A CRISPR-edited super plant, perhaps a variation on a chickpea, could take carbon dioxide out of the atmosphere.
16 May 2018

A plant that could save civilization, if we let it

Laura H. Kahn

The carbon dioxide level in Earth’s atmosphere reached its highest level in human history last month, at 410 parts per million. Humans are a factor: We put carbon dioxide into the atmosphere, where it contributes to the warming of the planet, by burning fossil fuels. So far, Earth has warmed by 1 degree Celsius (1.8 degrees Fahrenheit) above preindustrial levels, and 2 degrees of warming within this century are very likely, bringing drier weather, rising sea levels, and damaged ecosystems. Scientists are even contemplating what the world might be like at 3 or 4 degrees of warming or higher, temperatures that would lead to substantial species extinctions and areas where it is too hot to live outside.


Within decades, the changing temperature will have a negative effect on

agriculture and by extension food security. A 2010 World Bank report, Development and Climate Change, forecast that climate change would depress agricultural yields in most countries by 2050, assuming current crop varieties and agricultural practices remain the same. Countries in Africa, South America, and South Asia will be particularly hard hit, with the United States adversely affected as well. (Canada and Russia may be able to grow more crops than they currently do, if arctic soils are fertile enough for large-scale agriculture.)


Reducing carbon emissions would be one way to stop global warming, but efforts to do so have run into economic, technological, and political obstacles. Which is why there have also been serious efforts to remove carbon dioxide from the atmosphere. Energy researchers are pursuing a mix of technologies known as “carbon capture, utilization, and storage,” or CCUS, which entail capturing carbon dioxide from industrial emissions before it can be released into the atmosphere and converting it into something useful or storing it deep underground. Tax credits for implementing carbon-capture technologies, such as those passed as part of the 2018 US Congressional budget, could provide incentives. But these technologies are expensive to develop and implement, and environmental groups are concerned that they will prolong our dependence on fossil fuels.


But plants do something similar, albeit temporarily, capturing carbon dioxide after it has entered the atmosphere. Through photosynthesis, a type of carbon fixing, they pull in more than 860 gigatons of carbon dioxide each year from the atmosphere, storing it in their leaves, shoots, and roots. Unfortunately, much of the carbon dioxide is re-released back into the atmosphere when the plants—annual crops such as rice, wheat, and maize—are harvested or degraded by bacteria, fungi, or animals. (NASA’s three-minute video “A Year in the Life of Earth’s CO2” visualizes a computer simulation of the effects of photosynthesis on carbon dioxide levels during spring and summer months in the northern hemisphere.) Perennials—plants that live year after year—provide a potential strategy to combat climate change by storing carbon dioxide longterm in their roots. (Trees do this too, which is one of the many reasons cutting down forests is so deleterious to the environment.)


One scientist has a promising idea to solve two major problems at once—removing carbon dioxide from the atmosphere and feeding people and animals—by breeding a “super plant.” But her project, urgent though it is, might be unnecessarily slow for political reasons. Due to concerns about political opposition to genetically modified organisms (GMOs), she has chosen to genetically alter plants the old-fashioned way, through selective breeding, rather than through a newer, faster technology, the gene-editing tool CRISPR.


Joanne Chory, a plant biologist and geneticist, is director of the Plant Molecular and Cellular Biology laboratory at the Salk Institute for Biological Sciences and a Breakthrough Prize recipient. She created an initiative called “Harnessing Plants for the Future” to develop a super plant that will both provide food and store carbon dioxide in its roots.


All plants produce suberin, a waxy, water-repellent, carbon-rich compound, also known as cork, that protects roots and resists decay. Coastal grasses make a lot of it to keep water out of their roots. It is one of the most stable substances around, persisting in soil for hundreds, possibly thousands of years. One of Chory’s goals is to develop perennial plants that make more suberin than existing varieties.


Chory concluded that legumes—plants that include beans, chickpeas, lentils, and peanuts—would be ideal crops to develop as super plants because they are perennial and adapted to semi-arid climates. The popular Middle Eastern dish hummus, now ubiquitous across Western grocery stores, is made from mashed chickpeas, oil, garlic, and lemon juice; it is high in fiber and a good source of protein, healthy fats, folate, and iron.


Besides being edible and nutritious, any super plant would need to tolerate floods and droughts and be able to survive in a wide variety of climates ranging from arid regions in north Africa to temperate regions in northern Europe. Ultimately, Chory’s goal is to breed plants that grow extra-deep roots with lots of suberin for long-term carbon storage. She estimates that if 5 percent of the world’s cropland, approximately the total area of Egypt, were devoted to such super plants, they could capture about 50 percent of current global carbon dioxide emissions.


There are certainly challenges to Chory’s brilliant plan, not the least of which involve convincing farmers around the world to dedicate some land to the future super plant. One challenge, though, may be solvable through public education.


Chory plans to develop her novel super plant through cross-breeding, the same method long used to select for desired traits in domesticated plants and animals. For example, ancient farmers transformed a wild Mexican grass known as teosinte into maize by selectively breeding only those plants that exhibited slightly larger and tastier kernels. But bringing about such a change through selective breeding can take several hundred years or longer.


Even with advanced breeding techniques, Chory estimates that developing a super plant in this fashion would take around 10 years. CRISPR, meanwhile, has great potential to develop better crops. In the case of Chory’s project, the genes for suberin could be identified in the coastal grasses that make a lot of it in their roots and then, using CRISPR, transferred to the genome of the desired super plant.


Since major breakthroughs earlier this decade, CRISPR has become relatively cheap and easy for labs to deploy. So why isn’t Chory using it? In order to avoid political opposition from activists opposed to GMOs, as she said during the question-and-answer session of her Breakthrough Prize Symposium talk. Anti-GMO activists have held up the implementation of Golden Rice, a crop that could spare millions of people from blindness and death due to vitamin A deficiency, and have hindered development of crops resistant to disease.


Genetically modified crops have enormous potential to benefit humanity. Initial opposition to them appears to have started with the “Roundup Ready” crops developed by the company Monsanto in 1996, which were designed to be resistant to the herbicide glyphosate. These crops encouraged the use of glyphosate, a probable carcinogen. Unfortunately, this problematic GMO tainted all subsequent ones for some of the public, regardless of the benefits of other GMOs.


A gene-editing tool like CRISPR allows for much faster cross-breeding than once was possible, transferring special characteristics such as enhanced suberin production from one plant to another. Yes, the resulting organism would be genetically modified, but so are virtually all the other organisms we consume.


The stakes could not be higher, and we don’t have time to spare. Glaciers are melting. Sea levels are rising. Coral reefs are dying. And agriculture, our food security, is in peril. We need solutions sooner rather than later. Regaining the public’s trust in science is essential—but will not be easy in an era of fake news, propaganda, and conspiracy theories.

Working with nature to address the damage we have inflicted is a smart strategy, and Chory’s “super” carbon-fixing legumes provide a compelling plan of action, but waiting to develop them through cross-breeding is like trying to win a high-speed car race with a horse and buggy. Developing and deploying these plants should be a global priority.