The responsive expression of a caspase gene in Chinese shrimp Fenneropenaeus chinensis against pH stress

Caspases are a family of proteases, which play an important role in apoptosis. To evaluate the relationship between apoptosis and pH stress in crustaceans, a caspase gene (FcCasp) was cloned from the Chinese shrimp Fenneropenaeus chinensis. The full length of FcCasp was 1329 bp with a 972 bp ORF, encoding a polypeptide of 323 amino acids with a calculated molecular weight and pI of 36.0 kDa and 6.27 respectively. The deduced amino acid sequence of FcCasp contained a potential active site (QACRG pentapeptide) conserved in most caspases and two profile hits (p20 and p10 domain profile). Comparison of amino acid sequences revealed that FcCasp had an overall similarity of 76–83% with other penaeid shrimp caspases. The amino acid sequence of recombinant FcCasp protein expressed in Escherichia coli was identified by matrix‐assisted laser desorption/ionization‐time of flight‐mass spectrometer analysis. High‐level expression of FcCasp in six different tissues was detected by real‐time polymerase chain reaction after exposure to pH stress for 96 and 148 h. TUNEL analysis indicated that apoptosis began to appear in F. chinensis hepatopancreas exposed to extreme pH for 12 h. The amount of apoptosis seems positively correlated with the length of exposure to the pH stressor. The results suggested that FcCasp was involved in the response to environmental pH stress.