Gene Helps Crops Fight Heat Stress

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UF horticultural sciences researcher Bala Rathinasabapathi holds genetically modified tomato plants that contain a gene found in E. coli bacteria that enables plants to withstand heat better.

Though E. coli bacteria are notorious for making people sick, a University of Florida study shows that a gene found in the microbes can keep plants healthy by improving their resistance to heat stress — a discovery that may help researchers develop food crops that withstand harsh climates and global warming.

Tobacco plants carrying the gene thrived after spending a week in nonstop 95-degree heat, said Bala Rathinasabapathi, an associate professor of horticultural sciences with UF’s Institute of Food and Agricultural Sciences. The gene poses no threat to human health.

Researchers believe the plants were unusually resilient because they contained up to four times the normal amounts of vitamin B-5 and one of its components, the amino acid beta-alanine, he said.

The UF study appeared in the journal Plant Molecular Biology.

“We’re already researching the gene’s effect on tomatoes and lettuce, which are economically important to Florida and vulnerable to heat,” said Rathinasabapathi, who co-authored the study with graduate student Walid Fouad. “Large-scale application is several years away but we believe this technology will be practical and affordable. It’s certainly needed.”

Up to 20 percent of the world’s food crop is lost to heat stress each year, he said. That figure is likely to increase if predictions of future global warming prove correct.

According to the U.S. Environmental Protection Agency, many scientists believe the Earth’s average surface temperatures will increase by up to 10 degrees in the next century.

Besides fighting crop loss, the gene could enable farmers in tropical and subtropical areas to grow a wider variety of foods, Rathinasabapathi said.

The connection between the gene and heat tolerance was discovered by accident, as researchers tried to learn how plants make beta-alanine. The process is well understood in bacteria, so the researchers decided to take a gene that helps regulate beta-alanine production in E. coli and observe its effects in plants.

They transferred the gene to tobacco, a species popular in genetic research. During an experiment on heat stress, Fouad was surprised to find plants carrying the gene were taller than their ordinary counterparts.

“We hypothesized that the plants grew taller and larger under higher-than-optimal temperatures because something associated with the gene protected them from heat,” Rathinasabapathi said. “One possibility was that the large amounts of beta-alanine and vitamin B-5 they were producing played a role.”

In the current study, researchers found tobacco plants modified with the gene contained four times as much beta-alanine and vitamin B-5 as ordinary tobacco plants. And modified plants exposed to 95-degree heat for one week weighed almost twice as much as ordinary plants grown under the same conditions.

But when the modified plants were kept at temperatures typical for tobacco farming — about 75 degrees — they grew at the same rate as their ordinary counterparts.

“The practical applications for this gene may be limited to situations where crops will be exposed to temperatures of 90 degrees or more,” Rathinasabapathi said. “We’re conducting follow-up studies to learn more about how the gene works, so we can maximize its benefits.”

Bala Rathinasabapathi,
Tom Nordlie