Modified rice prompts weedy neighbors’ growth spurt
Rice containing an overactive gene that makes it resistant to a common herbicide can pass that genetic trait to weedy rice, prompting powerful growth even without a weed-killer to trigger the modification benefit, new research shows.
Previously, scientists have found that when a genetically modified trait passes from a crop plant to a closely related weed, the weed gains the crop’s engineered benefit – resistance to pests, for example – only in the presence of the offending insects.
This new study is a surprising example of gene flow from crops to weeds that makes weeds more vigorous even without an environmental trigger, researchers say.
The suspected reason: This modification method enhances a plant’s own growth control mechanism, essentially making it grow faster – an attractive trait in crops but a recipe for potential problems with weedy relatives that could out-compete the crop.
“Our next question is whether this method of enhancing plant growth could be developed for any crop. We want to know whether growers could get higher yields in the crop and then, if it happened to cross with a related weed, whether it might make the weed more prolific as well,” said Allison Snow, professor of evolution, ecology and organismal biology at The Ohio State University and a lead author of the paper.
“It’s unusual for any transgene to have such a positive effect on a wild relative and even more so for herbicide resistance,” she said. “But we think we know why: It’s probably because the pathway regulated by this gene is so important to the plant.”
The work is the result of Snow’s longtime collaboration with senior author Bao-Rong Lu, a professor at Fudan University in Shanghai. Their publication appears online in the journal New Phytologist.
The weed-killer glyphosate, sold under the brand name Roundup, kills plants by inhibiting a growth-related pathway activated by the epsps gene. Biotech companies have inserted mutated forms of a similar gene from microbes into crop plants, producing “Roundup Ready” corn and soybeans that remain undamaged by widespread herbicide application.
But in this study, the researchers used a different method, boosting activation of the native epsps gene in rice plants – a process called overexpressing – to give the plants enough strength to survive an application of herbicide. Because companies that genetically modify commercial crops don’t fully disclose their methods, Snow and her colleagues aren’t sure how prevalent this method might be, now or in the future.