The use of transgenic plants in the bioremediation of soils contaminated with trace elements

Abstract

The use of plants to clean-up soils contaminated with trace elements could provide a cheap and sustainable technology for bioremediation. Field trials suggested that the rate of contaminant removal using conventional plants and growth conditions is insufficient. The introduction of novel traits into high biomass plants in a transgenic approach is a promising strategy for the development of effective phytoremediation technologies. This has been exemplified by generating plants able to convert organic and ionic forms of mercury into the less toxic, volatile, elemental mercury, a trait that occurs naturally only in some bacteria and not at all in plants. The engineering of a phytoremediator plant requires the optimization of a number of processes, including trace element mobilization in the soil, uptake into the root, detoxification and allocation within the plant. A number of transgenic plants have been generated in an attempt to modify the tolerance, uptake or homeostasis of trace elements. The phenotypes of these plants provide important insights for the improvement of engineering strategies. A better understanding, both of micronutrient acquisition and homeostasis, and of the genetic, biochemical and physiological basis of metal hyperaccumulation in plants, will be of key importance for the success of phytoremediation.

Root-Specific Reduction of Cytokinin Causes Enhanced Root Growth, Drought Tolerance, and Leaf Mineral Enrichment in Arabidopsis and Tobacco

“…Evidently, it remains to be shown that the enhancement seen in the plants described here can also be obtained in the relevant organs of food crops. The fact that the uptake of Cd from contaminated soil is increased in the P10:CKX and W6:CKX transgenic plants indicates that an enhanced root system may also be applicable in phytoremediation (i.e., the cleanup of contaminated soils using plants) (Krä mer and Chardonnens, 2001;Krä mer, 2005), providing independent support for previous merely correlative evidence (Krä mer et al, 1997;Roosens et al, 2003).…”

Heavy metals and woody plants - biotechnologies for phytoremediation

“…It has been demonstrated in classic genetic studies that only a few genes are responsible for metal tolerance (Macnair et al 2000). Transfer and/or overexpression of genes re sponsible for metal uptake, translocation and sequestration may allow for the production of plants which, depending on the strategy, can be successfully exploited in phytore mediation (Krämer & Chardonnens 2001, Pi lon-Smits & Pilon 2002, Clemens et al 2002, Rugh 2004, Eapen & D'Souza 2005, Cherian & Oliveira 2005, Doty 2008. In this case, special attention must be paid to pro blems related to the introduction of geneti cally modified trees, particularly concerning their legal and social acceptance (Knowles & Adair 2007).…”

Heavy Metals in Crop Plants: Transport and Redistribution Processes on the Whole Plant Level

“…Genetic engineering of the metabolism may lead to increased concentrations of ligands important for xylem loading and to decreased levels of ligands leading to vacuolar sequestration causing a retention of heavy metals in the roots [59,62,65,105,106]. Transporters for heavy metals or heavy metal complexes represent other targets for classical breeding and genetic engineering to improve properties of plants envisaged for phytoremediation [107,108].…”