Plants and growth condition
Arabidopsis (Arabidopsis thaliana ) accession Columbia-0 (Col) was used in this study as the wild-type (WT) control. Mutants ofmtm1-1 (SALK 023286), mtm1-2 (SALK 054287C), mtm2-1(SALK 005166), mtm2-2 (SALK 103984), and mtm2-3 (SALK 025071) were obtained from the Arabidopsis Biological Resource Center (ABRC, Ohio State University). Plants were grown in growth chambers at 22-24°C under a 16-h light/8-h dark cycle at 80-100 µmol m-2 s-1. For root length assay, sterile seeds were placed on solid half-strength Murashige and Skoog basal medium (1/2 MS; Sigma M5519) (Murashige & Skoog, 1962) containing 1% Suc and 0.8% phytagel (Sigma). Transgenic plants ofAtMTM2 -promoter::GUS with pCAMBIA-1391Z vector, and35S ::AtMTM1 -overexpression (OE) and35S ::AtMTM2 -OE with pCAMBIA-3300 vectors in Arabidopsis Col background were generated by Agrobacterium tumefaciensGV3101-mediated transformation and the floral dip method (Clough & Bent, 1998). For post-translational regulation, metal stress, and metal ion homeostasis assays, two-week-old seedlings were transferred to the stressed medium under the normal 16-h light/8-h dark condition as described above.