Molecular cloning, mRNA expression, and characterization of HSP90 gene from Chinese mitten crab Eriocheir japonica sinensis.

HSP90 is a highly conserved molecular chaperone important in the maturation of a broad spectrum of proteins. Using expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE) techniques, an HSP90 gene designated as EjsHSP90 was cloned and characterized from the Chinese mitten crab Eriocheir japonica sinensis. The full-length cDNA of EjsHSP90 is 2,517 bp and contains an open reading frame of 2157 bp which encodes a 718 amino acid polypeptide (82.8 kDa) bearing characteristics of the HSP90 family and an ATP binding domain. Sequence alignment shows that EjsHSP90 shared 79%-96% identity with HSP90 sequences reported in other animals, and it shares identical structural features. Fluorescent real-time quantitative RT-PCR approach was performed to examine the expression profiles of EjsHSP90 mRNA by testing its relative level in three types of tissues at three different developmental stages, respectively. We found that EjsHSP90 is expressed throughout the three developmental stages but expression levels varied among different body parts of crabs. EjsHSP90 mRNA expression in the abdomen of the first crab stage is consistently higher than that of the other two stages, suggesting that EjsHSP90 gene is involved in the crabs' early developmental process, especially in the crab brachyurization process. Results from quantitative RT-PCR excluded the possibility that the expression of EjsHSP90 mRNA is induced primarily by osmotic stress. Phylogenetic analyses reveal that HSP90 gene is informative and complementary for reconstruction of arthropod phylogenetic relationships.