Plant tolerance to abiotic stress: Physiological and metabolic mechanisms

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We study a highly stress tolerant native plant, Eutrema salsugineum. In Canada, Eutrema is found on alkaline, saline soils in the Yukon and across the Prairies to western Ontario. As its distribution and soil preference implies, it has an extraordinary innate capacity to grow in cold areas where water is limiting and nutrients are low. Eutrema is an excellent model to study stress tolerance traits because of its close phylogenetic relationship to canola, Canada’s valuable oilseed crop. In the past four years many genetic and genomic resources have emerged to facilitate research on this plant and the Eutrema genomics group that I lead has made strong contributions to these advances. With fully sequenced genomes and transcriptomes available, we are in an excellent position to investigate the mechanisms underlying the exceptional capacity of this plant to withstand adverse conditions with a view to enhancing these traits in stress sensitive crops, including canola.     Drought and salt tolerant plants synthesize and accumulate non-perturbing organic solutes that enable them to establish a concentration gradient to drive water movement into the roots. Using physiology and metabolomics approaches, we reported that Eutrema shows plasticity with respect to the solutes they produce under stress. In the highly saline fields of the Yukon where nitrogen is low, Eutrema accumulates carbohydrates for osmotic adjustment and in our cabinets where salt-stressed plants are fertilized regularly, they accumulate the amino acid proline. Remarkably, salt-stressed cabinet plants provided low, but sufficient levels of nitrogen were visually indistinguishable from stressed plants given ample nitrogen. Normally a deficiency in nitrogen produces a severely stunted plant. Through our more recent transcriptome work we discovered that the Eutrema ecotype from the Yukon is actually sulfur deficient when grown in our cabinets although they are fertilized regularly and they do not look like they lack sulfur. Sulfur is a nutrient that also figures prominently in how plants respond to stress, particularly in suppressing the damage produced by reactive oxygen species. In the case of phosphorous, Eutrema can be extremely frugal and plants grow as well in a medium with a low content of phosphate as they do with a non-limiting supply of this nutrient, even in the presence of salt. It is clear that we have much to learn from how Eutrema manages low nutrient availability, particularly under stress. Our research objectives are focused on exploring mechanisms underlying the exceptional capacity for this plant to manage abiotic stresses, particularly under limiting nutrient conditions. High nutrient use efficiencies in crops that are more resilient against fluctuating weather patterns is an ideal combination of traits for sustainable crop production, particularly as the full impact of global climate change unfolds.