Characterization and SNP variation analysis of a HSP70 gene from miiuy croaker and its expression as related to bacterial challenge and heat shock

Heat shock proteins (HSPs) play crucial roles in the immune response of vertebrates. In order to study immune defense mechanism of heat shock protein gene in miiuy croaker (Miichthys miiuy), a cDNA encoding heat shock protein 70 (designated Mimi-HSP70) gene was cloned from miiuy croaker. The cDNA was 2195 bp in length, consisting of an open reading frame (ORF) of 1917 bp encoding a polypeptide of 638 amino acids with estimated molecular mass of 70.3 kDa and theoretical isoelectric point of 5.55. Genomic DNA structure analysis revealed that the Mimi-HSP70 gene contain no introns in coding region and four SNPs with 373 C/T, 789 G/A, 1005 C/T, and 1185 G/A were detected by direct sequencing of 20 samples from six different populations. BLAST analysis, structure comparison and phylogenetic analysis indicated that Mimi-HSP70 should be an inducible cytosolic member of the HSP70 family. The deduced amino acid sequence of Mimi-HSP70 had 82.4%–92.2% identity with those of vertebrate. A real-time quantitative RT-PCR demonstrated that the HSP70 gene was ubiquitously expressed in ten normal tissues. Under different temperature shock stress, the expression of Mimi-HSP70 gene in miiuy croaker increased at first and then decreased with the rise of temperature, finally, reached a maximum level in liver, spleen and kidney tissues. Infection of miiuy croaker with Vibrio anguillarum resulted in significant changes expression of Mimi-HSP70 gene in the immune-related tissues. These results indicated that expression analysis of Mimi-HSP70 gene provide theoretical basis to further study the mechanism of anti-adverseness in the miiuy croaker.