Engineering Forest Trees with Heavy Metal Resistance Genes

Abstract

Pollution of soil and water with heavy metals such as mercury, cadmium and arsenic, is a worldwide problem. Phytoremediation, the use of plants to remove, sequester or detoxify pollutants, including heavy metals, offers an environmentally-friendly alternative to engineering-based methods for remediation. Forest trees have multiple features that make them particularly useful for removal of toxic heavy metals, especially if they can be engineered with genes allowing them to handle high levels of these elements. Although still in its infancy, research with transgenic trees carrying genes allowing them to detoxify or sequester some heavy metals has already made promising progress. Most of the work to date has been performed using poplar species and hybrids, although other woody species could be equally as useful. Trees have been engineered with genes for the handling of mercury, cadmium, copper and arsenic following two main approaches, phytoextraction and phytotransformation /phytovolatilizaton. In vitro studies have shown the transgenic trees to have enhanced abilities to tolerate and/or accumulate these metals, and preliminary results from field tests indicate that the trees are functioning. New combinations of genes involved in metal transport or conversion may further enhance the heavy metal remediation capabilities of the transgenic trees. Given the environmentally friendly application, forest trees engineered for phytoremediation may be some of the first transgenic forest trees approved for operational deployment.

Net cadmium flux and accumulation reveal tissue‐specific oxidative stress and detoxification in Populus × canescens

“…Some herbaceous Cd hyperaccumulators such as Thlaspi caerulescens and Arabidopsis halleri have been identified but the quantities of Cd that can be accumulated by these plants are small because of their low biomass (Clemens 2006, Milner and Kochian 2008). Instead, the use of fast growing tree species with deep rooting systems such as Populus has been proposed (Merkle 2006).…”

Risk assessment of heavy metals in soil previously irrigated with industrial wastewater in Shenyang, China

“…Consequently, as part of a National Basic Research Program of China (973 Project) entitled "Forming mechanism of environmental pollution and ecological remediation of contaminated environment in old industrial base in northeastern China" (2004-2009), the aim of the project is to study the consistency of temporal change of metal concentrations in soil and assess the feasibility of agricultural crop cultivation in the SLIII and LR areas. Following risk assessment incorporating aspects of remediation technology [18][19][20][21][22], the management and remediation options for the ZIA were suggested.…”

An EST database for Liriodendron tulipifera L. floral buds: the first EST resource for functional and comparative genomics in Liriodendron

“…As the tallest hardwood species in eastern US forests, L. tulipifera grows rapidly and attains heights of 80-120 ft with a trunk diameter of 2 to 5 ft. L. tulipifera is amenable to genetic transformation and mass production of somatic clones (Wilde et al 1992), making it a system of choice for biotechnology applications, including the engineering of trees for phytoremediation of soils contaminated by heavy metals (Merkle 2006). Because of its rapid growth and biomass accumulation, unusual resistance to insects and disease, and its niche as an aggressive pioneer tree species on disturbed lands, yellow poplar has great future potential to be domesticated as a source of fiber for biologically based products, for biofuels, and chemicals.…”