and ethylene signaling pathways were significantly up-regulated in cotton plants after H. armigera induction, which led to a significant up-regulation of metabolites inducing plant resistance. These observations were corroborated by bioactivity analysis on metabolites, which showed that jasmonic acid, gossypol and tannins have significant inhibitory effects on A. gossypii populations. In contrast, methylparaben is associated with avoidance behaviors on A. gossypii populations.Our study suggests that the differences in the ability to induce plant resistance and tolerance between two non-predatory insects were lethal to low-tolerance A. gossypii insects, which might be a major factor determining their niche differentiation. This was further demonstrated by screening anti-insect and bio-hormonal metabolites. Our study provides a reference for investigating the evolutionary relationship between non-predatory insects and insights to implement effective insect biocontrol. © 2022 Society of Chemical Industry.

Cytochrome P450 monooxygenase (P450 or CYP) plays an important role in the metabolism of insecticides and plant allelochemicals by insects. CYP321B1, a novel Spodoptera litura P450 gene, was identified and characterized. CYP321B1 contains a 1488 bp open reading frame (ORF) that encodes a 495 amino acid protein. In fourth instar larvae, the highest CYP321B1 expression levels were found in the midgut and fat body. In the tannin feeding test, tannin can significantly induce the expression of CYP321B1 in the midgut and fat body of 4th instar larvae. To verify the function of CYP321B1, RNA interference and metabolome analysis were performed. The results showed that silencing CYP321B1 significantly reduced the rate of weight gain under tannin induction. Metabolome analysis showed silencing affected 47 different metabolites, mainly involved in secondary metabolite biosynthesis and amino acid metabolism, including amino acids, lipid fatty acids, organic acids and their derivatives. Henoxyacetic acid and cysteamine are the most highly regulated metabolites, respectively. These findings demonstrate that CYP321B1 plays an important role in tannin detoxification and metabolism. Functional knowledge about metabolite detoxification genes in this major herbivorous insect pest can provide new insights into this biological process and provide new targets for agricultural pest control.

Insect endosymbionts are widespread in nature and known to play key roles in regulating host biology. As a secondary endosymbiont, bacteria in the genus Hamiltonella help cotton aphids (Aphis gossypii) defend against parasitism by parasitoid wasps, however, the potential negative impacts of these bacteria on cotton aphid biology remain largely unclear.This study aims to evaluate the potential impacts of Hamiltonella on the growth and development of cotton aphids based on life table parameters and RNA sequencing. The results showed that infection with Hamiltonella resulted in smaller body type and lower body weight in aphids. Compared to the control group, there were significant differences in the finite and intrinsic rates of increase and mean generation time. Furthermore, the RNA sequencing data revealed that the genes related to energy synthesis and nutrient metabolism pathways were significantly downregulated and genes related to molting and nervous system pathways were significantly upregulated in the Hamiltonella population.Our results confirm that Hamiltonella retarded the growth and development of cotton aphids accompanied by the downregulation of genes related to energy synthesis and nutrient metabolism, which provides new insights into aphid-symbiont interactions and may support the development of improved aphid management strategies. © 2022 Society of Chemical Industry.

The lady beetle Propylea japonica is a dominant natural predator of insect pests in farmland ecosystems and an important non-target indicator insect for the environmental safety assessment of GM crops. The commercial cultivation of GM crops may cause P. japonica to frequently be exposed to the Bt protein environment. In this study, the biological characteristics, enzyme activity, and expression levels of detoxification and metabolism in P. japonica were studied after Cry1B protein treatment. No significant differences were observed in developmental duration, emergence rate, or body weight at different ages after feeding larvae 0.5 mg/mL of Cry1B protein compared with the control. Furthermore, there were no significant differences in the activities of glutathione S-transferase (GST), catalase (CAT), and peroxidase (POD) after feeding 0.25 mg/mL and 0.5 mg/mL Cry1B protein. However, when the concentration of Cry1B protein increased to 1.0 mg/mL, the activities of the GST, CAT, and POD increased significantly. Compared with the control group, there were no significant differences in the expression levels of most detoxification metabolism related genes; only a few genes had changed expression levels at the individual concentrations (CYP345B1, CYP4Q2, CYP9F2, GST, and microsomal GST). Overall, these results suggest that Cry1B protein has little or no effect on the biological characteristics of P. japonica. Genes related to enzyme activity and detoxification are differentially expressed at high concentration stimulation. Therefore, this research suggests that the potential risks of Cry1B for the predator P. japonica are negligible.

Background Aphis gossypii, a polyphagous and recurrent pest induced by pesticides, causes tremendous loss in the yield of crops each year. Previous studies of pesticide-induced sublethal effects mechanism mainly focus on gene level. The symbiotic bacteria are also important participants of this mechanism, but their roles in hormesis are still unclear. Results In this study, life table parameters and 16S rRNA sequencing were applied to evaluate the sublethal and transgenerational effects of sulfoxaflor on adult A. gossypii after 24-h LC20 (6.96 mg L-1 ) concentration exposure. The results indicated that the LC20 of sulfoxaflor significantly reduced the finite rate of increase (λ) and net reproductive rate (R0 ) of parent generation (G0), and significantly increased mean generation time (T) of G1 and G2, but not of G3 and G4. Both reproductive period and fecundity of G1 and G2 were significantly higher than those of the control. Furthermore, our sequencing data revealed that more than 95% bacterial communities were dominated by the phylum Proteobacteria, in which the maximum proportion genus was the primary symbiont Buchnera and the facultative symbiont Arsenophonus. Compared to those of the control, the abundance and composition of symbiotic bacteria of A. gossypii for three successive generations (G0-G2) were changed after G0 A. gossypii was exposed to sulfoxaflor: the diversity of the bacterial community was decreased, but the abundance of Buchnera was increased (G0), while the abundance of Arsenophonus was decreased. Contrary to G0, G1 and G2 cotton aphid exhibited an increased relative abundance of Arsenophonus in sublethal treatment group. Conclusion Taken together, our results provide an insight into the interactions among pesticide resistance, aphids, and symbionts, which will eventually help to better manage the resurgence of A. gossypii. This article is protected by copyright. All rights reserved.

In insects, cytochrome P450 monooxygenases (P450s or CYPs) play an important role in the detoxification and metabolism of exogenous plant allelochemicals. In this study, a P450 gene CYP6AB12 was identified and characterized from Spodoptera litura. The cDNA contains an open reading frame (ORF) encoding 511 amino acid residues. CYP6AB12 was expressed at different ages of S. litura, with the highest levels found in the third and fourth instar larvae. Its highest expression was found in the midgut and fat body of fourth instar larvae fed with gossypol. Moreover, these expression levels were substantially increased compared with those from larvae fed with control diet. Gene silencing was then conducted by smearing dsRNA mixed with nanomaterials onto the cuticle. CYP6AB12 expression was significantly decreased in the midgut and fat body, and the net weight increase was substantially lower than that of the control group, indicating that the treatment group had more sensitivity to gossypol than the control. These results reveal that CYP6AB12 plays an important role in the detoxification and metabolism of gossypol, thus further confirming that P450s have a broad ability to detoxify and metabolize plant allelochemicals. It provides an important molecular basis for the exploration of detoxification metabolism and pest control of S. litura.

Background Endosymbiotic bacteria have been reported to mediate interactions between parasitoids and their insect hosts. How parasitic wasps influence changes in host microbial communities and the relationship between them are of great importance to the study of host-parasitoid co-evolutionary and ecological interactions. However, these interactions remain largely unreported for interactions between in Aphis gossypii and Lysiphlebia japonica. Results In this study, we characterize the bacterial microbiota of L. japonica wasps at different developmental stages and monitor changes over time in the bacterial microbiota of their parasitized and non-parasitized aphid hosts, using metagenomic analysis of 16S rDNA sequencing data. Proteobacteria, Firmicutes, and Actinobacteria were the three most abundant bacterial phyla identified in L. japonica. We found that parasitism was associated with an increased abundance of Buchnera nutritional endosymbionts, but decreased abundance of Acinetobacter, Arsenophonus, Candidatus_Hamiltonella, and Pseudomonas facultative symbionts in aphid hosts. Functional analysis of enriched pathways of parasitized aphids showed significant differences in the 'transport and metabolism of carbohydrates' and 'amino acid, lipid, and coenzyme biosynthesis' pathways. Notably, the composition of symbiotic bacteria in wasp larvae was highly similar to that of their aphid hosts, especially the high abundance of Buchnera. Conclusion The results provide a conceptual framework for L. japonica interactions with A. gossypii in which the exchange of symbiotic microbes provides a means by which microbiota can potentially serve as evolutionary drivers of complex, multilevel interactions underlying the ecology and co-evolution of these hosts and parasites. This article is protected by copyright. All rights reserved.

Lysiphlebia japonica (Ashmead) is a predominant parasitoid of cotton-melon aphids in the fields of northern China with a proven ability to effectively control cotton aphid populations in early summer. For accurate normalization of gene expression in L. japonica using quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR), reference genes with stable gene expression patterns are essential. However, no appropriate reference genes is L. japonica have been investigated to date. In the present study, 12 selected housekeeping genes from L. japonica were cloned. We evaluated the stability of these genes under various experimental treatments by RT-qPCR using four independent (geNorm, NormFinder, BestKeeper and Delta Ct) and one comparative (RefFinder) algorithm. We identified genes showing the most stable levels of expression: DIMT, 18S rRNA, and RPL13 during different stages; AK, RPL13, and TBP among sexes; EF1A, PPI, and RPL27 in different tissues, and EF1A, RPL13, and PPI in adults fed on different diets. Moreover, the expression profile of a target gene (odorant receptor 1, OR1) studied during the developmental stages confirms the reliability of the chosen selected reference genes. This study provides for the first time a comprehensive list of suitable reference genes for gene expression studies in L. japonica and will benefit subsequent genomics and functional genomics research on this natural enemy.

Common varieties of genetically modified (GM) cotton increasingly display insect-resistant properties via expression of bacterial-derived toxins from Bacillus thuringiensis (Bt). This necessitates a deeper understanding of the possible effects of these crops on non-target insects. The mirid bug Apolygus lucorum is a major pest in cotton production in China, however, the effect of GM cotton on this non-target species is currently virtually unknown. This insect is exposed to these transgenic plants by consuming genetically modified (GM) leaves. In this study, laboratory experiments were conducted to assess the toxicity of CCRI41 and CCRI45, (genetically modified cotton varieties which express the toxins Cry1Ac and CpTI (Cowpea Trypsin Inhibitor)) on nymphs and adults of A. lucorum. There was no detectable increase in mortality after A. lucorum fed on GM cotton leaves for 20 days. While we detected trace amounts of Cry1Ac proteins in both A. lucorum nymphs and adults (10 ng/g fresh weight), the expression of genes related to detoxification did not detectably differ from those feeding on non-GM cotton. Our binding assays did not show Cry1Ac binding to receptors on the midgut brush border membrane from either A. lucorum nymphs or adults. Our findings collectively indicate that feeding on leaves of the GM cotton varieties CCRI41 and CCRI45 have few toxic effects on A. lucorum.