Molecular cloning and expression of two HSP70 genes in the prawn, Macrobrachium rosenbergii

Two complementary deoxyribonucleic acid (cDNA) clones encoding 2 different 70-kDa heat shock proteins (HSPs) were isolated from the prawn Macrobrachium rosenbergii. The cDNA clones were 2448 and 2173 bp in length and contained 1950- and 1734-bp open reading frames (ORFs), respectively. The ORFs encoded 649- and 577-amino acid polypeptides, which were named Mar-HSC70 and Mar-HSP70, respectively, according to the sequence identities with other known HSC70s and HSP70s and based on their inducibility in response to heat shock stress (at 35°C). Genomic DNA sequence analysis revealed no introns in either gene. The major structural differences between the 2 proteins were a 60-amino acid segment and a 14-amino acid segment present in the N-terminal and C-terminal, respectively, of Mar-HSC70 that were not found in Mar-HSP70. Northern blotting and semiquantitative reverse transcription-polymerase chain reaction analyses indicated that the Mar-HSP70 gene was expressed under heat shock (35°C) stress in a non-tissue-specific manner. In contrast, Mar-HSC70 messenger ribonucleic acid was constitutively expressed in every tissue except muscle, and its expression in response to heat shock (at 35°C) changed only in muscle.