Cloning and expression of two HSC70 genes in walking catfish Clarias

摘要

Two different cDNAs encoding heat shock cognate protein 70 genes were isolated from the liver of walking catfish. The complete cDNA sequences for walking catfish HSC70-1 and HSC70-2 were of identical length (2278 bp), with an open reading frame of 1950 bp and a predicted 649 amino acid protein. Genomic sequences of the walking catfish HSC70-1 and HSC70-2 genes were composed of eight exons and seven introns, but exon and intron sizes were different. Amino acid sequences of both proteins shared 94% similarity with 38 substitutions. The walking catfish HSC70-1 and HSC70-2 proteins shared 82-95% identity of amino acids with those of other teleosts, chicken and human. Phylogenetic analysis revealed that walking catfish HSC70-1 and HSC70-2 clustered with channel catfish HSC71. Under normal conditions, HSC70-1 and HSC70-2 transcripts were expressed at similar levels in liver, gills, brain and skeletal muscle of walking catfish. Bacterial infection by Aeromonas hydrophila differentially induced the expression of HSC70s in these tissues during 48 h. HSC70-1 was constitutively expressed at low levels in most tissues, whereas HSC70-2 was up-regulated at moderate and high levels in liver and skeletal muscle respectively. The significant increase in the expression of HSC70-2 in these tissues may relate to the role of HSC70-2 in the immune response of walking catfish