The physiology of metal-tolerance and metal-stress in plants

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Plants face a number of environmental stresses. In my lab, we study the stress imposed by cadmium, among other metals. Cadmium occurs naturally in soils but, in some regions of the world, its concentrations are enriched due to industrial activity, fuel combustion or long-term application of agricultural fertilizers that contain trace amounts of this metal. Cadmium is soluble in water, readily bioavailable and toxic in small doses. In some Canadian crops, including soybean and durum wheat, concentrations of cadmium in the edible parts approach or exceed the limits for safe consumption. Thus, there is a pressing need for a better understanding of the factors that control cadmium uptake and accumulation in plants. Our approach to investigating plant-metal interactions will be three-pronged. Some experiments will investigate the biological and chemical factors that make cadmium in the soil more, or less, available for plant uptake. Others will examine the distribution and chemical environment of cadmium in plant tissues - knowing where, and to what, the cadmium is bound provides information about how cadmium is detoxified and stored within the plant. Lastly, we will study the physiology and molecular biology of the plant response to metal-stress. Specifically, we will study the response of certain enzymes that are known to be involved in either (i) the production of molecules that can bind, detoxify and store cadmium or (ii) the plant stress response. By comparing the cadmium tolerance of plants that lack, or over-express, these enzymes we can better understand their role in cadmium tolerance and toxicity. In addition to improving our knowledge of plant stress physiology, this research will have implications for phytoremediation (choosing plants that maximize uptake of metal from the soil) as well as agriculture (e.g., agricultural practice or crop choice for mildly contaminated soils).