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 Zn2+ 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 Zn2+ while the expression of SnMTP1 was slightly inhibited. These data suggest that SaMTP1 can play an important role in Zn accumulation in HE plants.

► Two genes encoding metal tolerance proteins were isolated from two ecotypes of Sedum.
► Expression of SaMTP1 and SnMTP1 in yeast suppressed Zn hypersensitivity.
► SaMTP1 localized to the tonoplast of the protoplast from hyperaccumulator Sedum.
► SaMTP1 mRNA in the shoot of hyperaccumulator Sedum was over 80 times that of SnMTP1.