Why scientists want to help plants capture more carbon dioxide

By Casey Crownhart

In the ClimateTech conference last week, I sat down with Pamela Ronald, a plant geneticist at the University of California, Davis. She’s been working for years on helping rice survive floods, and now she’s turning her attention to using advanced genetics for carbon removal on farmland.

Genetics and plants

Scientists have a wide range of tools at their disposal to influence how plants grow. From standard genetic engineering to more sophisticated gene editing tools like CRISPR, we have more power than ever to influence what traits we want in crops.

But genetic tweaking isn’t anything new. ″Virtually everything we eat has been improved using some sort of genetic tool,″ Ronald pointed out in our interview at ClimateTech, with a few exceptions like foraged blueberries and mushrooms, and wild-caught fish.

Selective breeding and cross-pollination have been used by farmers for centuries to bring out certain traits in their crops. In the 20th century, researchers turned things up a notch and began using mutagenesis—using chemicals or radiation to cause random mutations, some of which were beneficial.

The difference is, in the last 50 years, genetic tools have become much more precise. Genetic engineering allowed the introduction of specific genes into a target plant. CRISPR has allowed scientists to have an even finer touch, influencing specific points in DNA.

″What's really exciting now is that we have a lot more tools,″ Ronald said.

The power of precision

To understand just how powerful genetic tools can be in agriculture, take a look at Ronald’s project developing flood-resistant rice.

Rice plants grow well in standing water, but most varieties will die if they’re submerged for more than three days, which can happen often in low-lying farmland. An estimated four million tons of rice are lost each year to floods—enough to feed 30 million people, Ronald said.

Ronald and her collaborators found a solution in an ancient, largely forgotten variety of rice that was especially resistant to flooding.

Using modern genetic tools including one called marker-assisted breeding, the researchers were able to breed the gene responsible for flood-tolerance, called Sub1, into popular rice varieties. In controlled experiments, researchers compared Sub1 rice to standard varieties by growing both for a four-month period that included a two-week flood. In flooded conditions, the Sub1 gene increased rice yields by 60%.

Ronald said the project was especially successful because of who has benefitted: some of the poorest farmers in the world. For more on the flood-resistant rice work, check out this profile of Ronald my colleague James wrote in 2017.

Next up: carbon removal?

Ronald and I also discussed a new project she’s been working on, which is focused on using crops for carbon removal. The research is spearheaded by the Innovative Genomics Institute, founded by Nobel Prize winner and CRISPR pioneer Jennifer Doudna.

I wrote about this project back in June when it was announced with funding from the Chan Zuckerberg Initiative. At ClimateTech, Ronald walked me through more details on the goal of the project.

″The most effective and amazing carbon removal technology is photosynthesis,″ Ronald said in our interview.

Plants naturally draw down carbon dioxide and transform it into complex compounds like sugars. Many of the sugars made in photosynthesis are eventually broken down again, returning to the atmosphere. But some carbon stays in the soil—and Ronald and her team want to help bump up how much.

There are a few prongs to this plan.

• Boost photosynthesis, so crops can grow more quickly and suck up more carbon.
  

• Grow plants with especially long roots, so that more carbon ends up deep underground.

• Help plants associate with specific bacteria. This one is a bit complicated, but basically some bacteria help mineralize carbon dioxide underground, trapping it.
  

In addition to tweaking plants, researchers will work to better understand how carbon is moving through plants and the surrounding environment to see how much they’re actually helping.