Molecular cloning and characterization of twist gene in Bombyx mori

Molecular cloning, tissue distribution and expression analysis of a manganese superoxide dismutase in blunt snout bream Megalobrama amblycephala

The full-length mitochondrial manganese superoxide dismutase cDNA of blunt snout bream Megalobrama amblycephala (denoted as MamMnSOD) was identified in liver using homology cloning and rapid amplification of cDNA ends. The full-length cDNA of MamMnSOD consisted of 986 bp, with an open reading frame encoding 224 amino acids, a 58-bp 5' untranslated region and a 256-bp 3' untranslated region. The deduced amino acid sequences of MamMnSOD showed high sequence homology to mitochondrial MnSODs from crustaceans. Several motifs, including three mitochondrial MnSOD signatures, amino acid residues responsible for coordinating the manganese, and the putative active center, were almost completely conserved in the deduced amino acid sequences of MamMnSOD. The mRNA expression of MamMnSOD in the tissues of heart, liver, spleen, kidney, muscle, intestine, and gill was examined by quantitative real-time PCR; the highest expression was in the liver. Transcription of MamMnSOD was kinetically modulated in response to nitrite stress in liver and gill tissues. The purified recombinant MamMnSOD showed potent antioxidant activity. Polyclonal antibodies generated from the recombinant product of MamMnSOD were used to specifically identify the native protein in liver of M. amblycephala. Collectively, the findings of this study strongly suggested that MamMnSOD combats oxidative stress and cellular damage induced by nitrite, by detoxifying harmful reactive oxygen species in M. amblycephala.

A manganese superoxide dismutase in blood clam Tegillarca granosa: molecular cloning, tissue distribution and expression analysis

Superoxide dismutase (SOD, EC 1.15.1.1) is one of the central enzymes involved in scavenging the high level of reactive oxygen species (ROS) by transforming O₂⁻ into hydrogen peroxide and oxygen. The full-length mitochondrial Mn-SOD cDNA of blood clam Tegillarca granosa (denoted as TgmMnSOD) was identified from haemocytes by homology cloning and rapid amplification of cDNA ends (RACE) approaches. The nucleotide sequence of TgmMnSOD consisted of 1106bp with a 5' UTR of 195bp, a 3' UTR of 227bp with a candidate polyadenylation signal sequence ATTAAA and a short polyA tail, and an open reading frame (ORF) of 648bp encoding a secreted polypeptide of 227 amino acids residues. The deduced amino acid sequence of TgmMnSOD shared significant homology to mMnSODs from other species, indicating that TgmMnSOD should be a novel member of the mMnSOD family. Several highly conserved motifs including three mMnSOD signatures, amino acid residues responsible for coordinating the manganese and the putative active center were almost completely conserved in the deduced amino acid of TgmMnSOD. The mRNA expression of TgmMnSOD in the tissues of mantle, foot, gill, haemocytes and hepatopancreas was examined by quantitative real-time PCR (qT-PCR) and mRNA transcripts of TgmMnSOD were mainly detected in hepatopancreas, haemocytes, and gill and weakly detected in the mantle and foot. The temporal expression of TgmMnSOD in haemocytes after heavy metal exposure revealed that TgmMnSOD could be induced by the three pollutants with different response profiles. The polyclonal antibodies generated from the recombinant product of TgmMnSOD could specifically identify not only the recombinant product, but also the native protein from haemocytes. The present results strongly suggested that TgmMnSOD was a cute response protein involved in marine heavy metal contaminants challenge in T. granosa.