Structure and expression of metallothionein gene in ducks

Metallothionein (MT) cDNAs were cloned and sequenced from two genera of ducks, Muscovy (Cairina muschata) and Tsai ya (Anas platyrhynchos). The two cDNAs show an extremely high sequence homology and contain an open reading frame encoding 63 amino acids. MT mRNA expressions were studied after metal induction using the cloned cDNA as a probe. Cadmium and copper induced MT gene efficiently, whereas zinc showed a markedly less effect. In addition, the MT mRNA accumulations in various developmental stages were also investigated. The result reveals a different pattern of expression from that of mammals. The discrepancy in MT gene between Tsai ya and Muscovy was further explored by examining genomic DNA structures. The duck MT showed three exons and two introns. The most significant variation of the genes occurs at intron II in which Tsai ya MT has 24 bases more than Muscovy MT. Moreover, MT expressions in the hybrids of Muscovy and Tsai ya were investigated using a reverse transcriptase-polymerase chain reaction. Those results demonstrated that parental MT genes are expressed in the hybrids after metal induction.