Abstract
It is recently suggested that ZIP family, one of the most important transporter families involved in metal uptake into the cytoplasm, plays a critical role on metal accumulation or tolerance in metal hyperaccumulator plants, but the detail role remains unclear. Here, we report the function of TjZNT1, a ZIP transporter of a Ni hyperaccumulatorThlaspi japonicum, in Ni tolerance. A sequence similarity search and yeast assay showed that TjZNT1 is an ortholog of a Zn/Cu transporter of Arabidopsis thaliana, AtZIP4. As a result of TjZNT1 promoter-GUS reporter assay in T. japonicum, GUS stain was observed in the steles of roots and veins, suggesting that TjZNT1 is involved in the root-to-shoot translocation of Zn/Cu as well as AtZIP4. A qRT-PCR study showed that the transcriptional level of TjZNT1 in T. japonicum was 1000-fold higher than that of AtZIP4 in A. thaliana, indicating that T. japonicum constitutively expresses TjZNT1 at high level. Furthermore, the yeast strain over expressing TjZNT1 showed high level Ni tolerance, suggesting that the uptake of Zn/Cu contributes to excess Ni tolerance. We presently investigate the Ni tolerance of transgenic A. thaliana expressing TjZNT1.
