The light that drives our crops’ photosynthetic process is dynamic, with the ability to fluctuate over and through their canopy of leaves at any given moment. Everything from wind to intermittent clouds to the sun rising and setting can change the amount of light a plant receives every second and in any given area. And there lies our problem.
When a plant experiences a change in light intensity, even if it’s a single area of a leaf suddenly being shaded for a few moments, the plant reacts, undergoing a set of internal processes. Unfortunately for us, the time it takes for our crops to adjust to changes in light isn’t immediate, and sometimes it’s painfully slow — as seen with C4 vs. C3 crops. In fact, in some crops, it’s estimated that potential photosynthetic productivity could be increased by 40% if we could genetically modify them to react and adjust to transitional periods of light more efficiently.
That’s the goal of a team of researchers from the University of Illinois, who are hoping to increase global food production by unlocking the keys to more efficient photosynthesis.
Led by Yu Wang, his team recently released a study published in The Plant Journal that showed when photosynthesis is treated as a dynamic process, response time and adjustments to light changes could be reduced. Wang led this work for the research project, Realizing Increased Photosynthetic Efficiency (RIPE). RIPE is funded by the Bill & Melinda Gates Foundation, Foundation for Food & Agriculture Research, and U.K. Foreign, Commonwealth & Development Office.
In particular, the RIPE project concluded from researching three species of C4 crops (corn, sorghum, and sugarcane), that Rubisco activase, pyruvate phosphate dikinase (PPDK) activation, and stomatal conductance were the main functions that stifled the time it takes for these plants to adjust to light fluctuations. C4 crops notably have a higher light energy-use efficiency compared to C3 crops in sunny conditions, but perform poorer in dynamic light environments due to a decrease in productivity.
The research team found if they could increase the concentration of pyruvate phosphate dikinase regulatory proteins (PDRP), the photosynthetic performance of C4 crops under fluctuating light conditions could improve. PDRP appears to be the most significant limiter in C4 crops with RIPE’s research noting that the concentration of PDRP is a major limitation for the first 180 seconds of induction for corn and roughly 250 seconds of induction for sorghum and sugarcane.
“When light changes, the plants need time to get used to it. It takes time and decreases efficiency,” Yu Wang told PHYS.org. “Our goal is in trying to limit the loss during the transition period. We are working to make the plants respond faster to the dynamic light environment.”
Stephen Long, Director at RIPE, hailed the importance of their research, noting that 99% of the investigations into what limits photosynthesis have concerned constant light and a photosynthetic process that either is or isn’t happening. And that’s something a crop in the field is unlikely to see.
RIPE says their model for dynamic photosynthesis could stimulate a 10 to 20% increase in yield by making adjustments to key proteins essential to photosynthesis. And by breeding these new GMO crops together over the years, Long hopes to see these numbers increase.
But the question remains, does Wang’s research team’s model for dynamic photosynthesis pan out? This summer, the research team hopes to find just that out. Once again partnering with RIPE, the team will look at modifying two proteins in corn to improve its ability to react to light fluctuations faster. To engineer these proteins, they will be enlisting the help of a team from the U.S. Department of Energy Center for Advanced Bioproducts & Bioenergy Innovation (CABBI) at Illinois in sorghum and sugarcane.