Minisymposium 22: Phytoremediation
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M2201: IRT3, a plasma membrane metal transporter, is involved in Zn uptake and responds to Zn deficiency
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Presenter: |
Lin, Ya-Fen Contact Presenter |
Authors | Lin, Ya-Fen (A) Yang, Shu-Yi (A) Huang, Jing-Ling (A) Baehrecke, Annegret (B) Clemens, Stephan (B) Yeh, Kuo-Chen (A) | | Affiliations: |
(A): Institute of BioAgricultural Sciences, Academia Sinica, Taiwan
(B): Leibniz-Institut fur Pflanzenbiochemie, Germany
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Zinc is an essential micronutrient for plant growth, and its uptake is controlled by active transporters in the membrane. Our previous data showed that the expression of IRT3 in Arabidopsis halleri, the Zn/Cd hyperaccumulator, was higher than that in Arabidopsis thaliana, which suggests a positive relation between IRT3 expression and high Zn accumulation in A. halleri. In this study, we first characterized the function and expression of both IRT3 genes from A. halleri and A. thaliana. In yeast, both AtIRT3 and AtIRT3 functionally complement the Zn uptake mutants zip1 and zrt1zrt2 but not the Fe uptake mutant fet3fet4 or the Mn uptake mutant smf1. They also cannot confer Cd uptake activities. The fusion proteins AtIRT3::GFP and AhIRT3::GFP
localize to the plasma membrane of hairy roots in tomato (Lycopersicon esculentum). Over expression of AtIRT3 in A. thaliana leads to increased accumulation of Zn in the root but not in the shoot. By fusing the AtIRT3 promoter to the β-glucuronidase (GUS) reporter gene, we show that the AtIRT3 promoter is active in the whole plant and its activity is regulated by Zn. The expression of AtIRT3 is apparently induced under zinc eficiency both in roots and shoots of A. thaliana but is slightly upregulated by zinc deficiency in roots and constitutively expressed in shoots of A. halleri. To account for our results, we propose that the IRT3 transporter is responsible for Zn uptake in response to Zn-limited conditions. The constitutive expression of AhIRT3 in shoots may be one of the reasons why A. halleri can accumulate more Zn than A. thaliana in above-ground tissues or reflect an intracellular Zn deficiency caused by high expression of other transporters for sequetration in A. halleri.
