Molecular cloning of heat shock protein 60 (Hsp60) and 10 (Hsp10) genes from the cosmopolitan and harmful dinoflagellate Scrippsiella trochoidea and their differential transcriptions responding to temperature stress and alteration of life cycle

Abstract

Heat shock protein 60 (Hsp60) and Hsp10 are two chaperones important to both stress responses and cellular metabolisms in most organisms. In this study, the cosmopolitan Scrippsiella trochoidea was used as a model of HAB-forming dinoflagellates to explore the possible functional roles of Hsp60 and Hsp10 in the adaptation of dinoflagellates to temperature stress and life cycle transition. The full-length cDNAs of a Hsp60 and a Hsp10 gene from S. trochoidea (StHsp60 and StHsp10) were obtained via rapid amplification of cDNA ends (RACE) and their deduced amino acid sequences both included family-characteristic conservative structures and motifs, indicating a conserved function for both among different taxa. Real-time qPCR revealed that StHsp60 and StHsp10 exhibited highly similar mRNA accumulation patterns in response to temperature stresses. Their mRNA amounts, compared to that at 20 °C (control), were rapidly up-regulated upon exposure to both lower (15 °C, 10 °C, 5 °C) and higher (25 °C, 30 °C) temperatures and showed a clear time-dependent manner, suggesting a possible involvement of StHsp60 and StHsp10 in the urgent adaptation of S. trochoidea to drastic temperature stress. Furthermore, significantly elevated mRNA levels of both genes were detected in resting cysts (newly formed and that maintained in dormancy for different durations) relative to that in vegetative cells, suggesting that higher levels of StHsp60 and StHsp10 are demanded by S. trochoidea resting cysts. The results of this work, as the first investigation to characterize Hsp60 and Hsp10 genes from dinoflagellates, enrich the knowledge about Hsps and lay an important foundation for further probing their functions in dinoflagellate resting cysts.