Overexpression of a yeast cadmium factor 1 (YCF1) enhances heavy metal tolerance and accumulation in Brassica juncea

A yeast cadmium factor 1 (YCF1) is a member of the ATP-binding cassette (ABC) transporter family associated with multi-drug resistance, and it is localized at the vacuolar membrane in Saccharomyces cerevisiae. To determine ability to increase heavy metal tolerance and accumulation, YCF1 was introduced into Brassica juncea plants by Agrobacterium-mediated genetic transformation. YCF1 gene presence in transgenic plants was demonstrated by polymerase chain reaction (PCR). Reverse transcriptase-PCR analysis confirmed YCF1 gene expression in the transgenic plants, but the degree of YCF1 expression varied among the lines. YCF1 overexpression in B. juncea conferred enhanced tolerance to cadmium (Cd[II]) and lead (Pb[II]) stress. Transgenic B. juncea seedlings showed 1.3- to 1.6-fold tolerance to Cd stress and 1.2- to 1.4-fold tolerance to Pb stress compared to wild type (WT) plants (per gram fresh weight). Most importantly, the shoot tissues of transgenic seedlings contained about 1.5- to 2-fold higher Cd(II) and Pb(II) levels than those of WT, demonstrating significantly increased accumulation of both Cd(II) and Pb(II) in transgenic plants.