AtHMA3, a plant P 1B-ATPase, functions as a Cd/Pb transporter in yeast

Abstract

The Arabidopsis thaliana AtHMA3 protein belongs to the P 1B-adenosine triphosphatase (ATPase) transporter family, involved in heavy metal transport. Functional expression of AtHMA3 phenotypically complements the Cd/Pb-hypersensitive yeast strain Δ ycf1, but not the Zn-hypersensitive mutant Δ zrc1. AtHMA3-complemented Δ ycf1 cells accumulate the same amount of cadmium as YCF1-complemented Δ ycf1 cells or wild-type cells, suggesting that AtHMA3 carries out an intracellular sequestration of Cd. A mutant of AtHMA3 altered in the P-ATPase phosphorylation domain did not complement Δ ycf1, suggesting that metal transport rather than chelation is involved. The fusion protein AtHMA3::green fluorescent protein (GFP) is localized at the vacuole, consistent with a role in the influx of cadmium into the vacuolar compartment. In A. thaliana, the mRNA of AtHMA3 was detected mainly in roots, old rosette leaves and cauline leaves. The expression levels were not affected by cadmium or zinc treatments.