Identification and characterization of heat shock protein 90 (HSP90) in the hard coral Acropora tenuis in response to Irgarol 1051

To elucidate the effects of the herbicide Irgarol 1051 on the gene expression of heat shock protein 90 (HSP90) in hard corals, we isolated a full-length cDNA encoding HSP90 from Acropora tenuis, which has a deduced open reading frame of 732-amino acid residues with a predicted molecular mass of 84.5 kDa. The amino acid sequence of A. tenuis HSP90 showed a high degree of similarity with the hermatypic-coral HSP90 families. After a 7-d exposure to 1 or 10 μg/L of Irgarol, the body colours of corals in the 10 μg/L treatment group were significantly whiter (bleached), whereas no such effects were observed in the corals in the 1 μg/L treatment group. However, the expression level of coral HSP90 was significantly downregulated after exposure to both 1 and 10 μg/L Irgarol. These results suggest that A. tenuis HSP90 may be a useful molecular biomarker to predict bleaching caused by herbicides.