Kris Niyogi, a graduate of Oak Ridge High School, led more than 10 years of research in Berkeley, Calif., Which resulted in explanations of how green plants protect themselves from excessive sunlight. The job gave him an election in 2016 at the National Academy of Sciences.
This prestigious honor was previously bestowed in 1998 on his mother, Audrey Stevens, a biochemist at Oak Ridge National Laboratory. She discovered the enzyme that copies DNA into the RNA molecules it makes, including the sent RNA.
Applying the new understanding of plant photo protection mechanisms, Niyogi and his collaborators are identifying ways to help improve crop productivity.
“Much of the research in my lab is motivated by the need to increase and support food production this century to meet growing demand,” Niyogi said during his recent Community Lecture by Dick Smyser, sponsored by ORNL Friends. and held through Zoom. This was FORNL’s first Smyser lecture for 2021, which honors Smyser, the first editor of The Oak Ridger and an active member of FORNL.
“The United Nations Food and Agriculture Organization estimates that food production should double by 2050 to meet the growing demand for food due to population growth and urbanization,” Niyogi noted. “The sustainability of our food supply in certain parts of the world is under threat due to rising temperatures, drought stress, flooding from extreme weather events and rising sea levels linked to climate change.”
Two-thirds of the calories consumed worldwide come from four main products – corn, rice, wheat and soybeans. Using funding from the Bill and Melinda Gates Foundation and other U.S. agencies, he said his lab at the University of California at Berkeley and associates have received “promising results.” These results show that they can increase crop growth in Southeast Asia, soybeans in the US and cassava and cows, staple foods in sub-Saharan Africa.
Niyogi is a researcher at the Howard Hughes Medical Institute, a professor in the Department of Plant and Microbial Biology at UC Berkeley, and a faculty scientist in the Division of Molecular Biophysics and Integrated Biography at the Lawrence Berkeley National Laboratory of the U.S. Department of Energy. He conducted research for two summers in the ORNL Biology Division (where his parents both worked), and he holds a Ph.D. in plant genetics and molecular biology from MIT.
Speaking on the topic “Understanding photosynthesis to improve crop productivity”, Niyogi explained that photosynthesis is the process by which a plant absorbs sunlight and converts light energy into chemical energy. As a result, the plant can break down carbon dioxide and water molecules it absorbs and rearrange them to make sugar molecules, generating plant biomass and oxygen.
In the multiplication efforts of the 20th century known as the Green Revolution, yields of wheat, rice and other crops have increased. But, Niyogi said, it is thought that crop yields could be further increased by improving the efficiency of plants in converting absorbed sunlight into biomass.
Theoretically, plants should be able to return 4.6% of the sunlight they receive to sugars through photosynthesis. But, he explained, the conversion efficiency is reduced by drought stress, insufficient fertilizers, temperature extremes and pathogens. Another stressor is “light saturation”, the absorption by plants of more sunlight than they can use during the day.
“When plants absorb sunlight that is greater than their capacity to use it for photosynthesis, non-photochemical quenching, or NPQ, begins,” Niyogi said, noting that he and his research team did not discover the process. but helped determine how it works.
“Like a safety valve for photosynthesis. As the intensity of light saturates photosynthesis, the NPQ lights up and forms like a dimmer switch and dissipates light energy as thermal energy, or heat. This protects the plant from the damaging effects of too much sunlight. ”
During the day, plants are exposed to fluctuations in sunlight levels as a result of passing clouds and the shadow of the lower leaf canopy. Under bright sunlight, NPQ photoprotection turns on, but as the light level decreases, NPQ does not turn off quickly. Thus, it dissipates energy that can be used to regulate carbon and grow the plant faster.
So, Niyogi and his colleagues looked for ways to genetically modify a model plant so that it would turn off photoprotection faster when light levels drop.
“Our goal was to accelerate recovery from NPQ to improve photosynthesis and increase crop yields,” he said.
The Niyogi Lab collaborated with a team led by Professor Stephen Long at the University of Illinois to conduct greenhouse experiments and field studies of genetically modified tobacco growing. They used tobacco as a crop model plant because it is easily transformed by inserting genes to change the amount or type of protein desired, and it grows as a three-dimensional tent similar to food crops.
In early experiments led by Niyogi, researchers made a variety of mutant plant “Arabidopsis thaliana” to identify which genes are needed to make NPQ (measured by video images of fluctuations in chlorophyll fluorescence) or other aspects of photosynthesis. This species is called the “fruit fly of the plant world” because it has a fast life cycle and its tiny genome is completely sequenced and can be easily mutated.
“It’s like understanding how a machine works by removing a part at the same time,” he said. If you want to determine what stops the car, he added, you will not discover it by removing the windshield wipers, but you will remove the brakes.
By manipulating three genes in tobacco to increase their production into three proteins, the researchers showed that they could accelerate plant regeneration from the inhibitory effects of NPQ on plant growth. Modified, or transgenic, plants grew larger than wild-type control plants in the greenhouse.
“We found that the NPQ goes out a little faster and more completely within minutes after the light intensity dropped, leaving the sun’s leaves in the shade,” Niyogi said. “During those few minutes, our carbon dioxide measurements showed that these plants fixed a little more carbon than the wild-type plants.”
The results became more exciting when the model plant was grown as a crop in an Illinois area.
“We found an increase in biomass over total tobacco production ranging from 14% to 20% higher than field control plants,” Niyogi said. “It was an amazing and wonderful result. In this way it exceeded my expectations of what we could achieve in this experiment. I was surprised and delighted with the results from Illinois. ”
Niyogi Berkeley Laboratory has partnered with other research institutions in Australia, China, the United Kingdom and the United States on RIPE (Realization of Photosynthetic Efficiency Increase), partly funded by the Gates Foundation. A strategy at the University of Illinois has increased crop biomass by up to 40%.
Niyogi Laboratory, he said, has also looked for ways to slow climate change by using plants not only to maintain rising levels of carbon dioxide above ground, but also to seize greenhouse gas more efficiently as ground carbon root.
In response to a question, he said “an interesting idea” is to place semi-transparent, electricity-generating solar arrays on a crop field. Such arrays can be designed to allow the right amount of light with specific wavelengths to illuminate genetically modified plants, or genetically modified plants, by increasing their photosynthesis and yield.
Memories of Oak Ridge
At the beginning of his talk, Niyogi told the audience and his Oak Ridge classmates, “I loved my time growing up in Oak Ridge (1966 to 1983). I remember playing with all the kids in the neighborhood. I played football in the youth league that my dad helped me get started.
“I met lifelong friends at school. Teachers at Oak Ridge Schools inspired me to pursue a career in science. I really loved biology, I am an excellent hybrid of my parents and I inherited a love for science from them. ”