The cytosolic manganese superoxide dismutase cDNA in swimming crab Portunus trituberculatus: Molecular cloning, characterization and expression

A cytosolic manganese superoxide dismutase (cMnSOD) cDNA was cloned from the haemocytes of swimming crab Portunus trituberculatus using reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) method. Analysis of the nucleotide sequence revealed that the cMnSOD full-length cDNA consisted of 1106 bp with an open reading frame of 861 bp encoding a protein of 286 amino acids. Four conserved amino acids responsible for binding manganese (H110, H158, D243 and H247) and MnSOD signatures from 243 to 250 (DVWHHAYY) were observed. Sequence comparison showed that the cMnSOD deduced amino acid sequence of P. trituberculatus had similarity of 92%, 78%, 77% and 75% to that of blue crab Callinectes sapidus, white shrimp Litopenaeus vannamei, giant tiger prawn Penaeus monodon and freshwater prawn Macrobrachium rosenbergii, respectively. Quantitative real-time RT-PCR analysis revealed that P. trituberculatus cMnSOD transcript was strongly detected in haemocytes, hepatopancreas, heart, stomach, intestine, gill, ovary and muscle. RT-PCR analysis indicated that cMnSOD transcripts both in haemocytes and hepatopancreas increased at 3 h and 6 h after infection. These facts indicate that cMnSOD is potentially involved in the acute response against invading bacteria in P. trituberculatus.