Catalase promotes whitefly adaptation to high temperature by eliminating reactive oxygen species

Cd exposure confers β-cypermethrin tolerance in Lymantria dispar by activating the ROS/CnCC signaling pathway-mediated P450 detoxification

Heavy metal pollutants are important abiotic environmental factors affecting pest habitats. In this study, Cd pre-exposure significantly increased the tolerance of Lymantria dispar larvae to β-cypermethrin, but did not significantly alter their tolerance to λ-cyhalothrin and bifenthrin. The activation of P450 by Cd exposure is the key mechanism that induces insecticide cross-tolerance in L. dispar larvae. Both before and after β-cypermethrin treatment, Cd exposure significantly increased the expression of CYP6AB224 and CYP6AB226 in L. dispar larvae. Silencing CYP6AB224 and CYP6AB226 reduced the tolerance of Cd-treated L. dispar larvae to β-cypermethrin. Transgenic CYP6AB224 and CYP6AB226 genes significantly increased the tolerance of Drosophila and Sf9 cells to β-cypermethrin, and the recombinant proteins of both genes could significantly metabolise β-cypermethrin. Cd exposure significantly increased the expression of CnCC and Maf. CnCC was found to be a key transcription factor regulating CYP6AB224- and CYP6AB226-activated insecticide cross-tolerance in Cd-treated larvae. Decreasing reactive oxygen species (ROS) levels in the Cd-treated larvae or increasing ROS levels in the untreated larvae reduced or enhanced the expression of CnCC, CYP6AB224 and CYP6AB226 and β-cypermethrin tolerance in L. dispar larvae, respectively. Collectively, Cd exposure confers β-cypermethrin tolerance in L. dispar larvae through the ROS/CnCC signalling pathway-mediated P450 detoxification.

Heat-stress memory enhances the acclimation of a migratory insect pest to global warming

In the face of rising global temperatures, the mechanisms behind an organism's ability to acclimate to heat stress remain enigmatic. The rice leaf folder, Cnaphalocrocis medinalis, traditionally viewed as temperature-sensitive, paradoxically exhibits robust larval acclimation to heat stress. This study used the heat-acclimated strain HA39, developed through multigenerational exposure to 39°C during the larval stage, and the unacclimated strain HA27 reared at 27°C to unravel the transgenerational effects of heat acclimation and its regulatory mechanisms. Heat acclimation for larvae incurred a fitness cost in pupae when exposed to high temperature, yet a significant transgenerational effect surfaced, revealing heightened fitness benefit in pupae from HA39, even without additional heat exposure during larval recovery at 27°C. This transgenerational effect exhibited a short-term memory, diminishing after two recovery generations. Moreover, the effect correlated with increased superoxide dismutase (SOD) enzyme activity and expression levels of oxidoreductase genes, representing physiological and molecular foundations of heat acclimation. Heat-acclimated larvae displayed elevated DNA methylation levels, while pupae from HA39, in recovery generations, exhibited decreased methylation indicated by the upregulation of a demethylase gene and downregulation of two methyltransferase genes at high temperatures. In summary, heat acclimation induces DNA methylation, orchestrating heat-stress memory and influencing the expression levels of oxidoreductase genes and SOD activity. Heat-stress memory enhances the acclimation of the migratory insect pest to global warming.

Molecular Mechanism Underlying ROS-Mediated AKH Resistance to Imidacloprid in Whitefly

Synthetic insecticides used to control Bemisia tabaci include organophosphorus, pyrethroids, insect growth regulators, nicotinoids, and neonicotinoids. Among these, neonicotinoids have been used continuously, which has led to the emergence of high-level resistance to this class of chemical insecticides in the whitefly, making whitefly management difficult. The adipokinetic hormone gene (AKH) and reactive oxygen species (ROS) play roles in the development of insect resistance. Therefore, the roles of AKH and ROS in imidacloprid resistance in Bemisia tabaci Mediterranean (MED; formerly biotype Q) were evaluated in this study. The expression level of AKH in resistant B. tabaci MED was significantly lower than that in sensitive B. tabaci (MED) (p < 0.05). AKH expression showed a decreasing trend. After AKH silencing by RNAi, we found that ROS levels as well as the expression levels of the resistance gene CYP6CM1 and its upstream regulatory factors CREB, ERK, and P38 increased significantly (p < 0.05); additionally, whitefly resistance to imidacloprid increased and mortality decreased (p < 0.001). These results suggest that AKH regulates the expression of resistance genes via ROS in Bemisia tabaci.

Integrated transcriptomic and proteomic analyses reveal the molecular mechanism underlying the thermotolerant response of Spodoptera frugiperda

Spodoptera frugiperda (Lepidoptera: Noctuidae) is a highly destructive invasive pest with remarkable adaptability to extreme climatic conditions, posing a substantial global threat. Although the effects of temperature stress on the biological and ecological properties of S. frugiperda have been elucidated, the molecular mechanisms underlying its responses remain unclear. Herein, we combined transcriptomic and proteomic analyses to explore the key genes and proteins involved in thermotolerance regulation in S. frugiperda larvae at 42 °C. Overall, 1528 differentially expressed genes (DEGs) and 154 differentially expressed proteins (DEPs) were identified in S. frugiperda larvae under heat stress, including antioxidant enzymes, heat shock proteins (Hsps), cytochrome P450s, starch and sucrose metabolism genes, and insulin signaling pathway genes, indicating their involvement in heat tolerance regulation. Correlation analysis of DEGs and DEPs revealed that seven and eight had the same and opposite expression profiles, respectively. After nanocarrier-mediated RNA interference knockdown of SfHsp29, SfHsp20.4, SfCAT, and SfGST, the body weight and mortality of S. frugiperda larvae significantly decreased and increased under heat stress, respectively. This indicates that SfHsp29, SfHsp20.4, SfCAT, and SfGST play a crucial role in the thermotolerance of S. frugiperda larvae. These results provide insight into the mechanism of heat tolerance in S. frugiperda.

Alkaline ceramidase (ClAC) inhibition enhances heat stress response in Cyrtorhinus lividipennis (Reuter)

Ceramidases (CDases) are vital sphingolipid enzymes involved in organismal growth and development. They have been reported as key mediators of thermal stress response. However, whether and how CDase responds to heat stress in insects remain unclear. Herein, we identified two CDase genes, C. lividipennis alkaline ceramidase (ClAC) and neutral ceramidase (ClNC), by searching the transcriptome and genome databases of the mirid bug, Cyrtorhinus lividipennis, an important natural predator of planthoppers. Quantitative PCR (qPCR) analysis showed that both ClNC and ClAC were highly expressed in nymphs than in adults. ClAC was especially highly expressed in the head, thorax, and legs, while ClNC was widely expressed in the tested organs. Only the ClAC transcription was significantly affected by heat stress. Knocking down ClAC increased the C. lividipennis nymph survival rate under heat stress. The transcriptome and lipidomics data showed that the RNA interference-mediated suppression of ClAC significantly upregulated the transcription level of catalase (CAT) and the content of long-chain base ceramides, including C16-, C18-, C24-, and C31- ceramides. In C. lividipennis nymphs, ClAC played an important role in heat stress response, and the upregulation of nymph survival rate might be caused by variation in the ceramide levels and transcriptional changes in CDase downstream genes. This study improves our understanding of the physiological functions of insect CDase under heat stress and provides valuable insights into the nature enemy application.

Genomic analyses provide insights into the genome evolution and environmental adaptation of the tobacco moth Ephestia elutella

Ephestia elutella is a major pest responsible for significant damage to stored tobacco over many years. Here, we conduct a comparative genomic analysis on this pest, aiming to explore the genetic bases of environmental adaptation of this species. We find gene families associated with nutrient metabolism, detoxification, antioxidant defense and gustatory receptors are expanded in the E. elutella genome. Detailed phylogenetic analysis of P450 genes further reveals obvious duplications in the CYP3 clan in E. elutella compared to the closely related species, the Indianmeal moth Plodia interpunctella. We also identify 229 rapidly evolving genes and 207 positively selected genes in E. elutella, respectively, and highlight two positively selected heat shock protein 40 (Hsp40) genes. In addition, we find a number of species-specific genes related to diverse biological processes, such as mitochondria biology and development. These findings advance our understanding of the mechanisms underlying processes of environmental adaptation on E. elutella and will enable the development of novel pest management strategies.