Diverse cis-regulation of a vacuolar metal transporter in Arabidopsis thaliana and Arabidopsis halleri.

The vacuolar metal transporter VMT is involved in metal hyperaccumulation. VMT isexpressed at higher levels in metal hyperaccumulators Arabidopsis halleri and Noccaeacaerulescens than in non-accumulator species, such as Arabidopsis thaliana. To gatherinformation about the different transcriptional cis-regulation of VMT, we performed an insilico comparison of promoter sequences amplified from a variety of Brassicaceae species,including both hyper- and non-accumulators, and three putative motifs were identified andchosen for further in vivo analysis. Three different sequences corresponding to the VMTpromoter were amplified in A. halleri. Truncated forms were generated isolating the coresequence and deleting two of the motifs, while site-directed mutagenesis was performedon the third motif. The cloned sequences were fused to the GUS reporter gene and theobtained constructs were used for A. thaliana transformation (AtVMT promoter was used ascontrol). Promoters of both A. thaliana and A. halleri VMT are active in roots, guard cellsand hydathodes, but only Ah-pVMT seems to be specific for leaf mesophyll and trichomes.