Functional analysis of metal tolerance proteins isolated from Zn/Cd hyperaccumulating ecotype and non-hyperaccumulating ecotype of Sedum alfredii Hance.

The Zn/Cd hyperaccumulating ecotype (HE) of Sedum alfredii Hance can accumulate 24- and 28-fold higher leaf and stem Zn concentrations when compared with the non-hyperaccumulating ecotype (NHE) of Sedum. Heterologous expression of a metal tolerance protein (MTP1) encoding gene from HE plants (SaMTP1) or the homologous gene from NHE plants (SnMTP1) suppressed Zn(2+) hypersensitivity in the Δzrc1 yeast mutant. In plants, SaMTP1 localized to the tonoplast. Furthermore, MTP1 transcript level in the shoot of HE plants was more than 80-fold higher than that of NHE plants. The transcript level of SaMTP1 in shoot was up-regulated 1-fold by Zn(2+) while the expression of SnMTP1 was slightly inhibited. These data suggest that SaMTP1 can play an important role in Zn accumulation in HE plants.