Cadmium availability at different soil pH to transgenic tobacco overexpressing ferritin

Abstract

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 Cd.

Cadmium in plants on polluted soils: Effects of soil factors, hyperaccumulation, and amendments

“…In Table 1, pH is given, if documented in the original paper. One can see, for example in the studies by Kuo et al (2004), Sappin-Didier et al, 2005, andTsadilas et al (2005) that, as pH decreases, the amount of Cd in the plants increases. There is a linear trend between soil pH and Cd uptake by plants (Tudoreanu and Phillips, 2004, p. 145).…”

“…In contrast, plants with good growth usually show low metal accumulation as well as low tolerance to heavy metals. An ideal plant for phytoremediation is one with high biomass production, easily harvestable, and with superior capacity for heavy-metal tolerance and accumulation (Sappin-Didier et al, 2005). This underpins the need for alternative phytoremediation options such as transgenic approaches.…”

“…Combining the genomes of a hyperaccumulator and a related, high-biomass, non-accumulator species, might become a promising alternative. Hence Sappin-Didier et al (2005) investigated metal-uptake capacity of transgenic tobaccos (Nicotiniana tabacum) overexpressing ferritin in plastids (P6) or in cytoplasm (C5) and a control tobacco (A) ( Table 1). They grew the plants in three polluted soils (designated 8b2, 8b3, S11) from the same soil series, with a similar Cd content, but having pHs from 5.8 to 7.…”

“…Table 1 shows studies in which the Cd concentration has been given in both the soil and the plant. Soils have been polluted with Cd by application of sludge Granato et al, 2004;Adams et al, 2004) or wastewater (Xiong et al, 2004;Ingwersen and Streck, 2005); by being near a smelter (Brown et al, 2004;Sappin-Didier et al, 2005) or by having Cd salts added to the soil (Jiang et al, 2003;Kuo et al, 2004;Turgut et al, 2004;Evangelou et al, 2004;Dechamps et al, 2005;Li et al, 2005;Treder and Cieslinski, 2005;Patel et al, 2005;). The only study in Table 1 that reports Cd naturally in the soil is in the one by Tsadilas et al (2005), who grew tobacco with no added Cd.…”

Field crops for phytoremediation of metal-contaminated land. A review

“…The increase of iron acquisition mediated by phytosiderophores was found to provide an advantage under Cd stress in maize (Meda et al 2007). Overproduction of ferritin through genetic modification also led to increased Fe uptake as well as Cd, Mn and Zn, but only at alkaline pH (Sappin-Didier et al 2005). This was due to high pH Fe deficiency, which stimulates metal uptake and translocation in shoots through an increase in root ferric reductase and H ?…”