Differential transcription of heat shock protein 90 (HSP90) in the dinoflagellate Prorocentrum minimum by copper and endocrine-disrupting chemicals

Abstract

The dinoflagellate algae survive variations in water temperature as well as sudden exposures to toxic substances; heat shock proteins (HSPs) seem to function as part of their cell survival strategy. In the present study, we determined the complete open reading frame (ORF) of HSP90 gene in the dinoflagellate Prorocentrum minimum (PmHSP90), and examined the expression levels of the gene after exposure to thermal stressors, copper metal, and endocrine-disrupting chemicals, including bisphenol A (BPA) and polychlorinated biphenyl (PCB). The complete ORF of PmHSP90 was 2,130-bp long, encoding a 709-amino acid-long polypeptide (81.62kDa), and bearing characteristics of the HSP90 family and conserved domains. Real-time (RT)-PCR analyses revealed different expression patterns after exposure to heat, metals, and chemicals. The expression of PmHSP90 was significantly upregulated by increased thermal stresses, with the highest changes of 2.4-fold and 1.9-fold occurring after 24h at 25°C and 30°C, respectively. The gene expression dramatically increased (2.1 to 8.9-fold changes) with increasing concentrations of copper (one-way ANOVA, P<0.01). Treatment with BPA or PCB, however, did not induce significant changes in PmHSP90 expression. These data suggest that the dinoflagellate HSP90 responds to thermal stressors, but may differentially respond to toxic substances such as metals and endocrine-disrupting chemicals.