A Novel Metallothionein Gene Putatively Related to Fatty Acid Biosynthesis in Camellia Oleifera Seeds Confronted to Heavy Metal Stress

Metallothionein (MT) is a family of low molecular mass and cysteine-rich metal-binding proteins which could maintain metal homeostasis and stress responses by binding physiological and xenobiotic heavy metals. The fatty acid biosynthesis could be achieved successfully in Camellia Oleifera seeds, however, the plants grow in the red soil with high content of heavy metals such as Cu and Cd. In order to understand the role of Co-MT gene during development period of seeds in response to heavy metal stress, a novel MT gene was obtained and named as Co-MT on the basis of constructed transcriptome library of Camellia Oleifera in the research. Bioinformatics analysis suggested that the 675bp cDNA was composed of a 234bp ORF, a 58bp 5′UTR and a 379bp 3′UTR that contained a 6-fold “TAG” tandem repeat. The characters of Co-MT protein showed it was 78aa in length, the molecular weight was 7864.9Da, the pI was 4.86, and 14 cysteine motifs were detected to distribute at both N- and C-terminals which were thought to be the putative metal irons binding domain. The phylogenetic investigation indicated that MTs in higher plants were mainly classified into two monophyletic groups, and the relationship between Co-MT and Camellia sinensis was very close. In order to study the function of Co-MT, the gene was expressed in E.coli and the result showed that Co-MT obviously enhanced cell survivability against heavy metal stress.