Molecular cloning and differential expression patterns of copper/zinc superoxide dismutase and manganese superoxide dismutase in Hypophthalmichthys molitrix

Copper/zinc superoxide dismutase (Cu,Zn-SOD) cDNA and manganese superoxide dismutase (Mn-SOD) cDNA were first cloned from silver carp Hypophthalmichthys molitrix using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) method. The open reading frame (ORF) of Cu,Zn-SOD is 465 bp and encodes a 154 amino acids (aa) protein, whereas the ORF of Mn-SOD is 675 bp and encodes a 224 aa protein. Multiple polypeptide sequence alignment showed high identity both of Cu,Zn-SOD (70–87%) and Mn-SOD (80–96%) with the species compared. Both Cu,Zn-SOD and Mn-SOD were detected in heart, brain, liver, kidney, spleen, muscle, gill and blood. Cu,Zn-SOD and Mn-SOD were expressed throughout the embryogenesis, indicating their important roles during embryonic development specially at the cleavage stage. Acute hypoxia suppressed expression of Cu,Zn-SOD and Mn-SOD in liver significantly, up-regulated them in gill relatively, indicating that tissue-specific expression of Cu,Zn-SOD and Mn-SOD is an important stress response adapted to hypoxia.