Metallothionein cDNA Cloning and Metallothionein Expression in Sea Cucumber (Apostichopus japonicus, Slenka) from the WeiHai Coast of China

Abstract

The aims of this work were (1) the identification of the metallothionein (MT) gene cDNA sequence in Apostichopus japonicus and (2) the quantification of MT mRNA expression in the intestine, body wall and respiratory tree of A. japonicas after exposure to cadmium or zinc. Using RT-PCR and RACE-PCR, we cloned the MT complete cDNA sequence of A. japonicus using the RNA extracted from Cadmium-exposed intestines. The 1351 bp MT cDNA consisted of a 126 bp 5’ untranslated region, a 1069 bp 3’ untranslated region, and a 156 bp open reading frame coding for 51 amino acids, including 16 cysteines. The MT sequence of A. japonicus was 47% identical to the sequence of MT from Strongylocentrotus purpuratus. Through real-time quantitative PCR analysis, we found that the MT expression levels were significantly higher when the specimens were exposed to heavy metals, and the response to combined metal ions exposure occurred earlier than that for single metal ion exposure. Additionally, the induction of MT transcription was more responsive to zinc and can be envisaged as a potential biomarker for zinc contamination.