New research may lead to more drought-tolerant Canadian canola

Faculty of Science researchers at the University of Calgary have identified how drought tolerance is controlled in a model plant system, which could lead to new ways to make Canada's valuable canola crop more drought-tolerant in a warming world.

The biological sciences research group — in an international collaboration that included the University of Toronto and the University of Tasmania in Australia — uncovered the molecular mechanisms that control drought tolerance in a standard plant system widely used by plant biologists.

Their study has been published in Nature Plants, one of the top-ranked Nature series of science journals.

'Crop yield could be improved by at least 20 per cent'

"This could lead to a generation of crop plants that are drought-tolerant, particularly in Canada," says Marcus Samuel, an author on the study and associate professor of integrative cell biology (plant biology) in the Department of Biological Sciences. "Our findings can be translated into a technology for canola, and possibly wheat, to make these crops more drought-tolerant. Under water-stressed conditions, crop yield could be improved by at least 20 per cent."

Canola, which produces oil for human consumption and meal for livestock feed, is Canada's most valuable crop, worth about $20 billion annually — including about $6 billion in Alberta.

Like crops around the world, canola is highly susceptible to extreme fluctuations in temperatures. In the past decade, due to global warming, crops are regularly exposed to severe drought conditions, leading to losses of up to 20 per cent in annual revenue in North America.
"Drought is a major problem, even in Alberta where most canola depends on rainfall rather than irrigation," Samuel notes.

Unlocking the key to drought tolerance

To find the molecular mechanisms that control drought tolerance, Samuel and his research group used a model plant species called Arabidopsis, a close relative of canola with 85-per-cent similar genes. They grew samples of Arabidopsis in a laboratory chamber under carefully controlled environmental conditions.

Using genetic and molecular analysis, they identified how drought tolerance is controlled by an interplay between two major plant hormones: abscisic acid (ABA) and a group of steroid plant hormones called Brassinosteroids (BR). They showed that reducing accumulation of the BR hormones in the plants can promote protection against drought stress. Plants with reduced BR levels were able to tolerate longer periods of reduced moisture.

"I was excited by this finding, which provides a brand new way to improve plant drought tolerance, by either genetically modifying plant BR levels or simply by spraying the plants with a commercially available BR inhibitor," says study primary co-author Siyu Liang, a PhD student in Samuel's group.

Unravelling the molecular pathway

At the molecular level, Samuel's research team showed that a lipid or fatty acid modification of a specific enzyme or protein molecule, called CYP85A2, is required in the plants for BR production. This cell-signalling process, called "protein farnesylation," occurs in the last step of the BR biosynthetic pathway and is necessary to produce the final BR hormone product, called brassinolide. "We figured out the mechanism behind this molecular pathway and how this operates, and how this can be translated into canola," Samuel says.

The team showed for the first time that the loss of either this specific enzyme, or the lipid modification of this enzyme, reduced brassinolide hormone accumulation and increased plant responsiveness to the hormone ABA and overall drought tolerance.

Samuel's group now plans to genetically modify canola in the laboratory to see if their findings also hold true in canola. The next step is to develop a non-genetically modified method to achieve the same result, which Samuel says would be less expensive to commercialize and more readily accepted by consumers concerned about genetically modified organisms.

Julian Northey, adjunct professor at the University of Ontario Institute of Technology and co-author with Siyu Liang on the new paper, patented earlier findings in the research (Samuel is on this patent) and formed a company called Frontier AgriScience Inc. in 2010 to commercialize the technology.

The group's research was funded by the Natural Sciences and Engineering Research Council of Canada, and Samuel's lab is also supported by the private, not-for-profit Alberta Crop Industry Development Fund Ltd.