Characteristic Expression of Three Heat Shock-Responsive Genes During Larval Diapause in the Bamboo Borer Omphisa fuscidentalis

ArHsp90 is important in stress tolerance and embryo development of the brine shrimp, Artemia franciscana

Females of the extremophile crustacean, Artemia franciscana, either release motile nauplii via the ovoviviparous pathway or encysted embryos (cysts) via the oviparous pathway. Cysts contain an abundant amount of the ATP-independent small heat shock protein that contributes to stress tolerance and embryo development, however, little is known of the role of ATP-dependent molecular chaperone, heat shock protein 90 (Hsp90) in the two processes. In this study, a hsp90 was cloned from A. franciscana. Characteristic domains of ArHsp90 were simulated from the deduced amino acid sequence, and 3D structures of ArHsp90 and Hsp90s of organisms from different groups were aligned. RNA interference was then employed to characterize ArHsp90 in A. franciscana nauplii and cysts. The partial knockdown of ArHsp90 slowed the development of nauplius-destined, but not cyst-destined embryos. ArHsp90 knockdown also reduced the survival and stress tolerance of nauplii newly released from A. franciscana females. Although the reduction of ArHsp90 had no effect on the development of diapause-destined embryos, the resulting cysts displayed reduced tolerance to desiccation and low temperature, two stresses normally encountered by A. franciscana in its natural environment. The results reveal that Hsp90 contributes to the development, growth, and stress tolerance of A. franciscana, an organism of practical importance as a feed source in aquaculture.

Regulatory Mechanism of Transcription Factor AhHsf Modulates AhHsp70 Transcriptional Expression Enhancing Heat Tolerance in Agasicles hygrophila (Coleoptera: Chrysomelidae)

Agasicles hygrophila is a classical biological agent used to control alligator weed (Alternanthera philoxeroides). Previous research has indicated that the heat shock factor (HSF) is involved in regulating the transcriptional expression of Hsp70 in response to heat resistance in A. hygrophila. However, the regulatory mechanism by which AhHsf regulates the expression of AhHsp70 remains largely unknown. Here, we identified and cloned a 944 bp AhHsp70 promoter (AhHsp70p) region from A. hygrophila. Subsequent bioinformatics analysis revealed that the AhHsp70p sequence contains multiple functional elements and has a common TATA box approximately 30 bp upstream of the transcription start site, with transcription commencing at a purine base approximately 137 bp upstream of ATG. Promoter deletion analyses revealed that the sequence from -944 to -744 bp was the core regulatory region. A dual-luciferase reporter assay indicated that overexpressed AhHsf significantly enhanced the activity of AhHsp70p. Furthermore, qPCR showed that AhHsp70 expression increased with time in Spodoptera frugiperda (Sf9) cells, and AhHsf overexpression significantly upregulated AhHsp70 expression in vitro. Characterization of the upstream regulatory mechanisms demonstrated that AhHsf binds to upstream cis-acting elements in the promoter region of AhHsp70 from -944 to -744 bp to activate the AhHSF-AhHSP pathway at the transcriptional level to protect A. hygrophila from high temperature damage. Furthermore, we proposed a molecular model of AhHsf modulation of AhHsp70 transcription following heat shock in A. hygrophila. The findings of this study suggest that enhancing the heat tolerance of A. hygrophila by modulating the upstream pathways of the Hsp family can improve the biocontrol of A. philoxeroides.

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.

Functional implication of heat shock protein 70/90 and tubulin in cold stress of Dermacentor silvarum

Background

The tick Dermacentor silvarum Olenev (Acari: Ixodidae) is a vital vector tick species mainly distributed in the north of China and overwinters in the unfed adult stage. The knowledge of the mechanism that underlies its molecular adaptation against cold is limited. In the present study, genes of hsp70 and hsp90 cDNA, named Dshsp70 and Dshsp90, and tubulin were cloned and characterized from D. silvarum, and their functions in cold stress were further evaluated.

Methods

The genome of the heat shock proteins and tubulin of D. silvarum were sequenced and analyzed using bioinformatics methods. Each group of 20 ticks were injected in triplicate with Dshsp90-, Dshsp70-, and tubulin-derived dsRNA, whereas the control group was injected with GFP dsRNA. Then, the total RNA was extracted and cDNA was synthesized and subjected to RT-qPCR. After the confirmation of knockdown, the ticks were incubated for 24 h and were exposed to − 20 °C lethal temperature (LT50), and then the mortality was calculated.

Results

Results indicated that Dshsp70 and Dshsp90 contained an open reading frame of 345 and 2190 nucleotides that encoded 114 and 729 amino acid residues, respectively. The transcript Dshsp70 showed 90% similarity with that identified from Dermacentor variabilis, whereas Dshsp90 showed 85% similarity with that identified from Ixodes scapularis. Multiple sequence alignment indicates that the deduced amino acid sequences of D. silvarum Hsp90, Hsp70, and tubulin show very high sequence identity to their corresponding sequences in other species. Hsp90 and Hsp70 display highly conserved and signature amino acid sequences with well-conserved MEEVD motif at the C-terminal in Hsp90 and a variable C-terminal region with a V/IEEVD-motif in Hsp70 that bind to numerous co-chaperones. RNA interference revealed that the mortality of D. silvarum was significantly increased after injection of dsRNA of Dshsp70 (P = 0.0298) and tubulin (P = 0.0448), whereas no significant increases were observed after the interference of Dshsp90 (P = 0.0709).

Conclusions

The above results suggested that Dshsp70 and tubulin play an essential role in the low-temperature adaptation of ticks. The results of this study can contribute to the understanding of the survival and acclimatization of overwintering ticks.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05056-y.

Induction of Heat Shock Protein Genes is the Hallmark of Egg Heat Tolerance in Agasicles hygrophila (Coleoptera: Chrysomelidae)

Insects are ecotothermic organisms. Their development, survival, reproduction as well as distribution and abundance are affected by temperature. Heat shock protein (HSP) gene expression is closely associated with temperature variation and influences the adaptation of organisms to adverse environments. The beetle Agasicles hygrophila has successfully been used for biological control of the invasive plant alligator weed (Alternanthera philoxeroides). As A. hygrophila populations are substantially inhibited by high temperatures in the summer, increasing global temperatures may limit the efficacy of this control agent. We previously established that A. hygrophila eggs have low tolerance to heat and this factored into the decreased numbers of A. hygrophila beetles at temperatures of 37.5°C and above. Here, we identified 26 HSP genes in A. hygrophila and examined the relationship between the transcript levels of these genes and heat tolerance. The temperature at which the expression of these 21 HSP genes peaked (Tpeak) was 37.5°C, which is in line with the limit of the high temperatures that A. hygrophila eggs tolerate. Therefore, we speculate that the Tpeak of HSP gene expression in eggs indicates the upper limit of temperatures that A. hygrophila eggs tolerate. This study identifies HSP genes as potential robust biomarkers and emphasizes that determining species' heat tolerance in their natural habitats remains an important consideration for biocontrol. HSP gene expression data provide information about a species' heat tolerance and may be used to predict its geographical distribution.

Transcriptional regulation of heat shock protein 70 genes by class I histone deacetylases in the red flour beetle, Tribolium castaneum

The regulatory function of histone acetylation in the expression of genes encoding heat shock proteins (Hsps) has been documented in Drosophila melanogaster; however, knowledge of the role of acetylation in modulating Hsps in other insect pests is limited. In this study, two full-length cDNAs encoding inducible Hsp70 (designated TcHsp70) and heat shock cognate 70 (TcHsc70) were isolated and characterized in the red flour beetle, Tribolium castaneum. TcHsp70 and TcHsc70 cDNAs were 2256 and 2132 bp and encoded 1941- and 1893-bp open reading frames, respectively. The deduced TcHsp70 and TcHsc70 proteins contained 646 and 630 amino acids, respectively, and contained sequences typical of the Hsp70 family, including the EEVD motif for cytoplasmic localization. Expression patterns after heat shock indicated that TcHsp70 was strongly heat-inducible, whereas the expression level of TcHsc70 remained unchanged under heat shock. RNA interference-mediated knock-down of three genes encoding class I histone deacetylases differentially influenced both basal and heat shock inducible expression of TcHsp70 and TcHsc70, suggesting the involvement of histone acetylation in epigenetic regulation of Hsp70 transcription in T. castaneum.

Comparative Transcriptomic Analysis Reveals Molecular Profiles of Central Nervous System in Maternal Diapause Induction of Locusta migratoria

Egg diapause in Locusta migratoria L. (Orthoptera: Acridoidea) is believed to be influenced by maternal photoperiod. However, the molecular mechanism regulating the phenomenon of maternal diapause induction is unclear. Here we performed transcriptomic analyses from the central nervous system (CNS) of migratory locusts under long and short photoperiods to identify differentially expressed genes (DEGs) related to diapause induction. There were total of 165750 unigenes from 569491 transcripts, and 610 DEGs were obtained in S_CNS (CNS of short photoperiod treated locusts) vs. L_CNS (CNS of long photoperiod treated locusts). Of these, 360 were up-regulated, 250 were down-regulated, and 84 DEGs were found to be related to FOXO signaling pathways, including citrate cycle/TCA cycle, glycolysis/ gluconeogenesis, oxidative phosphorylation, and PI3K-Akt. The qRT-PCR validation of mRNA expression of 12 randomly selected DEGs showed consistency with transcriptome analysis. Furthermore, the takeout gene thought to be involved in circadian rhythm was cloned and used for RNAi to observe its function in maternal diapause induction. We found that the mRNA level of Lm-takeout was significantly lower in dstakeout treatments as compared to the control under both long and short photoperiods. Similarly, the offspring diapause rate was significantly higher in dstakeout treatment as compared to the control only in short photoperiod. This shows that the Lm-takeout gene might be involved in the inhibition of maternal diapause induction of L. migratoria under short photoperiods. The present study provides extensive data of the CNS transcriptome and particular insights into the molecular mechanisms of maternal effects on egg diapause of L. migratoria. As well for the future, the researchers can explore other factors and genes that may promote diapause in insect species.

Expression profiles of 14 small heat shock protein (sHSP) transcripts during larval diapause and under thermal stress in the spruce budworm, Choristoneura fumiferana (L.)

Diapause is an important strategy for certain insect species to survive unfavorable environmental conditions, including low temperatures experienced when they overwinter in cold climate. Many studies have indicated that the increased expression of heat shock proteins during diapause improves the thermal tolerance of insects. However, the relationship between small heat shock proteins (sHSPs) and diapause is not clear or well-researched. In this study, we investigated the transcript levels of 14 sHSP genes in the spruce budworm, Choristoneura fumiferana, a major pest of spruce and fir in Canada, during pre-diapause, diapause, and post-diapause under normal rearing conditions and in response to a heat shock treatment. We found that sHSP expression profiles could be classified into five patterns under normal laboratory conditions: pattern I was upregulated only during pre-diapause, pattern II was upregulated only during diapause, pattern III was constantly expressed throughout diapause, pattern IV was upregulated in both pre-diapause and diapause, and pattern V was upregulated only during post-diapause. After heat shock, five different expression patterns were observed: pattern I responded weakly or not at all throughout diapause, pattern II responded weakly during the diapause stage but strongly at the onset of diapause and in the post-diapause period, pattern III was upregulated only during post-diapause, pattern IV was strongest during diapause, and pattern V was strongest only in early diapause. These complex expression profiles lead us to suggest that most of the sHSP genes are involved in the diapause process and that they may have multiple and important roles in different phases of this process.

Comparisons of Expression Levels of Heat Shock Proteins (hsp70 and hsp90) From Anaphothrips obscurus (Thysanoptera: Thripidae) in Polymorphic Adults Exposed to Different Heat Shock Treatments

Heat shock proteins (Hsps) are prominent proteins that greatly contribute to insect survival under stress conditions. In this study, we cloned two Hsp transcripts (Aohsp70 and Aohsp90) from the grass thrip, Anaphothrips obscurus (Müller) (Thysanoptera: Thripidae), which is a polymorphic winged pest of corn and wheat. The cDNA sequences of Aohsp70 and Aohsp90 are 2382 and 2504 bp long, and encode proteins with calculated molecular weights of 70.02 kDa and 83.40 kDa, respectively. Aohsp90 was highly expressed in adults of both brachypters and macropters. Aohsp70 had different expression patterns in brachypters and macropters and was also highly expressed in the pupae of macropters. After adults were exposed to an ascending series of heat shocks, the expression of both Aohsp70 and Aohsp90 were up-regulated. In macropters and brachypters, the maximum induced levels of Aohsp70 (approximately 90-fold and 280-fold, respectively) were higher than Aohsp90 (approximately 2.4-fold and 1.8-fold, respectively). In addition, the up-regulation of Aohsp70 was significantly higher in brachypters than in macropters. Brachypters had a significantly higher Ltem50 (43.2°C) than macropters (42.5°C), which implied that brachypters are more tolerant to thermal stress than macropters. This study has shown that the expression patterns of Aohsp70 and Aohsp90 are variable among different life stages and thermal stress induced different levels of expressions in macropterous and brachypterous adults.

Molecular characterization of three Hsp90 from Pieris and expression patterns in response to cold and thermal stress in summer and winter diapause of Pieris melete

Heat shock proteins (Hsps) have been linked to stresses and winter diapause in insects, but whether they are components of summer diapause is still unknown. In this study, complementary DNAs of Hsp90 from Pieris melete, Pieris rapae and Pieris canidia named PmHsp90, PrHsp90 and PcHsp90, respectively, were cloned and sequenced. The deduced amino acid sequence consisted of 718 amino acid residues with a putative molecular mass of 82.6, 82.6 and 82.7 kDa, respectively. The amino acid sequences contained all of the five conserved signature motifs in the Hsp90 family and a bHLH protein folding activity region. The differential expression pattern of PmHsp90 in response to summer diapause and winter diapause, which are related to heat/cold stress, was investigated. Cold stress induced Hsp90 up-regulation in summer and winter diapause pupae, but not in non-diapause individuals. Heat shock up-regulated PmHsp90 gradually with an increase in temperature in summer diapause, and PmHsp90 was rapidly up-regulated in winter diapause. After 30 min heat shock at 39°C, substantial up-regulation of PmHsp90 transcript levels were observed both in summer and winter diapause. However, in non-diapause a relatively stable expression was found under different durations of 39°C heat shock. Compared to the optimal treatment of 18°C for diapause development, a high temperature acclimation of 31°C induced PmHsp90 up-regulation in summer diapause, whereas a low temperature acclimation of 4°C induced up-regulation in winter diapause. The current results indicate that Hsp90 may play an important role in response to heat/cold stress both in summer and winter diapause.

Global Transcriptome Sequencing Reveals Molecular Profiles of Summer Diapause Induction Stage of Onion Maggot, Delia antiqua (Diptera: Anthomyiidae)

The onion maggot, Delia antiqua, is a worldwide subterranean pest and can enter diapause during the summer and winter seasons. The molecular regulation of the ontogenesis transition remains largely unknown. Here we used high-throughput RNA sequencing to identify candidate genes and processes linked to summer diapause (SD) induction by comparing the transcriptome differences between the most sensitive larval developmental stage of SD and nondiapause (ND). Nine pairwise comparisons were performed, and significantly differentially regulated transcripts were identified. Several functional terms related to lipid, carbohydrate, and energy metabolism, environmental adaption, immune response, and aging were enriched during the most sensitive SD induction period. A subset of genes, including circadian clock genes, were expressed differentially under diapause induction conditions, and there was much more variation in the most sensitive period of ND- than SD-destined larvae. These expression variations probably resulted in a deep restructuring of metabolic pathways. Potential regulatory elements of SD induction including genes related to lipid, carbohydrate, energy metabolism, and environmental adaption. Collectively, our results suggest the circadian clock is one of the key drivers for integrating environmental signals into the SD induction. Our transcriptome analysis provides insight into the fundamental role of the circadian clock in SD induction in this important model insect species, and contributes to the in-depth elucidation of the molecular regulation mechanism of insect diapause induction.

Cloning of heat shock protein genes (hsp70, hsc70 and hsp90) and their expression in response to larval diapause and thermal stress in the wheat blossom midge, Sitodiplosis mosellana

Sitodiplosis mosellana Géhin, one of the most important pests of wheat, undergoes obligatory diapause as a larva to survive unfavorable temperature extremes during hot summers and cold winters. To explore the potential roles of heat shock proteins (hsp) in this process, we cloned full-length cDNAs of hsp70, hsc70 and hsp90 from S. mosellana larvae, and examined their expression in response to diapause and short-term temperature stresses. Three hsps included all signature sequences of corresponding protein family and EEVD motifs. They showed high homology to their counterparts in other species, and the phylogenetic analysis of hsp90 was consistent with the known classification of insects. Expression of hsp70 and hsp90 were highly induced by diapause, particularly pronounced during summer and winter. Interestingly, hsp70 was more strongly expressed in summer than in winter whereas hsp90 displayed the opposite pattern. Abundance of hsc70 mRNA was comparable prior to and during diapauses and was highly up-regulated when insects began to enter the stage of post-diapause quiescence. Heat-stressed over-summering larvae (⩾30°C) or cold-stressed over-wintering larvae (⩽0°C) could further elevate expression of these three genes, but temperature extremes i.e. as high as 45°C or as low as -15°C failed to trigger such expression patterns. Notably, hsp70 was most sensitive to heat stress and hsp90 was most sensitive to cold stress. These results suggested that hsp70 and hsp90 play key roles in diapause maintenance and thermal stress; the former may be more prominent contributor to heat tolerance and the latter for cold tolerance. In contrast, hsc70 most likely is involved in developmental transition from diapause to post-diapause quiescence, and thus may serve as a molecular marker to predict diapause termination.

Insight into the possible mechanism of the summer diapause of Delia antiqua (Diptera: Anthomyiidae) through digital gene expression analysis

The onion fly, Delia antiqua, is a major underground agricultural pest that can enter pupal diapause in the summer and winter seasons. However, little is known about its molecular regulation due to the lack of genomic resources. To gain insight into the possible mechanism of summer diapause (SD), high-throughput RNA-Seq data were generated from non-diapause (ND) and SD (initial, maintenance and quiescence phase) pupae. Three pair-wise comparisons were performed and identified, 1380, 1471 and 435, and were significantly regulated transcripts. Further analysis revealed that the enrichment of several functional terms related to juvenile hormone regulation, cell cycle, carbon hydrate and lipid metabolism, innate immune and stress responses, various signalling transductions, ubiquitin-dependent proteosome, and variation in cuticular and cytoskeleton components were found between ND and SD and between different phases of SD. Global characterization of transcriptome profiling between SD and ND contributes to the in-depth elucidation of the molecular mechanism of SD. Our results also offer insights into the evolution of insect diapause and support the importance of using the onion fly as a model to compare the molecular regulation events of summer and winter diapauses.

Expression of Heat Shock Protein Genes in Different Developmental Stages and After Temperature Stress in the Maize Weevil (Coleoptera: Curculionidae)

The maize weevil, Sitophilus zeamais Motschulsky, is a major pest of rice and other postharvest grain stocks in tropical countries. Heating and cooling treatments have been adopted to control this pest. Because heat shock protein (hsp) genes respond to temperature stress, we examined the association of hsp genes with development and thermal stress in S. zeamais. The temperature response of the insect to heat and cold treatments was assessed at four developmental stages: egg, larva, pupa, and adult. LT50 values at high temperatures were similar among the four developmental stages, while adults were the most tolerant to low temperatures, and eggs, larvae, and pupae exhibited similar LT50 values. Expression levels of three hsps--Szhsp70, Szhsc70, and Szhsp90--fluctuated substantially throughout the four stages at a rearing temperature of 28°C. Heat shock and cold shock increased the expression of all three hsps, and the highest upregulation was observed at 40°C, although the intensity of upregulation varied among the three genes: strongly in Szhsp70, moderately in Szhsp90, and slightly in Szhsc70. Basal expression of the three hsps at 28°C and gene responses to heat and cold shock also varied significantly at the tissue level.

Insect heat shock proteins during stress and diapause

Insect heat shock proteins include ATP-independent small heat shock proteins and the larger ATP-dependent proteins, Hsp70, Hsp90, and Hsp60. In concert with cochaperones and accessory proteins, heat shock proteins mediate essential activities such as protein folding, localization, and degradation. Heat shock proteins are synthesized constitutively in insects and induced by stressors such as heat, cold, crowding, and anoxia. Synthesis depends on the physiological state of the insect, but the common function of heat shock proteins, often working in networks, is to maintain cell homeostasis through interaction with substrate proteins. Stress-induced expression of heat shock protein genes occurs in a background of protein synthesis inhibition, but in the course of diapause, a state of dormancy and increased stress tolerance, these genes undergo differential regulation without the general disruption of protein production. During diapause, when ATP concentrations are low, heat shock proteins may sequester rather than fold proteins.

Transcript analysis and expression profiling of three heat shock protein 70 genes in the ectoparasitoid Habrobracon hebetor (Hymenoptera: Braconidae)

Heat shock proteins (HSPs) are known as chaperones that help with folding of other proteins when cells are under environmental stresses. The upregulation of HSPs is essential for cold survival during insect diapause. The ectoparasitoid Habrobracon hebetor, a potential biological control agent, can enter reproductive diapause when reared at low temperature and short photoperiod. However, the expression of HSPs during diapause of H. hebetor has not been studied. In this study, we sequenced and characterized the full-length complementary DNAs of three Hsp70 genes (HhHsp70I, HhHsp70II and HhHsp70III) from H. hebetor. Their deduced amino acid sequences showed more than 80% identities to their counterparts from other insect species. However, the multiple sequence alignment among the three deduced amino acid sequences of HhHsp70s showed only 46% identities. A phylogenetic analysis of the three HhHsp70s and all other known Hsp70 sequences from Hymenoptera clustered all the Hsp70s into four groups, and the three HhHsp70s were distributed into three different groups. Real-time quantitative polymerase chain reaction analysis showed that the expression of the three HhHsp70 genes in H. hebetor reared at different conditions was quite different. HhHsp70I showed higher relative expression when H. hebetor were reared at 27.5°C than at two lower temperatures (17.5°C and 20°C) regardless of the photoperiod, whereas HhHsp70II showed higher expression when H. hebetor were reared at 20°C and 10 : 14 L : D than when reared at 17.5°C and either 16 : 8 L : D or 10 : 14 L : D. In contrast, HhHSP70III was expressed at similar levels regardless of the rearing conditions. These results may suggest functional differences among the three HhHsp70 genes in H. hebetor.

Three Heat Shock Protein Genes from Bactrocera (Tetradacus) minax Enderlein: Gene Cloning, Characterization, and Association with Diapause

Bactrocera (Tetradacus) minax Enderlein is a major pest to wild and cultivated species of citrus. Bactrocera minax produces one generation per year with a long pupal diapause period of over 6 months, which hinders efforts to obtain vast numbers of insects under standard room conditions. Determining the mechanisms of diapause is significantly important for obtaining large quantities of these insects. To characterize the heat shock protein (Hsp) genes of B. minax and to unravel their potential contribution to diapause, we performed 3' and 5' RACE to isolate the complementary DNA (cDNA) sequences, bioinformatics to examine the phylogenetic relationships, and real-time quantitative PCR to detect the expression patterns of three Hsp genes during various developmental stages. These results represent the first characterization of the three Hsp genes of B. minax; the open reading frames of Bmhsp23, Bmhsp70, and Bmhsp90 were 510, 1,911, and 1,089 bp, encoding 170, 636, and 363 amino acids, respectively. BmHsp70 and BmHsp90 displayed high identity to previously identified Hsp70 and Hsp90 genes, respectively. BmHsp23 displayed varying similarity, from 28 to 83%, to previously identified small Hsps. Bmhsp23 messenger RNA (mRNA) expression was found to be upregulated during diapause initiation, maintenance, and termination. Bmhsp70 mRNA expression peaked during diapause initiation. Bmhsp90 mRNA expression remained at a relatively low level during deep diapause. Our present results suggest that Bmhsp70 might play an important role in diapause initiation, while Bmhsp23 in diapause initiation and maintenance and Bmhsp90 in diapause regulation. These results improve our understanding of the mechanism of diapause in B. minax at the molecular level.

Identification of a novel strong and ubiquitous promoter/enhancer in the silkworm Bombyx mori

Transgenic techniques offer a valuable tool for determining gene functions. Although various promoters are available for use in gene overexpression, gene knockdown, and identification of transgenic individuals, there is nevertheless a lack of versatile promoters for such studies, and this dearth acts as a bottleneck, especially with regard to nonmodel organisms. Here, we succeeded in identifying a novel strong and ubiquitous promoter/enhancer in the silkworm. We identified a unique silkworm strain whose reporter gene showed strong and ubiquitous expression during the establishment of enhancer trap strains. In this strain, the transposon was inserted into the 5'UTR of hsp90, a housekeeping gene that is abundantly expressed in a range of tissues. To determine whether the promoter/enhancer of hsp90 could be used to induce strong gene expression, a 2.9-kb upstream genomic fragment of hsp90 was isolated (hsp90(P2.9k)), and its transcriptional activation activity was examined. Strikingly, hsp90(P2.9k) induced strong gene expression in silkworm cell cultures and also strongly induced gene expression in various tissues and developmental stages of the silkworm. hsp90(P2.9k) also exhibited significant promoter/enhancer activity in Sf9, a cell culture from the armyworm, suggesting that this fragment might possibly be used as a gene expression tool in other Lepidoptera. We further found that 2.0 kb of hsp90(P2.9k) is sufficient for the induction of strong gene expression. We believe that this element will be of value for a range of studies such as targeted gene overexpression, gene knockdown and marker gene expression, not only in the silkworm but also in other insect species.

Differential gene expression between summer and winter diapause pupae of the onion maggot Delia antiqua, detected by suppressive subtractive hybridization

To gain a better understanding of the molecular mechanisms regulating pupal diapause of the onion maggot Delia antiqua, PCR-based suppressive subtractive hybridization was performed to identify genes involved in summer and/or winter diapause. A total of 209 unique sequences were obtained including 89 in forward library for winter diapausing pupae and 120 in the reverse library for summer diapausing pupae. 76.4% (68/89) and 68.3% (82/120) unique sequences had significant hits to non-redundant proteins database. Gene functional annotation showed these non-redundant sequences are involved in stress response and innate immunity, metabolism and energy, information processing and regulation, binding, food storage, morphogenesis and development, cell skeleton and cycle, protein synthesis and folding. Approximately 28.2% (59/209) transcripts showed no significant similarity to any other sequence in the public databases, probably representing unique genes of the onion maggot. Semi-quantitative RT-PCR revealed that the relative expression levels of 18 genes were comparable between summer and winter diapause. This study elucidates the temporal expression of diapause-related genes in onion maggot, also provides new insights into the differences in the physiological changes in summer and winter pupae. Functional characterization of some candidate genes will further enhance the understanding of the generating, maintaining, and breaking mechanism of diapause.

Comparative analysis of hemolymph proteome maps in diapausing and non-diapausing larvae of Sesamia nonagrioides

Background

Sesamia nonagrioides is a noctuid that feeds on maize, sugar cane and sorghum in North Africa and Southern Europe. Larvae reared under long day conditions pupate after 5 or 6 larval instars, whereas larvae reared under short day conditions enter diapause and undergo up to 12 molts before dying or pupating. To better understand the mechanism of larval development and diapause, we identified proteins with different expressions in the sixth instar of diapausing and non-diapausing larvae.

Results

A total of 52 differentially regulated proteins were detected in the hemolymph of the diapausing or non-diapausing larvae at the beginning or end of the sixth instar. From these proteins, 11 were identified by mass spectrometry (MALDI-TOF MS or MALDI-TOF/TOF MS/MS): 5 were upregulated in the hemolymph of non-diapausing larvae and 6 in the hemolymph of the diapausing larvae. Interestingly, some proteins were expressed only in non-diapausing larvae but none was expressed only in the hemolymph of diapausing larvae. The possible functions of some of these proteins related to diapause maintenance or to larval-pupal metamorphosis are discussed.

Conclusions

The 2-DE proteomic map of S. nonagrioides hemolymph shows differential protein expression in diapausing and non-diapausing larvae. Some proteins that showed higher expression in the diapausing larvae at the end of the sixth instar could be involved in JH level maintenance thus in the diapause status maintenance. On the contrary, other proteins that showed the highest expression or that were expressed only in the non-diapausing larvae could be involved in larval-pupal metamorphosis.

First transcriptome of the testis-vas deferens-male accessory gland and proteome of the spermatophore from Dermacentor variabilis (Acari: Ixodidae)

Ticks are important vectors of numerous human diseases and animal diseases. Feeding stimulates spermatogenesis, mating and insemination of male factors that trigger female reproduction. The physiology of male reproduction and its regulation of female development are essentially a black box. Several transcriptomes have catalogued expression of tick genes in the salivary glands, synganglion and midgut but no comprehensive investigation has addressed male reproduction and mating. Consequently, a new global approach using transcriptomics, proteomics, and quantitative gene expression is needed to understand male reproduction and stimulation of female reproduction.

This first transcriptome to the reproductive biology of fed male ticks, Dermacentor variabilis, was obtained by 454 pyrosequencing (563,093 reads, 12,804 contigs). Gene Ontology (Biological Processes level III) recognized 3,866 transcripts in 73 different categories; spermiogenesis; spermatogenesis; peptidases, lipases and hydrolases; oxidative and environmental stress; immune defense; and protein binding. Reproduction-associated genes included serine/threonine kinase, metalloendoproteinases, ferritins, serine proteases, trypsin, cysteine proteases, serpins, a cystatin, GPCR and others. qRT-PCR showed significant upregulation from unfed versus fed adult male reproductive organs of zinc metalloprotease, astacin metalloprotease and serine protease, enzymes important in spermiogenesis and mating activity in insects, as well as a GPCR with the greatest similarity to a SIFamide receptor known to be important in regulating courtship behavior in Drosophila. Proteomics on these organs and the spermatophore by tryptic digestion/Liquid chromatography/Mass spectrometry/Mass spectrometry (LC/MS/MS) demonstrated expression of many of the same messages found by 454 sequencing, supporting their identification, and revealed differences in protein distribution in the reproductive system versus the spermatophore. We found Efα but no EF β in the transcriptome and neither of these proteins in the spermatophore. Thus, the previously described model for male regulation of female reproduction may not apply to other ticks. A new paradigm is needed to explain male stimulation of female tick reproduction.

Heat shock protein expression during stress and diapause in the marine copepod Calanus finmarchicus

Calanoid copepods, such as Calanus finmarchicus, are a key component of marine food webs. C. finmarchicus undergo a facultative diapause during juvenile development, which profoundly affects their seasonal distribution and availability to their predators. The current ignorance of how copepod diapause is regulated limits understanding of copepod population dynamics, distribution, and ecosystem interactions. Heat shock proteins (Hsps) are a superfamily of molecular chaperones characteristically upregulated in response to stress conditions and frequently associated with diapause in other taxa. In this study, 8 heat shock proteins were identified in C. finmarchicus C5 copepodids (Hsp21, Hsp22, p26, Hsp90, and 4 forms of Hsp70), and expression of these transcripts was characterized in response to handling stress and in association with diapause. Hsp21, Hsp22, and Hsp70A (cytosolic subfamily) were induced by handling stress. Expression of Hsp70A was also elevated in shallow active copepodids relative to deep diapausing copepodids, which may reflect induction of this gene by varied stressors in active animals. In contrast, expression of Hsp22 was elevated in deep diapausing animals; Hsp22 may play a role both in short-term stress responses and in protecting proteins from degradation during diapause. Expression of most of the Hsps examined did not vary in response to diapause, perhaps because the diapause of C. finmarchicus is not associated with the extreme environmental conditions (e.g., freezing and desiccation) experienced by many other taxa, such as overwintering insects or Artemia cysts.

Expression of heat shock protein 70a mRNA in Bombyx mori diapause eggs

In an effort to understand whether heat shock protein 70 (Hsp70) participates in the environmental 5 degrees C signal reception/transduction toward breaking embryonic diapause of the silkworm Bombyx mori, we isolated a cDNA for Hsp70a and examined the expression of Hsp70a mRNA in B. mori diapause and nondiapause eggs by quantitative real-time PCR. Hsp70a mRNA gradually increased in diapause eggs continuously kept at 25 degrees C after oviposition to maintain diapause. When diapause eggs were exposed to the diapause-terminating condition of 5 degrees C beginning at 2 days post-oviposition, Hsp70a mRNA increased beginning at 5 days post-cold treatment. Even in nondiapause eggs, Hsp70a mRNA increased slightly with exposure to 5 degrees C. These results suggest that Hsp70a is involved in reception/transduction of the diapause-terminating (5 degrees C) signal via gene activation. The expression patterns of Hsp70a mRNA are discussed in relation to those of the cold-response gene Samui.

Gene expression, metabolic regulation and stress tolerance during diapause

Diapause entails molecular, physiological and morphological remodeling of living animals, culminating in a dormant state characterized by enhanced stress tolerance. Molecular mechanisms driving diapause resemble those responsible for biochemical processes in proliferating cells and include transcriptional, post-transcriptional and post-translational processes. The results are directed gene expression, differential mRNA and protein accumulation and protein modifications, including those that occur in response to changes in cellular redox potential. Biochemical pathways switch, metabolic products change and energy production is adjusted. Changes to biosynthetic activities result for example in the synthesis of molecular chaperones, late embryogenesis abundant (LEA) proteins and protective coverings, all contributing to stress tolerance. The purpose of this review is to consider regulatory and mechanistic strategies that are potentially key to metabolic control and stress tolerance during diapause, while remembering that organisms undergoing diapause are as diverse as the processes itself. Some of the parameters described have well-established roles in diapause, whereas the evidence for others is cursory.

Molecular characterization of heat shock protein 90, 70 and 70 cognate cDNAs and their expression patterns during thermal stress and pupal diapause in the corn earworm

Three heat shock protein transcripts, hsp90, hsp70, hsc70, isolated from the corn earworm, Helicoverpa zea, were evaluated for their responsiveness to diapause and thermal stress. These Hsps showed high homology to their counterparts in other species. A phylogenetic analysis of the Hsp90 sequence was consistent with the known classification of insects. Northern blot hybridization indicated the presence of hsp90 transcripts in all tissues, but expression in the brain-subesophageal complex was especially pronounced. The genomic organization of hsp90 examined by Southern blot suggested the presence of a single copy of hsp90 in the H. zea genome. The expression patterns after heat shock indicated that hsp70 and hsp90 were heat-inducible, although hsp70 was more strongly induced than hsp90, and hsc70 was indeed a constitutively expressed member of the hsp70 family. Expression of hsp70 and hsc70 were not altered by the diapause program, but hsp90 was down-regulated at this time. Low temperatures (0-4 degrees C) and recovery from low temperature elicited hsp70 and hsp90 responses, but not an hsc70 response. Thus, unlike several other species, H. zea does not up-regulate hsp70 during pupal diapause, but the down-regulation of hsp90 is consistent with the pattern observed in several other species during diapause. Our results also indicate that hsp90 and hsp70 are responsive to low temperature in both diapausing and nondiapausing pupae.