Modified rice prompts weedy neighbors’ growth spurt
“This is a relatively new way to get a trait into a crop: taking the plant’s own gene and ramping it up,” Snow said. “We don’t know yet if our findings are going to be generalizable, but if they are, it’s definitely going to be important.”
To overexpress the native gene in rice, the scientists attached a promoter to it, giving the plant an extra copy of its own gene and ensuring that the gene is activated at all times.
The researchers conducted tests in rice and four strains of a relative of the same species, weedy rice, a noxious plant that infests rice fields around the world. By crossing genetically altered herbicide-resistant rice with weedy rice to mimic what happens naturally in the field, the researchers created crop-weed hybrids that grew larger and produced more offspring than unaltered counterparts – even without any herbicide present.
In regulated field experiments, the hybrids containing the overexpressed gene produced 48 percent to 125 percent more seeds per plant than did hybrid plants with no modified genes. They also had higher concentrations of a key amino acid, greater photosynthetic rates and better fledgling seed growth than controls – all presumed signs of better fitness in evolutionary terms.
“Fitness is a hard thing to measure, but you can conclude that if a gene gives you a lot more seeds per plant compared to controls, it’s likely to increase the plants’ fitness because those genes would be represented at a higher percentage in future generations,” Snow said.
When Snow and Lu set out to study this new genetic engineering method, they didn’t know what to expect.
“Our colleagues developed this novel transgenic trait in rice and we didn’t know if it would have a fitness benefit, or a cost, or be neutral,” Snow said. “With most types of herbicide resistant genes, there’s no benefit to a wild plant unless the herbicide is sprayed. A lot of transgenes in crop plants are either selectively neutral in wild plants or, if they have a benefit, it depends on environmental factors like insects, diseases or herbicides being present.”
Snow has a history in this area of research. She has found that genes from crop plants can persist in related weeds over many generations. In 2002, she led a study that was the first to show that a gene artificially inserted into crop plants to fend off pests could migrate to weeds in a natural environment and make the weeds stronger. She also has served on national panels that monitor and make recommendations about the release of genetically engineered species into the environment.