In a groundbreaking study, biologists at Brown University have investigated tomato varieties that flourish in scorching growing seasons, uncovering the critical growth cycle phase where these plants are most vulnerable to extreme heat. They also identified the molecular processes that enhance the plants’ heat resilience. The findings hold the potential to revolutionize strategies aimed at safeguarding our food supply amid the challenges posed by climate change.
As agricultural productivity increasingly faces threats from rising temperatures—predicted to reduce crop yields by 2.5% to 16% for every additional 1 degree Celsius of seasonal warming—this research is timely and important.
The scientists drew inspiration from evolutionary principles to explore effective methods for accelerating the adaptation of tomato plant varieties, noted study collaborator Sorel V. Yimga Ouonkap, a research associate in molecular biology, cell biology, and biochemistry at Brown. Relying solely on evolution to gradually phase out heat-sensitive tomato varieties, such as Heinz, in favor of those more resilient to extreme heat would take considerable time and might also threaten the attributes that make these vulnerable crops commercially appealing.
“We’re trying to figure out thermoregulation at a molecular and cellular level and identify what and where we need to improve so that we can target those in commercial plant cultivars and conserve everything about them except for this one aspect that makes them vulnerable to extreme heat,” Ouonkap said. “Over time, you can start accumulating different resistance mechanisms as the growing conditions continue to change.”
Understanding thermotolerance—essentially, a plant’s ability to thrive under extreme temperatures—represents a groundbreaking approach to climate adaptation, asserts Mark Johnson, a professor of biology at Brown University.
“Imagine if you could just make a Heinz tomato more resilient to temperature stress without affecting the flavor profile or the way people experience the tomato,” Johnson said. “That would be a great advantage.”
Plant reproduction—is a critical area for exploration. Johnson’s lab has dedicated extensive research to the reproductive phase of plants for years. While existing studies have examined the impacts of heat stress on overall plant growth and the formation of vital reproductive structures, a crucial gap persists regarding the events that unfold after pollen lands on the stigma, according to Johnson. For Ouonkap’s thesis project, he zoomed in on the pollen tube growth phase of the reproductive cycle.
He explored various tomato plant cultivars known for their capacity to yield fruit during extremely hot growing seasons. The tomato varieties included in the research originated from the Philippines, Russia, and Mexico and were cultivated in Brown’s Plant Environment Center. In collaboration with researchers at the University of Arizona, Ouonkap examined how heat stress influences the growth of pollen in tomato flowers. He investigated the changes in gene expression that occur when tomato pollen, produced by plants in ideal greenhouse conditions, is subjected to high temperatures while grown in a petri dish.
Recent findings from the team’s partners in Arizona reveal that exposure to high temperatures during the critical pollen tube growth phase drastically reduces fruit and seed production, particularly in heat-sensitive tomato cultivars compared to their heat-tolerant counterparts.
Ouonkap found that pollen tubes from the Tamaulipas tomato variety, recognized for their heat tolerance, exhibit enhanced growth when exposed to high temperatures. Through his molecular analysis of these tomato pollen tubes, the research team was able to identify the mechanisms linked to thermotolerance.
Researchers indicated that tomatoes serve as an excellent model for this type of study. Their capacity to adapt across various extreme climatic conditions provides scientists with a valuable understanding of how different species respond to environmental stressors. Furthermore, tomatoes represent a significant commercial crop in many nations around the globe, including the Mediterranean, Egypt, Turkey, and California—regions that are particularly susceptible to extreme heat events.
Having identified the relevant molecular mechanisms, the next step would be exploring specific methods to promote tomato growth across different climates. In a possible scenario, scientists might create a small molecule that could prepare the pollen in these plants to endure a heat wave, Johnson clarified.
“When the weather forecast showed two weeks of high temperatures during the pollen tube growth phase, the farmer would apply a product to plants that would change the gene expression so that the pollen would be resilient to heat,” he said.
Although this kind of manipulation is still far from being explored, the researchers mentioned that this field of study is ready for investigation.
Journal reference:
- Sorel V. Yimga Ouonkap, et al. Enhanced pollen tube performance at high temperature contributes to thermotolerant fruit and seed production in tomato. Current Biology, 2024; DOI: 10.1016/j.cub.2024.10.025