Photosynthesis is the foundation of life on Earth. It is the process by which plants use sunlight to make food. The process is made possible thanks to a big molecule, a protein, inside the leaves of most plants called Rubisco, which is short for an actual chemical name that’s very long and hard to remember.
Amanda Cavanagh, a biologist and postdoctoral researcher at the University of Illinois, said, “It’s probably the most abundant protein in the world,” and it’s also super-important because, without it, photosynthesis wouldn’t be possible. Rubisco is responsible for picking up carbon dioxide from the air and then using the carbon to make sugar molecules. It gets the energy to do this from the sun.
Cavanagh continued, “But it has what we like to call one fatal flaw. Unfortunately, Rubisco isn’t picky enough about what it grabs from the air. It also picks up oxygen. When it does that, it makes a toxic compound, so the plant has to detoxify it.” Plants have a whole complicated chemical assembly line to carry out this detoxification, and the process uses up a lot of energy, which means the plant has less energy for making leaves or food for us.
This little flaw is what Cavanagh and her colleagues in a research program called Realizing Increased Photosynthetic Efficiency (RIPE), based at the University of Illinois, have spent the last five years trying to fix. To solve Rubisco’s problem, they are “sort of hacking photosynthesis,” Cavanagh said.
To begin with, they experimented with tobacco plants because they are easy to work with. By inserting some new genes into the plants, the researchers were able to shut down the existing detoxification assembly line and set up a new one that’s way more efficient, thus creating super tobacco plants! “They grew faster, and they grew up to 40% bigger than normal tobacco plants,” Cavanagh said. These measurements were done both in open-air field plots and greenhouses. The study has been published in the journal Science.
Now, the team is trying to do the same thing with plants that people actually rely on for food, for example, tomatoes and soybeans. However, much of their current work is with cowpeas, or black-eyed peas, “because it’s a staple food crop for a lot of farmers in sub-Saharan Africa, which is where our funders are interested in making the biggest impact,” Cavanagh said.
Not only could plants with these new genes grow bigger and faster, but they could remove carbon dioxide from the atmosphere faster to mitigate the effects of climate change.
Maureen Hanson, who is carrying out similar research on photosynthesis at Cornell University, said, “This is a very important finding. It’s really the first major breakthrough showing that one can indeed engineer photosynthesis and achieve a major increase in crop productivity.”
The U.S. Department of Agriculture (USDA) has applied for a patent on plants that are engineered in this way, and the funders for the project include the USDA and the Bill and Melinda Gates Foundation.
Although, it will be many years before any farmers plant crops with this new version of photosynthesis because more research will have to be done to find out whether it means that a food crop like soybeans actually produces more beans—or just more stalks and leaves. A different route to the same goal is water-saving photosynthesis borrowed from tropical trees, where recent field trials suggest the water benefit is proving harder to engineer than the yield gain. Furthermore, they will have to ensure government regulators and consumers that the crops are safe to grow and eat.
