Comparative Transcriptome and Proteome Analysis of Heat Acclimation in Predatory Mite Neoseiulus barkeri

Comparative Transcriptome Analysis of Henosepilachna vigintioctomaculata Reveals Critical Pathways during Development

Henosepilachna vigintioctomaculata is distributed in several Asian countries. The larvae and adults often cause substantial economic losses to Solanaceae crops such as potato, tomato, eggplant, and Chinese boxthorn. Even though a chromosome-level genome has been documented, the expression profiles of genes involved in development are not determined. In this study, we constructed embryonic, larval, pupal, and adult transcriptomes, generated a comprehensive RNA-sequencing dataset including ~52 Gb of clean data, and identified 602,773,686 cleaned reads and 33,269 unigenes. A total of 18,192 unigenes were successfully annotated against NCBI nonredundant protein sequences, Swissprot, Eukaryotic Orthologous Groups, Gene Ontology (GO), or Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. There were 3580, 2040, 5160, 2496, 3008, and 3895 differentially expressed genes (DEGs) between adult/egg, egg/larval, larval/pupal, adult/pupal, egg/pupal, and adult/larval samples, respectively. GO and KEGG analyses of the DEGs highlighted several critical pathways associated with specific developing stages. This is the first comprehensive transcriptomic dataset encompassing all developmental stages in H. vigintioctomaculata. Our data may facilitate the exploitation of gene targets for pest control and can serve as a valuable gene resource for future molecular investigations.

Comparative gut proteomics study revealing adaptive physiology of Eurasian spruce bark beetle, Ips typographus (Coleoptera: Scolytinae)

The bark beetle, Ips typographus (L.), is a major pest of Norway spruce, Picea abies (L.), causing enormous economic losses globally. The adult stage of the I. typographus has a complex life cycle (callow and sclerotized); the callow beetles feed ferociously, whereas sclerotized male beetles are more aggressive and pioneers in establishing new colonies. We conducted a comparative proteomics study to understand male and female digestion and detoxification processes in callow and sclerotized beetles. Proteome profiling was performed using high-throughput liquid chromatography-mass spectrometry. A total of >3000 proteins were identified from the bark beetle gut, and among them, 539 were differentially abundant (fold change ±2, FDR <0.05) between callow and sclerotized beetles. The differentially abundant proteins (DAPs) mainly engage with binding, catalytic activity, anatomical activity, hydrolase activity, metabolic process, and carbohydrate metabolism, and hence may be crucial for growth, digestion, detoxification, and signalling. We validated selected DAPs with RT-qPCR. Gut enzymes such as NADPH-cytochrome P450 reductase (CYC), glutathione S-transferase (GST), and esterase (EST) play a crucial role in the I. typographus for detoxification and digesting of host allelochemicals. We conducted enzyme activity assays with them and observed a positive correlation of CYC and GST activities with the proteomic results, whereas EST activity was not fully correlated. Furthermore, our investigation revealed that callow beetles had an upregulation of proteins associated with juvenile hormone (JH) biosynthesis and chitin metabolism, whereas sclerotized beetles exhibited an upregulation of proteins linked to fatty acid metabolism and the TCA cycle. These distinctive patterns of protein regulation in metabolic and functional processes are specific to each developmental stage, underscoring the adaptive responses of I. typographicus in overcoming conifer defences and facilitating their survival. Taken together, it is the first gut proteomic study comparing males and females of callow and sclerotized I. typographus, shedding light on the adaptive ecology at the molecular level. Furthermore, the information about bark beetle handling of nutritionally limiting and defence-rich spruce phloem diet can be utilized to formulate RNAi-mediated beetle management.

Selection, Identification, and Transcript Expression Analysis of Antioxidant Enzyme Genes in Neoseiulus barkeri after Short-Term Heat Stress

Phytoseiid mite Neoseiulus barkeri is a crucial biological control agent utilized to control pest mites and many insects in crops all over the world. However, they are vulnerable to multiple environmental pressures, with high-temperature stress being the most significant challenge. Heat stress disrupts the balance of reactive oxygen species (ROS) levels in organisms, resulting in oxidative stress within the body. Antioxidant enzymes play a crucial role in effectively neutralizing and clearing ROS. In this study, comparative transcriptomics and quantitative real-time PCR (qRT-PCR) were employed to assess the impact of short-term heat stress on the transcript expression of antioxidant enzyme genes in N. barkeri. We primarily identified four antioxidant enzyme genes (NbSOD, NbPrx, NbCAT, and NbGPX) in N. barkeri after exposure to short-term heat stress. Then, new data on the expression patterns of these genes were generated. RNA sequencing and bioinformatics analysis revealed that NbSOD belongs to the Fe/Mn family of superoxide dismutase (SOD), which was identified as MnSOD. NbPrx was classified as a 1-Cys peroxiredoxin of the peroxidase family, whereas NbCAT was recognized as a classical catalase, and NbGPX was determined as cytoplasmic glutathione peroxidase-1 (GPX1). Transcriptional expression analysis of these four genes was conducted at different high temperatures: 36 °C, 38 °C, and 40 °C for 2, 4, and 6 h. The results also showed that all four genes exhibited significant up-regulation in response to short-term heat stress. Similarly, the highest expression levels for NbSOD, NbPrx, and NbCAT were observed at 40 °C for 4 h. However, NbGPX displayed its maximum expression value at 38 °C for 4 h. Overall, the obtained data suggest that short-term heat stress increases levels of ROS generated inside living organisms, which disrupts the oxidative balance and leads to alterations in the expression levels of antioxidant enzyme genes.

Proteomic differences in seminal fluid of social insects whose sperm differ in heat tolerance

In the coming years, climate change is likely to increase the frequency and intensity of heatwaves. In many organisms, heat stress provokes physiological perturbations and can lead to decreased male fertility. Bumblebees are endo-heterothermic but display interspecific differences in thermotolerance that could have conservation implications. For the species of concern Bombus magnus, exposure to high temperatures can severely reduce sperm quality and, consequently, reproductive success. Such is not the case for B. terrestris, a ubiquitous species. To decipher the mechanisms at play, we characterized the seminal fluid proteomes of the two species. We quantified 1121 proteins, of which 522 were differentially expressed between B. terrestris and B. magnus. Several proteins with protective functions, such as proteases, antioxidant proteins and various heat-shock proteins, were present at higher levels in B. terrestris than in B. magnus under both control and heat-stress conditions. The same was true for proteins involved in cellular homeostasis, immunity, lipid/sugar metabolism and thermotolerance. Furthermore, proteins involved in the capture and elimination of reactive oxygen species also occurred at much high levels in B. terrestris. Overall, these results clearly indicate differences in the seminal proteome of the more thermotolerant B. terrestris versus B. magnus. The differences may contribute to explaining interspecific differences in sperm survival.

Cataglyphis desert ants use distinct behavioral and physiological adaptations to cope with extreme thermal conditions

Some ant species live in hot and arid environments, such as deserts and savannas. Worker polymorphism-variation in worker size and/or morphology within colonies-is adaptive in such ecosystems because it enhances resistance to heat stress and increases the efficiency of resource exploitation. However, species with small, monomorphic workers are also frequently found in these environments. How species with distinct worker size and degrees of polymorphism deal with such stressful environments remains poorly studied. We investigated the behavioral, physiological, and molecular adaptations that may enhance heat and desiccation tolerance in two sympatric species of Cataglyphis desert ants that differ dramatically in worker size and polymorphism: C. viatica is polymorphic, while C. cubica is small and monomorphic. We found that worker size, water content, water loss, and protein regulation play a key role in thermal resistance. (i) Large C. viatica workers better tolerated heat and desiccation stress than did small C. viatica or C. cubica workers. The former had greater water content and lost proportionally less water to evaporation under thermal stress. (ii) Despite their similar size distribution, workers of C. cubica are more heat tolerant than small C. viatica. This higher degree of tolerance likely stemmed from C. cubica workers having greater relative water content. (iii) Under thermal stress, small C. viatica workers metabolized larger quantities of fat and differentially expressed proteins involved in cellular homeostasis. In contrast, C. cubica downregulated the expression of numerous proteins involved in mitochondrial respiration likely reducing ROS accumulation. (iv) Consistent with these results, large C. viatica workers remained active throughout the day; C. cubica workers displayed a bimodal activity pattern, and small C. viatica remained poorly active outside the nest. Our study shows that ecologically similar ant species with different degrees of worker size polymorphism evolved distinct strategies for coping with extreme heat conditions.

Transcription dynamics of heat shock proteins in response to thermal acclimation in Ostrinia furnacalis

Acclimation to abiotic stress plays a critical role in insect adaption and evolution, particularly during extreme climate events. Heat shock proteins (HSPs) are evolutionarily conserved molecular chaperones caused by abiotic and biotic stressors. Understanding the relationship between thermal acclimation and the expression of specific HSPs is essential for addressing the functions of HSP families. This study investigated this issue using the Asian corn borer Ostrinia furnacalis, one of the most important corn pests in China. The transcription of HSP genes was induced in larvae exposed to 33°C. Thereafter, the larvae were exposed to 43°C, for 2 h, and then allowed to recover at 27 C for 0, 0.5, 1, 2, 4, 6, and 8 h. At the recovery times 0.5–4 h, most population tolerates less around 1–3 h than without recovery (at 0 h) suffering continuous heat stress (43 C). There is no difference in the heat tolerance at 6 h recovery, with similar transcriptional levels of HSPs as the control. However, a significant thermal tolerance was observed after 8 h of the recovery time, with a higher level of HSP70. In addition, the transcription of HSP60 and HSC70 (heat shock cognate protein 70) genes did not show a significant effect. HSP70 or HSP90 significantly upregulated within 1–2 h sustained heat stress (43 C) but declined at 6 h. Our findings revealed extreme thermal stress induced quick onset of HSP70 or HSP90 transcription. It could be interpreted as an adaptation to the drastic and rapid temperature variation. The thermal tolerance of larvae is significantly enhanced after 6 h of recovery and possibly regulated by HSP70.

Integrative Analysis of lncRNA-mRNA Co-expression Provides Novel Insights Into the Regulation of Developmental Transitions in Female Varroa destructor

Varroa destructor is a major pathogenic driver of the Western honeybee colony losses globally. Understanding the developmental regulation of V. destructor is critical to develop effective control measures. Development is a complex biological process regulated by numerous genes and long non-coding RNAs (lncRNAs); however, the underlying regulation of lncRNAs in the development of V. destructor remains unknown. In this study, we analyzed the RNA sequencing (RNA-Seq) data derived from the four stages of female V. destructor in the reproductive phase (i.e., egg, protonymph, deutonymph, and adult). The identified differentially expressed mRNAs and lncRNAs exhibited a stage-specific pattern during developmental transitions. Further functional enrichment established that fat digestion and absorption, ATP-binding cassette (ABC) transporters, mitogen-activated protein kinase (MAPK) signaling pathway, and ubiquitin-proteasome pathway play key roles in the maturation of female V. destructor. Moreover, the lncRNAs and mRNAs of some pivotal genes were significantly upregulated at the deutonymph stage, such as cuticle protein 65/6.4/63/38 and mucin 5AC, suggesting that deutonymph is the key stage of metamorphosis development and pathogen resistance acquisition for female V. destructor. Our study provides novel insights into a foundational understanding of V. destructor biology.

Sustaining induced heat shock protein 70 confers biological thermotolerance in a high-temperature adapted predatory mite Neoseiulus barkeri (Hughes)

BACKGROUND

In fluctuating climatic environments, heat acclimation in predatory mites is a superior adaptation strategy for effective agricultural pest management and can be used to enhance the abilities critical in biological control efficiency. We investigated the regulatory mechanism governing the remarkable plastic response of thermotolerance in a high-temperature adapted strain (HTAS) and discerned the differences in the defensive reactions between the HTAS and the conventional strain (CS) in the predatory mite Neoseiulus barkeri.

RESULTS

At 42 °C, the relative expression levels of four identified HSP70 genes increased rapidly in both N. barkeri strains; meanwhile the expression of NbHSP70-1 and NbHSP70-2 in CS sharply decreased after 4 h, displaying a distinct contrast with the remaining elevated expression in HTAS. Western blot analysis showed that the protein level of NbHSP70-1 in CS was dramatically elevated at 0.5 h and decreased at 6 h at 42 °C. Conversely, in HTAS, NbHSP70-1 was constantly induced and peaked at 6 h at 42 °C. Furthermore, HSP70 suppression by RNAi knockdown had a greater influence on the survival of HTAS, causing a higher mortality under high temperature than CS. Finally, the recombinant exogenous NbHSP70-1 protein enhanced the viability of E. coli BL21 under a lethal temperature of 50 °C.

CONCLUSION

Sustained accumulation of HSP70 proteins results in predatory phytoseiid mites with the thermotolerance advantage that could promote their biological control function to pests. The divergent constitutive regulation of HSP70 to a thermal environment is conducive to the flexible adaptability of predators in the higher trophic level to trade off under extremely adversity stress.