RIPE: Realizing the Next Green Revolution

LSU Researchers Explore Creative Solutions to Improving Crop Yield

RIPE

The idea that the world’s demand for food could outpace food production may be a difficult concept for many to digest, but this notion could be an imminent reality. For the past 50 years, the green revolution has allowed crop production to keep pace with population growth. However, recently crop yields in wheat and rice have leveled off. A forecast by the Food and Agricultural Organization of the United Nations asserts that food production must increase by 70 percent to support the world’s population in 2050, which is estimated to increase to 9.6 billion.

In an effort to develop an innovative solution to this looming agricultural crisis, the Bill & Melinda Gates Foundation initiated the Realizing Increased Photosynthetic Efficiency (RIPE) project, and LSU biologist James Moroney is playing an active role in this undertaking. RIPE is a $25 million research effort aimed towards developing plants that will increase crop yields by using sunlight more effectively through the process of photosynthesis.

Photosynthesis is the method that plants use to transform light energy into chemical energy. Carbon dioxide (CO2) and light are the raw materials that fuel the plant growth process. Millions of years ago, natural selection optimized this system in plants. However, even though the atmospheric CO2 concentration has increased over the past 50 years, the CO2 concentration in the atmosphere is still limiting to most crops. This is largely due to the inefficiency of the enzyme Rubisco, which catalyzes the first reaction of CO2 fixation (photosynthesis). Rubisco requires high concentrations of CO2 to
be efficient.

Photo

Write The RIPE research group at LSU: Madelinn Fink, Robert DiMario, James Moroney, Jimmie Mickler and Mary Machingura.Photo Credit: April Buffington

Led by the University of Illinois, RIPE is made up of an international team of scientists from Australian National University (Canberra), the Chinese Academy of Sciences-Max Plank Institute (Shanghai), Lancaster University, Liverpool John Moores University, the University of Essex (all in Great Britan), the University of California-Berkeley, and LSU. These scientists are redesigning the photosynthetic production line to make it more efficient for the future. For the next Green Revolution, RIPE is cultivating plants that can photosynthesize more efficiently to produce plants with more biomass.

RIPE is exploring solutions to stagnant crop yield from a series of angles. Increasing mesophyll conductance focuses on optimizing CO2 diffusion inside of the leaf. Optimizing canopies centers on improving plant architecture to maximize light energy absorption. Relaxing photoprotection minimizes damage caused by high light levels. Optimizing carbon metabolism enhances the investment of resources in the Calvin cycle by altering gene expression of several enzymes in the leaf. Transplanting Rubisco replaces the inefficient Rubisco enzyme with better Rubisco isoforms. Photorespiratory bypass replaces the carbon cycling pathway of photorespiration in crop plants with a more efficient bacterial pathway. Finally, algal mechanisms focus on inserting carbon-concentrating mechanics from algae into plants to elevate CO2 concentrations around the plant Rubisco.

Moroney’s work falls within the algal mechanisms approach. In 2013, he was awarded a $700,000 contract with the University of Illinois to identify new inorganic carbon transporters from the algae Chlamydomonas reinhardtii. This alga contains a robust CO2 concentrating mechanism, which is essential for photosynthesis at atmospheric levels of CO2. At LSU, Moroney has worked to characterize the CO2 concentrating mechanism of C. reinhardtii. He and his students have discovered a number of proteins that assist in delivering CO2 to Rubisco in the alga.

“We have four different algal transporters that we are interested in. We are presently putting them into higher plants to see if these algal proteins can improve photosynthesis. One of them is working very nicely and is going to the right place in the plant, so we feel like we have it localized to the chloroplast like we want it to be,” said Moroney, Glenda Wooters Streva Alumni Professor in LSU’s Department of Biological Sciences. “Our hope is that these algal proteins will help deliver CO2 to Rubisco in the plant, increasing photosynthesis and
crop yields.”

In over 85 percent of plant species, CO2 entering a leaf simply diffuses to Rubisco. Rubisco, though vital to the photosynthesis process, is fairly inefficient due to its tendency to bind with O2 instead of CO2. A number of algae have moved past this limitation by forming a structure called the pyrenoid within the chloroplast, and have transport proteins that help the CO2 reach Rubisco. RIPE’s mathematical modeling suggests that a large increase in photosynthesis could be achieved by re-engineering the pyrenoid apparatus back into crop plant chloroplasts. Since many proteins are required to form a pyrenoid, this strategy is considered quite risky.

“It is definitely a high risk, high reward situation,” Moroney said. “The RIPE team has some projects that were expected to produce tangible results in five years, but other projects, like ours, were longer term. Projects with shorter timelines like those at UC Berkeley, which is relaxing photoprotection and the optimizing carbon metabolism project at the University of Essex really look promising. They had plants undergoing field tests at the University of Illinois this past summer.”

Moroney and his team may have encountered a few roadblocks to developing an improved plant, but they are still working towards a successful outcome.

“One of the problems we are facing is that these transporters are very tightly controlled,” Moroney said. “Basically, they are active in the light and inactive at night, so there are other proteins controlling their functions. So our plants with the algal proteins have not shown any improvements yet. We think that when we place the transporters in the plants that we may be missing other components needed to control them. Now, we are trying to identify other proteins required for their activation.”

In addition to improving photosynthesis, Moroney hopes that introducing these algal transport proteins might result in more resilient plants that can thrive in harsh, dry climates. “There are little pores in leaves called stomates,” Moroney said. “For every CO2 that enters, hundreds of water molecules escape. So, the plants are losing lots of water by keeping their stomates open. If we could get the plant to be a bit more efficient in using CO2, it would use less water and not require much irrigation.”

Moroney has a stellar group of scientists working with him on the RIPE project. The team includes postdoctoral researchers Mary Machingura and Robert DiMario and undergraduate researchers Jimmie Mickler, Madelinn Fink and Joshua Schwartzenburg. Machingura brings a unique knowledge set to the group. She worked on cassava research in Zimbabwe, Africa, where she received a higher understanding of food production issues in harsh climates. One priority of this project is to improve crops like cassava that are important crops in Africa. Machingura’s work has been featured in Plant Science, Plant Physiology and Biochemistry and other scientific journals. DiMario, who received his BS (2010) and PhD (2016) in biology from LSU, coauthored studies published in Photosynthesis Research, Plant Physiology and Molecular Plant.

Moroney’s work with the RIPE program began in 2011, when he was one of only 13 scientists invited to a Bill & Melinda Gates Foundation workshop to share his views on how photosynthesis research could positively impact agricultural productivity. Fast forward five years and the RIPE project has made significant gains in their work to create a more resilient high-yield plant. Though Moroney admits that while he hoped that his team’s work would be further along, significant progress has been made and the research continues to move forward.

“This project is like my dream,” Moroney said. “I always considered my work on algae to be basic research. I was interested in how algae became so efficient at capturing CO2 for photosynthesis. It is really fun to see that our work on algal photosynthesis might someday help improve crops and perhaps boost food production.”