Cadmium availability at different soil pH to transgenic tobacco overexpressing ferritin

Knowledge on physiological mechanisms and plant metabolism can be used to enhance metal uptake. The capacity to uptake metals of transgenic tobaccos overexpressing ferritin in plastids (P6) or in cytoplasm (C5) and a control tobacco (A) is assessed in three polluted soils from the same soil series, with a similar Cd content, but displaying pH from 5.8 to 7 (8b2, 8b3, S11). Differences in dry leave weight were not significant between the three tobaccos growing on each soil. Iron concentration in ferritin overexpression either in P6 or in C5 tobaccos increased only on the S11 soil, which had a soil pH 7, in comparison to A tobacco. In both 8b2 and 8b3 soils at pH lower than 7, the leaf Fe content was not different between the three tobaccos. Only the P6 tobacco growing in the S11 soil accumulated more Cd, Zn and Mn compared with the A and C5 tobaccos. This increase represents, compared to A tobacco, 88% for Fe, 120% for Mn, 30% for Cd, 80% for Zn. In soils with a pH higher than 7, the ferritin synthesis is over-expressed in the P6 tobacco cells inducing a iron deficiency. These metal accumulations were increased, owing to a rhizosphere modification. The A and P6 tobaccos uptake Cd in the same soil pool. The Cd totality in the 8b2 soil is labile and in the S11 soil, the labile Cd represents 86–88% of the total C