Research on stress responses in animals has increased greatly during the last decades. Though most studies focus on the cellular and molecular bases of the stress response mechanisms, the ecological and evolutionary aspects of stress responses gain more and more interest. Here, we use species and parthenogenetic strains of the genus Artemia, an extremophile model organism, to study, for the first time, a protein well known for its chaperone activity and its involvement in stress responses. More specifically, transcription and protein accumulation of an FK506-Binding Protein (FKBP) homologue were investigated under heat and salt stresses. Additionally, the mRNA levels of ubiquitin, a heat-inducible protein related to the proteasomal pathway, were quantitated under these conditions. Biochemical and phylogenetic analyses showed that the studied FKBP orthologue is a typical representative of the family that clusters with other crustacean sequences. The expression was increased in both fkbp and ubiquitin genes after salt and heat stresses. However, our results in combination with the fact that Artemia species and parthenogenetic strains, selected for this study, exhibit different heat or salt tolerance provide useful hints about the evolutionary significance of FKBP and ubiquitin. Regarding FKBP, mRNA expression and protein accumulation seem to depend on the environmental conditions and the evolutionary history of each Artemia population while ubiquitin has a clear and more conserved role under heat shock.
Keywords: Brine shrimp; Chaperones; Extremophiles; Thermal history; Ubiquitin–proteasome pathway.
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