Accumulation des métaux lourds chez le Peuplier: Localisation tissulaire et expression de quelques transporteurs

Abstract

In plants, non-essential elements such as Cd and Pb can be absorbed and constitute a potential hazard because they enter the food chain. Trace elements such as Zn, Fe, Cu, Co, Mn, Mo and Ni are necessary biological processes, but their excessive accumulation can be toxic. In this study it was shown that the poplar (Populus spp.) Could accumulate relatively high concentrations of some metals (Cd, Zn and Ni) compared to other woody species. Different cultivars were tested in hydroponics and it was shown that hybrids of Populus trichocarpa accumulated more than others. These hybrids were implanted in two polluted sites, and it follows that, combined to produce a high biomass that can be used to produce energy, the character accumulator Poplar, makes this tree a good candidate for phytoremediation. A study of tissue localization of metals in leaves and stems of poplars subjected to polycontamination metal was also taken by scanning electron microscopy (SEM) and Mass Spectrometry Secondary Ion (SIMS). The latter technique showed that Zn was mostly concentrated in the mesophyll. To analyze some determinants of metal tolerance, measures of expression and functional characterization of transporters belonging to the CDF family (Cation Diffusion Facilitator) were conducted in different tissues and under different physiological conditions. The specificity of genes expressed and their localization were studied respectively by functional complementation and heterologous expression following GFP fusion in yeast. These techniques allowed to identify a carrier of Zn (PtMTP2) and a transporter of Mn (PtMTP9).