Expression of the Tribolium castaneum (Coleoptera: Tenebrionidae) hsp83 gene and its relation to oogenesis during ovarian maturation

The interspecific variations in molecular responses to various doses of heat and cold stress: the case of cereal aphids

Insects are currently subjected to unprecedented thermal stress due to recent increases in the frequency and amplitude of temperature extremes. Understanding molecular responses to thermal stress is critically important to appreciate how species react to thermal stress. Three co-occurring cosmopolitan species are found within the guild of cereal aphids: Sitobion avenae, Ropalosiphum padi and Metopolophium dirhodum. Earlier reports have shown that increasing frequency of temperature extremes causes a shift in dominant species within guilds of cereal aphids by differently altering the population's growth. We hypothesize that a differential molecular response to stress among species may partially explain these changes. Heat shock proteins (HSPs) are molecular chaperones well known to play an important role in protecting against the adverse effects of thermal stress. However, few studies on molecular chaperones have been conducted in cereal aphids. In this study, we compared the heat and cold tolerance between three aphid species by measuring the median lethal time (Lt₅₀) and examined the expression profiles of seven hsp genes after exposures to comparable thermal injury levels and also after same exposure durations. Results showed that R. padi survived comparatively better at high temperatures than the two other species but was more cold-sensitive. Hsp genes were induced more strongly by heat than cold stress. Hsp70A was the most strongly up-regulated gene in response to both heat and cold stress. R. padi had more heat inducible genes and significantly higher mRNA levels of hsp70A, hsp10, hsp60 and hsp90 than the other two species. Hsps ceased to be expressed at 37°C in M. dirhodum and S. avenae while expression was maintained in R. padi. In contrast, M. dirhodum was more cold tolerant and had more cold inducible genes than the others. These results confirm species-specific differences in molecular stress responses and suggest that differences in induced expression of hsps may be related to species' thermal tolerance, thus causing the changes in the relative abundance.

Identification and expression analysis of heat shock protein family genes of gall fly (Procecidochares utilis) under temperature stress

Heat shock proteins (HSP) are molecular chaperones involved in many normal cellular processes and environmental stresses. At the genome-wide level, there were no reports on the diversity and phylogeny of the heat shock protein family in Procecidochares utilis. In this study, 43 HSPs were identified from the genome of P. utilis, including 12 small heat shock proteins (sHSPs), 23 heat shock protein 40 (DNAJs), 6 heat shock protein 70 (HSP70s), and 2 heat shock protein 90 (HSP90s). The characteristics of these candidates HSP genes were analyzed by BLAST, and then phylogenetic analysis was carried out. Quantitative real-time PCR (qRT-PCR) was used to analyze the spatiotemporal expression patterns of sHSPs and HSP70s in P. utilis after temperature stress. Results showed that most sHSPs could be induced under heat stress during the adult stage of P. utilis, while a few HSP70s could be induced at the larval stage. This study provides an information framework for the HSP family of P. utilis. Moreover, it lays an important foundation for a better understanding of the role of HSP in the adaptability of P. utilis to various environments.

Sitobion miscanthi L type symbiont enhances the fitness and feeding behavior of the host grain aphid

BACKGROUND

Symbiotic bacteria affect physiology and ecology of insect hosts. The Sitobion miscanthi L type symbiont (SMLS) is a recently discovered and widely distributed secondary symbiont in the grain aphid Sitobion miscanthi Takahashi in China.

RESULTS

In this study, SMLS-infected (SI) and SMLS-uninfected (SU) aphid strains were obtained from field population. The artificially SMLS-re-infected (SRI) strain was established by injecting SU aphids with the SI strain hemolymph containing SMLS. The SRI and SU strains had identical genetic backgrounds and similar microbial community structures. Compared with the SU strain, adult longevity, survival rate, and fecundity were significantly greater in the SRI strain (biological fitness of 1.48). Moreover, the SRI strain spent more time ingesting phloem than the SU strain. A comparative transcriptome analysis indicated that reproduction- and longevity-related genes were more highly expressed in the SRI strain than in the SU strain.

CONCLUSION

The findings indicated that the infection with SMLS enhanced the Sitobion miscanthi fitness and feeding behavior. The beneficial effect of the SMLS on hosts could explain why it frequently infects the field populations in the grain aphid Sitobion miscanthi Takahashi in China. © 2022 Society of Chemical Industry.

Proteomic investigation of Peristenus spretus ovary and characterization of an ovary-enriched heat shock protein

Peristenus spretus (Hymenoptera: Braconidae) is one of the most important endoparasitoids used for biological control of the green mirid bug, Apolygus lucorum Meyer-Dür (Heteroptera: Miridae). However, what we know about its reproductive genetics is very limited. Here, the composition of ovarian proteins in P. spretus was analyzed. Mass spectrum data searched against the non-redundant NCBI protein and UniProt protein database identified 1382 proteins and revealed an enrichment of the heat shock protein 83 (HSP83) in P. spretus ovary. The Pshsp83 complete cDNA is 2175 bp in length and encodes a protein of 724 amino acids with a calculated molecular mass of 83.4 kDa and a theoretical isoelectric point of 4.87. Transcription of Pshsp83 appeared from days 1 to 13 post-emergence and peaked at 13th day. Immuno-localization showed that the HSP83 protein was present in cytoplasm of germarium and in egg chambers of the whole ovariole. The transcript abundance of Pshsp83 fluctuated drastically after heat shocks at different temperatures and the maximum emerged at 35°C. The exposure to 35°C caused no dramatic effects on reproductive parameters of adult females such as pupation rate, cocoon weight, emergence rate, sex ratio and developmental duration, but did on longevity. These results suggested that the HSP83 protein is involved in life-span regulation in the P. spretus.

Identification and Characterization of Three Heat Shock Protein 90 (Hsp90) Homologs in the Brown Planthopper

Hsp90 (heat shock protein 90) chaperone machinery is considered to be a key regulator of proteostasis under both physiological and stress growth conditions in eukaryotic cells. The high conservation of both the sequence and function of Hsp90 allows for the utilization of various species to explore new phenotypes and mechanisms. In this study, three Hsp90 homologs were identified in the brown planthopper (BPH), Nilaparvata lugens: cytosolic NlHsp90, endoplasmic reticulum (ER) NlGRP94 and mitochondrial NlTRAP1. Sequence analysis and phylogenetic construction showed that these proteins belonged to distinct classes consistent with the predicted localization and suggested an evolutionary relationship between NlTRAP1 and bacterial HtpG (high-temperature protein G). Temporospatial expression analyses showed that NlHsp90 was inducible under heat stress throughout the developmental stage, while NlGRP94 was only induced at the egg stage. All three genes had a significantly high transcript level in the ovary. The RNA interference-mediated knockdown of NlHsp90 its essential role in nymph development and oogenesis under physiological conditions. NlGRP94 was also required during the early developmental stage and played a crucial role in oogenesis, fecundity and late embryogenesis. Notably, we first found that NlHsp90 and NlGRP94 were likely involved in the cuticle structure of female BPH. Together, our research revealed multifunctional roles of Hsp90s in the BPH.

Molecular characterization of eight ATP-dependent heat shock protein transcripts and their expression profiles in response to stresses in the spruce budworm, Choristoneura fumiferana (L.)

Heat shock proteins (HSPs) greatly contribute to insect stress tolerance and enhance survival and adaptation in severe environmental conditions. To investigate the potential roles of HSPs in the spruce budworm, Choristoneura fumiferana (L.), an important native pest of forests in North America, we found eight ATP-dependent HSP transcripts (CfHSPs). Based on molecular characteristics, the identified HSP genes were classified into HSP70 and HSP90 families, and phylogenetic results showed that they had orthologues in other insects. The transcript levels of these HSPs were measured using RT-qPCR under normal and stressful conditions in the laboratory. Under normal conditions, three HSP genes were consistently expressed in all life stages, whereas expression of the other five genes was dependent on the developmental stage. In the larvae, most CfHSP transcripts displayed similar expression levels among different tissues. Under heat shock conditions, one HSP70 gene and one HSP90 gene were upregulated in all life stages. One HSP70 gene was upregulated after cold injury in the larval stage. With starvation, HSP gene expression exhibited complex expression patterns; most of them were downregulated. These results suggest that the ATP-dependent HSPs have multiple roles during normal development as well as under stressful conditions including heat, cold injury and starvation.

Expression of heat shock proteins in adult honey bee (Apis mellifera L.) workers under hot-arid subtropical ecosystems

Heat stress elicits the expression of heat shock proteins (HSPs) in honey bee subspecies. These highly conserved proteins have significant role in protecting cells from thermal-induced stresses. Honey bees in subtropical regions face extremely dry and hot environment. The expression of HSPs in the nurses and foragers of indigenous (Apis mellifera jemenitica) and imported European (Apis mellifera ligustica and Apis mellifera carnica) honey bee subspecies after heat shock treatment were compared using SDS-PAGE. Hsp70 and Hsp82 were equally expressed in the nurses of all tested bee subspecies when exposed to 40 °C and 45 °C for 4 h. The forager bees exhibited differential expression of HSPs after heat stress. No HSPs was expressed in the foragers of A. m. jemenitica, and Hsp70 was expressed only in the foragers of A. m. ligustica and A. m. carnica at 40 °C. A prominent diversity in HSPs expression was also exhibited in the foragers at 45 °C with one HSP (Hsp70) in A. m. jemenitica, two HSPs (Hsp40 and Hsp70) in A. m. carnica, and three HSPs (Hsp40, Hsp60 and Hsp70) in A. m. ligustica. No HSPs was expressed in the control nurse and forager bees at any of the tested temperatures. These findings illustrated the differences in HSP expression among nurse and forager bees. It is obvious that the native foragers are more heat tolerant with least HSPs expression than exotic bee races. Further investigations will help to understand the potential role of HSPs in the adaptability, survival, and performance of bee subspecies in harsh climate of the subtropical regions.

Transcriptome profiling of the Plutella xylostella (Lepidoptera: Plutellidae) ovary reveals genes involved in oogenesis

BACKGROUND

As a specialized organ, the insect ovary performs valuable functions by ensuring fecundity and population survival. Oogenesis is the complex physiological process resulting in the production of mature eggs, which are involved in epigenetic programming, germ cell behavior, cell cycle regulation, etc. Identification of the genes involved in ovary development and oogenesis is critical to better understand the reproductive biology and screening for the potential molecular targets in Plutella xylostella, a worldwide destructive pest of economically major crops.

RESULTS

Based on transcriptome sequencing, a total of 7.88Gb clean nucleotides was obtained, with 19,934 genes and 1861 new transcripts being identified. Expression profiling indicated that 61.7% of the genes were expressed (FPKM≥1) in the P. xylostella ovary. GO annotation showed that the pathways of multicellular organism reproduction and multicellular organism reproduction process, as well as gamete generation and chorion were significantly enriched. Processes that were most likely relevant to reproduction included the spliceosome, ubiquitin mediated proteolysis, endocytosis, PI3K-Akt signaling pathway, insulin signaling pathway, cAMP signaling pathway, and focal adhesion were identified in the top 20 'highly represented' KEGG pathways. Functional genes involved in oogenesis were further analyzed and validated by qRT-PCR to show their potential predominant roles in P. xylostella reproduction.

CONCLUSIONS

Our newly developed P. xylostella ovary transcriptome provides an overview of the gene expression profiling in this specialized tissue and the functional gene network closely related to the ovary development and oogenesis. This is the first genome-wide transcriptome dataset of P. xylostella ovary that includes a subset of functionally activated genes. This global approach will be the basis for further studies on molecular mechanisms of P. xylostella reproduction aimed at screening potential molecular targets for integrated pest management.

Comparative Proteomic Profiling Reveals Molecular Characteristics Associated with Oogenesis and Oocyte Maturation during Ovarian Development of Bactrocera dorsalis (Hendel)

Time-dependent expression of proteins in ovary is important to understand oogenesis in insects. Here, we profiled the proteomes of developing ovaries from Bactrocera dorsalis (Hendel) to obtain information about ovarian development with particular emphasis on differentially expressed proteins (DEPs) involved in oogenesis. A total of 4838 proteins were identified with an average peptide number of 8.15 and sequence coverage of 20.79%. Quantitative proteomic analysis showed that a total of 612 and 196 proteins were differentially expressed in developing and mature ovaries, respectively. Furthermore, 153, 196 and 59 potential target proteins were highly expressed in early, vitellogenic and mature ovaries and most tested DEPs had the similar trends consistent with the respective transcriptional profiles. These proteins were abundantly expressed in pre-vitellogenic and vitellogenic stages, including tropomyosin, vitellogenin, eukaryotic translation initiation factor, heat shock protein, importin protein, vitelline membrane protein, and chorion protein. Several hormone and signal pathway related proteins were also identified during ovarian development including piRNA, notch, insulin, juvenile, and ecdysone hormone signal pathways. This is the first report of a global ovary proteome of a tephritid fruit fly, and may contribute to understanding the complicate processes of ovarian development and exploring the potentially novel pest control targets.

Real-time cell analysis and heat shock protein gene expression in the TcA Tribolium castaneum cell line in response to environmental stress conditions

The rust red flour beetle, Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae), is a pest of stored grain and one of the most studied insect model species. Some of the previous studies involved heat response studies in terms of survival and heat shock protein expression, which are regulated to protect other proteins against environmental stress conditions. In the present study, we characterize the impedance profile with the xCELLigence Real-Time Cell Analyzer and study the effect of increased temperature in cell growth and viability in the cell line BCIRL-TcA-CLG1 (TcA) of T. castaneum. This novel system measures cells behavior in real time and is applied for the first time to insect cells. Additionally, cells are exposed to heat shock, increased salinity, acidic pH and UV-A light with the aim of measuring the expression levels of Hsp27, Hsp68a, and Hsp83 genes. Results show a high thermotolerance of TcA in terms of cell growth and viability. This result is likely related to gene expression results in which a significant up-regulation of all studied Hsp genes is observed after 1 h of exposure to 40 °C and UV light. All 3 genes show similar expression patterns, but Hsp27 seems to be the most affected. The results of this study validate the RTCA method and reveal the utility of insect cell lines, real-time analysis and gene expression studies to better understand the physiological response of insect cells, with potential applications in different fields of biology such as conservation biology and pest management.

Heat shock protein 83 plays pleiotropic roles in embryogenesis, longevity, and fecundity of the pea aphid Acyrthosiphon pisum

Heat shock protein 83 (HSP83) is homologous to the chaperone HSP90. It has pleiotropic functions in Drosophila melanogaster, including the control of longevity and fecundity, and facilitates morphological evolution by buffering cryptic deleterious mutations in wild populations. In the pea aphid Acyrthosiphon pisum, HSP83 expression is moderately induced by bacterial infection but upregulated more strongly in response to heat stress and fungal infection. Stress-inducible heat shock proteins are of considerable evolutionary and ecological importance because they are known to buffer environmental variation and to influence fitness under non-optimal conditions. To investigate the functions of HSP83 in viviparous aphids, we used RNA interference to attenuate its expression and studied the impact on complex parameters. The RNA interference (RNAi)-mediated depletion of HSP83 expression in A. pisum reduced both longevity and fecundity, suggesting this chaperone has an evolutionarily conserved function in insects. Surprisingly, HSP83 depletion reduced the number of viviparous offspring while simultaneously increasing the number of premature nymphs developing in the ovaries, suggesting an unexpected role in aphid embryogenesis and eclosion. The present study indicates that reduced HSP83 expression in A. pisum reveals both functional similarities and differences compared with its reported roles in holometabolous insects. Its impact on aphid lifespan, fecundity, and embryogenesis suggests a function that determines their fitness. This could be achieved by targeting different client proteins, recruiting distinct co-chaperones or transposon activation.

Comprehensive evaluation of candidate reference genes for qRT-PCR studies of gene expression in mustard aphid, Lipaphis erysimi (Kalt)

Mustard aphid, also known as turnip aphid (Lipaphis erysimi) is a major insect pest of rapeseed-mustard group of crops. Tremendous economic significance has led to substantial basic research involving gene-expression studies in this insect species. In qRT-PCR analysis of gene-expression, normalization of data against RNA variation by using appropriate reference gene is fundamental. However, appropriate reference genes are not known in case of L. erysimi. We evaluated 11 candidate reference genes for their expression stability in 21 samples of L. erysimi subjected to various regimes of experimental treatments. Unlike other studies, we validated true effects of the treatments on the samples either by gene-expression study of an associated marker gene or by biochemical tests. In the validated samples, expression stability of the reference genes was analysed by employing four different statistical softwares geNorm, NormFinder, BestKeeper and deltaCt. Drawing consensus on the results from different softwares, we recommend three best reference genes 16S, RPS18 and RPL13 for normalization of qRT-PCR data in L. erysimi. This study provides for the first time a comprehensive list of suitable reference genes for mustard aphid and demonstrates the advantage of using more than one reference gene in combination for certain experimental conditions.

Downregulation of the evolutionary capacitor Hsp90 is mediated by social cues

The relationship between robustness and evolvability is a long-standing question in evolution. Heat shock protein 90 (HSP90), a molecular chaperone, has been identified as a potential capacitor for evolution, since it allows for the accumulation and release of cryptic genetic variation, and also for the regulation of novel genetic variation through transposon activity. However, to date, it is unknown whether Hsp90 expression is regulated upon demand (i.e. when the release of cryptic genetic variation is most needed). Here, we show that Hsp90 has reduced transcription under conditions where the mobilization of genetic variation could be advantageous. We designed a situation that indicates a stressful environment but avoids the direct effects of stress, by placing untreated (focal) red flour beetles, Tribolium castaneum, into groups together with wounded conspecifics, and found a consistent reduction in expression of two Hsp90 genes (Hsp83 and Hsp90) in focal beetles. We moreover observed a social transfer of immunity in this non-eusocial insect: there was increased activity of the phenoloxidase enzyme and downregulation of the immune regulator, imd. Our study poses the exciting question of whether evolvability might be regulated through the use of information derived from the social environment.

Low doses of the common alpha-cypermethrin insecticide affect behavioural thermoregulation of the non-targeted beneficial carabid beetle Platynus assimilis (Coleoptera: Carabidae)

Sub-lethal effects of pesticides on behavioural endpoints are poorly investigated in non-targeted beneficial carabids. Conspicuous changes in locomotor activity of carabids exposed to sub-lethal doses of neurotoxic insecticides suggest that many other behaviours of these insects might be severely injured as well. We hypothesize that behavioural thermoregulation of carabids may be affected by low doses of neurotoxic pyrethroid insecticide alpha-cypermethrin which may have direct deleterious consequences for the fitness and populations of the beetles in the field. Automated video tracking of the carabid beetle Platynus assimilis Paykull (Coleoptera: Carabidae) on an experimental thermal mosaic arena using EthoVision XT Version 9 software (Noldus Information Technology, Wageningen, The Netherlands) showed that brief exposure to alpha-cypermethrin at sub-lethal concentrations (0.1-10mgL(-1)) drastically reduces the ability of the beetles for behavioural thermoregulation. At noxious high temperature, a considerable number of the beetles died due to thermo-shock. Other intoxicated beetles that survived exposure to high temperature displayed behavioural abnormalities. During heating of the arena from 25 to 45°C, insecticide treated beetles showed a significant fall in tendency to hide in a cool shelter (20°C) and prolonged exposure to noxious high temperatures, accompanied by changes in locomotor activity. Next day after insecticide treatment the beetles recovered from behavioural abnormalities to a large extent but they still were considerably longer exposed to noxious high temperatures compared to the negative control beetles. Our results demonstrated that behavioural thermoregulation is a sensitive and important etho-toxicological biomarker in ground-dwelling carabids. Prolonged exposure to unfavourably high temperatures has an array of negative effects decreasing fitness and survival of these insects at elevated thermal conditions with deep temperature gradients, typical of agricultural habitats. These results may have importance in IPM programs promoting reduced insecticide use.

Identification and characterization of novel ER-based hsp90 gene in the red flour beetle, Tribolium castaneum

Heat-shock protein 90 (HSP90) is a highly conserved molecular chaperone found in all species except for Archaea, which is required not only for stress tolerance but also for normal development. Recently, it was reported that HSP83, one member of the cytosolic HSP90 family, contributes to oogenesis and responds to heat resistance in Tribolium castaneum. Here, a novel ER-based HSP90 gene, Tchsp90, has been identified in T. castaneum. Phylogenetic analysis showed that hsp90s and hsp83s evolved separately from a common ancestor but that hsp90s originated earlier. Quantitative real-time polymerase chain reaction illustrated that Tchsp90 is expressed in all developmental stages and is highly expressed at early pupa and late adult stages. Tchsp90 was upregulated in response to heat stress but not to cold stress. Laval RNAi revealed that Tchsp90 is important for larval/pupal development. Meanwhile, parental RNAi indicated that it completely inhibited female fecundity and partially inhibited male fertility once Tchsp90 was knocked down and that it will further shorten the lifespan of T. castaneum. These results suggest that Tchsp90 is essential for development, lifespan, and reproduction in T. castaneum in addition to its response to heat stress.

Characterizing heat shock protein 90 gene of Apolygus lucorum (Meyer-Dür) and its expression in response to different temperature and pesticide stresses

In this study, we cloned a full-length cDNA of heat shock protein (HSP) gene of Apolygus lucorum (Meyer-Dür) [AlHSP90, KC109781] and investigated its expression in response to temperature and pesticide stresses. The open reading frame (ORF) of AlHSP90 is 2,169 bp in length, encoding a 722 amino acid polypeptide with a predicted molecular weight of 82.99 kDa. Transcriptional and translational expression profiles of AlHSP90 under extreme temperature or pesticide stresses were examined by fluorescent real-time quantitative PCR and Western blot. Results showed that the expression profiles of AlHSP90 protein were in high agreement with those of AlHSP90 RNA and indicated that AlHSP90 was not only an important gene for A. lucorum adults in response to extremely high temperature, but also involved in the resistance or tolerance to cyhalothrin, imidacloprid, chlorpyrifos, and emamectin benzoate, especially for female adults to emamectin benzoate and for male adults to cyhalothrin. Transcriptional results of AlHSP90 also confirmed that AlHSP90 was an important gene involved in the resistance or tolerance to both temperature and pesticide stresses. In addition, our study also revealed that ∼24 °C may be the suitable temperature range for A. lucorum survival, which is also confirmed by the results of the expression of AlHSP90, the nymph mortality, and the intrinsic rate of increase (r m) when A. lucorum is reared at six different temperatures. Therefore, these studies are significant in elucidating the AlHSP90 in response to temperature and pesticide stresses and would provide guidance for A. lucorum management with different pesticides or temperatures in fields.

Tribolium castaneum as a model for high-throughput RNAi screening

Coleopteran insects are a highly diverse and successful order, and many beetle species are significant agricultural pests. New biorational strategies for managing populations of beetles and other insect species are needed as pests develop resistance to chemical insecticides and Bt toxins. There is now an opportunity to use genome sequence data to identify genes that are essential for insect growth, development, or survival as new targets for designing control technology. This goal requires a method for high-throughput in vivo screening of thousands of genes to identify candidate genes that, when their expression is disrupted, have a phenotype that may be useful in insect pest control. Tribolium castaneum, the red flour beetle, is a model organism that offers considerable advantages for such screening, including ease of rearing in large numbers, a sequenced genome, and a strong, systemic RNAi response for specific depletion of gene transcripts. The RNAi effect in T. castaneum can be elicited in any tissue and any stage by the injection of dsRNA into the hemocoel, and injection of dsRNA into adult females can even be used to identify phenotypes in offspring. A pilot RNAi screen (iBeetle) is underway. Several T. castaneum genes with promising RNAi phenotypes for further development as mechanisms for plant protection have been identified. These include heat shock protein 90, chitin synthase, the segmentation gene hairy, and a matrix metalloprotease. Candidate genes identified in T. castaneum screens can then be tested in agricultural pest species (in which screening is not feasible), to evaluate their effectiveness for use in potential plant-based RNAi control strategies. Delivery of dsRNA expressed by genetically modified crops to the midgut of phytophagous insects is under investigation as a new tool for very specific protection of plants from insect pest species. The T. castaneum screening platform offers a system for discovery of candidate genes with high potential benefit.

The involvement of heat shock protein and cytochrome P450 genes in response to UV-A exposure in the beetle Tribolium castaneum

Sunlight is an important environmental factor that affects all living organisms on Earth. Ultraviolet A (UV-A) is one of the many frequency bands found in sunlight. Many animals use UV-A to attain visual cues, for example, in foraging and mate selection. However, UV-A can also induce damage, such as oxidative stress, DNA lesions and apoptosis. In the present study, we investigated the effects of UV-A on the survival, fecundity and expression profiles of several stress-responsive genes belonging to the heat shock protein (Hsp) and the cytochrome CYP6BQ families from the adult red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). The results showed that short-term UV-A exposure (365 nm, <4h) did not influence the survival or fecundity of the beetles; however, Hsp27, Hsp68, Hsp83, CYP6BQ4 and CYP6BQ8 mRNA levels significantly increased during the first 2h of UV-A exposure. Among them, Hsp68 was the most highly up-regulated, increasing by 8.9-fold. These results indicate that these genes may participate in the defense against harmful UV-A radiation. In addition, we investigated the potential transcription factor binding motifs (TFBMs) in the promoter sequences of genes induced in similar pattern from the Hsp and P450 gene families; the results indicated that, these motifs are highly homologous to environmental stress transcription factor binding sites in mammals. Our experiments revealed that UV-A irradiation could influence the expression profile of stress-responsive genes, such as Hsps and P450s, which have universal TFBMs, and that these genes may be involved in reducing the ecological challenges posed by irradiation.

Post-embryonic functions of HSP90 in Tribolium castaneum include the regulation of compound eye development

Heat shock protein 90 (HSP90) belongs to a family of conserved chaperons with multiple roles in stress adaptation and development, including spermatogenesis, oogenesis and embryogenesis in insects. In the red flour beetle, Tribolium castaneum, we found that HSP90 is transiently upregulated during larval development, in prepupae, in female pupae and in adults, suggesting multiple post-embryonic roles. We found that silencing HSP90 expression by RNA interference was lethal within 10 days at all developmental stages. Titration experiments revealed that larvae were more susceptible than pupae or beetles. Interestingly, HSP90 silencing in final instar larvae resulted in abnormal pupal phenotypes lacking compound eyes and exhibiting prepupal features, suggesting developmental arrest at the prepupal stage. Our results suggest that HSP90 functions can be expanded beyond the known ones in insect embryogenesis to include roles in post-embryonic development such as the regulation of compound eye development.