Exposure to Herbicides Prime P450-Mediated Detoxification of Helicoverpa armigera against Insecticide and Fungal Toxin

Cd Exposure Confers Cross-Tolerance of Hyphantria cunea Larvae to β-Cypermethrin through miRNA-Mediated Post-Transcriptional Regulation

Heavy metals are prevalent environmental contaminants in pest habitats. This study investigates the tolerance of Hyphantria cunea larvae to β-cypermethrin under cadmium (Cd) stress. Exposure to Cd markedly enhanced larval tolerance to β-cypermethrin. The P450 enzyme was found to be crucial in triggering this cross-tolerance. Notably, Cd exposure significantly upregulated the expression of HcCYP333A29 and HcCYP6AE184 both before and after β-cypermethrin treatment. Silencing these genes reduced the β-cypermethrin tolerance in Cd-exposed larvae. Furthermore, overexpression of HcCYP333A29 and HcCYP6AE184 significantly improved the tolerance of Sf9 cells and Drosophila to β-cypermethrin. Silencing of HcDicer-1, a key gene in the miRNA synthesis pathway, significantly diminished the β-cypermethrin tolerance in Cd-treated larvae. The miR-2739 controlled overexpression of HcCYP333A29, while miR-2854 controlled HcCYP6AE184 overexpression, both of which were essential for β-cypermethrin cross-tolerance in H. cunea larvae under Cd exposure. Collectively, Cd exposure induces cross-tolerance to β-cypermethrin in H. cunea larvae through miRNA-mediated post-transcriptional regulation.

Binding Properties of the General Odorant-Binding Protein GOBP2 to Herbicides and Insecticides in Spodoptera litura

We previously reported that the general odorant-binding protein GOBP2 enhances chlorpyrifos tolerance in Spodoptera litura by perceiving the herbicides. However, the direct interaction between GOBP2 and pesticides remains unknown. Herein, we verified the effect of the direct binding of GOBP2 to pesticides on the herbicide-induced insecticide tolerance in S. litura. Fluorescence competitive binding assays indicated that GOBP2 exhibits high binding affinities to the herbicide trifluralin and the insecticides indoxacarb, chlorpyrifos, and fipronil, with Ki values ranging from 1.95 to 13.01 μM. Moreover, Ala136 and Thr30 were determined as the key binding sites of GOBP2 to the pesticides through molecular docking and site-directed mutagenesis. Finally, the knockdown of GOBP2 significantly increased the larval susceptibility to trifluralin and three types of insecticides. Our findings provide a valuable reference for the further exploration of the molecular mechanisms underlying herbicide-induced insecticide tolerance in S. litura, laying the foundation for innovative pest management strategies.

The Effects of Different Cotton Varieties on the Growth and Feeding Preferences of Helicoverpa armigera

Xinjiang is an autonomous province in northwest China [...].

Sulfoxaflor effects depend on the interaction with other pesticides and Nosema ceranae infection in the honey bee (Apis mellifera)

Honey bees health is compromised by many factors such as the use of agrochemicals in agriculture and the various diseases that can affect them. Multiple studies have shown that these factors can interact, producing a synergistic effect that can compromise the viability of honey bees. This study analyses the interactions between different pesticides and the microsporidium Nosema ceranae and their effect on immune and detoxification gene expression, sugar consumption and mortality in the Iberian western honey bee (Apis mellifera iberiensis). For this purpose, workers were infected with N. ceranae and subjected to a sugar-water diet with field concentrations of the pesticides sulfoxaflor, azoxystrobin and glyphosate. Increased sugar intake and altered immune and cytochrome P450 gene expression were observed in workers exposed to sulfoxaflor and infected with N. ceranae. None of the pesticides affected Nosema spore production in honey bee gut. Of the three pesticides tested (alone or in combination) only sulfoxaflor increased mortality in honey bees. Taken together, our results suggest that the effects of sulfoxaflor were attenuated in contact with other pesticides, and that Nosema infection leads to increase sugar intake in sulfoxaflor-exposed bees. Overall, this underlines the importance of studying the interaction between different stressors to understand their overall impact not only on honey bee but also on wild bees health.

Cross-protection interactions in insect pests: Implications for pest management in a changing climate

Agricultural insect pests display an exceptional ability to adapt quickly to natural and anthropogenic stressors. Emerging evidence suggests that frequent and varied sources of stress play an important role in driving protective physiological responses; therefore, intensively managed agroecosystems combined with climatic shifts might be an ideal crucible for stress adaptation. Cross-protection, where responses to one stressor offers protection against another type of stressor, has been well documented in many insect species, yet the molecular and epigenetic underpinnings that drive overlapping protective responses in insect pests remain unclear. In this perspective, we discuss cross-protection mechanisms and provide an argument for its potential role in increasing tolerance to a wide range of natural and anthropogenic stressors in agricultural insect pests. By drawing from existing literature on single and multiple stressor studies, we outline the processes that facilitate cross-protective interactions, including epigenetic modifications, which are understudied in insect stress responses. Finally, we discuss the implications of cross-protection for insect pest management, focusing on the consequences of cross-protection between insecticides and elevated temperatures associated with climate change. Given the multiple ways that insect pests are intensively managed in agroecosystems, we suggest that examining the role of multiple stressors can be important in understanding the wide adaptability of agricultural insect pests. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Cytochrome P450-mediated mycotoxin metabolism by plant-feeding insects

Mycotoxins are secondary metabolites produced primarily by filamentous fungi that when consumed cause pathological responses in animal hosts or consumers. Defined functionally rather than structurally, mycotoxins derive from numerous primary metabolic pathways. Through opportunistic or mutualistic associations, insect herbivores inflict damage that can predispose plants to infection by mycotoxin-producing phytopathogens, resulting in economically significant contamination. The few cytochrome P450 subfamilies implicated in mycotoxin detoxification by insects, including CYP6 and CYP9, are also known to detoxify phytochemicals. Some insect P450s bioactivate, rather than detoxify, mycotoxins, suggestive of an 'escalation' in arms-race interactions between these herbivores and fungi. Characterizing insect P450s that detoxify mycotoxins can be useful for developing biological remediation technologies and for ensuring the safety of insects reared for human or livestock consumption.

Proteomic analysis reveals the damaging role of low redox laccase from Yersinia enterocolitica strain 8081 in the midgut of Helicoverpa armigera

OBJECTIVE

Earlier, we have found that the enteropathogenic Yersinia enterocolitica have evolved the survival mechanisms that regulate the expression of laccase-encoding genes in the gut. The present study aims to characterize the purified recombinant laccase from Y. enterocolitica strain 8081 biovar 1B and understand its effect on the midgut of cotton bollworm, Helicoverpa armigera (Hübner) larvae.

RESULTS

The recombinant laccase protein showed high purity fold and low molecular mass (~ 43 kDa). H. armigera larvae fed with laccase protein showed a significant decrease in body weight and damage in the midgut. Further, transmission electron microscopy (TEM) studies revealed the negative effect of laccase protein on trachea, malpighian tubules, and villi of the insect. The proteome comparison between control and laccase-fed larvae of cotton bollworm showed significant expression of proteolytic enzymes, oxidoreductases, cytoskeletal proteins, ribosomal proteins; and proteins for citrate (TCA cycle) cycle, glycolysis, stress response, cell redox homeostasis, xenobiotic degradation, and insect defence. Moreover, it also resulted in the reduction of antioxidants, increased melanization (insect innate immune response), and enhanced free radical generation.

CONCLUSIONS

All these data collectively suggest that H. armigera (Hübner) larvae can be used to study the effect of microbes and their metabolites on the host physiology, anatomy, and survival.