Abstract
Zinc is a trace element essential for all organisms as a cofactor for various enzymes and proteins. However, excess zinc becomes toxic. We study on zinc transporters in plants. In Arabidopsis thaliana, MTP1 and MTP3 function as Zn2+/H+ antiporter in vacuolar membrane and play a key role in zinc tolerance. In this study, we investigated MTP4. GFP-tag analysis and subcellular fractionation disclosed that MTP4 is localized in the plasma membrane. Yeast complementation assay using a zinc-hypersensitive strain showed the zinc transport activity of MTP4. Promoter GUS assay revealed that MTP4 is expressed in mature pollens and vascular bundles. Analysis using a construct of own promoter driven MTP4-GFP showed that MTP4 exists in pollen tubes. With consideration of structural similarity to MTP1, MTP4 may function as a zinc efflux transporter in the plasma membrane. We also showed the phenotypic properties of the T-DNA inserted mutant lines.
