Molecular cloning of hsf1 and hsbp1 cDNAs, and the expression of hsf1, hsbp1 and hsp70 under heat stress in the sea cucumber Apostichopus japonicus

The heat shock response (HSR) is known for the elevated synthesis of heat shock proteins (HSPs) under heat stress, which is mediated primarily by heat shock factor 1 (HSF1). Heat shock factor binding protein 1 (HSBP1) and feedback control of heat shock protein 70 (HSP70) are major regulators of the activity of HSF1. We obtained full-length cDNA of genes hsf1 and hsbp1 in the sea cucumber Apostichopus japonicus, which are the second available for echinoderm (after Strongylocentrotus purpuratus), and the first available for holothurian. The full-length cDNA of hsf1 was 2208 bp, containing a 1326 bp open reading frame encoding 441 amino acids. The full-length cDNA of hsbp1 was 2850 bp, containing a 225 bp open reading frame encoding 74 amino acids. The similarities of A. japonicus HSF1 with other species are low, and much higher similarity identities of A. japonicus HSBP1 were shared. Phylogenetic trees showed that A. japonicus HSF1 and HSBP1 were clustered with sequences from S. purpuratus, and fell into distinct clades with sequences from mollusca, arthropoda and vertebrata. Analysis by real-time PCR showed hsf1 and hsbp1 mRNA was expressed constitutively in all tissues examined. The expression of hsf1, hsbp1 and hsp70 in the intestine at 26 °C was time-dependent. The results of this study might provide new insights into the regulation of heat shock response in this species.