Tracing a Path from Photosynthesis to Food Security
URBANA, Ill. — The energy plants harvest from sunlight through photosynthesis fuels nearly all of humanity’s food. Yet the process has inefficiencies that limit crop productivity, especially in a world that keeps changing rapidly. A new review by University of Illinois scientists and collaborators reflects on how boosting photosynthesis could bring us closer to reliable food security.
The review, published in Cell, was coauthored by plant biology professors Stephen Long, Amy Marshall-Colon, and Lisa Ainsworth, along with chemical and biomolecular engineering professor Diwakar Shukla and colleagues at eight partner institutions. They evaluated biological strategies aimed at improving the efficiency of photosynthesis, the process by which crops convert sunlight into sugar.
A plant that can capture more sunlight can produce more food or fuel. In a landmark review from ten years ago, Long, Marshall-Colon, and Xin-Guang Zhu described the promising potential of focusing on photosynthesis to develop higher-yield crops and mapped out possible improvement pathways. The current review updates that progress and reaffirms the value of this research route.
“At the pace we’ve gained knowledge over the last decade, the momentum is extraordinary,” Ainsworth noted. “As we confront agricultural challenges, photosynthesis holds the potential to address many of them. Research progress has accelerated, and we anticipate exponential growth in understanding photosynthesis in the coming decade.”
Ainsworth leads Realizing Increased Photosynthetic Efficiency (RIPE), an international project based in the Carl R. Woese Institute for Genomic Biology that concentrates on this field. Long, Marshall-Colon, Shukla, and several coauthors are RIPE investigators. RIPE receives support from Gates Agricultural Innovations (Gates Ag One).
Why center on photosynthesis? This core plant process, in which chlorophyll captures sunlight to convert carbon dioxide and water into sugars and oxygen, underpins terrestrial life. Photosynthesis is the ultimate source of the calories we eat. Yet although it sustains plant life, photosynthesis is, like many complex systems, an evolution-built, ad hoc solution not optimized for today’s environment.
“What’s exciting about this work is that many proposed changes to photosynthesis have already been put into crops and tested in the field. Several approaches have shown promise in boosting daily carbon gain and increasing yields,” said Ainsworth. “The review also highlights strategies that remain untested or unrealized—the next frontier. We describe the tools needed to reach that frontier.”
The review identifies several key targets for boosting photosynthesis. A major focus is engineering the enzyme Rubisco, which fixes atmospheric carbon dioxide into sugars. Rubisco occasionally reacts with oxygen instead, triggering a costly recycling process known as photorespiration.
The review surveys multiple solutions to this challenge. Approaches include directing laboratory-directed evolution to yield a less error-prone Rubisco; increasing the enzyme’s abundance to raise throughput; prompting plants to develop cell or tissue structures that concentrate carbon dioxide around Rubisco to shield it from competing oxygen; and introducing synthetic pathways to bypass costly photorespiration and keep Rubisco active under a wider range of conditions.
Other avenues aim to improve light capture. In dense crop rows, leaves at different heights can shade one another, reducing overall light use. Crops can be bred to be more cooperative—so leaves at all levels receive adequate light—by adjusting leaf angle and chlorophyll content. Research is also exploring how plants can shift more quickly from protective responses used in intense light to optimal light gathering in cloudy conditions.
Advances across these areas have progressed faster than the authors initially expected, aided by new technologies.
“Dynamic protein models help us understand protein interactions, and advanced imaging now lets us visualize leaf intercellular airspaces, yielding fresh insights,” Ainsworth said.
The publication serves as both a retrospective on what’s been accomplished and a call to action. It also carries a legacy: Long and Marshall-Colon passed away earlier this year. For Long, refocusing the research community on the feasibility and potential impact of improving photosynthetic efficiency to feed the world was especially important.
“In a decade, we’ve moved from theory and proof-of-concept in model crops to field testing in food crops,” Ainsworth observed. “This review shows that we’re not just close to enhancing photosynthesis—we’re actively doing it. Improving photosynthetic efficiency is achievable and can be integrated now into crop improvement strategies.”
— Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign
Source: EurekAlert! via University of Illinois news release
