Good news for those despairing at our rapidly warming planet: we can supercharge plants to help fight the effects of climate change. Scientists have found two ways to make plants better at turning carbon dioxide into energy — and these techniques could help plants help us create better biofuels and produce more food to save the world.
Two studies published today in Science show different ways that beefing up the process by which plants create energy — called carbon fixation, or photosynthesis — could lead to a better future. In one, scientists decided that the entire process of carbon fixation was too slow and created a new, and faster, cycle. In the other, researchers engineered plants so they could absorb more sunlight. These enhanced plants grew up to 20 percent bigger, which is a big deal for food supply.
Plants are some of our best allies in the climate change fight. Global warming happens because of too much carbon dioxide in the atmosphere, and we add CO2 through activities like burning fossil fuels for energy. Because plants absorb carbon dioxide, they suck up some of the extra CO2 in the air and can even buy us extra time on global warming. But photosynthesis isn’t as efficient as it could be, so scientists are teaching plants how to do their jobs better to make our own lives easier. There may be other benefits besides locking down carbon: better plant growth means more food for a booming human population.
To make carbon fixation happen, organisms use molecules called enzymes. But the main enzyme doesn’t work very fast, says Tobias Erb, a synthetic biologist at the Max Planck Institute for Terrestrial Microbiology who is a co-author of one of the Science papers.
His team decided that they could design a way to make the process happen more quickly. They spent years figuring out which combination of enzymes would work together to get the job done. In the end, a combination of 17 enzymes fit the bill. These enzymes come from nine organisms (including e. coli bacteria and the human liver). Three of the enzymes were designed using a computer; that’s how delicate the balance is. When these enzymes are combined together, they can turn carbon dioxide into organic compounds better than plants and other organisms currently do.
This work is in very early stages — that is, inside a tube, because it hasn’t been tested in actual living organisms. In theory, it should work on all organisms that do photosynthesis because the cycle is the same for all of them. But in practice, things can get tricky. Think of the process like a heart transplant, says Erb. When you transplant a heart, you first have to suppress the immune system so that the body doesn’t reject the new organ. To transplant this new pathway into plants, Erb’s team also has to tinker with all the other plant processes — such as its metabolism — to make sure everything still works. “This paper is really pushing the technical boundaries,” says Christine Raines, a biologist at the University of Essex. “You’re designing a completely new pathway, and the big question is whether it’ll hold up in living organisms, but this is an interesting proof of concept.”
Plants are very complex, so Erb’s team will first focus on bacteria and algae, which also undergo carbon fixation. “The idea is first to create organisms that can make any compound from carbon dioxide — like making biofuels more efficient or making chemical building blocks for pharmaceuticals,” says Erb.
Instead of creating a new photosynthetic process entirely, you could take a shortcut by making plants’ existing energy processes more efficient, says Krishna Niyogi, a UC Berkeley biologist also affiliated with the Howard Hughes Medical Center and the Lawrence Livermore National Laboratory. He is the co-author of a separate study on photosynthesis.
Plants need sunlight, but the dosage they require varies — so when they detect too much light, they quench some of the chlorophyll, which absorbs light, so that they take in less of it. But when a plant does that, it can take a long time for it to recover to their usual level of light absorption, slowing their growth. And it doesn’t take much to trigger this coping mechanism, either, says Niyogi. So his team targeted this “recovery” process, in the hopes of helping plants use as much sunlight as possible to grow big.
All plants have three specific proteins that regulate how quickly they “recover” after shutting down the chlorophyll. Niyogi’s team added more of these proteins to certain tobacco plants. This way, the plants still absorb less light when there’s too much sun, but go back to their normal level of light absorption much more quickly.
Compared to the non-engineered plants, the new ones grew anywhere from 14 percent to 20 percent bigger. The United Nations already said that we’re going to need to produce 70 percent more food by 2050 to feed everyone, and climate change is likely to cause food shortages. If this method becomes widely adapted, it could help us produce a lot more food without needing more land.
The initial experiments are on tobacco because the plant is very easy to modify. Since no one eats tobacco, Niyogi’s team is now working on crops like rice, sorghum, and cassava. (The research is funded by the Bill and Melinda Gates Foundation, so they’re focusing on plants that are readily available in sub-Saharan Africa.) “They’ll still need to explore a wide range of different conditions to make sure this is really a generally useful tool, and that they don’t accidentally mess up one of the plant’s backup systems,” says Robert Blankenship, a biologist at Washington University in St. Louis. “But this is a really excellent study — it’s well-designed and well-carried-out and exciting.”