October 15, 2019
Tuning up photosynthesis to feed the world
At some point in school, you probably learned about photosynthesis—how plants use energy from sunlight to convert carbon dioxide and water into food. This remarkable process is responsible for virtually all life on Earth, providing us with the energy we need and the oxygen we breathe.
But you might not have heard that photosynthesis has some flaws.
It turns out that plants are quite inefficient when it comes to using the sun’s energy. Just a fraction of the sunlight shining on a plant ends up fueling its growth, which means our crops are producing far less food than they could be.
An international group of researchers is aiming to fix that by giving photosynthesis a tune-up. If successful, their research is expected to double the productivity of some of our most important crops—like rice, maize, cowpea, soybeans, and cassava.
That would be a much-needed breakthrough because the world is facing a crisis at the dinner table. With a growing population and changes in diets—like a greater demand for more meat as people earn higher incomes—we’ll need to produce 60 to 70 percent more food by 2050. At the same time, climate change is putting additional stresses on our food supply because of erratic rainfall, severe droughts, and the spread of pests and crop diseases.
Those who are at greatest risk of hunger in the years ahead are the world’s poorest people. They live in regions with high population growth and often rely on farming both to feed their families and to earn an income.
No single solution will solve this global food crisis. We’ll need to develop innovations in all areas of agriculture to increase productivity. Improved seed varieties for crops that are resistant to drought, flood, pests, and disease. Better data to help farmers manage their crops and livestock more efficiently. And some game-changing discoveries that will lead to bigger harvests.
That’s why our foundation along with the U.S. Foundation for Food and Agriculture Research and the U.K. Government's Department for International Development is investing in the global effort to make photosynthesis more efficient. This research program, known as Realizing Increased Photosynthetic Efficiency or RIPE, is being led by the University of Illinois.
RIPE scientists began their research by modeling the entire 170-step chemical process of turning sunlight into energy. Using computer simulations, they explored which changes might lead to the biggest increases in productivity—in the same way an efficiency expert might make improvements to a car production line to maximize output.
One promising area of research involves making plants absorb sunlight more effectively. While light is essential for a plant’s survival, too much high-intensity light can cause damage to the plant. To protect themselves, plants have developed mechanisms to siphon off some of the sun’s energy as heat when they are in direct sunlight. But this creates a problem when the sun goes behind a cloud and the plant is in the shade. The plant’s protective mechanism doesn’t adjust quickly to the reduced light, inhibiting the process of photosynthesis for minutes or sometimes hours. RIPE researchers discovered a way to speed up this transition, allowing the plant to continue with photosynthesis even with light fluctuations.
Another critical area of research involves an enzyme known as Rubisco, which captures carbon dioxide and turns it into sugars for the plant. Some researchers are working to speed up Rubisco activity in the plant, which would result in higher crop productivity.
Other researchers are trying to fix an inefficiency created by Rubisco: It has a hard time distinguishing carbon dioxide from oxygen. So, about 20 percent of the time Rubisco accidently grabs an oxygen molecule instead of a carbon dioxide molecule. This results in the creation of a compound that must be recycled by the plant through a process known as photorespiration. Photorespiration is long and complicated, costing a plant energy and resources that it could use for growth. To solve this, researchers have engineered an alternative pathway to drastically shorten the photorespiration process and save energy. When tested in the lab, this fix boosted plant growth by up to 40 percent.
Much of the field testing of these improvements to photosynthesis has been done using tobacco plants. While tobacco plants are not food crops, they are a convenient proof-of-concept crop because they are easy to transform genetically and they produce a large amount of seed, shortening testing cycles. In the next phase of research, scientists are working to transfer these new genetic traits to food crops, including cowpea, cassava, and soybeans.
Still, these high yielding crops are years away from being grown on farms around the world. And they would need to pass safety tests to gain consumer acceptance. I’m excited about the progress made by the RIPE team and I look forward to hearing more about their discoveries in the future.