Heat shock protein expression pattern (HSP70) in the hydrothermal vent mussel Bathymodiolus azoricus

Transcriptome analysis of gene expression profiling from the deep sea in situ to the laboratory for the cold seep mussel Gigantidas haimaensis

Background

The deep-sea mussel Gigantidas haimaensis is a representative species from the Haima cold seep ecosystem in the South China Sea that establishes endosymbiosis with chemotrophic bacteria. During long-term evolution, G. haimaensis has adapted well to the local environment of cold seeps. Until now, adaptive mechanisms responding to environmental stresses have remained poorly understood.

Results

In this study, transcriptomic analysis was performed for muscle tissue of G. haimaensis in the in situ environment (MH) and laboratory environment for 0 h (M0), 3 h (M3) and 9 h (M9), and 187,368 transcript sequences and 22,924 annotated differentially expressed genes (DEGs) were generated. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, these DEGs were enriched with a broad spectrum of biological processes and pathways, including those associated with antioxidants, apoptosis, chaperones, immunity and metabolism. Among these significantly enriched pathways, protein processing in the endoplasmic reticulum and metabolism were the most affected metabolic pathways. These results may imply that G. haimaensis struggles to support the life response to environmental change by changing gene expression profiles.

Conclusion

The present study provides a better understanding of the biological responses and survival strategies of the mussel G. haimaensis from deep sea in situ to the laboratory environment.

Protein expression profiles in Bathymodiolus azoricus exposed to cadmium

Proteomic changes in the "gill-bacteria complex" of the hydrothermal vent mussel B. azoricus exposed to cadmium in pressurized chambers ((Incubateurs Pressurises pour l'Observation en Culture d'Animaux Marins Profonds - IPOCAMP) were analyzed and compared with the non-exposed control group. 2-D Fluorescence Difference Gel Electrophoresis (2D-DIGE) showed that less than 1.5% of the proteome of mussels and symbiotic bacteria were affected by a short-term (24 h) Cd exposure. Twelve proteins of the more abundant differentially expressed proteins of which six were up-regulated and six were down-regulated were excised, digested and identified by mass spectrometry. The identified proteins included structural proteins (actin/actin like proteins), metabolic proteins (calreticulin/calnexin, peptidyl-prolyl cis-trans isomerase, aminotransferase class-III, electron transfer flavoprotein, proteasome, alpha-subunit and carbonic anhydrase) and stress response proteins (chaperone protein htpG, selenium-binding protein and glutathione transferases). All differently expressed proteins are tightly connected to Cd exposure and are affected by oxidative stress. It was also demonstrated that B. azoricus was well adapted to Cd contamination therefore B. azoricus from hydrothermal vent areas may be considered a good bioindicator.

Metatranscriptomics profile of the gill microbial community during Bathymodiolus azoricus aquarium acclimatization at atmospheric pressure

Background

The deep-sea mussels Bathymodiolus azoricus (Bivalvia: Mytilidae) are the dominant macrofauna subsisting at the hydrothermal vents site Menez Gwen in the Mid-Atlantic Ridge (MAR). Their adaptive success in such challenging environments is largely due to their gill symbiotic association with chemosynthetic bacteria. We examined the response of vent mussels as they adapt to sea-level environmental conditions, through an assessment of the relative abundance of host-symbiont related RNA transcripts to better understand how the gill microbiome may drive host-symbiont interactions in vent mussels during hypothetical venting inactivity.

Results

The metatranscriptome of B. azoricus was sequenced from gill tissues sampled at different time-points during a five-week acclimatization experiment, using Next-Generation-Sequencing. After Illumina sequencing, a total of 181,985,262 paired-end reads of 150 bp were generated with an average of 16,544,115 read per sample. Metatranscriptome analysis confirmed that experimental acclimatization in aquaria accounted for global gill transcript variation. Additionally, the analysis of 16S and 18S rRNA sequences data allowed for a comprehensive characterization of host-symbiont interactions, which included the gradual loss of gill endosymbionts and signaling pathways, associated with stress responses and energy metabolism, under experimental acclimatization. Dominant active transcripts were assigned to the following KEGG categories: “Ribosome”, “Oxidative phosphorylation” and “Chaperones and folding catalysts” suggesting specific metabolic responses to physiological adaptations in aquarium environment.

Conclusions

Gill metagenomics analyses highlighted microbial diversity shifts and a clear pattern of varying mRNA transcript abundancies and expression during acclimatization to aquarium conditions which indicate change in bacterial community activity. This approach holds potential for the discovery of new host-symbiont associations, evidencing new functional transcripts and a clearer picture of methane metabolism during loss of endosymbionts. Towards the end of acclimatization, we observed trends in three major functional subsystems, as evidenced by an increment of transcripts related to genetic information processes; the decrease of chaperone and folding catalysts and oxidative phosphorylation transcripts; but no change in transcripts of gluconeogenesis and co-factors-vitamins.

Molecular identification of methane monooxygenase and quantitative analysis of methanotrophic endosymbionts under laboratory maintenance in Bathymodiolus platifrons from the South China Sea

Deep-sea mussels of the genus Bathymodiolus are numerically dominant macrofauna in many cold seep and hydrothermal vent ecosystems worldwide, and they depend on organic carbon produced by symbionts present in the epithelial cells of the gills. Although Bathymodiolus platifrons represents typical methanotrophic endosymbiosis, our understanding of molecular mechanisms of methane oxidization and carbon fixation is still in its infancy. Moreover, the laboratory maintenance of B. platifrons and the symbiont abundance dynamics during maintenance has not been reported. In the present study, we report the first systematic identification and phylogenetic analysis of three subunits of methane monooxygenase (pmoA, pmoB, and pmoC) obtained from the endosymbiotic bacteria found in B. platifrons. The coding sequences (CDS) of the three genes in the B. platifrons endosymbiont were 750, 1,245, and 753 bp, encoding 249, 414, and 250 amino acids, respectively. Sequence alignment and phylogenetic analysis revealed that the symbiont of B. platifrons belongs to the type I methanotrophs. In order to clarify the impact of environmental methane on symbiont abundance, a 34-day laboratory maintenance experiment was conducted in which B. platifrons individuals were acclimatized to methane-present and methane-absent environments. Symbiont abundance was evaluated by calculating the relative DNA content of the methane monooxygenase gene using quantitative real-time PCR. We found that symbiont quantity immediately decreased from its initial level, then continued to gradually decline during maintenance. At 24 and 34 days of maintenance, symbiont abundance in the methane-absent environment had significantly decreased compared to that in the methane-present environment, indicating that the maintenance of symbionts relies on a continuous supply of methane. Our electron microscopy results validated the qPCR analysis. This study enriches our knowledge of the molecular basis and the dynamic changes of the methanotrophic endosymbiosis in B. platifrons, and provides a feasible model biosystem for further investigation of methane oxidization, the carbon fixation process, and environmental adaptations of deep-sea mussels.

HSP70 expression in Biomphalaria glabrata snails exposed to cadmium

In this study, the effects of the heavy metal cadmium on the stress protein HSP70 are investigated in freshwater mollusks Biomphalaria glabrata. Adult snails were exposed for 96h to CdCl₂ at concentrations ranging from 0.09 to 0.7mgL^-1 (LC_50/96h=0.34 (0.30-0.37). Time and concentration-dependent increases in the expression of HSP70 were observed at sub-lethal levels in the immunoblotting assay. Further, an increased survival to a lethal heat shock was observed in animals pre-exposed to a nonlethal concentration of cadmium, evidencing the induction of acquired tolerance. The present study demonstrated the inducibility of B. glabrata HSP70 by cadmium, a relevant environmental contaminant, at non-lethal levels, providing evidences that the assessment of HSP70 in B. glabrata can be regarded as a suitable biomarker for ecotoxicological studies.

Adaptation to deep-sea chemosynthetic environments as revealed by mussel genomes

Hydrothermal vents and methane seeps are extreme deep-sea ecosystems that support dense populations of specialized macro-benthos such as mussels. But the lack of genome information hinders the understanding of the adaptation of these animals to such inhospitable environments. Here we report the genomes of a deep-sea vent/seep mussel (Bathymodiolus platifrons) and a shallow-water mussel (Modiolus philippinarum). Phylogenetic analysis shows that these mussel species diverged approximately 110.4 million years ago. Many gene families, especially those for stabilizing protein structures and removing toxic substances from cells, are highly expanded in B. platifrons, indicating adaptation to extreme environmental conditions. The innate immune system of B. platifrons is considerably more complex than that of other lophotrochozoan species, including M. philippinarum, with substantial expansion and high expression levels of gene families that are related to immune recognition, endocytosis and caspase-mediated apoptosis in the gill, revealing presumed genetic adaptation of the deep-sea mussel to the presence of its chemoautotrophic endosymbionts. A follow-up metaproteomic analysis of the gill of B. platifrons shows methanotrophy, assimilatory sulfate reduction and ammonia metabolic pathways in the symbionts, providing energy and nutrients, which allow the host to thrive. Our study of the genomic composition allowing symbiosis in extremophile molluscs gives wider insights into the mechanisms of symbiosis in other organisms such as deep-sea tubeworms and giant clams.

Vibrio diabolicus challenge in Bathymodiolus azoricus populations from Menez Gwen and Lucky Strike hydrothermal vent sites

Menez Gwen (MG) and Lucky Strike (LS) deep-sea hydrothermal vents are located at 850 m and 1730 m depths respectively and support chemosynthesis-based ecosystems partially differing in heavy metal concentration, temperature range, and faunistic composition. The successfully adapted deep-sea vent mussel Bathymodiolus azoricus is found at both vent locations. In such inhospitable environments survival strategies rely on the establishment of bacteria-vent animal symbiosis In spite of the toxic nature of deep-sea vents, the problem of microbial threat and the need for immunity exist in B. azoricus. This study aims at investigating the immune system of B. azoricus from MG and LS populations by comparing immune gene expressions profiles using the deep-sea vent-related Vibrio diabolicus. Expression of nineteen immune genes was analyzed from gill, digestive gland and mantle tissues upon 3 h, 12 h and 24 h V. diabolicus challenges. Based on quantitative-Polymerase Chain Reaction (qPCR) significant gene expression differences were found among MG and LS populations and challenge times MG mussels revealed that gill and digestive gland gene expression levels were remarkably higher than those from LS mussels. Expression of Carcinolectin, Serpin-2, SRCR, IRGs, RTK, TLR2, NF-κB, HSP70 and Ferritin genes was greater in MG than LS mussels. In contrast, mantle tissue from LS mussels revealed the highest peak of expression at 24 h for most genes analyzed. The activation of immune signaling pathways demonstrated that gene expression profiles are distinct between the two mussel populations. These differences may possibly ensue from intrinsic immune transcriptional activities upon which host responses are modulated in presence of V. diabolicus. mRNA transcript variations were assessed during 24 h acclimatization taking into account the partial depuration to which mussels were subjected to. Additionally, gene expression differences may reflect still accountable effects from the presence of vent remaining microfluidic environments within the tissues analyzed.

Post-capture immune gene expression studies in the deep-sea hydrothermal vent mussel Bathymodiolus azoricus acclimatized to atmospheric pressure

Deep-sea hydrothermal vents are extreme habitats that are distributed worldwide in association with volcanic and tectonic events, resulting thus in the establishment of particular environmental conditions, in which high pressure, steep temperature gradients, and potentially toxic concentrations of sulfur, methane and heavy metals constitute driving factors for the foundation of chemosynthetic-based ecosystems. Of all the different macroorganisms found at deep-sea hydrothermal vents, the mussel Bathymodiolus azoricus is the most abundant species inhabiting the vent ecosystems from the Mid-Atlantic Ridge (MAR). In the present study, the effect of long term acclimatization at atmospheric pressure on host-symbiotic associations were studied in light of the ensuing physiological adaptations from which the immune and endosymbiont gene expressions were concomitantly quantified by means of real-time PCR. The expression of immune genes at 0 h, 12 h, 24 h, 36 h, 48 h, 72 h, 1 week and 3 weeks post-capture acclimatization was investigated and their profiles compared across the samples tested. The gene signal distribution for host immune and bacterial genes followed phasic changes in gene expression at 24 h, 1 week and 3 weeks acclimatization when compared to other time points tested during this temporal expression study. Analyses of the bacterial gene expression also suggested that both bacterial density and activity could contribute to shaping the intricate association between endosymbionts and host immune genes whose expression patterns seem to be concomitant at 1 week acclimatization. Fluorescence in situ hybridization was used to assess the distribution and prevalence of endosymbiont bacteria within gill tissues confirming the gradual loss of sulfur-oxidizing (SOX) and methane-oxidizing (MOX) bacteria during acclimatization. The present study addresses the deep-sea vent mussel B. azoricus as a model organism to study how acclimatization in aquaria and the prevalence of symbiotic bacteria are driving the expression of host immune genes. Tight associations, unseen thus far, suggest that host immune and bacterial gene expression patterns reflect distinct physiological responses over the course of acclimatization under aquarium conditions.

The contrasted evolutionary fates of deep-sea chemosynthetic mussels (Bivalvia, Bathymodiolinae)

Bathymodiolinae are giant mussels that were discovered at hydrothermal vents and harboring chemosynthetic symbionts. Due to their close phylogenetic relationship with seep species and tiny mussels from organic substrates, it was hypothesized that they gradually evolved from shallow to deeper environments, and specialized in decaying organic remains, then in seeps, and finally colonized deep-sea vents. Here, we present a multigene phylogeny that reveals that most of the genera are polyphyletic and/or paraphyletic. The robustness of the phylogeny allows us to revise the genus-level classification. Organic remains are robustly supported as the ancestral habitat for Bathymodiolinae. However, rather than a single step toward colonization of vents and seeps, recurrent habitat shifts from organic substrates to vents and seeps occurred during evolution, and never the reverse. This new phylogenetic framework challenges the gradualist scenarios “from shallow to deep.” Mussels from organic remains tolerate a large range of ecological conditions and display a spectacular species diversity contrary to vent mussels, although such habitats are yet underexplored compared to vents and seeps. Overall, our data suggest that for deep-sea mussels, the high specialization to vent habitats provides ecological success in this harsh habitat but also brings the lineage to a kind of evolutionary dead end.

Molecular cloning and characterization of cDNA encoding a putative stress-induced heat-shock protein from Camelus dromedarius

Heat shock proteins are ubiquitous, induced under a number of environmental and metabolic stresses, with highly conserved DNA sequences among mammalian species. Camelus dromedaries (the Arabian camel) domesticated under semi-desert environments, is well adapted to tolerate and survive against severe drought and high temperatures for extended periods. This is the first report of molecular cloning and characterization of full length cDNA of encoding a putative stress-induced heat shock HSPA6 protein (also called HSP70B′) from Arabian camel. A full-length cDNA (2417 bp) was obtained by rapid amplification of cDNA ends (RACE) and cloned in pET-b expression vector. The sequence analysis of HSPA6 gene showed 1932 bp-long open reading frame encoding 643 amino acids. The complete cDNA sequence of the Arabian camel HSPA6 gene was submitted to NCBI GeneBank (accession number HQ214118.1). The BLAST analysis indicated that C. dromedaries HSPA6 gene nucleotides shared high similarity (77–91%) with heat shock gene nucleotide of other mammals. The deduced 643 amino acid sequences (accession number ADO12067.1) showed that the predicted protein has an estimated molecular weight of 70.5 kDa with a predicted isoelectric point (pI) of 6.0. The comparative analyses of camel HSPA6 protein sequences with other mammalian heat shock proteins (HSPs) showed high identity (80–94%). Predicted camel HSPA6 protein structure using Protein 3D structural analysis high similarities with human and mouse HSPs. Taken together, this study indicates that the cDNA sequences of HSPA6 gene and its amino acid and protein structure from the Arabian camel are highly conserved and have similarities with other mammalian species.

2-DE proteomic analysis of HSP70 in mollusc Chamelea gallina

Bidimensional electrophoresis (2-DE) protocols were adapted on Chamelea gallina digestive glands studies by the analysis of Heat Shock Proteins (HSP) compared with monodimensional electrophoresis (1-DE) results. Because polycyclic aromatic hydrocarbons (PAH) act on HSPs, C. gallina specimens were exposed to 0.5 mg/L of benzo[a]pyrene (B[a]P) for 24 h, 7 and 12 days. Immunoblotting after 1-DE showed a single band of 70 kDa significantly induced after 7 days of B[a]P exposure. After 2-DE, eight major high-resolved spots between 17 and 98 kDa were revealed. Three spots fell within the range of 62-98 kDa and of 5-6 pI, parameters which could include HSP70. Two spots of 77 and 72 kDa, obtained after 2-DE immunoblotting, could correspond to constitutive HSC70 and to inducible HSP70 forms respectively. Changes observed in inducible and in constitutive forms might be related to an adaptation to stress and to a normal protein synthesis capability, respectively. Employment of 2-DE and relationship between HSP70 and HSC70 may be useful to clarify their role in molluscs subjected to stress events.

The influence of nutritional conditions on metal uptake by the mixotrophic dual symbiosis harboring vent mussel Bathymodiolus azoricus

The vent mussel Bathymodiolus azoricus, host thioautotrophic and methanotrophic bacteria, in their gills and complementary, is able to digest suspended organic matter. But the involvement of nutritional status in metal uptake and storage remains unclear. The influence of B. azoricus physiological condition on its response to the exposure of a mixture of metals in solution is addressed. Mussels from the Menez Gwen field were exposed to 50 μgL(-1) Cd, plus 25 μgL(-1) Cu and 100 μgL(-1) Zn for 24 days. Four conditions were tested: (i) mussels harboring both bacteria but not feed, (ii) harboring only methanotrophic bacteria, (iii) without bacteria but fed during exposure and (iv) without bacteria during starvation. Unexposed mussels under the same conditions were used as controls. Eventual seasonal variations were assessed. Metal levels were quantified in subcellular fractions in gills and digestive gland. Metallothionein levels and condition indices were also quantified. Gill sections were used for fluorescence in situ hybridization (FISH) to assess the temporal distribution of symbiotic associations. Starvation damages metal homeostasis mechanisms and increase the intracellular Zn and MT levels function. There is a clear metallic competition for soluble and insoluble intracellular ligands at each condition. Seasonal variations were observed at metal uptake and storage.

In vivo genotoxicity and stress defences in three flatfish species exposed to CuSO4

We have used the comet assay to analyse, after 3h, 24h and 6 days, the genotoxic effect in vivo of applying a single intraperitoneal injection of CuSO4, at a concentration of 2mg/kg, to adult specimens of Solea senegalensis, Dicologlossa cuneata and Scophthalmus rhombus. Metals content (Cu, Zn and Cd) in liver was also measured. The activity of key stress defences was evaluated by analysing antioxidant enzyme activity (catalase (CAT), superoxide dismutase (SOD), total glutathione peroxidase (t-GPX), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH)), metallothionein (MT) and heat shock proteins (HSP70 and HSP60). The results show that CuSO4 intake generates high and cumulative levels of genotoxicity throughout the 6 days in all 3 species. After 6 days, metals content detected in specimens showed significant differences from controls. Inter-species differences were detected in enzyme activity (P<0.05). A clear response to CuSO4 was detected only in S. rhombus, with an increase of MT and a decrease of HSPs. Variations in antioxidant defence levels and their comparative responses to the stress-inducing agent are discussed.

Molecular characterization and expression of a heat shock protein gene (HSP90) from the carmine spider mite, Tetranychus cinnabarinus (Boisduval)

In this study, the cDNA of Tetranychus cinnabarinus (Boisduval) (Acarina: Tetranychidae) HSP90 (designated TcHSP90) was cloned using a combination of the homology cloning and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of TcHSP90 is 2595 bp, including a 5′-untranslated region (UTR) of 177 bp, 3′-UTR of 249 bp, and an open reading frame (ORF) of 2169 bp. The ORF encodes a polypeptide of 722 amino acids with a predicted molecular weight of 83.45 kDa and a theoretical isoelectric point of 4.81. There is an mRNA polyadenylation signal of ATTAAA at the positions 2558-2564. In addition, the expression pattern of TcHSP90 mRNA relative to that of beta-actin gene in the three stains of T. cinnabarinus (AbR, abamectin-resistant strain; HR, heat-resistant strain; SS, the susceptible strain) were examined by using fluorescent real time quantitative PCR after the impact of abamectin, high and low temperature, respectively. The results showed that under the normal condition, the mRNA level of TcHSP90 was 1.64 and 1.29-fold higher in the AbR and HR than in SS, respectively. After 8 h treatment with abamectin, the TcHSP90 mRNA levels of SS, AbR, and HR were 1.25, 1.87, and 2.05-fold higher than those of their untreated controls, respectively. The TcHSP90 mRNA levels of SS, AbR, and HR were also significantly increased after being induced at 40 degrees C for 1 h, and they were 3.76, 3.42, and 3.79-fold higher than those of their untreated controls, respectively. The mRNA level of TcHSP90 was also significantly increased after being induced at 4 degrees C for 1 h. These results suggest that TcHSP90 might be involved in the abamectin and extreme temperature resistance or tolerance.

Molecular identification of differentially regulated genes in the hydrothermal-vent species Bathymodiolus thermophilus and Paralvinella pandorae in response to temperature

BACKGROUND

Hydrothermal vents and cold seeps represent oases of life in the deep-sea environment, but are also characterized by challenging physical and chemical conditions. The effect of temperature fluctuations on vent organisms in their habitat has not been well explored, in particular at a molecular level, most gene expression studies being conducted on coastal marine species. In order to better understand the response of hydrothermal organisms to different temperature regimes, differentially expressed genes (obtained by a subtractive suppression hybridization approach) were identified in the mussel Bathymodiolus thermophilus and the annelid Paralvinella pandorae irlandei to characterize the physiological processes involved when animals are subjected to long term exposure (2 days) at two contrasting temperatures (10 degrees versus 20 degrees C), while maintained at in situ pressures. To avoid a potential effect of pressure, the experimental animals were initially thermally acclimated for 24 hours in a pressurized vessel.

RESULTS

For each species, we produced two subtractive cDNA libraries (forward and reverse) from sets of deep-sea mussels and annelids exposed together to a thermal challenge under pressure. RNA extracted from the gills, adductor muscle, mantle and foot tissue were used for B. thermophilus. For the annelid model, whole animals (small individuals) were used. For each of the four libraries, we sequenced 200 clones, resulting in 78 and 83 unique sequences in mussels and annelids (about 20% of the sequencing effort), respectively, with only half of them corresponding to known genes. Real-time PCR was used to validate differentially expressed genes identified in the corresponding libraries. Strong expression variations have been observed for some specific genes such as the intracellular hemoglobin, the nidogen protein, and Rab7 in P. pandorae, and the SPARC protein, cyclophilin, foot protein and adhesive plaque protein in B. thermophilus.

CONCLUSION

Our results indicate that mussels and worms are not responding in the same way to temperature variations. While the results obtained for the mussel B. thermophilus seem to indicate a metabolic depression (strong decrease in the level of mRNA expression of numerous genes) when temperature increased, the annelid P. pandorae mainly displayed a strong regulation of the mRNA encoding subunits and linkers of respiratory pigments and some proteins involved in membrane structure. In both cases, these regulations seem to be partly due to a possible cellular oxidative stress induced by the simulated thermal environment (10 degrees C to 20 degrees C). This work will serve as a starting point for studying the transcriptomic response of hydrothermal mussels and annelids in future experiments in response to thermal stress at various conditions of duration and temperature challenge.

Seasonal variations in lipid composition of the hydrothermal vent mussel Bathymodiolus azoricus from the Menez Gwen vent field

Specimens of the hydrothermal mussel Bathymodiolus azoricus collected in Menez Gwen hydrothermal vent field (NE Atlantic) during 2002-2003 were examined for feeding patterns variations through three seasons. The fatty acid profile and lipid classes of the mussels were studied, together with the MODIS/AQUA-derived near-surface chlorophyll a to test the hypothesis that surface productivity might be related to the feeding patterns of this species. The lipid levels showed pronounced seasonal fluctuations with the highest values occurring in January and August. Seasonal variations in lipid classes and fatty acid composition of neutral and polar lipids in the mussels are presented. Differences in the fatty acid profile of lipid classes in different seasons suggest that the higher energy requirements in summer and winter were supplied by bacterial biomarkers omega7 MUFA (monounsaturated fatty acids), whereas omega6 PUFA (polyunsaturated fatty acids) and NMI (non-methylene-interrupted) fatty acids predominated during the spring. The MODIS/AQUA data show marked seasonal variability and an anomalous peak during January of 2003, although this cannot be directly linked to lipid composition variation.

Molecular characterization and expression of three heat shock protein70 genes from the carmine spider mite, Tetranychus cinnabarinus (Boisduval)

Three heat shock protein 70 (Hsp70) cDNAs were isolated from the carmine spider mite, Tetranychus cinnabarinus. They were tentatively named as TCHsp70-1, TCHsp70-2 and TCHsp70-3. Structural analyses showed that all of the three TCHsp70 cDNAs held the full open reading frame (ORF). Putative protein sequences and a phylogenetic tree suggested that TCHsp70-1 and TCHsp70-3 were cytoplasm HSP70 and TCHsp70-2 was endoplasmic reticulum HSP70. Comparison of deduced amino acid sequences of TCHsp70-1 and TCHsp70-3 showed 84.78% identity, TCHsp70-1 and TCHsp70-2 showed 57.33% identity, TCHsp70-2 and TCHsp70-3 showed 58.26% identity. Real-time comparative quantitative PCR revealed that the relative expression of TCHsp70-2 was lower than TCHsp70-1 and TCHsp70-3 at each temperature tested. TCHsp70-1 and TCHsp70-3 shared a similar expression pattern after cold and heat shock compared with their expression at normal temperature (26 degrees C), but the mRNA expression of TCHsp70-1 was significantly higher and lower than that of TCHsp70-3 at cold and heat shock temperatures (except for 34 degrees C), respectively. This result possibly indicated the expression patterns of TCHsp70 were affected by their location in different cellular compartments. The results also indicated that three TCHsp70s, especially TCHsp70-1 and TCHsp70-3, may play an important role in mediating tolerance to cold, thermal stress for Tetranychus cinnabarinus.