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Research Highlights
Using 'Gene Silencing' to Examine Soybean Disease Resistance

By Barb Baylor Anderson

Soybeans are consistently threatened by pests and pathogens that can cause serious yield losses. A collaborative team of Ohio Agricultural Research and Development Center (OARDC) scientists are helping combat diseases by searching for resistant varieties and pinpointing their genes. And they are using a unique virus-induced gene silencing (VIGS) approach to do it.

“To ensure soybean plants perform optimally in the field, we must understand the roles of each of the soybean’s genes and then try to combine the high-performance genes in one or a few varieties. Gene silencing is a tool we can use to use to figure gene functions,” says Feng Qu, Ohio State University plant pathologist and principal investigator for the research funded by the Ohio Soybean Council. “This research effort is expected to benefit Ohio and other soybean farmers by developing superior seed stocks with enhanced disease resistance traits.”

So, what exactly is VIGS? Qu uses a car analogy to describe it. “When you open the hood of a car, you see lots of nuts, screws and wires. If you wonder what a specific wire is for, you can disconnect or loosen it and then try to start the car to find out what goes wrong,” he says. “Disconnecting or loosening the connection silences the function of that particular wire.”

Similarly, soybeans have tens of thousands of genes acting as wires and screws to ensure the seed grows into a healthy plant that can overcome diseases and adverse environments.

“For most of these genes, we still do not know what their specific functions are,” he says. “Different varieties can have unique genes just like different car models have specific features.”

Qu says other tools exist that can silence genes. However, those tools require scientists to produce transgenic soybeans, a slow process in comparison to the VIGS approach. With VIGS, soybeans can fight viruses by mobilizing a defense mechanism to silence invading virus genes.

“VIGS can modify a virus to make it carry a portion of a soybean gene. The soybean defense mechanism then attempts to silence genes of the modified virus, along with the part of the soybean gene carried in the modified virus. This causes the corresponding soybean gene to be silenced,” Qu says. “This is fairly quick and can interrogate multiple genes at a time.”

However, it is not without challenges, Qu adds. VIGS often just loosens but does not completely disconnect a soybean gene which can make it difficult for scientists to interpret results.

“We are still trying to figure out how to scale up VIGS experiments so that more genes can be studied simultaneously. More VIGS vectors need to be developed, because currently available vectors are often specific to certain varieties,” says Qu. “Finally, VIGS procedures need to be further calibrated for use with soybean genes whose effects are quantitative.”

Scientists at Iowa State University have already successfully used VIGS to identify resistant genes that counteract soybean rust. VIGS has also been used to characterize a resistance gene to fight soybean cyst nematode. Field adoption of both genes is expected in the future.

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.