지구 온난화와 벼농사 (WP)
Could this gene hold the secret to growing rice in a warming world?
Rising global temperatures are threatening rice, a staple food that nourishes billions of people around the world. But researchers say they may have discovered a way to improve harvests and grain quality: by turning off a temperature-sensitive gene found within some common rice varieties.
A team of scientists in China recently announced that they had identified a gene that, when overheated, appears to have a negative impact on crops, lowering yield and producing chalky-looking, pasty-tasting grains. But when that gene is deactivated — through gene editing or through breeding that capitalizes on a naturally occurring off switch — rice plants produce more and better grains, according to a peer-reviewed paper published last month in the journal Cell.
The finding represents “a breakthrough for breeding highyield, superior rice varieties resilient to rising temperatures,” emailed Yibo Li, the paper’s lead author and a plant geneticist with Huazhong Agricultural University in China.
Outside experts said there was great potential in the idea of a single gene that can be easily regulated to control both yield and quality.
“We just have this ability to go in and, to use a crude analogy, flip a light switch,” said Jarrod Hardke, a rice extension agronomist for the University of Arkansas System’s division of agriculture, who was not involved in the new research. “No exchange of genetic material, it’s still the same plant. We just reached in and pushed a stop button on something.”
‘Not in our control’
Hotter conditions driven by climate change, and particularly warmer nighttime temperatures, have posed a major challenge to rice breeders and farmers. One study found that rice yields dropped 10 percent for every degree Celsius that average nighttime air temperature rose between 1979 and 2003.
“Farmers and breeders are doing an excellent job of releasing new varieties and coming up with methods to improve productivity,” said Vibha Srivastava, a professor of plant biotechnology at the University of Arkansas. “But the climate is not in our control.”
And while breeders have made good progress on increasing yield in heat-stressed plants, often that benefit has come at the cost of quality, said Steve Linscombe, director of the Rice Foundation with USA Rice, a trade organization.
Li and his team in China set out to study the mechanics of what happens when rice plants are exposed to hotter temperatures. They planted more than 530 varieties in four locations where nighttime temperatures have increased. Then they examined the appearance of the harvested grains, looking at how many were chalky (bad) vs. translucent (good). They identified two varieties that grew especially well, and, by tracking genetic markers, were able to pinpoint the gene that appeared to control the plants’ response to heat.
Through gene editing, they showed that modifying expression of the gene could produce more heat-tolerant crops. The modified rice maintained its yield in hotter conditions, while unmodified crops produced 58 percent less grain, according to the study.
They also observed a naturally occurring on-off switch — variations of the gene that weren’t activated by hotter conditions. Using traditional breeding techniques to select for that variant, they found that plants could be encouraged to produce less chalky grain and higher yields in hot conditions, with increases between 31 and 78 percent compared to plants that didn’t carry the gene variant. bearing 31% to 78% more grain than regular Huazhan, depending on the location. And only 10% of harvested rice was chalky, compared with 60% from the regular Huazhan.
“Since simultaneously improving quality and yield has always been the ultimate goal for breeders, and high temperature represents the most severe challenge from global climate change, our finding holds tremendous significance for addressing heat-induced yield reduction and quality deterioration in rice,” he said.
“Our research employs fieldbased natural high-temperature treatments rather than controlled greenhouse conditions with fixed temperature and humidity,” Li said. “This approach more accurately reflects real-world environments, making the identified resistance genes more authentic and readily applicable to breeding programs.”
The future of rice
Srivastava and other rice experts who were not involved in the research said the finding is significant, and praised the study’s methodology.
Li’s team also noted in its paper that under normal weather conditions, the heat-resistant version of the gene doesn’t appear to impact crops.
“When you try to put stress-resilience traits in plants, you often have to address the question of, ‘Okay, under stress it will do better, what will happen under normal conditions?’” Srivastava said. While the discovery of the gene is promising, Linscombe said, more study is needed.
Li said his team’s research could be applied to most types of indica rice and all japonica rice varieties — two main kinds of rice grown around the world. He added that the finding could also be helpful for the breeding of other staple crops, such as wheat.
“Ultimately, we aim to break the traditional trade-off between yield and quality by developing innovative breeding strategies for high-yield, superior-quality crops,” he said.