Expression of heat shock protein 90 genes during early development and infection in Megalobrama amblycephala and evidence for adaptive evolution in teleost

Heat shock protein 90 (HSP90) are highly conserved molecular chaperones, playing a pivotal role in cellular progress. In this study, we reported the characterization of the Hsp90 alpha and Hsp90 beta genes in Megalobrama amblycephala, the expression profiling during early development, in various healthy tissues and in response to bacterial infection, and the assessment of their adaptive evolution. The Hsp90 alpha cDNA contains an open reading frame (ORF) of 2193 bp encoding 731 amino acids and the Hsp90 beta cDNA has an ORF of 2184 bp encoding 728 amino acids. Using quantitative real-time PCR (qRT-PCR) analysis, the mRNA of both Hsp90a and Hsp90 beta reached the highest level at 15th day post-hatch. Using qRT-PCR and Western blot, both Hsp90 alpha and Hsp90 beta were widely expressed in various healthy tissues and significantly higher in blood than in other tissues. Expression of both Hsp90 alpha and Hsp90 beta were up-regulated upon bacterial infection and reached the peak level at 4 h post infection. Site model analysis indicated that one positive selection site (T717) in Hsp90 alpha was found, while no positive selection site was observed in Hsp90 beta. Branch-site model test showed that there were adaptively evolutionary evidences in the branches of Salmoniformes and Gasterosteiformes for Hsp90 alpha gene, and in the branch of Salmoniformes for Hsp90 beta gene. (C) 2013 Elsevier Ltd. All rights reserved.