Molecular characterization of heat shock protein 90 from the dinoflagellate Prorocentrum donghaiense and its transcriptional response to thermal, copper and nutrient stresses

In this study, a novel HSP90 gene (PdHSP90) was cloned from Prorocentrum donghaiense. The full length of PdHSP90 is 2443 bp, with 5 '-UTR of 111 bp, 3 '-UTR of 199 bp, and open reading frame (ORF) of 2133 bp. The ORF encodes a polypeptide of 710 amino acid residues, with molecular weight of approximately 85.81 kDa and isoelectric point of 4.95. Phylogenetic analysis revealed that PdHSP90 belongs to the dinoflagellate clade and is closely related to HSP90s from P. minimum and P. micans. PdHSP90 expression increased under the thermal stress (p < 0.05), with the highest changes of 7.6-fold at 10 degrees C 2 h post treatment compared to the control. PdHSP90 expression was significantly upregulated (1- to 10.8-fold change) (p < 0.05) with increasing concentrations of copper from 0 mu M to 31.25 mu M. PdHSP90 expression level under 176 mu M nitrogen was nearly equal to that under 88 mu M nitrogen, which were 4.5- and 4.6-fold higher, respectively, compared with the control (p < 0.05). Upon treatment with phosphorus limitation from 36 mu M to 3.6 mu M, PdHSP90 transcription level increased 11.4-fold (p < 0.05) and then decreased. These results provide new insights into the molecular mechanism underlying adaptation of P. donghaiense and other harmful dinoflagellates in response to diverse environmental factors.