Ecophysiology and genetic analysis of plant adaptation to soil metal contamination

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Excessive soil concentrations of metals represent serious threats to plant ecosystem sustainability. This research program aims to acquire new fundamental knowledge on how key plant species with high potential in bioremediation cope with metal contamination. Our lab has demonstrated for the first time that Deschampsia cespitosa (tufted hair grass) is a metal excluder; Populus tremuloides (trembling aspen), Betula papyrifera (white birch), and Quercus rubra (red oak) are accumulators, and Acer rubrum (red maple) uses avoidance to cope with metals. We have established the genetics of nickel resistance in B. papyrifera, A.rubrum, and A. saccharum (silver maple). Importantly; we have completed and characterized the first transcriptome of B. papyrifera. We have identified five candidate genes for nickel resistance from this transcriptome. We believe that the most robust alternative to facilitate a better understanding of plant coping mechanisms to metal contamination is to use a combination of approaches. Comparative analysis of five targeted plant species using genetic analysis, transcriptome sequencing and RT-qPCR will allow the identification of functional gene sets that are differentially regulated during the response to excess nickel and copper. Electron microscopy, fluorescence in situ, and protein characterization techniques will be used to establish cellular and extracellular distribution maps as well as main effects of Ni and Cu along with the transport proteins involved. We will deepen our understanding of DNA methylation by using LC- MS/MS, methylation-sensitive amplified polymorphism (MSAP), and reduced representation sequencing (RRS). The information from our research program will contribute to building a picture of how heavy metal homeostasis is achieved, and the role of different genes, recognizing that there may be major differences in the operation of transporters in different species e.g. metal accumulators and excluders. The challenge is to define and manipulate the mechanisms by which plants take up, extrude and compartmentalize metals, and also redistribute them in the different tissues. If we achieve these goals as scientists, we will not only have answered a number of fundamental questions but also can address significant biotechnological applications, which can be exploited, both in terms of human nutrition and phytoremediation. Thus strategies to engineer or select plants for such applications will undoubtedly be very important.