Use of plant roots for phytoremediation and molecular farming

Abstract

Alternative agriculture, which expands the uses of plants well beyond food and fiber, is beginning to change plant biology. Two plant-based biotechnologies were recently developed that take advantage of the ability of plant roots to absorb or secrete various substances. They are (i) phytoextraction, the use of plants to remove pollutants from the environment and (ii) rhizosecretion, a subset of molecular farming, designed to produce and secrete valuable natural products and recombinant proteins from roots. Here we discuss recent advances in these technologies and assess their potential in soil remediation, drug discovery, and molecular farming.Biotechnology is transforming world agriculture, adding new traits to crop plants at a greatly accelerated rate. Plants are becoming more efficient producers of food, fiber, medicines, and construction materials. In addition to these conventional uses, biotechnology opens doors to unique uses of plants that are gaining greater acceptance from the public and attention from the scientific community. These so-called ''value-added'' uses include phytoremediation, the use of plants to remove pollutants from the environment or to render them harmless (1), and molecular farming (phytomanufacturing), the use of plants for the production of valuable organic molecules and recombinant proteins (2, 3). Because of the growing number of commercially successful applications and the lack of serious environmental concerns, both technologies are gaining acceptance from the scientific community, the general public, and regulators.With the exception of root crops, plant roots are less utilized and studied than shoots. However, this situation may be changing because of the emerging biotechnologies described below that exploit the ability of plants to transport valuable molecules into and out of their roots. These root-based technologies include metal phytoextraction, a subset of phytoremediation, which uses plants to remove toxic heavy metals from soil; and rhizosecretion, a subset of molecular farming, which relies on the ability of plant roots to exude valuable compounds. Both technologies exploit plants' innate biological mechanisms for human benefit.Phytoextraction. Giant underground networks formed by the roots of living plants function as solar-driven pumps that extract and concentrate essential elements and compounds from soil and water. Absorbed substances are used to support reproductive function and carbon fixation within shoots. Metal phytoextraction relies on metal-accumulating plants to transport and concentrate polluting metals, such as lead, uranium, and cadmium, from the soil into the harvestable aboveground shoots (1, 4, 5). Hydroponically grown plant roots can also directly absorb, precipitate, and concentrate toxic metals from polluted effluents in a process termed rhizofiltration (6).Chelate-assisted phytoextraction (1) has been successfully used to remove lead from contaminated soils using specially selected varieties of Indian mustard (Brassica juncea L.). These v...

Differential mercury volatilization by tobacco organs expressing a modified bacterial merA gene

“…A strong root system could be used as a bioreactor for phytoremediation as it used for molecular farming [17]. A mobile ionic mercuric pollution could be reduced by draining through a strong root system of hyroponically grown tobacco or other merA transgenic plants.…”

A critical review on the bio-removal of hazardous heavy metals from contaminated soils: Issues, progress, eco-environmental concerns and opportunities

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Behavior of Cd and Zn in rhizosphere ofBrassicaplants grown in an andosol contaminated with Cd and Zn

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