IDENTIFICATION OF A FAMILY OF ZINC TRANSPORTER GENES FROM ARABIDOPSISTHAT RESPOND TO ZINC-DEFICIENCY

Millions of people worldwide suffer from nutritional imbalances of ess ential metals like zinc. These same metals, along with pollutants like cadmium and lead, contaminate soils at many sites around the world. I n addition to posing a threat to human health, these metals can poison plants, livestock, and wildlife. Deciphering how metals are absorbed, transported, and incorporated as protein cofactors may help solve bot h of these problems. For example, edible plants could be engineered to serve as better dietary sources of metal nutrients, and other plant s pecies could be tailored to remove metal ions from contaminated soils. We report here the cloning of the first zinc transporter genes from p lants, the ZIP1, ZIP2, and ZIP3 genes of Arabidopsis thaliana. Express ion in yeast of these closely related genes confers zinc uptake activi ties. In the plant, ZIP1 and ZIP3 are expressed in roots in response t o zinc deficiency, suggesting that they transport zinc from the soil i nto the plant. Although expression of ZIP2 has not been detected, a fo urth related Arabidopsis gene identified by genome sequencing, ZIP4, i s induced in both shoots and roots of zinc-limited plants. Thus, ZIP? may transport zinc intracellularly or between plant tissues; These ZIP proteins define a family of metal ion transporters that are found in plants, protozoa, fungi, invertebrates, and vertebrates, making it now possible to address questions of metal ion accumulation and homeostas is in diverse organisms.