Abstract
Thus far, only one gene from the heat shock protein 70 (HSP70) family has been identified in Artemia franciscana. Here, we used the draft Artemia transcriptome database to search for other genes in the HSP70 family. Four novel HSP70 genes were identified and designated heat shock cognate 70 (HSC70), heat shock 70 kDa cognate 5 (HSC70-5), Immunoglobulin heavy-chain binding protein (BIP), and hypoxia up-regulated protein 1 (HYOU1). For each of these genes, we obtained nucleotide and deduced amino acid sequences, and reconstructed a phylogenetic tree. Expression analysis revealed that in the juvenile state, the transcription of HSP70 and HSC70 was significantly (P < 0.05) higher in a population of A. franciscana selectively bred for increased induced thermotolerance (TF12) relative to a control population (CF12). Following non-lethal heat shock treatment at the nauplius stage, transcription of HSP70, HSC70, and HSC70-5 were significantly (P < 0.05) up-regulated in TF12. In contrast, transcription of the other HSP70 family members in A. franciscana (BIP, HYOU1, and HSPA4) showed no significant (P > 0.05) induction. Gene expression analysis demonstrated that not all members of the HSP70 family are involved in the response to heat stress and selection and that especially altered expression of HSC70 plays a role in a population selected for increased thermotolerance.
Highlights
Heat shock proteins (HSPs) are a family of highly conserved proteins which expression responds to environmental stressors, such as high temperature, ultraviolet light, inflammation, infection and cellular toxins
In the control population (CF12), we found that heat shock cognate 70 (HSC70)-5 and binding protein (BIP) (3 h post-non-lethal heat shock (NLHS)) and heat shock protein 70 (HSP70) expression (6 h post-NLHS) were significantly (P < 0.05) up-regulated
We identified four novel putative genes from the HSP70 family in A. franciscana: HSC70, heat shock 70 kDa cognate 5 (HSC70-5), BIP and HYOU 1
Summary
Heat shock proteins (HSPs) are a family of highly conserved proteins which expression responds to environmental stressors, such as high temperature, ultraviolet light, inflammation, infection and cellular toxins. The HSP70 family is a group of stress response proteins that has been studied extensively in prokaryotic and eukaryotic organisms[3]. The expression of HSC70 can be induced by heat stress[8], but again that can be species-dependent. The fourth group is glucose-regulated protein 76 (GRP75) which is predominantly expressed in the mitochondria and is not induced in response to stress[7]. Acknowledging that in all eukaryotes this family has multiple members, it is of particular interest to investigate this family of genes in stress tolerant organism as Artemia. We investigated the expression of the identified HSP70 members in two populations of Artemia: a control population (CF12) that experienced 12 generations of isothermal laboratory culture conditions and a selected population (TF12) featuring the survivors of over 12 generations of an induced thermotolerance treatment. Our results showed that members of the HSP70 family respond differentially at the transcriptional level to “thermal” selection or to NLHS, or to both
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