ARCHIVED - A genetic boost for canola
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December 07, 2007— Ottawa, Ontario
NRC plant scientists have found a gene that boosts the productivity and resilience of canola. The discovery may ultimately help canola growers increase oil production to meet the growing demand for biodiesel fuel – and thereby lower Canada's greenhouse gas emissions.
The gene, which produces a hydroxysteroid dehydrogenase (HSD) protein, occurs naturally in Brassica napus (canola) and likely other plants as well. "It shows up in the DNA sequence of Arabidopsis thaliana – a close relative of canola," says Dr. Adrian Cutler, who leads the signaling and plant metabolism research group at the NRC Plant Biotechnology Institute in Saskatoon.
|The canola plant with an over-expressed HSD gene (right) has more flower buds than the unmodified plant (left). More flowers produce more seeds and therefore higher oil yields.|
Dr. Fengling Li, a former postdoctoral fellow in Dr. Cutler's lab, identified this HSD gene as part of a research project conducted for the NRC Genomics and Health Initiative and a Genome Canada/Genome Prairie research program. "Its DNA sequence suggested that it could be involved in steroid metabolism. Since steroids can have profound effects on plant growth, we selected the gene for more detailed studies," explains Dr. Cutler.
Dr. Cutler and Dr. Li chose to "over-express" the gene – a common experimental strategy for enhancing a gene's effects. They created "transgenic" Arabidopsis and Brassica plants by introducing a modified HSD gene so it would produce higher levels of the HSD protein than in normal plants.
"When we did that, we saw taller plants with thicker stems," he says. "There were more branches, more flowering stems, more flowers on each plant and more seeds produced. So the average yield of oil from each transgenic canola plant was increased substantially – by about 23 percent compared to our control plants."
"In addition, we established that there is no change in the canola oil composition," says Dr. Cutler. "The quality of the oil produced by our transgenic plants is just as good, but the plants are more productive."
In December 2006, the Government of Canada announced it would regulate a two percent minimum requirement for renewable diesel (biodiesel) in diesel fuel and heating oil by 2012.
According to a University of British Columbia study, one litre of diesel generates the equivalent of 4 kg of carbon dioxide, while one litre of biodiesel generates just 0.5-1 kg of carbon dioxide. Therefore, by replacing two percent of 600 million litres of diesel consumed annually, Canada will reduce its total greenhouse gas emissions by 1.8 million tonnes – the equivalent of taking 300,000 cars off the road.
In other experiments, the HSD gene made canola plants more tolerant to naturally occurring environmental stresses. "For example, they were much more resistant to high levels of salt in the soil, which could be quite a valuable trait on the prairies where large areas are too saline for crops to grow well," says Dr. Cutler. The experimental plants were also heat-stress tolerant – better able to withstand short blasts of temperature above 40 degrees Celsius.
According to Dr. Cutler, the HSD gene somehow acts via brassinosteroids – powerful, naturally occurring plant hormones that control many aspects of plant growth and development. "Its effects are very similar to the short-term effects of spraying brassinosteroids directly on plants, but spraying would be an enormously expensive way to improve plant growth," he notes.
He adds that more research is required to understand how the HSD gene works. "We don't know exactly how it produces these striking effects, so we need to do more research on the gene to discover its precise function. We're also interested in studying other genes in Arabidopsis that have similar DNA sequences, because they may have beneficial functions too."
Next summer, the goal is to test transgenic plants under real growth conditions in field studies. "It's a bit premature to discuss commercialization now," says Dr. Cutler. "But if, after a couple of years of field trials, we see similar effects to what we saw in the greenhouse, we can look at licensing this technology to a seed or a biotech company."
Dr. Cutler and his colleagues view the HSD gene primarily as a tool for increasing the production of canola oil. "It could be used to produce more cooking oil – its major use right now – as well as oil for biodiesel or other kinds of industrial oils. It's basically a general method for increasing the productivity of the crop – and that benefits producers, crushers and industry," he says.
It would also be good for Canadian consumers, adds Dr. Cutler. "Because of the rising demand for biodiesel, there's a concern that growing crops for energy will take acreage away from food crops – causing food prices to rise. Any new technology that can increase the productivity of agricultural land could help keep prices down," he says.
According to the Canola Council of Canada, canola is now grown on approximately 13 million acres of Canadian farm land. A recent study by BBI Biofuels Canada estimated that if Canada substitutes five percent of the diesel now used with domestically produced biodiesel, this would increase Canadian farm income by more than $1.1 billion per year.
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