Mystery of plant’s roots targeted by OWU project
An Ohio Wesleyan University faculty member and three students have published a paper in a scientific journal that helps explain one of the many reasons plants behave the way they do.
Directing the study was Chris Wolverton, Ph.D., an associate professor of botany and microbiology.
The paper, “Low Phosphate Alters Lateral Root Setpoint Angle and Gravitropism,” appears in the January edition of the American Journal of Botany.
Its title might be dry scientific terminology, but Wolverton said the work someday could be part of a larger body of research that yields big dividends in agriculture.
The study focused on sideways-growing lateral roots, which make up the vast majority of a plant’s root system, of Arabidopsis thaliana seedlings.
“What were hoping to understand,” he said, “in the big picture … is how plants regulate how and where they grow. These lateral roots that come out, they all choose a different angle and they stick to that angle for a period of time. If you move them away from that angle they find it again. They go back to it. So what we’re trying to do is figure out what is the system, what is the series of switches and regulators inside the plant, in the molecular sense, that’s guiding the plant to that particular angle.”
The small plants were grown in Petri dishes to gauge their roots’ reaction to the location of phosphate, a plant nutrient. The plants were watched to see if the angle of their lateral roots changed in reaction to the phosphate.
“We’re interested in the kind of raw molecular signals that tune this particular angle,” he said, “and we speculated that because roots grow at different angles under different nutrient conditions that maybe if we altered nutrient status, we should see a difference in the overall angle that the root system sets itself at, and that’s in fact what we saw.”
Understanding the behavior someday might enable science to control it, Wolverton said.
“For example, for plants to be drought-tolerant, we could tune it so their roots went deeper in the soil rather than staying closer to the surface. There’s a greater probability that water is deeper. For growing in conditions where there’s a different soil profile, for example, if there are lots of phosphate ions toward the top of the profile and not much toward the bottom. Maybe you’d want a variety that’s been more tuned to stay horizontal rather than going more vertical.”
He emphasized such technology is many years in the future, but “if you picture lateral roots as kind of the foot soldiers of the root system, you can imagine that maybe under a given situations the general would want to redeploy troops to a new pocket of soil or to a new front in the battle.” Those changes, he said, someday might help plants thrive under stressful conditions.
Arabidopsis thaliana is being studied by as many as 1,000 labs worldwide, he said,and its genome has been sequenced. Wolverton used samples from Ohio State University, which were made to order.
“We can order a defect in any gene we want and test its effect. We made use of that in this study. We ordered some plants that were mutant for phosphate carriers,” he said.
That made Arabidopsis more sensitive to variables in the study, he said, and under different conditions the plants responded the same way.
A potential goal of such work, he said, would be identifying “the molecular switch that causes the root to swith this angle … some molecule, some gene that encodes a protein that the plant … something that’s integrating all of these cues.”
Students working with Wolverton on the project were Evan Bai, Bhavna Murali and Kevin Barber. All three have since graduated and are pursuing doctoral studies.
Wolverton earned his doctorate at the Ohio State University and joined the Ohio Wesleyan faculty in 2002.