Expression of the P1B-type ATPase AtHMA4 in tobacco modifies Zn and Cd root to shoot partitioning and metal tolerance

Siemianowski, Oskar, Mills, Rebecca Fay, Williams, Lorraine Elizabeth and Antosiewicz, Danuta Maria (2010) Expression of the P1B-type ATPase AtHMA4 in tobacco modifies Zn and Cd root to shoot partitioning and metal tolerance. Plant Biotechnology Journal, 9 (1), 64-74. (doi:10.1111/j.1467-7652.2010.00531.x). (PMID:20492550)

Abstract

Genetic modification of Zn/Cd accumulation in roots and shoots for biofortification or phytoremediation is a focus of this manuscript. We expressed AtHMA4 (a P1BATPase involved in Zn and Cd transport), AtHMA4-trunc (lacking the C-terminal region) and AtHMA4-C terminus (the C-terminal region alone) in tobacco under the CaMV 35S constitutive promoter and examined accumulation and tolerance to both metals. Expression of AtHMA4 enhanced Zn translocation to the shoots only at 10 ?m Zn but not at 0.5, 100 and 200 ?m Zn. AtHMA4-trunc did not show this effect and instead reduced Zn translocation to the shoot. AtHMA4-expressing plants showed a decrease in cadmium uptake when exposed to 0.25 and 5 ?m Cd; this was also observed with AtHMA4-trunc-expressing lines, although to a lesser extent. Expression of AtHMA4-C-terminus containing potential metal binding sites increased cadmium and zinc concentrations in roots and shoots up to fourfold. We have demonstrated that both AtHMA4 and AtHMA4 C-terminus could be candidate genes/sequences for engineering modifications of zinc and cadmium root/shoot partitioning. However, the phenotype of transformants depended on the external metal concentration, thus it might be difficult to engineer a plant displaying the desired metal-related phenotype when grown under varying conditions of metal supply.

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