Why do your tomato plants sometimes turn into tomato plant wannabes in the summer heat?
Wake Forest University researchers wanna find out.
They’ve won a $3 million National Science Foundation grant to study why tomato plants won’t bear fruit when the temperature rises above a certain level in the summer.
The grant supports a team of researchers led by Gloria Muday, Ph.D., the university’s Charles M. Allen Professor of Biology and director of its Center for Molecular Signaling. The scientists want to determine why most tomato plants fail to pollinate when summer temperatures stay at 93.2 degrees Fahrenheit or higher for more than a few hours.
The goal: develop more heat-tolerant tomatoes for future crops.
Tomatoes make the perfect study subject because the plant has varieties that can reproduce under heat stress, the researchers say. Their aim is to map how the reproductive genes in the heat-tolerant varieties work. The insight provided may help breed or engineer varieties that yield dependable crops even as global temperatures rise.
“We’re working with tomatoes because they’re a very approachable experimental system,” Muday said in an interview with the North Carolina Biotechnology Center. “But we hope it leads the way for other crops.”
Excessive heat explodes pollen tubes
Muday notes, “Looking at the data over the last few hundred years, the average temperature is going up, there are higher nighttime temperatures, and short bursts of elevated temperature that are sufficient to prevent plant reproduction.”
That heat causes the tomato blossom’s pollen tube to explode before fertilization, preventing the pollen from reaching the plant ovary and making fat, juicy tomatoes.
Some tomato varieties and other crops produce flavonoids, protective anti-oxidants, giving them a measure of heat and stress tolerance, Muday said. “We’re working with plants that don’t produce the flavonoids, and part of this grant is to understand that. We hope to breed or engineer plants that produce more of these protectives.”
Looking at the genome for clues
The grant will allow the team to screen lots of gene-expression events, looking for patterns that make the plants good at dealing with stress, Muday explains. But James Pease, an assistant professor of biology at Wake Forest and part of the research team, will look at the plants’ genomes. “Gene expression changes in varieties,” said Muday. “James will go in and look at the genome to ask why gene expression changes.”
Pease will examine which genes in the genome foster heat tolerance in some tomato varieties. Pease has published papers on the evolutionary history of wild tomatoes, which originated as a desert plant in the Andes of South America. Their adaptability has helped make tomatoes one of the largest cash crops for food in the world.
“Tomatoes have an interesting biological story, and they’re really important to the global food supply,” Pease said. “We have this context where species are spread out across various habitats. Do these domesticated varieties have any genetic similarities to their distant relatives in extremely hot places?”
Pease heads an evolutionary genetics lab at Wake Forest.
Others on the team include pollen expert Mark Johnson of Brown University, who was an undergraduate student of Muday’s at Wake Forest; Ann Loraine of the University of North Carolina at Charlotte; and Ravishankar Palanivelu of the University of Arizona.
Pandemic slows start of research
Muday said work on the project has just started and the COVID-19 pandemic has slowed its initial progress. “It’s a three-year grant, but it may take longer because we’re not doing a lot right now.” Even once the work is underway and they have candidate genes, engineering the genome to make tomatoes or other plants more resistant to stress takes a lot of time, Muday said.
“It takes more than a year to get a good gene-expression line.” Findings from the project are likely to lead to additional funding down the line.
The NSF grant also includes funding to expand a science outreach program to local high schools that Muday started with her students about a decade ago. The researchers and their students will be trained to teach plant genetics and the science of plant breeding and genetic engineering, focusing on the effects of temperature stress.
Muday’s program has reached more than 1,000 ninth graders in North Carolina. It led to published research. The research showed that college students who learn about genetically modified organisms (GMOs) and teach the science behind them to high school students are more likely to accept the use of GMOs in our food supply.