FUNCTIONAL ANALYSIS OF POPLAR (Populus nigra L. and P. nigra x P. deltoids) DURING ENVIRONMENTAL EXPOSURE TO METALS

Dispersal of trace elements, metals and organics is relevant for environmental contamination and for fresh water utilization. Plant species have been used to decrease or remove the contaminants in polluted sites and in particular, tolerant and hyperaccumulator species seem promising for removal of metals in contaminated soils. The practical application of natural hyperaccumulators in phytoremediation is difficult because of their small biomass at maturity and reduced growth rates. For these reasons the metal uptake capacity of plants with higher biomass, such as trees belonging to Salicaceae family like poplar and willow, has been investigated. Laboratory and field trials have found that different clones of the genus Populus have different tolerance and metal uptake in contaminated environments. In this work we studied the behavior of three Italian selected poplar clones: P.nigra (clones 58-861 and Poli) and a hybrid P.nigra x deltoides (A4A), which showed different Cd tolerance and capacity and Cd uptake, accumulation and traslocation. The modifications occurring in the proteome of the three clones subjected to Cd treatments were investigated by comparing also the physiological behaviour of the clones. Rooted cuttings of three poplar clones were grown in hydroponic cultures with 0 ?M CdSO4 (control), 20 ?M CdSO4 for 48 hours (short term treatment) and 20 ?M CdSO4 for 14 days (long term treatment). (i) Different physiological parameters were analyzed: total leaf area, stem growth and elongation of the roots. Metal uptake and root to shoot translocation were observed by mineral analysis by Atomic Absorption Spectroscopy (ASS). Metal compartmentalization in leaves, roots and stems were analyzed by Scanning Electron Microscopy with microanalysis (SEM/EDX). (ii) Proteomic analysis was performed on crude protein extracts, obtained from leaves. Proteins with different isoelectric point (pI) and hydrophobicity were separated by a 2D liquid chromatography technique (ProteomeLab PF2D, Beckman). Qualitative and quantitative differences between protein profiles of treated and untreated samples were evidenced by DeltaVue Software (Eprogen). Proteins differently abundant in various conditions were characterized by MALDI-TOF/MS to infer their possible role in metal response. The results will be discussed with the aim to understand the different processes at the basis of accumulation and tolerance of metal by plant species.