Plant molecular strategies in response to soil contaminants

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Past and current industrial activities, such as mining and petrochemical refinement, have had major deleterious effects on the environment, leaving large areas of degraded and contaminated lands throughout Canada. The majority of contaminated sites is affected by both organic and inorganic compounds. The predominant organic contaminants include petroleum by-products, volatile organic compounds, aromatic hydrocarbons and pesticides. Common inorganic contaminants are metals and metalloids, referred to as trace elements. Phytoremediation is the environmental technique that aims to take advantage of these natural mechanisms in plants and of their associated properties of accumulation or degradation of soil contaminants. For plants growing in such polluted soils the potentially toxic contaminants induce physiological and molecular changes that are characteristic of abiotic stress. Although their co-occurrence is well known, their respective role and sequence (antecedent, mechanism and output) remain poorly described. The long-term goal of my research program is to understand how plants grow on contaminated soils. The general hypothesis of this program is that plants induce metabolic pathways that alter physiological processes allowing them to tolerate, extract or degrade contaminants in response to the abiotic stress induced by soil pollutants, and that these pathways can be specific or shared between species. Taking advantage of recent advances in next generation sequencing, I will use a strategy based on both field experiments and controlled environments to explore the transcriptomes and physiology of plants growing in contaminated soils. The specific objectives of this project are to: 1) Describe the transcriptomic effects of establishing fast-growing pioneer plant species in contaminated soil environments and, 2) evaluate if the changes in root gene expression are reflected in altered physiological mechanisms such as osmotic regulation, secondary metabolites and rhizosphere biology. This combined approach should allow the separation the environmental variables inherent to field conditions by taking advantage of the results obtained in controlled greenhouse experiments. Each of the objectives of the program will be assigned to a trainee under my supervision. This research program will contribute to our understanding of the plant responses to abiotic stresses and to soil contamination in particular. The potential applications of this research program are to develop molecular biomarkers that can be used as indicators of soil contamination as well as provide a basis for plant selection, knowledge which can advance the development of phytoremediation in order to make it a suitable attractive option for ecosystem rehabilitation.