Discovery by Researchers Could Help Increase Plant Yield Caused by Looming Phosphate Shortage

Scientists at the University of North Carolina at Chapel Hill have identified a key genetic switch that helps soil bacteria that lives on and inside plant roots to harvest phosphate, a vital nutrient for plant yield that is limited in global supply.

The form of phosphate that plants can use is in danger of reaching its peak. The scientists show precisely how PHR1, a key switch protein, controls plant response to low levels of phosphate and the plant immune system as well. Jeff Dangl, John N. Couch Distinguished Professor and Howard Hughes Medical Institute Investigator said, "When the plant is stressed for this important nutrient, it turns down its immune system so it can focus on harvesting phosphate from the soil. Essentially, the plant sets its priorities on the cellular level."

The research team found evidence that soil bacteria use this tradeoff between nutrient-seeking and immune defense, potentially to help establish symbiotic relationships with plants. Bacteria seem to enhance this phosphate stress response, in part simply by competing for phosphate but also by actively ‘telling' the plant to turn on its phosphate stress response. The team showed that PHR1 and probably its closely related protein, PHL1, not only activates a plant's phosphate stress response, but also triggers a pattern of gene expression that reduces immune activity, and thus makes it easier for resident microbes to survive.

The study suggests that soil-dwelling microbes have figured out how to get along with their plant hosts, in part by activating PHR1/PHL1 to suppress immune responses to them. The research team also thinks these microbes may even be necessary for plants response to low-phosphate conditions. It is possible, then, to harness this relationship – via probiotic or related crop treatments – to enable plants to use less phosphate.

For more details, read the news release at UNC-Chapel Hill.