Effect of temperature on survival and cuticular composition of three different ant species

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

Cuticular proteins (CPs) play important roles in insect growth and development. However, it is unknown whether CPs are related to heat tolerance. Cnaphalocrocis medinalis, a serious pest of rice, occurs in summer and exhibits strong adaptability to high temperature, but the underlying mechanism is unclear. Here, the role of CP genes in heat acclimation was studied. Heat tolerance of the heat-acclimated larvae was significantly stronger than the unacclimated larvae. The cuticular protein content in the heat-acclimated larvae was higher than that of the unacclimated larvae. 191 presumed CP genes of C. medinalis (CmCPs) were identified. Expression patterns of 14 CmCPs were different between the heat acclimated (S39) and unacclimated (S27) larvae under heat stress. CmCPs were specifically expressed in epidermis and the head except CmCPR20 mainly expressed in Malpighian tubules. CmCPR20 was upregulated in S39 while downregulated in S27, but CmTweedle1 and CmCPG1 were upregulated in S27 and downregulated in S39. RNAi CmTweedle1 or CmCPG1 remarkably decreased heat tolerance and cuticular protein content of the heat-acclimated larvae but not the unacclimated larvae. RNAi CmCPR20 decreased heat tolerance and cuticular protein content of the unacclimated larvae but not the heat-acclimated larvae. CmTweedle1 and CmCPG1 genes involve heat acclimation of C. medinalis.

Cuticular Hydrocarbon Plasticity in Three Rice Planthopper Species

Insect cuticular hydrocarbons (CHCs) are organic compounds of the surface lipid layer, which function as a barrier against water loss and xenobiotic penetration, while also serving as chemical signals. Plasticity of CHC profiles can vary depending upon numerous biological and environmental factors. Here, we investigated potential sources of variation in CHC profiles of Nilaparvata lugens, Laodelphax striatellus and Sogatella furcifera, which are considered to be the most important rice pests in Asia. CHC profiles were quantified by GC/MS, and factors associated with variations were explored by conducting principal component analysis (PCA). Transcriptomes were further compared under different environmental conditions. The results demonstrated that CHC profiles differ among three species and change with different developmental stages, sexes, temperature, humidity and host plants. Genes involved in cuticular lipid biosynthesis pathways are modulated, which might explain why CHC profiles vary among species under different environments. Our study illustrates some biological and ecological variations in modifying CHC profiles, and the underlying molecular regulation mechanisms of the planthoppers in coping with changes of environmental conditions, which is of great importance for identifying potential vulnerabilities relating to pest ecology and developing novel pest management strategies.

Is It Possible to Obtain the Chemical Profile From Ethanol-Preserved Specimens? The Hydrocarbon and Fatty Acid Composition of the Social Wasp Polybia paulista (Hymenoptera: Vespidae: Epiponini)

Cuticular hydrocarbons perform multiple functions in insects such as protecting against desiccation and pathogenic infection, and signaling interactions. Evaluation of cuticular hydrocarbon (CHC) profiles of insects is commonly performed by extraction using a nonpolar solvent such as hexane. Specimens intended for CHC analysis are ideally handled by avoiding contact with solvents such as ethanol. However, insects are frequently stored in ethanol after collection, especially if intended for molecular analysis. To determine if it is possible that chemical compounds in the cuticles of specimens can withstand previous exposure to ethanol, we evaluated the efficiency of CHC extraction from specimens preserved in 95% ethanol. We extracted cuticular compounds from specimens of the social wasp Polybia paulista (Ihering) with no contact with ethanol solvents and compared them with those from specimens stored in 95% ethanol. We analyzed chemical composition from wasps and the 95% ethanol in which they had been stored by a gas chromatograph coupled to a mass spectrometer. In total, 56 compounds were detected: 50 that were classified as hydrocarbons which were mostly branched alkanes, followed by linear alkanes and alkenes. Three compounds were identified as fatty acids, and three compounds were unidentifiable. The ethanol-preserved specimens showed similar chemical profiles to those of specimens that had no contact with ethanol. Thus, we suggest that it is possible to study the chemical profiles of ethanol-preserved specimens.

Low temperatures induce physiological changes in lipids, fatty acids and hydrocarbons, in two rare winter scorpions of genus Urophonius (Scorpiones, Bothriuridae)

Different organisms (mainly poikilotherms) are subject to environmental fluctuations that could affect their normal physiological functioning (e.g., by destabilization of biomembranes and rupture of biomolecules). As a result, animals regulate their body temperature and adapt to different environmental conditions through various physiological strategies. These adaptations are crucial in all organisms, although they are more relevant in those that have reached a great adaptive diversity such as scorpions. Within scorpions, the genus Urophonius presents species with winter activity, being this a peculiarity within the Order and an opportunity to study the strategies deployed by these organisms when facing different temperatures. Here, we explore three basic issues of lipid remodeling under high and low temperatures, using adults and juveniles of Urophonius achalensis and U. brachycentrus. First, as an indicator of metabolic state, we analyzed the lipidic changes in different tissues observing that low temperatures generate higher quantities of triacylglycerols and fewer amount of structural lipids and sphyngomielin. Furthermore, we studied the participation of fatty acids in adaptive homeoviscosity, showing that there are changes in the quantity of saturated and unsaturated fatty acids at low temperature (mainly 16:0, 18:0, 18:1 and 18:2). Finally, we observe that there are quantitative and qualitative variations in the cuticular hydrocarbons (with possible water barrier and chemical recognition function). These fluctuations are in some cases species-specific, metabolic-specific, tissue-specific and in others depend on the ontogenetic state.

Evolution of Protein Structure and Stability in Global Warming

This review focuses on the molecular signatures of protein structures in relation to evolution and survival in global warming. It is based on the premise that the power of evolutionary selection may lead to thermotolerant organisms that will repopulate the planet and continue life in general, but perhaps with different kinds of flora and fauna. Our focus is on molecular mechanisms, whereby known examples of thermoresistance and their physicochemical characteristics were noted. A comparison of interactions of diverse residues in proteins from thermophilic and mesophilic organisms, as well as reverse genetic studies, revealed a set of imprecise molecular signatures that pointed to major roles of hydrophobicity, solvent accessibility, disulfide bonds, hydrogen bonds, ionic and π-electron interactions, and an overall condensed packing of the higher-order structure, especially in the hydrophobic regions. Regardless of mutations, specialized protein chaperones may play a cardinal role. In evolutionary terms, thermoresistance to global warming will likely occur in stepwise mutational changes, conforming to the molecular signatures, such that each "intermediate" fits a temporary niche through punctuated equilibrium, while maintaining protein functionality. Finally, the population response of different species to global warming may vary substantially, and, as such, some may evolve while others will undergo catastrophic mass extinction.

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.

The physiology of Venezillo arizonicus: water balance and the cuticular water barrier

This study investigated the water balance physiology of Venezillo arizonicus, a land isopod endemic to the Southwest Desert Ecoregion of North America. Evaporative water losses were measured in two ways: gravimetric in dry air, and by perfusing animals with dry air in a respirometry chamber and monitoring downstream relative humidity (RH). The respective mean loss flux estimates were 0.140 and 0.177 μg h^-1 cm^-2 Pa^-1, lower than other N. American Oniscidea described to date (≥0.491 μg h^-1 cm^-2 Pa^-1). Humidity monitoring revealed intermittent sharp peaks in RH, attributed to the release of maxillary urine. Whole-animal flux increased as a function of temperature, with a critical temperature (T_c) between 38 and 42 °C identifiable by a clear Arrhenius break point. Hexane-rinsed whole animals yielded straight-chain, saturated hydrocarbons (C₂₁-C₃₃). The surface density of extracted alkanes (0.64 µg cm^-2) was somewhat higher than previously determined values for mesic species, although modest compared to insects and arachnids. Dehydrated animals exposed to high RH (>88%) demonstrated active water vapor absorption (WVA) like other Crinocheta, with an extrapolated uptake threshold of approximately 85% RH (A_w = 0.85), the lowest value reported for Oniscidea. The maximum uptake flux increased linearly as a function of ambient RH. Mass-specific uptake in 100% RH was 49% d^-1, similar to values determined previously for Armadillidium vulgare and Porcellio scaber. The low WVA threshold of V. arizonicus, and the species' low permeability, are consistent with its known range in the arid desert southwest and the desiccation stress of its typical aeolian sand and seasonal wash habitats.

Physiological Metabolic Responses of Ophraella communa to High Temperature Stress

Considering the predicted rising temperatures under current climate change and heat wave scenarios, organisms are expected to suffer more intense and frequent thermal stress. Induced heat is accumulated by organisms and can cause a variety of physiological stress responses. Ophraella communa is an effective biological control agent of common ragweed, Ambrosia artemisiifolia, but the responses of this biocontrol agent to heat stress have not been fully elucidated and, therefore, its potential responses to climate change are uncertain. We investigated the physiological metabolism of subsequent O. communa adults after: (1) different developmental stages (egg, larval, pupal, and adult) were exposed to thermal stress for 3 h each day for 3, 5, 5, and 5 days, respectively (by stage); and (2) individuals were exposed to thermal stress throughout the egg-to-adult period for 3 h each day. The high temperatures of 40, 42, and 44°C were used to induce thermal stress. A control group was reared at 28 ± 2°C. The results showed that short- or long-term exposure to daily phasic high temperatures significantly decreased water and lipid contents and significantly increased glycogen and glycerol contents in all adults (i.e., after exposure of different stages or throughout the egg-to-adult period). However, the total sugar content significantly increased in adults after the eggs and larvae were exposed to brief short-term thermal stress. Compared to the control, the total sugar content was also significantly higher in the adults and pupae exposed to 44°C. Total sugar content in females increased significantly in response to long-term phasic thermal stress at 40°C. However, sugar content of males exposed to 44°C decreased significantly. After long-term phasic thermal stress, water and glycogen contents in males were significantly higher than in females; however, females had higher total sugar and lipid contents. Therefore, our study provides a basic understanding of the metabolic responses of O. communa to thermal stress and offers insights into its potential as a natural biocontrol agent against A. artemisiifolia during the summer season and under predicted climate change scenarios.