Giving plants the green light for growth

Genetically modified rice, right, shows more heads than its parent variety Nipponbare and rice modified with an inactive version of FTO as a control. Field trials in northern, central and southern China yielded similar results.  |  Yu et al photo

When the plants in the greenhouse grew at three times the normal rate, Chuan He and his colleagues knew they were onto something big.

When they took their genetically modified rice and potatoes into the field, they were sure. The crops yielded 50 percent more, were 50 percent bigger, and they grew more and longer roots, making them more resistant to drought. The plants even increased their rate of photosynthesis.

“When we saw the rice we were, ‘holy smoke,’ ” said He, a biologist at the University of Chicago. “But when we saw the potato, we’re like, ‘OK, that’s it. We’ve got it.’ ”

The breakthrough could put some lofty goals within easy reach. For example, a 50 percent boost of 2020’s Canadian canola yield of 41 bushels per acre would be about 61 bu. per acre, well above the ambitious 52 bu. per acre target set by the Canola Council of Canada for 2025.

The work builds on the discovery of He and his colleagues a decade ago. They found that living things use something called RNA methylation to regulate which genes get expressed.

“We’re the ones who discovered the RNA demethylation as a new sort of regulatory layer of gene expression,” he said. “We’ve done lots of work in animals to show that reversible RNA methylation is critical to tune gene expression.”

FTO potatoes, right, yielded much higher than the unmodified Emalingshu3 variety. | Yu et al photo

The substances that do this reversal are called demethylases. One of He’s collaborators, Guifang Jia, now with Peking University in China, has particular expertise in one called FTO that regulates growth and development. In humans, it’s associated with fat mass and a variant form is linked to obesity.

Think of FTO as a “switch” that controls the traffic lights of plant growth, He said. Specifically, it turns off the “red light” that tells the plant to stop growing, and leaves the light green.

Some version of FTO exists in most living things. He and Jia had found that reversible demethylation also exists in plants. They decided to introduce one of the more well-known FTO versions — human — into Arabidopsis, a common laboratory plant, and also into rice.

“When we did it in Arabidopsis it was very nice, but when we tried this in rice, it was just incredible,” He said. “From there, we tried it in potatoes and other things, and consistently in these crops, we get roughly 50 percent increase in yields and biomass.”

While their initial published work focuses on rice and potatoes, He said the FTO tweak has worked in every plant they’ve tried so far, and should work in other cereal crops as well as oilseeds and pulses. In fact, the team has applied it successfully in grasses and trees, opening up possibilities for agroforestry, biofuels and even remediating desert land.

“I’m also excited about the potential around climate change,” He said. “These (plants) are drought resistant and they offer a lot more biomass, so for ecosystem preservation or even improved ecosystems.”

Another “big picture” implication is more production on less land, preserving natural ecosystems.

“These are all sort of possibilities we’re dreaming of. I can say we’re dreaming because I’m a basic scientist. I work on science,” He said. “But hopefully people will become interested in this technology and apply it to improve our lives.”

He and his colleagues have already removed one possible roadblock: public sentiments on genetically modified organisms. While genetic modification was used for proof of concept, they have already worked out another way to achieve the same result.

Their initial results are published in Nature Biotechnology, with more papers on the way as the team explores some of the ramifications such as drought tolerance.

For example, He wants to know why the human version of FTO has such a dramatic effect on plants.

The plants’ own version is more “careful,” limiting growth to a specific size. He speculates that evolution has shaped the plants this way to ensure their survival in the wild, but crop plants, with human support, can afford an FTO switch that stays “green.”

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