Comparative transcriptome analysis of Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) reveals novel insights into heat stress tolerance in insects

Effect of acute exposure of Hg on physiological parameters and transcriptome expression in silkworms (Bombyx mori)

Mercury (Hg) contamination poses a global threat to the environment, given its elevated ecotoxicity. Herein, we employed the lepidopteran model insect, silkworm (Bombyx mori), to systematically investigate the toxic effects of Hg-stress across its growth and development, histomorphology, antioxidant enzyme activities, and transcriptome responses. High doses of Hg exposure induced evident poisoning symptoms, markedly impeding the growth of silkworm larvae and escalating mortality in a dose-dependent manner. Under Hg exposure, the histomorphology of both the midgut and fat body exhibited impairments. Carboxylesterase (CarE) activity was increased in both midgut and fat body tissues responding to Hg treatment. Conversely, glutathione S-transferase (GST) levels increased in the fat body but decreased in the midgut. The transcriptomic analysis revealed that the response induced by Hg stress involved multiple metabolism processes. Significantly differently expressed genes (DEGs) exhibited strong associations with oxidative phosphorylation, nutrient metabolisms, insect hormone biosynthesis, lysosome, ribosome biogenesis in eukaryotes, and ribosome pathways in the midgut or the fat body. The findings implied that exposure to Hg might induce the oxidative stress response, attempting to compensate for impaired metabolism. Concurrently, disruptions in nutrient metabolism and insect hormone activity might hinder growth and development, leading to immune dysfunction in silkworms. These insights significantly advance our theoretical understanding of the potential mechanisms underlying Hg toxicity in invertebrate organisms.

Comparative transcriptome analysis of false codling moth, Thaumatotibia leucotreta in response to high and low-temperature treatments

The false codling moth (FCM), Thaumatotibia leucotreta, is a major quarantine pest native to Africa. Physical postharvest phytosanitary measures such as cold and heat treatments are championed to control its spread to new regions. However, the molecular changes that T. leucotreta undergoes as it attempts to adjust to its surroundings during the treatments and withstand the extreme temperatures remain largely unknown. The current study employs RNA-seq using the next-generation Illumina HiSeq platform to produce transcriptome profiles for differential gene expression analysis of T. leucotreta larvae under thermal stress. The transcriptome assembly analysis revealed 226,067 transcripts, clustering into 127,018 unigenes. In comparison to the 25 °C treated group, 874, 91, 159, and 754 individual differentially expressed genes (DEGs) co-regulated at -10, 0, 40, and 50 °C, respectively were discovered. Annotation of the DEGs by gene ontology (GO) revealed several genes, previously implicated in low and high-temperature stresses, including heat shock proteins, cytochrome P450, cuticle proteins, odorant binding proteins, and immune system genes. Kyoto Encyclopedia of Genes and Genomics (KEGG) classification analysis revealed that substantive DEGs were those involved in metabolic pathways such as thiamine, purine, folate, and glycerolipid metabolism pathways. The RT-qPCR validation of several significantly up- and down-regulated DEGs showed congruence between RNA-seq and qPCR data. This baseline study lays a foundation for future research into the molecular mechanisms underlying T. leucotreta's cold/heat tolerance by providing a thorough differential gene expression analysis that has identified multiple genes that may be associated with the insect's ability to withstand cold and heat.

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.

Thermal acclimation uncovers a simple genetic basis of adaptation to high temperature in a cosmopolitan pest

Understanding a population's fitness heterogeneity and genetic basis of thermal adaptation is essential for predicting the responses to global warming. We examined the thermotolerance and genetic adaptation of Plutella xylostella to exposure to hot temperatures. The population fitness parameters of the hot-acclimated DBM strains varied in the thermal environments. Using genome scanning and transcription profiling, we find a number of genes potentially involved in thermal adaptation of DBM. Editing two ABCG transporter genes, PxWhite and PxABCG, confirmed their role in altering cuticle permeability and influencing thermal responses. Our results demonstrate that SNP mutations in genes and changes in gene expression can allow DBM to rapidly adapt to thermal environment. ABCG transporter genes play an important role in thermal adaptation of DBM. This work improves our understanding of genetic adaptation mechanisms of insects to thermal stress and our capacity to predict the effects of rising global temperatures on ectotherms.

Trehalose 6-phosphate synthase gene rdtps1 contributes to thermal acclimation in Rhyzopertha dominica

BACKGROUND

The lesser grain borer (Rhyzopertha dominica), a worldwide primary pest of stored grain, causes serious economic losses and threatens stored food safety. R. dominica can respond to changes in temperature, especially the adaptability to heat. In this study, transcriptome analysis of R. dominica exposed to different temperatures was performed to elucidate differences in gene expression and the underling molecular mechanism.

RESULTS

Isoform-sequencing generated 17,721,200 raw reads and yielded 20,416 full-length transcripts. A total of 18,880 (92.48%) transcripts were annotated. We extracted RNA from R. dominica reared at 5 °C (cold stress), 15 °C (cold stress), 27 °C (ambient temperature) and 40 °C (heat stress) for RNA-seq. Compared to those of control insects reared at 27 °C, 119, 342, and 875 differentially expressed genes (DEGs) were identified at 5 °C, 15 °C, and 40 °C, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that pathways associated with "fatty acid metabolism", "fatty acid biosynthesis", "AMPK signaling pathway", "neuroactive ligand receptor interaction", and "longevity regulating pathway-multiple species" were significantly enriched. The functional annotation revealed that the genes encoding heat shock proteins (HSPs), fatty acid synthase (FAS), phospholipases (PLA), trehalose transporter (TPST), trehalose 6-phosphate synthase (TPS), and vitellogenin (Vg) were most likely involved in temperature regulation, which was also validated by RT-qPCR. Seven candidate genes (rdhsp1, rdfas1, rdpla1, rdtpst1, rdtps1, rdvg1, and rdP450) were silenced in the RNA interference (RNAi) assay. RNAi of each candidate gene suggested that inhibiting rdtps1 expression significantly decreased the trehalose level and survival rate of R. dominica at 40 °C.

CONCLUSIONS

These results indicated that trehalose contributes to the high temperature resistance of R. dominica. Our study elucidates the molecular mechanisms underlying heat tolerance and provides a potential target for the pest management in R. dominica.

High and Low Temperatures Differentially Affect Survival, Reproduction, and Gene Transcription in Male and Female Moths of Spodoptera frugiperda

In this study, we found that both heat and cold stresses significantly affected the survival and reproduction of both sexes in Spodoptera frugiperda adults, with larvae showing relatively higher extreme temperature tolerance. Further transcriptomic analysis in adults found remarkable differences and similarities between sexes in terms of temperature stress responses. Metabolism-related processes were suppressed in heat stressed females, which did not occur to the same extend in males. Moreover, both heat and cold stress reduced immune activities in both sexes. Heat stress induced the upregulation of many heat shock proteins in both sexes, whereas the response to cold stress was insignificant. More cold tolerance-related genes, such as cuticle proteins, UDP-glucuronosyltransferase, and facilitated trehalose transporter Tret1, were found upregulated in males, whereas most of these genes were downregulated in females. Moreover, a large number of fatty acid-related genes, such as fatty acid synthases and desaturases, were differentially expressed under heat and cold stresses in both sexes. Heat stress in females induced the upregulation of a large number of zinc finger proteins and reproduction-related genes; whereas cold stress induced downregulation in genes linked to reproduction. In addition, TRPA1-like encoding genes (which have functions involved in detecting temperature changes) and sex peptide receptor-like genes were found to be differentially expressed in stressed moths. These results indicate sex-specific heat and cold stress responses and adaptive mechanisms and suggest sex-specific trade-offs between stress-resistant progresses and fundamental metabolic processes as well as between survival and reproduction.

Digestive enzyme activity and macromolecule content in the hemolymph of differentially adapted Lymantria dispar L. populations after short-term increases in ambient temperature

Global, unpredictable temperature increases have strong effects on all organisms, especially insects. Elucidating the effects of short-term temperature increases on midgut digestive enzymes (α-glucosidase, lipase, trypsin, and leucine aminopeptidase - LAP) and metabolic macromolecules in the hemolymph (proteins, lipids, and trehalose) of phytophagous pest larvae of Lymantria dispar is important for general considerations of insect adaptation to a warming climate and potential pest control options. We also wanted to determine whether the different adaptations of L. dispar populations to environmental pollution might affect their ability to cope with heat stress using larvae from the undisturbed, Kosmaj forest and disturbed, Lipovica forest. Heat treatments at 28 °C increased α-glucosidase activity in both larval populations, inhibited LAP activity in larvae from the polluted forest, and had no significant effect on trypsin and lipase activities, regardless of larval origin. The concentration of proteins, lipids, and trehalose in the hemolymph of larvae from the disturbed forest increased, whereas the population from the undisturbed forest showed only an increase in proteins and lipids after the heat treatments. Larval mass was also increased in larvae from the undisturbed forest. Our results suggest a higher sensitivity of digestive enzymes and metabolism to short-term heat stress in L. dispar populations adapted to pollution in their forest habitat, although climate warming is not beneficial even for populations from unpolluted forests. The digestive and metabolic processes of L. dispar larvae are substantially affected by sublethal short-term increases in ambient temperature.

Characteristics of the Accessible Chromatin Landscape and Transcriptome under Different Temperature Stresses in Bemisia tabaci

Bemisia tabaci is an important invasive pest with worldwide distribution and strong temperature tolerance. Previous studies have shown that temperature tolerance varies significantly between the different invasive populations. Several key factors involved in epigenetic regulation have been identified and verified in B. tabaci; therefore, epigenetic adaptation mechanisms may also exist. This study aimed to detect changes in the chromatin accessibility landscape and genome-wide transcriptome under different temperature stresses in B. tabaci. Assay for transposase-accessible chromatin with high-throughput sequencing and RNA-seq analyses indicated that transcriptional activity of the genes strongly correlates with chromatin accessibility. Chromatin transcription-activated gene expression regulation is dominant during high-temperature stress in B. tabaci, mainly through the transcriptional repression of genes related to low-temperature stress resistance. Furthermore, B. tabaci resists low-temperature stress by regulating enzyme activities and withstands high-temperature stress by regulating metabolism and synthesis of organic substances, both achieved by altering chromatin accessibility. In summary, this study provides a theoretical basis for exploring changes in gene expression and chromatin accessibility under different temperature stresses, offering a new approach to unravelling regulatory mechanisms underlying the onset of molecular regulation in response to various temperature stress conditions.

Unique and generic crossed metabolism in response to four sub-lethal environmental stresses in the oriental fruit fly, Bactrocera dorsalis Hendel

Bactrocera dorsalis is a well-known invasive pest that causes considerable ecological and economic losses worldwild. Although it has a wide environmental tolerance, few studies have reported its mechanism of adaptation to multiple sub-lethal environmental stresses. In this study, 38, 41, 39 and 34 metabolites changed significantly in B. dorsalis under four sub-lethal stresses (heat, cold, desiccation and hypoxia), as found by the metabolomic method. Therein, lactic acid and pyruvic acid were induced, whereas metabolites in the tricarboxylic acid (TCA) cycle such as citric acid, α-ketoglutarate acid, malic acid and fumaric acid were reduced under at least one of the stresses. Enzyme activity and quantitative polymerase chain reaction (qPCR) analyses verified the repression of pyruvic acid proceeding into the TCA cycle. In addition, the levels of several cryoprotectants and membrane fatty acids in B. dorsalis were altered. The findings indicated that B. dorsalis has evolved shared metabolic pathways to adapt to heat, hypoxia and desiccation stresses, such as reducing energy consumption by activating the anaerobic glycolytic metabolism. Cryoprotectants and membrane fatty acids were produced to improve the efficiency of stress resistance. This study revealed the unique and generic crossed physiological mechanism of insects to adapt to various environmental stresses.

Heat shock protein 70 and Cathepsin B genes are involved in the thermal tolerance of Aphis gossypii

BACKGROUND

Elevated temperature can directly affect the insect pest population dynamics. Many experimental studies have indicated that high temperatures affect the biological and ecological characteristics of the widely distributed crop pest Aphis gossypii, but the molecular mechanisms underlying its response to heat stress remain unstudied. Here, we used transcriptomic analysis to explore the key genes and metabolic pathways involved in the regulation of thermotolerance in A. gossypii at 29 °C, 32 °C, and 35 °C.

RESULTS

The results of bioinformatics analysis show that few genes were consistently differentially expressed among the higher temperature treatments compared to 29 °C, and a moderate temperature increase of 3 °C can elicit gene expression changes that help A. gossypii adapt to warmer temperatures. Based on KEGG pathway enrichment analysis, we found that genes encoding four heat shock protein 70 s (Hsp70s) and nine cathepsin B (CathB) proteins were significantly upregulated at 35 °C compared with 32 °C. Genes related to glutathione production were also highly enriched between 32 °C and 29 °C. Silencing of two Hsp70s (ApHsp70A1-1 and ApHsp68) and two CathBs (ApCathB01 and ApCathB02) with RNA interference using a nanocarrier-based transdermal dsRNA delivery system significantly increased sensitivity of A. gossypii to high temperatures.

CONCLUSION

A. gossypii is able to fine-tune its response across a range of temperatures, and Hsp70 and CathB genes are essential for adaption of A. gossypii to warmer temperatures. © 2023 Society of Chemical Industry.

Gene Expression Analysis Reveals Potential Regulatory Factors Response to Temperature Stress in Bemisia tabaci Mediterranean

Exposure to extreme temperatures can hinder the development of insects and even reduce their survival rate. However, the invasive species Bemisia tabaci exhibits an impressive response to different temperatures. This study aims to identify important transcriptional changes of B. tabaci occupying different temperature habitats by performing RNA sequencing on populations originating from three regions of China. The results showed that the gene expression of B. tabaci populations inhabiting regions with different temperatures was altered and identified 23 potential candidate genes that respond to temperature stress. Furthermore, three potential regulatory factors' (the glucuronidation pathway, alternative splicing, and changes in the chromatin structure) response to different environmental temperatures were identified. Among these, the glucuronidation pathway is a notable regulatory pathway. A total of 12 UDP-glucuronosyltransferase genes were found in the transcriptome database of B. tabaci obtained in this study. The results of DEGs analysis suggest that UDP-glucuronosyltransferases with a signal peptide may help B. tabaci resist temperature stress by sensing external signals, such as BtUGT2C1 and BtUGT2B13, which are particularly important in responding to temperature changes. These results will provide a valuable baseline for further research on the thermoregulatory mechanisms of B. tabaci that contributes to its ability to effectively colonize regions with considerable temperature differences.

Elevated temperature affects energy metabolism and behavior of bumblebees

Bumblebees (Bombus eximius) are one of the most prominent pollinators in the agricultural industry because of their adaptation to temperate climates and pollination behavior (buzz pollination). Several studies have explained the need to increase conservation efforts for bumblebees due to climate change, but studies on the impact of climate change on pollination behavior of bumblebees have been limited. The present study investigated the effect of elevated temperatures on the survival and physiology of bumblebees. The behavioral changes in flight ability and pollen collection were also determined. We found that elevated temperature affects the survival rate and appetite of bumblebees. Gene expression analysis suggested that the energy metabolic pathway tends to involve anaerobic respiration during heat stress. The energy produced is mainly used to maintain essential physiological functions, such as expression of heat shock proteins and conversion of peroxides to harmless molecules. Energy distributed to flight muscles is reduced during heat stress, resulting in lower wing beating frequency. In addition, the flight path of bumblebees is shortened during heat stress, thereby further contributing to reduced pollen collection. These results demonstrate that elevated temperatures cause detrimental effects to bumblebees and can also potentially reduce crop production.

Transcriptome profiling for developmental stages Protaetia brevitarsis seulensis with focus on wing development and metamorphosis

A white-spotted flower chafer Protaetia brevitarsis seulensis widely distributed in Asian countries is traditionally used in oriental medicine. This study explored gene expression abundance with respect to wing development and metamorphosis in P. b. seulensis based on the large-scale RNA-seq data. The transcriptome assembly consists of 23,551 high-quality transcripts which are approximately 96.7% covered. We found 265 wing development genes, 19 metamorphosis genes, and 1,314 candidates. Of the 1,598 genes, 1,594 are included exclusively in cluster 4 with similar gene co-expression patterns. The network centrality analyses showed that wing development- and metamorphosis-related genes have a high degree of betweenness centrality and are expressed most highly in eggs, moderately in pupa and adults, and lowest in larva. This study provides some meaningful clues for elucidating the genetic modulation mechanism of wing development and metamorphosis in P. b. seulensis.

Transcriptome Analysis of the Differentially Expressed Heat-resistant Genes between Calliptamus italicus and Gomphocerus sibiricus

Calliptamus italicus and Gomphocerus sibiricus are indicator species in Xinjiang's low-altitude (700-1,900 m) and high-altitude (2,000-3,400 m) grasslands, respectively. C. italicus is tolerant to high-temperature stress, with its semilethal temperature (LT50) being 10.5°C higher than that of G. sibiricus. The two locust species were subjected to high-temperature stress to explore the molecular mechanisms and differences in high temperature tolerance between the two locust species. Next, the next generation sequencing (NGS) data were mapped to reference transcripts obtained using single molecule real Time (SMRT) sequencing to construct a nonparameter transcriptome. The transcriptomic response of these two locust species displayed different patterns. C. italicus had 126 differentially expressed genes (DEGs), with 59 and 67 being significantly up-regulated and down-regulated, respectively. The heat shock protein (Hsp) genes were highly expressed upon two locust species exposure to high-temperature stress, with Hsp70 being expressed the most. G. sibiricus had 86 DEGs, of which 45 were significantly up-regulated and 41 significantly down-regulated. In addition, the expression of the key enzyme encoding gene Myo-inositol oxygenase (MIOX) in inositol degradation was the highest in G. sibiricus. In the KEGG pathway, the biological processes and metabolic pathways were the most enriched pathways in C. italicus and G. sibiricus, respectively. Moreover, the quantitative fluorescence results were consistent with the transcriptome results, implying that the transcriptome results were accurate. The findings in this study provide valuable information for future research exploring the evolution mechanisms of heat resistance in C. italicus and G. sibiricus.

Comparative transcriptome analysis of Callosobruchus chinensis (L.) (Coleoptera: Chrysomelidae-Bruchinae) after heat and cold stress exposure

Callosobruchus chinensis is regarded as one of the cosmopolitan pests of legume crops and can cause tremendous losses to a variety of beans. This study focused on comparative transcriptome analyses of C. chinensis exposed to 45 °C (heat stress), 27 °C (ambient temperature) and -3 °C (cold stress) for 3 h to investigate the gene differences and underlying molecular mechanisms. There were 402 and 111 differentially expressed genes (DEGs) identified in the heat and cold stress treatments, respectively. "cell process", "cell" and "binding" were the main enriched functions and biological processes revealed by gene ontology (GO) analysis. The clusters of orthologous genes (COG) showed that DEGs were assigned to the categories: "posttranslational modification, protein turnover, chaperones", "lipid transport and metabolism", and "general function prediction only". With respect to the Kyoto Encyclopedia of Genes and Genomes (KEGG), the "longevity regulating pathway-multiple species", "carbon metabolism", "peroxisome", "protein processing in endoplasmic", "glyoxylate and dicarboxylate metabolism" pathways were significantly enriched. The annotation and enrichment analysis revealed that genes encoding heat shock proteins (Hsps) and cuticular proteins were significantly upregulated under high and low-temperature stresses, respectively. In addition, some DEGs encoding "Protein lethal essential for life", "Reverse transcriptase", "DnaJ domain", "Cytochrome" and "Zinc finger protein" were also upregulated to varying degrees. Transcriptomic data were validated using qRT‒PCR, which confirmed that they were consistent. In this paper, the temperature tolerance of C. chinensis adults was evaluated and the results showed that female adults were more sensitive to heat and cold stress than males, and the upregulation of heat shock protein and epidermal protein was the largest in DEGs after heat and cold stress, respectively. These findings provide a reference for further understanding the biological characteristics of C. chinensis adults and the molecular mechanisms underlying the response to low and high temperatures.

Genome-wide identification and comparative analysis of lipocalin families in Lepidoptera with an emphasis on Bombyx mori

Lipocalins exhibit functional diversity, including roles in retinol transport, invertebrate cryptic coloration, and stress response. However, genome-wide identification and characterization of lipocalin in the insect lineage have not been thoroughly explored. Here, we found that a lineage-specific expansion of the lipocalin genes in Lepidoptera occurred in large part due to tandem duplication events and several lipocalin genes involving insect coloration were expanded more via tandem duplication in butterflies. A comparative analysis of conserved motifs showed both conservation and divergence of lepidopteran lipocalin family protein structures during evolution. We observe dynamic changes in tissue expression preference of paralogs in Bombyx mori, suggesting differential contribution of paralogs to specific organ functions during evolution. Subcellular localization experiments revealed that lipocalins localize to the cytoplasm, nuclear membrane, or nucleus in BmN cells. Moreover, several lipocalin genes exhibited divergent responses to abiotic and biotic stresses, and 1 lipocalin gene was upregulated by 300 fold in B. mori. These results suggest that lipocalins act as signaling components in defense responses by mediating crosstalk between abiotic and biotic stress responses. This study deepens our understanding of the comprehensive characteristics of lipocalins in insects.

Reference genes selection for expression studies in Maconellicoccus hirsutus (Green) (Pseudococcidae: Hemiptera) under specific experimental conditions

BACKGROUND

Maconellicoccus hirsutus is a destructive pest which causes severe losses of agricultural and horticultural crops. For the management of M. hirsutus, many insecticides have been used and it has been exposed to insufficient dosage or uneven spray coverage which resulted in the development of insecticide resistance. Xenobiotic metabolism can be better understood with the help of gene expression studies by unveiling the underlying molecular mechanisms. The qRT-PCR is the simplest method to analyse gene expression, however, it highly relies on suitable reference genes concerning the different experimental conditions.

METHODS AND RESULTS

We evaluated the stability of five reference genes in two sets of experimental conditions viz. developmental stages (nymphs and adults) and agrochemical stress (GA3 and Buprofezin sprayed) against M. hirsutus, using different softwares-NormFinder, geNorm, BestKeeper, and RefFinder. The study revealed that ATP51a and GAPDH can be used as reference genes for gene expression studies when exposed to Gibberellic acid. Additionally, the study revealed that the ideal pair of reference genes for data validation in M. hirsutus treated with Buprofezin was GAPDH and β-tubulin. The ideal reference gene combination for various developmental stages was found to be 28S and Actin.

CONCLUSION

According to the study, GAPDH can be utilized as a reliable reference gene in the agrochemical (GA3 and Buprofezin) exposure set. The genes can be utilized as a suitable reference for qRT-PCR gene expression studies of xenobiotic metabolism to understand the underlying molecular mechanism, which will help further to design suitable management strategies.

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.

Three-Dimensional Organization of Chicken Genome Provides Insights into Genetic Adaptation to Extreme Environments

The high-throughput chromosome conformation capture (Hi-C) technique is widely used to study the functional roles of the three-dimensional (3D) architecture of genomes. However, the knowledge of the 3D genome structure and its dynamics during extreme environmental adaptations remains poor. Here, we characterized 3D genome architectures using the Hi-C technique for chicken liver cells. Upon comparing Lindian chicken (LDC) liver cells with Wenchang chicken (WCC) liver cells, we discovered that environmental adaptation contributed to the switching of A/B compartments, the reorganization of topologically associated domains (TADs), and TAD boundaries in both liver cells. In addition, the analysis of the switching of A/B compartments revealed that the switched compartmental genes (SCGs) were strongly associated with extreme environment adaption-related pathways, including tight junction, notch signaling pathway, vascular smooth muscle contraction, and the RIG-I-like receptor signaling pathway. The findings of this study advanced our understanding of the evolutionary role of chicken 3D genome architecture and its significance in genome activity and transcriptional regulation.

Unraveling the Role of Lac Insects in Providing Natural Industrial Products

In the current era, products made from organic materials enjoy a privileged position because of their inherent safety. The eco-friendly properties of natural lac resins have increased their demand in many industries. It is secreted by sucking insects (Hemiptera, Kerriidae) and comprises three major components, viz., resin, dye, and wax. Lac insects are generally bivoltine in nature and are distributed in tropical and sub-tropical regions with complex multi-trophic habitats. Because of their sedentary habits, lac insects are more vulnerable to predators, parasitoids, squirrels, and rats, leading to a more than 50% reduction in production yield. To increase lac production, advanced-level molecular research is required to figure out the mechanism behind lac synthesis and secretion to improve lac yield and quality. The present review highlights metamorphosis, sexual dimorphism, multi-trophic habitat, host plants, and natural enemies of lac insects, lac composition, and applications, emphasizing the role of microbes, potential lac genes, and lac synthesis mechanisms in enhancing lac quality and production. The information provided here might be useful for lac researchers and for stakeholders aiming to make their products more eco-friendly.

Effect of thyme essential oil and its two components on toxicity and some physiological parameters in mulberry pyralid Glyphodes pyloalis Walker

Extensive usage of synthetic pesticides has proved to be destructive to all living being and the resurgence of pest resistance. Compounds derived from certain plants are usually safer compared to chemical control of pest. The present study thus intended to use Thymus vulgaris essential oil (EO) and two of its derivatives including thymol and carvacrol in order to see their deleterious effects on Glyphodes pyloalis (Walker). We also studied the oil components. This pest has recently become a serious concern for the silk industry. Our results showed that the thyme EO contain several components including thymol (26.9%), ρ-Cymene (14.54%), linalool (13.39%) and carvacrol (5.7%). Our toxicity tests revealed an estimated LD₅₀ values for thyme EO, thymol and carvacrol 2.82, 32.18 and 56.54 μg/larva, respectively. However, the thyme EO was more toxic than its two tested compounds. The activity of certain detoxifying enzymes such as α- and β-esterase, glutathione S-transferase and cytochrome P450 were significantly inhibited by thymol-treated larvae compared to the control group. Similarly, the activity of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase and alkaline phosphatases enzymes in thymol-treated larvae decreased while the activity of acid phosphatases increased. Our results suggest that thyme EO and its components have potential for the control of G. pyloalis larvae in mulberry orchards, where no synthetic chemicals are allowed.

Protein and volatile contents in the mandibular gland of the sugarcane borer Diatraea saccharalis (Lepidoptera: Crambidae)

The sugarcane borer Diatraea saccharalis (Lepidoptera: Crambidae) is an important sugarcane pest and mechanical injuries caused through the mandibles can allow pathogen infections. The mandibles of D. saccharalis, as well as other insects, are associated with mandibular glands with a possible function in food intake and mouthparts lubrication; however, the chemical composition of the secretion is poorly known and its elucidation is important for the comprehensive understanding of plant-insect interactions. This study characterized some proteins and volatiles in the mandibular glands of D. saccharalis larvae. MALDI-TOF/TOF mass spectrometry allowed the identification of 24 predicted proteins within 10 functional classes, including the transport and metabolism of carbohydrates, lipids, amino acids, and nucleotides; Posttranslational protein modifications; energy conversion; intracellular trafficking; transcription; translation; and cytoskeleton function. Metabolites identified from GC/MS analysis revealed the presence of hydrocarbons classified as alcohols, ether, alkanes, and esters with differences in their relative abundance. Linolenic acid, the most abundant metabolite found in this gland, when conjugated with amino acids, can be an elicitor in the plant-herbivore interaction. The results suggest the occurrence of digestive and defensive biochemical components, which may contribute to understanding of the multifunctional roles of the mandibular gland secretion of D. saccharalis larvae during feeding activity.

Cross effects of heat stress and three insecticides on the survival of the codling moth Cydia pomonella (L.): Investigating the molecular and biochemical mechanisms

As temperature is expected to strongly increase in the future, understanding temperature-mediated toxicity of insecticides is determinant to assess pest management efficiency in a warming world. Investigating molecular and biochemical mechanisms associated with cross mechanisms of temperature and insecticides on pests' tolerance would also be useful in this context. This study aimed to investigate cross effects between temperature and insecticides on the survival of a major pest, the codling moth Cydia pomonella, and their underlying mechanisms. The effect of three insecticidal active ingredients, i.e. chlorantraniliprole, emamectin and spinosad, was assessed at different temperatures on: (i) C. pomonella larval survival; (ii) detoxification enzymes activities (cytochrome P450 multi-function oxygenases, carboxylesterases and glutathione S-transferases) and (iii) genes expression of some detoxification enzymes, heat shock proteins and receptors targeted by the insecticides. We observed a decreased efficiency of emamectin and spinosad at high temperature to control the codling moth while no influence of temperature on chlorantraniliprole efficacy was observed. Detoxification enzymes activities were improved by heat stress alone but not by double stress (temperature + insecticides). Moreover, two detoxification genes (Cyp9A61 and Gst1) were over-expressed by a single stress but not by two stresses while Hsp70 and Cyp6B2 genes may be involved in tolerance to two stresses in C. pomonella. These results confirmed the cross effects of temperature and insecticides on C. pomonella for emamectin and spinosad and provided clues to understand how temperature affects the susceptibility of C. pomonella to insecticides. They illustrate however the complexity of molecular and biochemical responses of individuals facing multiple stresses.

Determination of the optimal maturation temperature for adult honey bee toxicity testing

Honey bees are exposed to various pesticides through pollinating and in-hive Varroa mite control. The most basic method for evaluating pesticide toxicity is the indoor bioassay using worker bees, in which newly emerged adults are matured in incubators for conditioning before use. However, little information is available on the optimum maturation temperature from a toxicological point of view, even though it can affect honey bee responses to pesticides. In this paper, to evaluate the optimal maturation temperature for pesticide toxicity testing, several indices related to the development, gene transcription, and toxicological properties of honey bee adults following maturation at 25, 30, and 35 °C were compared with those of field bees. The body weight and developmental state of hypopharyngeal glands were highest in the bees matured at 30 °C, and the overall transcription profiles of detoxification-related genes in the field bees were closest to those of bees matured at 30 °C, whereas immaturity and features of thermal stress were observed in the 25 °C and 35 °C bee groups, respectively. In the bioassay results, the effects of maturation temperature on the toxic response of honey bees varied significantly depending on the type of pesticide. By considering all the biological and toxicological aspects examined, we confirmed that 30 °C is a recommended maturation temperature for adult honey bee toxicity test.

Comparative transcriptome analysis of Tamarixia radiata (Hymenoptera: Eulophidae) reveals differentially expressed genes upon heat shock

Temperature is a key parameter that affects insect population, abundance, and distribution in tropical and subtropical regions. Tamarixia radiata Waterson (Hymenoptera: Eulophidae) is a species-specific ectoparasitoid widely used as a biological control agent for the major citrus pest Diphornia citri Kuwayama (Hemiptera: Liviidea). To date, T. radiata response to high temperature at the molecular level still is unclear. In this study, we conducted a comparative analysis of the transcriptomes of T. radiata exposed at 25 °C and 38 °C for 15 min. A total of 51,072 unigenes were obtained, 22,413 annotated with a mean length of 1054 bp. Differential expression analysis showed that 502 genes were identified, including 476 genes significantly up-regulated and 26 genes down-regulated after heat stress exposure. The Gene Ontology analysis showed that most enriched DEGs are categorized into "cellular process", "metabolic process" and "DNA binding." In addition, "Lysosome," "Longevity regulating pathway-multiple species," and "starch and sucrose metabolism" were highly enriched in Kyoto Encyclopedia of Genes and Genomes pathways. Transcriptome analyses showed that heat stress significantly induced the transcription of the molecular chaperone, immune response, stress signaling transduction, and oxidation resistance, including highly expressed heat shock proteins, ATPases, and detoxifying enzymes. Furthermore, the expression patterns of thirteen genes including heat shock proteins (HSP), glutathione S-transferase (GST) and cytochrome P450 were consistent with the transcriptome results obtained through qRT-PCR. Together, our results provided a comprehensive study of the molecular response of T. radiata to heat stress and provides new insight for the future functional validation of heat resistance-related genes.

Differential Transcriptome Analysis Reveals Genes Related to Low- and High-Temperature Stress in the Fall Armyworm, Spodoptera frugiperda

The fall armyworm (FAW), Spodoptera frugiperda, is regarded as one of the world’s most harmful plant pests. This research examines the molecular response processes of FAW to low temperature (4°C) and high temperature (40°C) when gene expression is compared to controls (25°C). A total of 211,967 unigenes were collected, at least 14,338 of which were annotated with gene descriptions, gene ontology terms, and metabolic pathways. There were 50 Gene Ontology (GO) functional sub-groups and 21 EggNOG words as a result. Differentially expresses genes (DEGs) with log₂FC ≥ 2 were identified and compared at various temperatures. In comparison to the 25°C treated group, we discovered 199 and 1,248 individual DEGs co-regulated at 4 and 40°C, respectively. Comparing transcriptome profiles for differential gene expression revealed a number of DEGs, including cytochrome P450, odorant binding proteins (OBPs), and immune system genes previously implicated in cold and high temperature stresses. The enrichment pathways were identified using Kyoto Encyclopedia of Genes and Genomics (KEGG) analysis, and heatmaps of similar unigenes from both treatment groups (T4 and T40) were plotted. We used quantitative reverse transcription PCR (RT-qPCR) to confirm the RNA-seq data on 10 up- and down-regulated DEGs. These findings provide a foundation for future understanding of FAW adaptation mechanisms and the underlying basis underlying the response to low and high temperatures.

Actin Contributes to the Hyperexpression of Baculovirus Polyhedrin (polh) and p10 as a Component of Transcription Initiation Complex (TIC)

Hyperexpression of polh and p10, two very late genes, is one of the remarkable characteristics in the baculovirus life cycle. However, the mechanisms underlying the hyperexpression of these two genes are still incompletely understood. In this study, actin was identified as a highly potential binding partner of polh and p10 promoters by conducting DNA pull-down and LC–MS/MS analyses. Inhibiting actin dynamics delayed and decreased the transcription of polh and p10. Actin interacted with viral RNA polymerase and transcription regulators, and the nuclear import of viral polymerase was inhibited with the disruption of actin dynamics. Simultaneously, the high enrichment of actin in polh and p10 promoters discovered via a chromatin immunoprecipitation (ChIP) assay indicated that actin was a component of the viral polymerase TIC. Moreover, overexpression of actin surprisingly upregulated the expression of luciferase (Luc) under the control of polh and p10 promoters. Taken together, actin participated in the hyperexpression of polh and p10 as a component of TIC. These results facilitate the promotion of the expression efficiency of foreign genes in the baculovirus expression vector system (BEVS).

Isolation of two new genes encoding heat shock protein 70 in Bemisia tabaci and analysis during thermal stress

The heat shock protein 70 family (HSP70) is among the most varied HSP family with respect to structure and function. The phloem-feeding insect Bemisia tabaci (Gennadius) is an important pest of cotton, vegetables and ornamentals that transmits several plant viruses and causes enormous agricultural losses. In this study, two new HSP70 genes (Bthsp70-2 and Bthsp70-3) were isolated from the MED cryptic species B. tabaci, an important phloem-feeding pest of vegetables and ornamentals. Bthsp70-2 and Bthsp70-3 encoded proteins comprised of 652 and 676 amino acids, and the deduced proteins were closely related to other HSP70s in Hemiptera. Expression analyses using real-time quantitative PCR indicated that Bthsp70-2 and Bthsp70-3 were induced in B. tabaci pupae and adults during high and low thermal stress. Bthsp70-2 and Bthsp70-3 exhibited similar, but not identical, expression patterns when exposed to different durations of high temperature stress. Oral ingestion of dsBthsp70 reduced the expression level of Bthsp70-2 and Bthsp70-3 in B. tabaci and increased the mortality of B. tabaci during heat shock. In conclusion, Bthsp70-2 and Bthsp70-3 exhibit different expression patterns during thermal stress, thus expanding the roles of HSPs in B. tabaci.

Large-scale genome-wide study reveals climate adaptive variability in a cosmopolitan pest

Understanding the genetic basis of climatic adaptation is essential for predicting species' responses to climate change. However, intraspecific variation of these responses arising from local adaptation remains ambiguous for most species. Here, we analyze genomic data from diamondback moth (Plutella xylostella) collected from 75 sites spanning six continents to reveal that climate-associated adaptive variation exhibits a roughly latitudinal pattern. By developing an eco-genetic index that combines genetic variation and physiological responses, we predict that most P. xylostella populations have high tolerance to projected future climates. Using genome editing, a key gene, PxCad, emerged from our analysis as functionally temperature responsive. Our results demonstrate that P. xylostella is largely capable of tolerating future climates in most of the world and will remain a global pest beyond 2050. This work improves our understanding of adaptive variation along environmental gradients, and advances pest forecasting by highlighting the genetic basis for local climate adaptation.

A role of peptidoglycan recognition protein in mediating insecticide detoxification in Glyphodes pyloalis

Glyphodes pyloalis Walker has become one of the most significant mulberry pests, and it has caused serious economic losses in major mulberry growing regions in China. Peptidoglycan recognition proteins (PGRPs) are responsible for initiating and regulating immune signalling pathways in insects. However, their roles responding to chemical pesticides is still less known. This study aimed to investigate the possible detoxication function of GpPGRP-S2 and GpPGRP-S3 in G. pyloalis in response to chlorfenapyr and phoxim. The chlorfenapyr and phoxim treatment significantly induced the expression level of GpPGRP-S3 at 48 h. In addition, the expression levels of GpPGRP-S2 and GpPGRP-S3 in the chlorfenapyr/phoxim treatment group were significantly higher in midgut than those in the control group at 48 h. The results of the survival experiment showed that silencing either GpPGRP-S2 or GpPGRP-S3 would not influence the survival rate of G. pyloalis which treated with phoxim, however, silencing GpPGRP-S2 or GpPGRP-S3 would cause G. pyloalis to be more easily killed by chlorfenapyr. The expression of carboxylesterase GpCXE1 was significantly induced by chlorfenapyr/phoxim treatment, while it was suppressed once silenced GpPGRP-S2 followed with chlorfenapyr treatment or silenced GpPGRP-S3 followed with phoxim treatment. These results might suggest that under the chlorfenapyr/phoxim treatment condition, the connection between GpPGRPs and detoxification genes in insect was induced to maintain physiological homeostasis; and these results may further enrich the mechanisms of insects challenged by insecticides.

Characterization, and Functional Analysis of Hsp70 and Hsp90 Gene Families in Glyphodes pyloalis Walker (Lepidoptera: Pyralidae)

Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) is a destructive mulberry pest, causing great damage to mulberry in China. Heat shock proteins (Hsps) are involved in various signal pathways and regulate lots of physiological processes in insects. The function of Hsps in G. pyloalis, however, has still received less attention. Here, we identified five Hsp genes from G. pyloalis transcriptome dataset including two Hsp70 family genes (GpHsp71.3 and GpHsp74.9) and three Hsp90 family genes (GpHsp82.4, GpHsp89, and GpHsp93.4). Quantitative Real-time PCR validation revealed that all Hsps of G. pyloalis have significant expression in pupal and diapause stage, at which the larvae arrest the development. Expressions of GpHsp71.3 and GpHsp82.4 were increased significantly after thermal treatment at 40°C, and this upregulation depended on heat treatment duration. Furthermore, silencing GpHsp82.4 by RNA interference led to a significant increase in mortality of G. pyloalis larvae under the heat stress compared to the control group. After starvation stress, the expression levels of GpHsp82.4 and GpHsp93.4 were significantly increased. At last, after being parasitized by the parasitoid wasp Aulacocentrum confusum, Hsp70 and Hsp90 genes of G. pyloalis were decreased significantly in the early stage of parasitization and this moderation was affected by time post-parasitization. This study highlights the function of G. pyloalis Hsps in response to environmental stress and provides a perspective for the control of this pest.

Comparative RNA-Seq Analyses of Solenopsis japonica (Hymenoptera: Formicidae) Reveal Gene in Response to Cold Stress

Solenopsis japonica, as a fire ant species, shows some predatory behavior towards earthworms and woodlice, and preys on the larvae of other ant species by tunneling into a neighboring colony's brood chamber. This study focused on the molecular response process and gene expression profiles of S. japonica to low (9 °C)-temperature stress in comparison with normal temperature (25 °C) conditions. A total of 89,657 unigenes (the clustered non-redundant transcripts that are filtered from the longest assembled contigs) were obtained, of which 32,782 were annotated in the NR (nonredundant protein) database with gene ontology (GO) terms, gene descriptions, and metabolic pathways. The results were 81 GO subgroups and 18 EggNOG (evolutionary genealogy of genes: Non-supervised Orthologous Groups) keywords. Differentially expressed genes (DEGs) with log₂fold change (FC) > 1 and log₂FC < -1 with p-value ≤ 0.05 were screened for cold stress temperature. We found 215 unigenes up-regulated and 115 unigenes down-regulated. Comparing transcriptome profiles for differential gene expression resulted in various DE proteins and genes, including fatty acid synthases and lipid metabolism, which have previously been reported to be involved in cold resistance. We verified the RNA-seq data by qPCR on 20 up- and down-regulated DEGs. These findings facilitate the basis for the future understanding of the adaptation mechanisms of S. japonica and the molecular mechanisms underlying the response to low temperatures.

De Novo Transcriptome Analysis Reveals Potential Thermal Adaptation Mechanisms in the Cicada Hyalessa fuscata

Simple Summary

In metropolitan Seoul and its vicinity, cicadas of the species Hyalessa fuscata living in warmer areas could tolerate the heat better than those living in cooler areas, but genetic mechanisms involved in better heat tolerance remained unclear. In this study, we examined differences in gene expression of cicadas living in a warm urban area, a cool urban area and a suburban area in three experimental treatments: no heating, 10 min heating and heating until the cicadas lost their mobility. Cicadas from the warm urban area changed their gene expressions the most. Activated genes were mostly related to heat shock, energy metabolism, and detoxification. These results suggested that under heat stress, cicadas inhabiting warm areas could differentially express genes to increase their thermal tolerance.

Abstract

In metropolitan Seoul, populations of the cicada Hyalessa fuscata in hotter urban heat islands (“high UHIs”) exhibit higher thermal tolerance than those in cooler UHIs (“low UHIs”). We hypothesized that heat stress may activate the expression of genes that facilitate greater thermal tolerance in high-UHI cicadas than in those from cooler areas. Differences in the transcriptomes of adult female cicadas from high-UHI, low-UHI, and suburban areas were analyzed at the unheated level, after acute heat stress, and after heat torpor. No noticeable differences in unheated gene expression patterns were observed. After 10 min of acute heat stress, however, low-UHI and suburban cicadas expressed more heat shock protein genes than high-UHI counterparts. More specifically, remarkable changes in the gene expression of cicadas across areas were observed after heat torpor stimulus, as represented by a large number of up- and downregulated genes in the heat torpor groups compared with the 10 min acute heat stress and control groups. High-UHI cicadas expressed the most differentially expressed genes, followed by the low-UHI and suburban cicadas. There was a notable increase in the expression of heat shock, metabolism, and detoxification genes; meanwhile, immune-related, signal transduction, and protein turnover genes were downregulated in high-UHI cicadas versus the other cicada groups. These results suggested that under heat stress, cicadas inhabiting high-UHIs could rapidly express genes related to heat shock, energy metabolism, and detoxification to protect cells from stress-induced damage and to increase their thermal tolerance toward heat stress. The downregulation of apoptosis mechanisms in high-UHI cicadas suggested that there was less cellular damage, which likely contributed to their high tolerance of heat stress.

Genome-wide gene expression profiles of the pea aphid (Acyrthosiphon pisum) under cold temperatures provide insights into body color variation

Cold temperatures are one of the factors influencing color polymorphisms in Acyrthosiphon pisum, resulting in a change from a red to greenish color. Here we characterized gene expression profiles of A. pisum under different low temperatures (1°C, 4°C, 8°C, and 14°C) and durations (3, 6, 12, and 24 h). The number of differentially expressed genes (DEGs) increased as temperatures decreased and time increased, but only a small number of significant DEGs were identified. Genes involved in pigment metabolism were downregulated. An interaction network analysis for 506 common DEGs in comparisons among aphids exposed to 1°C for four durations indicated that a cytochrome P450 gene (CYP, LOC112935894) significantly downregulated may interact with a carotenoid metabolism gene (LOC100574964), similar to other genes encoding CYP, lycopene dehydrogenase and fatty acid synthase. We proposed that the body color shift in A. pisum responding to low temperatures may be regulated by CYPs.

Comparison of gene expression in the red imported fire ant (Solenopsis invicta) under different temperature conditions

The red imported fire ant (RIFA), Solenopsis invicta Buren is native to South America and is known as a global problematic invasive species. This study focused on the molecular response of RIFA by comparing gene expression profiles after exposing ants to low (10 °C) and high (40 °C) temperature stress and comparing them to untreated controls (30 °C). A total of 99,085 unigenes (the clustered non-redundant transcripts that are filtered from the longest assembled contigs) were obtained, of which 19,154 were annotated with gene descriptions, gene ontology terms, and metabolic pathways. 86 gene ontology (GO) functional sub-groups and 23 EggNOG terms resulted. Differentially expressed genes (DEGs) with log₂FC ≥ 10 were screened and were compared at different temperatures. We found 203, 48, and 66 specific DEGs co-regulated at 10, 20, and 40 °C. Comparing transcriptome profiles for differential gene expression resulted in various DE genes, including cytochrome P450, NADH dehydrogenase subunit 1, cuticle protein and heat shock protein (HSP), which have previously been reported to be involved in cold and high temperature resistance. GO analysis revealed that antioxidant activity is up-regulated under high temperature stress. We verified the RNA-seq data by qPCR on 20 up- and down-regulated DEGs. These findings provide a basis for future understanding of the adaptation mechanisms of RIFA and the molecular mechanisms underlying the response to low and high temperatures.

High temperature stress induces expression of CYP450 genes and contributes to insecticide tolerance in Liriomyza trifolii

Liriomyza trifolii is an invasive leafminer fly that inflicts damage on many horticultural and vegetable crops. In this study, the effects of elevated temperatures on L. trifolii tolerance to insecticides abamectin (AB), monosultap (MO) and a mixture of abamectin and monosultap (AM) were firstly investigated, then five CYP450 genes (LtCYPs) were cloned, and expression patterns and NADPH cytochrome C reductase (NCR) activity in L. trifolii were compared in response to high temperature stress and insecticide exposure. Results showed elevated temperatures induced expression of LtCYP450s, the expression level of LtCYP4g1, LtCYP4g15 and LtCYP301A1 after exposed to different high temperature were significantly up-regulated compared with the control (25 °C), while there was no significant difference in LtCYP4E21 and LtCYP18A1. Under the joint high temperature and insecticide stress, the expression of LtCYP4g15, LtCYP18A1 and LtCYP301A1 was significantly higher under elevated temperatures than that of only under AB exposure. For MO and AM exposure, only 40 °C could induce the expression of LtCYP4g15, LtCYP18A1 and LtCYP301A1. In general, the LtCYPs expression pattern was correlated with increased NCR activity and decreased mortality in response to insecticide exposure under elevated temperatures. These all demonstrated that insecticide tolerance in L. trifolii could be mediated by high temperature. This study improves our understanding of L. trifolii physiology and offers a theoretical context for improved control that ultimately reduces the abuse of insecticides and decreases exposure to non-target organisms.

Transcriptome Analysis of Myzus persicae to UV-B Stress

As an environmental stress factor, ultraviolet-B (UV-B) radiation directly affects the growth and development of Myzus persicae (Sulzer) (Homoptera: Aphididae). How M. persicae responds to UV-B stress and the molecular mechanisms underlying this adaptation remain unknown. Here, we analyzed transcriptome data for M. persicae following exposure to UV-B radiation for 30 min. We identified 758 significant differentially expressed genes (DEGs) following exposure to UV-B stress, including 423 upregulated and 335 downregulated genes. In addition, enrichment analysis using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases illustrated that these DEGs are associated with antioxidation and detoxification, metabolic and protein turnover, immune response, and stress signal transduction. Simultaneously, these DEGs are closely related to the adaptability to UV-B stress. Our research can raise awareness of the mechanisms of insect responses to UV-B stress.

Transcriptome responses to heat and cold stress in prepupae of Trichogramma chilonis

Trichogramma is a useful species that is widely applied in biocontrol. Temperature profoundly affects the commercial application of T. chilonis. Different developmental transcriptomes of prepupae and pupae of T. chilonis under 10, 25, and 40°C were obtained from our previous study. In this study, transcriptomic analysis was further conducted to gain a clear understanding of the molecular changes in the prepupae of T. chilonis under different thermal conditions. A total of 37,295 unigenes were identified from 3 libraries of prepupae of T. chilonis, 17,293 of which were annotated. Differential expression analysis showed that 408 and 108 differentially expressed genes (DEGs) were identified after heat and cold treatment, respectively. Under heat stress, the pathway of protein processing in endoplasmic reticulum was found to be active. Most of the genes involved in this pathway were annotated as lethal (2) essential for life [l(2)efl] and heat shock protein genes (hsps), which were both highly upregulated. Nevertheless, most of the genes involved in another significantly enriched pathway of starch and sucrose metabolism were downregulated, including 1 alpha-glucosidase gene and 2 beta-glucuronidase genes. Under cold stress, no significantly enriched pathway was found, and the significantly enriched GO terms were related to the interaction with host and immune defenses. Together, these results provide us with a comprehensive view of the molecular mechanisms of T. chilonis in response to temperature stresses and will provide new insight into the mass rearing and utilization of T. chilonis.

Characterization and Functional Analysis of trehalase Related to Chitin Metabolism in Glyphodes pyloalis Walker (Lepidoptera: Pyralidae)

Simple Summary

Sericulture has always been threatened by Glyphodes pyloalis Walker (G. pyloalis). Trehalase is an essential enzyme in chitin metabolism and energy supply. In this study, two trehalase genes in G. pyloalis (GpTre1 and GpTre2) were identified and functionally analyzed. Knockdown of the two genes led to the significant downregulation of chitin metabolism pathway-related genes, the difficulty in molting of larvae, and the deformation of adult wings. Moreover, the trehalase inhibitor, Validamycin A, treatment increased GpTre1 and GpTre2 expression and affected the expressions of chitin metabolism pathway-related genes. The inhibitor also caused a significantly increased cumulative mortality of larvae. The results suggested that GpTre1 and GpTre2 played a vital role on G. pyloalis development, which could be useful for providing information for insect pest control in the future.

Abstract

Glyphodes pyloalis Walker (G. pyloalis) is a serious pest on mulberry. Due to the increasing pesticide resistance, the development of new and effective environmental methods to control G. pyloalis is needed. Trehalase is an essential enzyme in trehalose hydrolysis and energy supply, and it has been considered a promising target for insect pest control. However, the specific function of trehalase in G. pyloalis has not been reported. In this study, two trehalase genes (GpTre1 and GpTre2) were identified from our previous transcriptome database. The functions of the trehalase in chitin metabolism were studied by injecting larvae with dsRNAs and trehalase inhibitor, Validamycin A. The open reading frames (ORFs) of GpTre1 and GpTre2 were 1,704 bp and 1,869 bp, which encoded 567 and 622 amino acid residues, respectively. Both of GpTre1 and GpTre2 were mainly expressed in the head and midgut. The highest expression levels of them were in 5th instar during different development stages. Moreover, knockdown both of GpTre1 and GpTre2 by the dsRNAs led to significantly decreased expression of chitin metabolism pathway-related genes, including GpCHSA, GpCDA1, GpCDA2, GpCHT3a, GpCHT7, GpCHSB, GpCHT-h, GpCHT3b, GpPAGM, and GpUAP, and abnormal phenotypes. Furthermore, the trehalase inhibitor, Validamycin A, treatment increased the expressions of GpTre1 and GpTre2, increased content of trehalose, and decreased the levels of glycogen and glucose. Additionally, the inhibitor caused a significantly increased cumulative mortality of G. pyloalis larvae on the 2nd (16%) to 6th (41.3%) day, and decreased the rate of cumulative pupation (72.3%) compared with the control group (95.6%). After the activities of trehalase were suppressed, the expressions of 6 integument chitin metabolism-related genes decreased significantly at 24 h and increased at 48 h. The expressions of GpCHSB and GpCHT-h, involved in chitin metabolism pathway of peritrophic membrane in the midgut, increased at 24 h and 48 h, and there were no changes to GpCHT3b and GpPAGM. These results reveal that GpTre1 and GpTre2 play an essential role in the growth of G. pyloalis by affecting chitin metabolism, and this provides useful information for insect pest control in the future.

Comparative transcriptome and metabolome analysis of Ostrinia furnacalis female adults under UV-A exposure

Ultraviolet A (UV-A) radiation is a significant environmental factor that causes photoreceptor damage, apoptosis, and oxidative stress in insects. Ostrinia furnacalis is an important pest of corn. To understand the adaptation mechanisms of insect response to UV-A exposure, this study revealed differentially expressed genes (DEGs) and differently expressed metabolites (DEMs) in O. furnacalis under UV-A exposure. Three complementary DNA libraries were constructed from O. furnacalis adult females (CK, UV1h, and UV2h), and 50,106 expressed genes were obtained through Illumina sequencing. Of these, 157 and 637 DEGs were detected in UV1h and UV2h after UV-A exposure for 1 and 2 h, respectively, compared to CK, with 103 and 444 upregulated and 54 and 193 downregulated genes, respectively. Forty four DEGs were detected in UV2h compared to UV1h. Comparative transcriptome analysis between UV-treated and control groups revealed signal transduction, detoxification and stress response, immune defense, and antioxidative system involvement. Metabolomics analysis showed that 181 (UV1h vs. CK), 111 (UV2h vs. CK), and 34 (UV2h vs. UV1h) DEMs were obtained in positive ion mode, while 135 (UV1h vs. CK), 93 (UV2h vs. CK), and 36 (UV2h vs. UV1h) DEMs were obtained in negative ion mode. Moreover, UV-A exposure disturbed amino acid, sugar, and lipid metabolism. These findings provide insight for further studies on how insects protect themselves under UV-A stress.

Horizontal Gene Transfer and Gene Duplication of β-Fructofuranosidase Confer Lepidopteran Insects Metabolic Benefits

Horizontal gene transfer (HGT) is a potentially critical source of material for ecological adaptation and the evolution of novel genetic traits. However, reports on posttransfer duplication in organism genomes are lacking, and the evolutionary advantages conferred on the recipient are generally poorly understood. Sucrase plays an important role in insect physiological growth and development. Here, we performed a comprehensive analysis of the evolution of insect β-fructofuranosidase transferred from bacteria via HGT. We found that posttransfer duplications of β-fructofuranosidase were widespread in Lepidoptera and sporadic occurrences of β-fructofuranosidase were found in Coleoptera and Hymenoptera. β-fructofuranosidase genes often undergo modifications, such as gene duplication, differential gene loss, and changes in mutation rates. Lepidopteran β-fructofuranosidase gene (SUC) clusters showed marked divergence in gene expression patterns and enzymatic properties in Bombyx mori (moth) and Papilio xuthus (butterfly). We generated SUC1 mutations in B. mori using CRISPR/Cas9 to thoroughly examine the physiological function of SUC. BmSUC1 mutant larvae were viable but displayed delayed growth and reduced sucrase activities that included susceptibility to the sugar mimic alkaloid found in high concentrations in mulberry. BmSUC1 served as a critical sucrase and supported metabolic homeostasis in the larval midgut and silk gland, suggesting that gene transfer of β-fructofuranosidase enhanced the digestive and metabolic adaptation of lepidopteran insects. These findings highlight not only the universal function of β-fructofuranosidase with a link to the maintenance of carbohydrate metabolism but also an underexplored function in the silk gland. This study expands our knowledge of posttransfer duplication and subsequent functional diversification in the adaptive evolution and lineage-specific adaptation of organisms.

Identification of key genes associated with overwintering in Anoplophora glabripennis larva using gene co-expression network analysis

BACKGROUND

Anoplophora glabripennis (Coleoptera: Cerambycidae) is a major quarantine pest in forestry. It is widely distributed throughout many regions such as Asia, Europe, and North America, and has enormous destructive potential for forests. The larvae of A. glabripennis overwinter in a dormant state with strong cold tolerance, and whether the larvae survive winter determines the population density in the following year. However, the molecular mechanisms of this process are not clear.

RESULTS

RNA sequencing (RNA-Seq) analysis of A. glabripennis larvae at five overwintering stages identified 6876 differentially expressed genes (DEGs). Among these, 46 functional genes that might respond to low temperature were identified. Weighted gene co-expression network analysis revealed that the MEturquoise module was correlated with the overwintering process. The STPK, PP2A, DGAT, and HSF genes were identified as hub genes using visualization of gene network. In addition, four genes related to sugar transport, gluconeogenesis and glycosylation were screened, which may be involved in the metabolic regulation of overwintering larvae. The protein-protein interaction network indicated that ribosomal protein and ATP synthase may play an important role in connecting with other proteins. The expression levels of fifteen hub genes were further validated by quantitative RT-PCR, and the results were consistent with RNA-Seq.

CONCLUSION

This study demonstrates key genes that may reveal the molecular mechanism of overwintering in A. glabripennis larvae. The genes may be the potential targets to prevent larvae from surviving the cold winter by developing new biological agents using genetic engineering.

Bombyx mori nucleopolyhedrovirus F-like protein Bm14 is a factor for viral-induced cytopathic effects via regulating oxidative phosphorylation and cellular ROS levels

Bombyx mori nucleopolyhedrovirus (BmNPV) is highly pathogenic to Bombyx mori, silkworm, which causes serious cytopathic effects (CPEs) during infection. However, the role of viral protein in the virus-induced CPEs remains unclear. Here, we discovered that BmNPV infection induced severe CPEs including titer-dependent cell floating and changes in cellular surface morphology. Further explorations revealed the involvement of F-like protein (Bm14), a viral envelope protein, in inducing cytotoxicity and detachment of adherent BmN cells, and its disruption significantly impaired the virus infection-mediated CPEs. Intriguingly, transcriptomic analysis identified the tight association of Bm14 deletion with the activation of cellular oxidative phosphorylation pathway, consistent with the elevated mitochondrial membrane potential (MMP) levels and ATP concentrations as well as reduced ROS levels. Collectively, our results characterized for the first time the novel role of Bm14 in accelerating viral-induced cytopathogenicity via suppressing the cellular oxidative phosphorylation levels and upregulating the ROS levels.

Comparative transcriptome analysis of the rice leaf folder (Cnaphalocrocis medinalis) to heat acclimation

Background

The rice leaf folder Cnaphalocrocis medinalis Güenée is a serious insect pest of rice in Asia. This pest occurs in summer, and it is sensitive to high temperature. However, the larvae exhibit heat acclimation/adaptation. To understand the underlying mechanisms, we established a heat-acclimated strain via multigenerational selection at 39 °C. After heat shock at 41 °C for 1 h, the transcriptomes of the heat-acclimated (S-39) and unacclimated (S-27) larvae were sequenced, using the unacclimated larvae without exposure to 41 °C as the control.

Results

Five generations of selection at 39 °C led larvae to acclimate to this heat stress. Exposure to 41 °C induced 1160 differentially expressed genes (DEGs) between the heat-acclimated and unacclimated larvae. Both the heat-acclimated and unacclimated larvae responded to heat stress via upregulating genes related to sensory organ development and structural constituent of eye lens, whereas the unacclimated larvae also upregulated genes related to structural constituent of cuticle. Compared to unacclimated larvae, heat-acclimated larvae downregulated oxidoreductase activity-related genes when encountering heat shock. Both the acclimated and unacclimated larvae adjusted the longevity regulating, protein processing in endoplasmic reticulum, antigen processing and presentation, MAPK and estrogen signaling pathway to responsed to heat stress. Additionally, the unacclimated larvae also adjusted the spliceosome pathway, whereas the heat-acclimated larvae adjusted the biosynthesis of unsaturated fatty acids pathway when encountering heat stress. Although the heat-acclimated and unacclimated larvae upregulated expression of heat shock protein genes under heat stress including HSP70, HSP27 and CRYAB, their biosynthesis, metabolism and detoxification-related genes expressed differentially.

Conclusions

The rice leaf folder larvae could acclimate to a high temperature via multigenerational heat selection. The heat-acclimated larvae induced more DEGs to response to heat shock than the unacclimated larvae. The changes in transcript level of genes were related to heat acclimation of larvae, especially these genes in sensory organ development, structural constituent of eye lens, and oxidoreductase activity. The DEGs between heat-acclimated and unacclimated larvae after heat shock were enriched in the biosynthesis and metabolism pathways. These results are helpful to understand the molecular mechanism underlying heat acclimation of insects.

Comparative transcriptome analysis of differentially expressed genes in Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae) at different acute stress temperatures

The gnat, Bradysia odoriphaga Yang et Zhang, is an important underground pest in Asia. B. odoriphaga differ in heat and cold tolerance and exhibit quite different developmental strategies. To understand the underlying mechanisms, we sequenced and compared the transcriptome of B. odoriphaga under 40 °C (a stressful high temperature), 25 °C, and 4 °C (a stressful low temperature) for 1 h. We found that metabolism- and ribosome-related genes were modulated. In high temperature (40 °C), heat shock protein (HSP) genes, detoxication genes, metabolism genes, protein turnover genes, and stress signal transduction genes were differentially expressed. In low temperature (4 °C), genes related with heat shock protein (HSP) and detoxication were differentially expressed. Our study increases our understanding of the complex molecular mechanisms involved in the responses of B. odoriphaga to acute temperature stress and provides a potential strategy for pest management.

Identifications, Characteristics, and Expression Patterns of Small Heat Shock Protein Genes in a Major Mulberry Pest, Glyphodes pyloalis (Lepidoptera: Pyralidae)

Six candidate sHSP genes were identified from the Glyphodes pyloalis transcriptome. All sHSP genes included full-length open reading frames and shared high similarity with the sequences of other lepidopteran species. These sHSP genes encoded 175-191 amino acid residues, and the predicted proteins had a molecular weight from 19.5 to 21.8 kDa. All GpsHSPs were expressed at lower levels at larval stages. All GpsHSPs were expressed at higher levels at diapaused, prepupal, or pupal stages, suggesting that sHSPs may be involved in metamorphosis in G. pyloalis. In addition to the developmental stage, extreme temperatures can induce variations in the expression of sHSPs genes. All GpsHSPs were significantly upregulated in larvae following exposure to heat shock, except GpHSP21.4 which downregulated at 4 h following exposure to the cold shock treatment. Furthermore, Starvation influenced the expression patterns of GpsHSPs as a function of the duration of food deprivation. Four GpsHSPs increased their expression with time of starvation until reaching to the peak level at 6 d of starvation. Finally, parasitism by the endoparasitoid Aulacocentrum confusum He et van Achterberg (Hymenoptera: Braconidae)-induced fluctuations in the expression of all GpsHSPs, and the expression varied with time after parasitization. Our results from this study strongly suggest functional differentiation within the sHSPs subfamily in G. pyloalis. The present study would provide further insight into the roles of sHSPs in G. pyloalis and novel avenues for promoting integrated management of this pest.