August 18, 2022
Scientists Boost Crop Performance by Engineering a Better Leaf
Improved crop yields could particularly benefit poorer parts of the world. A soybean harvest near Campos Lindos, Brazil. Credit: Ueslei Marcelino/Reuters
For decades, scientists have pursued a tantalizing possibility for bolstering food supplies and easing hunger for the world’s poorest: improving photosynthesis, the biological process in plants that sustains nearly all life on Earth.
Now, researchers say that by using genetic modifications to increase the efficiency of photosynthesis, they significantly increased yields in a food crop, soybeans, providing a glimmer of potential that such methods could someday put more food on tables as climate change and other threats make it harder for vulnerable populations across the globe to feed their families.
The scientists tested their gene alterations on soy plants grown in a single location during just two crop seasons. In interviews, they acknowledged that more trials were needed to see whether their results would hold up across different environments and weather conditions. Their methods will also have to pass muster with government regulators before crops transformed this way will ever reach farmers’ fields.
And soy — much of which is grown to feed livestock, not humans — is just a start. Longer term, the researchers are hoping to raise yields in staple foods like rice, cowpea and cassava.
But with the world projected to require big increases in food production in order to meet demand in the coming decades, the findings suggest that such genetic tinkering holds promise for meeting those needs, said Amanda P. De Souza, a crop scientist at the University of Illinois Urbana-Champaign and lead author of a new study describing the results, which was published Thursday in the journal Science.
“There is a long road to get there,” Dr. De Souza said. But “now is the hour,” she said, to work toward as many new solutions as possible.
Humankind’s ability to feed itself is under pressure as societies use land and water resources in unsustainable ways. Human-caused climate change is threatening to exacerbate the problem, with increased droughts and storms causing more disruptions to food supplies. Food production is itself a major contributor to global warming, including through the clearing of forested land for crops and grazing animals.
Without major changes to agriculture, governments’ targets for mitigating climate change are at risk, scientists warn. Yet addressing malnutrition and hunger in the short term might require pressing more land and other resources into service, which could accentuate warming.
That is why scientific advancements that could help us produce more nourishment without using more land, whether by improving photosynthesis or otherwise, hold such promise.
“Human civilization is at a point where we just have to get a lot more from less,” said Daniel Nepstad, executive director of Earth Innovation Institute, a research group.
Even so, there are other solutions that might provide relief more quickly than engineering better crops, said Jonathan Foley, a climate scientist who runs Project Drawdown, a nonprofit that promotes efforts to reduce greenhouse gas emissions. He cited shifting diets away from meat, for instance. Or reducing food waste.
“I always wonder,” Dr. Foley said. “Why are we missing the elephants in the room while chasing the mice?”
In the second half of the 20th century, many scientists saw tweaks to photosynthesis, the process through which plants use sunlight, water and carbon dioxide to produce oxygen and energy-rich carbohydrates, as a next frontier for improving crop performance. But they struggled to make progress. Some scientists came to believe there were biological factors preventing plants from translating more efficient photosynthesis into additional growth.
The new research in Illinois focuses on “non-photochemical quenching,” a mechanism in plants that protects them from sun damage. When plants are in bright sunlight, they often receive more light energy than they can use for photosynthesis. This mechanism helps them shed the excess energy harmlessly as heat. But after the plant is shaded again, it doesn’t stop very quickly, which means the plant wastes precious time and energy that could be put toward producing carbohydrates.
The researchers’ genetic transformations help plants adjust more quickly to shade. In multilayered plants like rice, wheat, maize and soy, this extra nimbleness could theoretically increase photosynthesis in the middle layers of leaves, which are constantly flitting between sunlight and shadow during the day.
The work was funded by the Bill & Melinda Gates Foundation; the Foundation for Food and Agriculture Research, a nonprofit in Washington, D.C., that receives money from government, industry and academic sources; and Britain’s Foreign, Commonwealth and Development Office.
In 2016, another of the study’s authors, Stephen P. Long, who is also at the University of Illinois Urbana-Champaign, showed that these alterations increased growth in tobacco plants by up to 20 percent. But such findings have encountered skepticism. Some scientists have suggested that the modifications might have boosted crop performance not by enhancing photosynthesis, but by affecting hormone levels. Other researchers have argued that if a process as fundamental as photosynthesis could be improved upon, then surely natural selection would have done so by now.
Dr. Long said he considered this a misunderstanding of evolution. Plants have evolved to reproduce, he said, not to be maximally efficient at producing bulkier seeds or other parts of interest to hungry humans.
“Evolution is about genes getting themselves into the next generation,” he said. “And productivity is only a small part of that.”
He and his colleagues’ next step was to try their genetic transformations in a food crop. When they grew gene-altered soy on a University of Illinois farm in Urbana in 2020, the yield per hectare in five of their eight different varieties of transformed plants was 24.5 percent higher, on average, than that of normal soy plants they grew for comparison. (The other three varieties also had higher yields, though the differences were not statistically significant.) The seeds from the engineered plants were also similarly rich in protein compared with those from the unaltered plants.
The results from a second crop, in 2021, were less conclusive. A storm caused the plants’ leaves to collapse on top of one another, causing the lower leaves to be, in effect, permanently shaded.
Thomas R. Sinclair, a crop scientist at North Carolina State University who was not part of the new study, said he would need to see trial data from more years, and more locations, before he could be convinced these methods were effective. Dr. Sinclair has written skeptically of this line of research, arguing that the only proven way of raising crop yields is helping plants take in more nutrients such as nitrogen, the key ingredient in many fertilizers.
Dr. Long said his team ultimately hoped to conduct five years of trials. He is also planning to try the same modifications in tropical soybeans and test them in Puerto Rico, he said. One of his team’s aims is to ensure that higher-yielding seeds are available to farmers in the developing world.
By: Raymond Zhong and Clare Toeniskoetter || The New York Times