Sequencing and expression of metallothionein mRNA in freshwater murrel after cadmium exposure

Abstract

Metallothionein (MT) is a cysteine-rich, low molecular weight metal sequestering protein that has been shown to be involved in essential metal homeostasis and in detoxification of heavy metals. In the study sequences of MT genomic DNA and cDNA of freshwater murrel, Channa punctata (Bloch) were reported. cDNA was verified as the C. punctata MT gene by the characteristics of its predicted translation product, namely a high cysteine content, conserved Cys-Cys, Cys-X-Y-Cys, and Cys-X-Cys motifs, and a molecular weight of around 6 kDa. The quantitative real-time reverse-transcriptase polymerase chain reaction (q-RT-PCR) study was carried out in liver, kidney and gill tissues after exposure of the organism to waterborne cadmium for 8 h. At all the time points (viz. 1, 2, 4 & 8 h), a significant up regulation of MT transcript level was observed only in the liver. The results of time kinetics study indicated that expression pattern of C. punctata MT mRNA was found to be in tissue specific manner and the transcript level in the liver could be used as a biomarker of heavy metal contamination in water bodies.