Can We Hack DNA in Plants to Help Fight Climate Change?

by Madeleine Stone (National Geographic) Using CRISPR genome editing on a few common crops, a team of plant and soil scientists seeks to vastly increase and speed up carbon storage to help fight climate change. -- ... we will also need to pull carbon out of the air and secure it.

Plants are among the best tools we have to do this, since these living solar collectors already capture billions of tons of carbon dioxide each year from the atmosphere through photosynthesis. About half of that carbon winds up in roots and eventually the soil, where it can stay for hundreds to thousands of years.

But what if we could create plants and soils that are even better at capturing carbon?

With an $11-million (£9.3 million) gift from the Chan Zuckerberg Institute, a team of plant geneticists, soil scientists, and microbial ecologists embarked on a three-year effort using CRISPR to create new crop varieties that photosynthesise more efficiently and funnel more carbon into the soil. Eventually, the researchers hope to create gene-edited rice and sorghum seeds that could—if planted around the globe—pull more than a billion extra tons of carbon out of the air annually.

Plants’ ability to sequester carbon naturally begins inside tiny cellular compartments called chloroplasts. There, energy from sunlight is used to strip electrons from water molecules and add them to carbon dioxide, transforming it into glucose, a simple sugar. The plant then uses the organic carbon to grow new leaves, shoots, and roots.

Based on previously published estimates, Savage believes that stacking multiple beneficial genetic edits together could increase the efficiency of photosynthesis—and hence, the amount of carbon rice plants capture in their tissue—by 30 percent or more.

Deeper in the ground

To boost carbon sequestration in croplands, though, some of that extra carbon needs to get below ground. In parallel research led by crop geneticist Pamela Ronald at the University of California, Davis, researchers will screen a library of 3,200 mutant strains of rice housed at the IGI for varieties with beneficial root traits. These include long-rooted rice strains that can funnel carbon into deeper layers of the soil, as well as strains whose roots release more sugar-heavy molecules, called exudates, that fuel the growth of soil microbial communities.

A complex community of microorganisms and fungi decomposes the carbon that plants put into soil, transforming it into a huge variety of different compounds. Some of that carbon is fast-burning fuel for microbes, which gobble it up and release carbon dioxide back to the atmosphere. But another portion of the carbon isn’t so easy for microbes to break down, because of its chemistry, its location inside large particles called aggregates, or its tendency to stick to mineral surfaces. These molecules form a stable soil carbon pool that can last decades or longer.

Scientists are still trying to understand how the physical, chemical, and biological diversity of soils shape that stable carbon pool. The soil experts on the IGI research team hope to add to this knowledge base—and ultimately, use what they learn to enhance carbon sequestration.

As the microbial research is ongoing, Lawrence Livermore National Laboratory soil scientist Jennifer Pett-Ridge and her colleagues have an all-important task: Counting carbon atoms to make sure the entire concept, from plant cells to soils, actually works.

By placing gene-edited crops in special growth chambers and flooding them with CO2 containing a rare, heavy isotope known as carbon-13, the researchers will be able to see exactly how much carbon their plants are taking up, and where it’s winding up.

“Lots of people are making claims around increasing soil carbon, but there is a lack of evidence around attribution,” Zelikova (Jane Zelikova, the director of the Soil Carbon Solutions Center at Colorado State University) says. “Can you actually show that the solution you’ve developed is making measurable impacts on soil carbon stocks, and especially on the molecules that tend to stick around for a long time? Doing that in a rigorous way is key.” READ MORE