Cuticular protein genes involve heat acclimation of insect larvae under global warming

Mitochondrial Fission Is Involved in Heat Resistance in Zebrafish

Global warming and extreme weather events pose a significant threat to global biodiversity, with rising water temperatures exerting a profound influence on fish conservation and fishery development. In this study, we used zebrafish as a model organism to explore the impact of a heat acclimation period on their survival rates. The results demonstrated that a 2-month heat acclimation period almost completely mitigated heat stress-induced mortality in zebrafish. Subsequent analysis of the surviving zebrafish revealed a predominance of hepatic mitochondria in a fission state. Remarkably, a short-term fasting regimen, which induced hepatic mitochondrial fission, mirrored the outcomes of the protective effect of heat acclimation and augmented animal survival under heat stress. Conversely, treatment with a mitochondrial fission inhibitor within the fasting group attenuated the elevated survival rate. Furthermore, zebrafish embryos subjected to brief heat acclimation also exhibited increased heat resistance, a trait diminished by a chemical intervention inhibiting mitochondrial fission. This suggests a shared mechanism for heat resistance between embryos and adult zebrafish. These findings underscore the potential use of inducing mitochondrial fission to enhance heat resistance in zebrafish, offering promise for fish biodiversity conservation in the face of global warming.

Reduced cold tolerance of viral-infected leafhoppers attenuates viral persistent epidemics

Most arthropod-borne viruses produce intermittent epidemics in infected plants. However, the underlying mechanisms of these epidemics are unclear. Here, we demonstrated that rice stripe mosaic virus (RSMV), a viral pathogen, significantly increases the mortality of its overwintering vector, the leafhopper species Recilia dorsalis. Cold-stress assays indicated that RSMV reduces the cold tolerance of leafhoppers, a process associated with the downregulation of leafhopper cuticular protein genes. An RSMV-derived small RNA (vsiR-t00355379) was found to facilitate the downregulation of a leafhopper endocuticle gene that is mainly expressed in the abdomen (named RdABD-5) and is conserved across dipteran species. The downregulation of RdABD-5 expression in R. dorsalis resulted in fewer and thinner endocuticle lamellae, leading to decreased cold tolerance. This effect was correlated with a reduced incidence rate of RSMV in early-planted rice plants. These findings contribute to our understanding of the mechanism by which viral pathogens reduce cold tolerance in arthropod vectors and suggest an approach to managing the fluctuating prevalence of arboviruses.

IMPORTANCE

Increasing arthropod vector dispersal rates have increased the susceptibility of crop to epidemic viral diseases. However, the incidence of some viral diseases fluctuates annually. In this study, we demonstrated that a rice virus reduces the cold tolerance of its leafhopper vector, Recilia dorsalis. This effect is linked to the virus-derived small RNA-mediated downregulation of a gene encoding a leafhopper abdominal endocuticle protein. Consequently, the altered structural composition of the abdominal endocuticle reduces the overwinter survival of leafhoppers, resulting in a lower incidence of RSMV infection in early-planted rice plants. Our findings illustrate the important roles of RNA interference in virus-vector insect-environment interactions and help explain the annual fluctuations of viral disease epidemics in rice fields.

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.

The molecular basis of heat stress responses in plants

Global warming impacts crop production and threatens food security. Elevated temperatures are sensed by different cell components. Temperature increases are classified as either mild warm temperatures or excessively hot temperatures, which are perceived by distinct signaling pathways in plants. Warm temperatures induce thermomorphogenesis, while high-temperature stress triggers heat acclimation and has destructive effects on plant growth and development. In this review, we systematically summarize the heat-responsive genetic networks in Arabidopsis and crop plants based on recent studies. In addition, we highlight the strategies used to improve grain yield under heat stress from a source-sink perspective. We also discuss the remaining issues regarding the characteristics of thermosensors and the urgency required to explore the basis of acclimation under multifactorial stress combination.

Identification of cuticular protein genes and analysis of their roles in phosphine resistance of the rusty grain beetle Cryptolestes ferrugineus

The rusty grain beetle, Cryptolestes ferrugineus (Stephens) is one of the most economically important stored grain pests, and it has evolved the high resistance to phosphine. Cuticular proteins (CPs) are the major structural components of insect cuticle, and previous studies have confirmed that CPs were involved in insecticide resistance. However, the CPs of C. ferrugineus are still poorly characterized, and thus we conducted transcriptome-wide identification of CP genes and analyze their possible relationships with phosphine resistance in this pest. In this study, a total of 122 putative CPs were annotated in the C. ferrugineus transcriptome data by blasting with the known CPs of Tribolium castaneum. The analysis of conserved motifs revealed these CPs of C. ferrugineus belonging to 9 different families, including 87 CPR, 13 CPAP1, 7 CPAP3, 3 Tweedle, 1 CPLCA, 1 CPLCG, 5 CPLCP, 2 CPCFC, and 3 CPFL proteins. The further phylogenetic analysis showed the different evolutionary patterns of CPs. Namely, we found some CPs (CPR family) formed species-specific protein clusters, indicating these CPs might occur independently among insect taxa, and while some other CPs (CPAP1 and CPAP3 family) shared a closer correlation based on the architecture of protein domains. Subsequently, the previous RNA-seq data were applied to establish the expression profiles of CPs in a phosphine susceptible and resistant populations of C. ferrugineus, and a large amount of CP genes were found to be over-expressed in resistant insects. Lastly, an up-regulated CP gene (CPR family) was selected for the further functional analysis, and after this gene was silenced via RNA interference (RNAi), the sensitivity to phosphine was significantly enhanced in C. ferrugineus. In conclusion, the present results provided us an overview of C. ferrugineus CPs, and which suggested that the CPs might play the critical roles in phosphine resistance.

Glucose Dehydrogenases-Mediated Acclimation of an Important Rice Pest to Global Warming

Global warming is posing a threat to animals. As a large group of widely distributed poikilothermal animals, insects are liable to heat stress. How insects deal with heat stress is worth highlighting. Acclimation may improve the heat tolerance of insects, but the underlying mechanism remains vague. In this study, the high temperature of 39 °C was used to select the third instar larvae of the rice leaf folder Cnaphalocrocis medinalis, an important insect pest of rice, for successive generations to establish the heat-acclimated strain (HA39). The molecular mechanism of heat acclimation was explored using this strain. The HA39 larvae showed stronger tolerance to 43 °C than the unacclimated strain (HA27) persistently reared at 27 °C. The HA39 larvae upregulated a glucose dehydrogenase gene, CmGMC10, to decrease the reactive oxygen species (ROS) level and increase the survival rate under heat stress. The HA39 larvae maintained a higher activity of antioxidases than the HA27 when confronted with an exogenous oxidant. Heat acclimation decreased the H₂O₂ level in larvae under heat stress which was associated with the upregulation of CmGMC10. The rice leaf folder larvae may acclimate to global warming via upregulating CmGMC10 to increase the activity of antioxidases and alleviate the oxidative damage of heat stress.

Reference Genes for Expression Analysis Using RT-qPCR in Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)

Cnaphalocrocis medinalis is a destructive migratory rice pest. Although many studies have investigated its behavioral and physiological responses to environmental changes and migration-inducing factors, little is known about its molecular mechanisms. This study was conducted to select suitable RT-qPCR reference genes to facilitate future gene expression studies. Here, thirteen candidate housekeeping genes (EF1α, AK, EF1β, GAPDH, PGK, RPL13, RPL18, RPS3, 18S rRNA, TBP1, TBP2, ACT, and UCCR) were selected to evaluate their stabilities under different conditions using the ∆CT method; the geNorm, NormFinder, BestKeeper algorithms; and the online tool RefFinder. The results showed that the most stable reference genes were EF1β, PGK, and RPL18, related to developmental stages; RPS3 and RPL18 in larval tissues; EF1β and PGK in larvae feeding on different rice varieties; EF1α, EF1β, and PGK in larvae temperature treatments; PGK and RPL13, related to different adult ages; PGK, EF1α, and ACT, related to adult nutritional conditions; RPL18 and PGK, related to adult mating status; and, RPS3 and PGK, related to different adult take-off characteristics. Our results reveal reference genes that apply to various experimental conditions and will greatly improve the reliability of RT-qPCR analysis for the further study of gene function in this pest.