Formation of glutathione-heavy metal complexes in the cytosol and their subsequent sequestration to the vacuole of the cell are critical steps for plants’ resistance to heavy metal toxicity. However, the identity and nature of such complex transporters remains elusive in plants. Here we report that TIP2;2 (tonoplast intrinsic protein 2;2) of the aquaporin superfamily is a tonoplast-localized glutathione-zinc transporter in Arabidopsis thaliana. TIP2;2 is expressed in the root where it facilitates the transport and sequestration of excess zinc from the cytosol to the vacuole of the root cell, thus limiting zinc translocation from the root to the vulnerable shoot tissues under zinc toxicity conditions. In the shoot, TIP2;2 also facilitates zinc transport to the leaf/stem trichome, a sink pool for storage and detoxification of heavy metals in plants. In conclusion, we have identified a unique cellular component that plays critical roles in resistance to zinc toxicity in Arabidopsis.
Coauthors: Yuqi Wang – Guangzhou University;Yan Kang – Inner Mongolia University;Wancong Yu – Tianjin Research Center of Agricultural Biotechnology;Sangbom Lyi – USDA-ARS;Yu Cao – South China Agricultural University;Yanfei Cai – South China Agricultural University;Hyong Woo Choi – Boyce Thompson Institute;Li Li – USDA-ARS;Daniel Klessig – Boyce Thompson Institute