## 1 Introduction  
Phytoremediation, including mainly phytoextraction and phytostabilization, consists of recently developed and improved technologies of soil cleaning with the use of innate plant abilities [1, 2]. New species, genotypes adapted to local environmental conditions, are being investigated and tested [3, 4]. Studies particularly focus on hyperaccumulators, unique plant species defined by two coefficients, the bioaccumulation factor (ratio of the metal content in plants to its content in soils) and the translocation factor (ratio of the metal content in the plant shoots to that in their roots), reaching above one and the high shoot content of heavy metal reaching 100-10,000 mg kg\({}^{-1}\) (at least), depending on the metal [5]. Direct use of hyperaccumulators is not without its limitations, such as low biomass and slow growth of many tolerant genotypes. Different methods, includingtraditional breeding or genetic engineering, are employed to either improve the growth rate and biomass of hyperaccumulators or introduce hyperaccumulation traits [6]. Transgenic plants with enhanced ability to tolerate and hyperaccumulate metals are obtained via somatic hybridization, mutagenesis including gene stacking, epigenetic modifications, or gene editing (for a revision, see [7; 8; 9]). Despite the obvious advantages, such as the short time to obtain transgenic plants compared to traditional breeding, such modifications are not without drawbacks. Genetic manipulation of many genes underlying metal tolerance, e.g., encoding heavy metal transporters, chelators, and genes encoding components or even chloroplasts, genomes of antioxidant machinery and accumulation, is a complex procedure [1; 10]. Moreover, such plants often arouse public opposition; hence there are difficulties in obtaining approval for their field testing [11]. Some, therefore, believe that the natural potential of plants that have evolved to adapt to high concentrations of heavy metals in the soil should be explored [3]. Thus, it is important to look for the ecotypic variability of metalloproteinases populations [12]. _Arabidopsis arenasa_ ([PERSON] (formerly _Cardaminopsis arenasa_ ([PERSON]) is one such species with high potential for phytoremediation, occurring as a dominant species (metal tolerant populations) on calamine (Zn/Pb/Cd) soils in Western Europe [13]. This montane and subalpine species of Central and Western Europe, and Scandinavia (lower altitudes), could be either diploid (\(2n=2x=16\)) or tetraploid (\(2n=4x=32\)). Tetraploid cytotypes are commonly distributed across the whole range, while diploid cytotypes were exclusively found on the Balkan Peninsula and in the Carpathians [14]. Though the tetraploid cytotype is autopolyploid, tetraploid individuals of _A. arenasa_ run meiosis typical for diploids, where bivalents are selected randomly from four homologs [15; 16]. Recent studies have shown that these polyploid populations can rapidly adapt to adverse, extreme soil conditions based on pre-existing and novel variations [17]. Thereby they inhabit heterogeneous habitats, including serpentine outcrops, calamine soils, and railway lines going beyond the sites occupied by diploids [18; 19]. The tolerance to heavy metals in this species is induced (metal tolerance is developed only in some populations after contact with heavy metals), and metalloproteinases populations differ morphologically from non-metallicolous ones [14; 20; 21; 22; 23; 24; 25; 26; 27]. Metal-tolerant populations from extremely polluted sites could accumulate or even hyperaccumulate Zn and Cd [25; 26; 27]. _A. arenasa_ does not appear to be a typical metallophyte; however it is a heavy metal tolerant species, possibly also related to drought tolerance, similar to _Viola nupestris_[14; 28; 29]. Extreme environmental adaptation could be favored by gene duplication that have evolved new functions or increased the protein content [30]. A good example is the split of _Arabidopsis halleri_ and _A.