Identification of genes involved in haevy metals tolerance and hyperaccumulation in Arabidopsis halleri and characterisation of a bZIP transcription factor responsible for Cd uptake and translocation to the shoot in Arabidopsis thaliana

Cadmium (Cd) is a main risk for human health and agriculture: this is due to its high solubility in water, which causes its rapid distribution into the environment, an immediate availability to plants and its access into the food-chain. An alternative strategy of environmental remediation from heavy metals, for example Cd, is the phytoremediation: a process applied in situ, ecologically safe (environment friendly) and inexpensive, which has as aim the strip of organic and inorganic contaminants from sites by plants. Particularly, the phytoextraction provide the use of plants able to remove heavy metals and accumulate them in the above-ground tissues (Pilon-Smits, 2005). The identification of numerous hyperaccumulator plants capable to tolerate and accumulate high heavy metal amounts in their tissues, demonstrates that plants own the genetic capacity to tolerate and remove heavy metals from contaminated sites. An example is Arabidopsis halleri (belonging to Brassicaceae family), a plant species tolerant to Cd, Zn and Pb and hyperaccumulator of Cd and Zn (van Rossum et al., 2004). Being phylogenetically related to Arabidopsis thaliana, A. halleri is considered an important model system in studies that concern phytoremediation. Much remains still unknown about the molecular components of the metal-induced signal transduction, and only recently, thanks to differential-expression analyses, it has been possible to identify several genes, for example transcription factors (TFs), involved in heavy metal stress response. Moreover it important to consider the role of microbial community of rhizosphere in heavy metal uptake and translocation to the shoot processes: rhizosphere microorganisms, in fact, are able to modify (alter), directly or indirectly, the heavy metal mobility in soil, influencing their absorption by plant roots (Lovley, 1995).