Scientists hope to find ways to use the ABI3 gene to remove chlorophyll, thus de-greening the seed after frost
LACOMBE, Alta. — Researchers at the University of Calgary have developed a canola trait they say can reduce green seeds in canola hit by an early frost and improve shatter resistance.
Marcus Samuel, associate professor at the University of Calgary, said canola hit by frost 22 to 30 days after flowering is the most susceptible time for green seed damage.
He said green seed dockage costs Canadian growers more than $150 million each year.
The research team Samuel heads at the University of Calgary is studying the ABI3 gene’s role in the canola seed degreening process. It was found to help in activation of other genes that remove chlorophyll from the seeds.
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“It could provide dual protection against green seed and pod shatter. The long-term goal is to integrate this technology into a germplasm, said Samuel during Murray Hartman’s ScienceOramma in Lacombe., Alta.
He said the research has used genetic modified plants in developing the technology, but re-searchers are working on ways to improve ABI3 expression with a non-GMO approach.
The research team first discovered that ABI3 is important in the degreening process through its research with Arabidopsis thaliana, a relative of canola commonly used in developing new canola traits.
“If we can understand how the degreening works in the model organism, it’s easy to take that methodology and shift it over,” Samuel said.
Researchers proved ABI3 plays a major role in reducing green colour by removing the gene from Arabidopsis and observing the degreening process in the plant’s seeds.
“With the ABI3 mutant at maturity, the green colour is fixed; the seeds looked green. While in the controls, the green colour completely disappears and it’s a normal-looking seed at maturity.”
Researchers found that the ABI3 gene controls two genes responsible for degreening.
Then the research team overexpressed the AVI3 gene in an Arabidopsis plant, exposed it to frost and examined its ability to degreen its seeds.
“In the untransformed controls you clearly see the green colour was fixed after two or three days of frost. But when you overexpress this gene, like when you put in more of this gene, you clearly see the green colour was completely gone. It was able to tolerate the frost and continue to decolourize and move the chlorophyll even after frost exposure,” Samuel said.
Researchers then put the gene into canola and produced multiple transgenic plants in which the ABI3 gene was shown to be active and overexpressed.
We “checked plants frozen at -3 C for six hours and they were more tolerant than the check,” Samuel said.
“So now (researchers) wanted to test the seeds to see if they were able to degreen after a frost exposure. It did this beautifully and gave a solution to the degreen problem. It was able to completely eliminate the green colour.”
Transgenic canola lines with an overexpressed ABI3 gene had the same yield, but their pod mass increased compared to the check.
“We also think ABI3 can induce factors that can make the pods stronger, the replum thicker, and pods are more tolerant to frost and desiccation. That’s why the seeds are able to degreen with no problem under frost conditions,” Samuel said.
The research team performed a shaker test to assess pod shatter, which was lower with the transgenic lines compared to the check.
There is a cell line that holds pods together. It is lignified and acts as a strong polymer. When pods dry out, a tension pulls on this layer and when it breaks, pod shatter occurs.
“What we see on our cases is that there is an extra lignified layer throughout the pods in the ABI3 overexpression lines and that tension from drying is never transferred to the lignified layer.”
He said the pods are shatter tolerant not resistant, and he foresees no problems with combining.
