The identification of metallothionein in rare minnow (Gobiocypris rarus) and its expression following heavy metal exposure

Heavy metal, such as cadmium (Cd), lead (Pb) and copper (Cu) poses serious toxin to aquatic organisms. These exogenous materials affect biological processes including physiology, biochemistry and development. Metallothionein (MT), one of the metal-regulated genes, participates in regulating essential and detoxifying non-essential metals in living animals. In this study, MT EST in rare minnow (Gobiocypris rarus) (GrMT) was obtained from the cDNA subtraction library and the GrMT cDNA was firstly cloned by RACE with a sequence of 379 bp, which can code 60 amino acids. After Cd exposure, the GrMT expression levels dramatically changed in liver, spleen, gill, kidney, intestine, but moderately in muscle. Significantly positive relationships were found between Cd dosages and MT expression levels in liver. And there distinction existed at the GrMT transcript level in fish gender and developmental stages during Cd exposure. While Pb exposure, the expression alteration happened in spleen, gill, intestine, muscle, and moderately in liver. In the Cu treatment test, there were slight changes in intestine and kidney, but more significant changes occurred in spleen, gill, muscle, and liver. This study had investigated the effects of diverse heavy metals on GrMT expression patterns. The results suggest that GrMT would be a potential biomarker to metal contamination monitoring in aquatic environments and rare minnow could be one of the perfect experimental fishes for surveying the freshwater pollution in China.