Abstract
We have isolated Cd-tolerant clones from natural habitat plants growing in a former mining site. Of those, we further characterize a cDNA, termed DcCDT1, from Digitaria ciliaris. It confers Cd tolerance to the yeast cells which accumulate almost 2-fold lower Cd levels than control cells. DcCDT1 cDNA encodes a cysteine-rich-peptide composed of 55 amino acid residues. Five DcCDT1-homologues are found in rice and termed OsCDT1-5. All of them are up-regulated to varying degrees in above-ground tissues upon CdCl2 treatment. Localization of GFP fusions suggests that DcCDT1 and OsCDT1 are targeted to the cellular boundary in plant cells. Transgenic A. thaliana plants overexpressing DcCDT1 or OsCDT1 display a CdCl2-tolerant phenotype and, consistent with our yeast data, contain lower amounts of Cd when grown on CdCl2. Collectively, our data suggest that DcCDT1 and the related peptide function to prevent Cd entry into yeast and plant cells.