According to a new study published in Nature Plants, scientists from the University of Essex have resolved two major photosynthetic bottlenecks to boost plant productivity by 27% in real-world field conditions. This is the third breakthrough for the research project Realizing Increased Photosynthetic Efficiency (RIPE). This improvement in photosynthesis shows that it saves water as well.
As we all know that plants have a long and complex process called photosynthesis in which it takes in light, carbon dioxide, and water to create energy for itself and yield for us. Like all other processes, this process also has some blockages which reduce the yield.
What is RIPE?
Realizing Increased Photosynthetic Efficiency (RIPE) is a project a translational research project that is genetically engineering plants to photosynthesize more efficiently to increase crop yields. Basically it aims to improve the process of photosynthesis. It is led by the University of Illinois at Urbana-Champaign and is funded by Bill & Melinda Gates Foundation, the U.S. Foundation for Food and Agriculture Research (FFAR), and the U.K. Government’s Department for International Development (DFID).
To optimize any process, we first need to know all the steps involved in the process. So, to optimize photosynthesis, researchers have modeled all the 170 steps involved in photosynthesis.
The team found two constraints in photosynthesis out of which one is in the first part of photosynthesis where light energy is converted to chemical energy and the second one is in the second part of the process where CO2 is fixed into sugars.
The First Bottleneck: Plastocyanin
The first problem was in a transport protein called Plastocyanin. This moves electrons into the photosystem to fuel this process. It has been found that the protein has more affinity to the acceptor protein in the photosystem which hinders smooth transportation by Plastocyanin.
This problem was solved by the addition of cytochrome c6 which is a more efficient transport protein that has a similar function in algae. This requires iron and plastocyanin needs copper to function. So, this new protein could share the load with plastocyanin depending on the availability of the required nutrients.
The Second Bottleneck: Calvin-Benson Cycle
The team has improved a photosynthetic bottleneck in the Calvin-Benson Cycle, wherein carbon dioxide is fixed into sugars, by bulking up the amount of a key enzyme called SBPase, borrowing the additional cellular machinery from another plant species and cyanobacteria.
Researchers improved the crop’s water-use efficiency by adding “cellular forklifts” to shuttle electrons into the photosystems and “cellular machinery” for the Calvin Cycle.
These two improvements have given a boost in plant productivity by 52 percent in greenhouse and 26 percent in field trials.
“In our field trials, we discovered that these plants are using less water to make more biomass,” said principal investigator Christine Raines, a professor in the School of Life Sciences at Essex where she also serves as the Pro-Vice-Chancellor for Research. “The mechanism responsible for this additional improvement is not yet clear, but we are continuing to explore this to help us understand why and how this works.”
Patricia E. López-Calcagno, Kenny L. Brown, Andrew J. Simkin, Stuart J. Fisk, Silvere Vialet-Chabrand, Tracy Lawson, and Christine A. Raines. Stimulating photosynthetic processes increases productivity and water-use efficiency in the field. Nature Plants, 2020 nature.com/articles/s41477-020-0740-1