Plants and mycorrhizal fungi have a unique partnership. Plants allow fungi to live among their roots, while feeding them fat and sugar. In return, fungi use their far-reaching filamentous branches called hypha to capture vital soil nutrients for plants, including the important mineral phosphorus. A team of researchers at the University of Copenhagen's Department of Plant and Environmental Sciences has discovered an extraordinary plant gene, the CLE53 gene, which regulates cooperation between fungi and plants.
Phosphorous is an important component of plant growth. However, more phosphorous is applied for fertilization than what can be actually absorbed by crops. The study estimated that only 30 percent of phosphorous applied to plants reaches them, whereas 70 percent accumulates in the soil. With rain, there is an ever-present risk that some of the accumulated phosphorus will be discharged into streams, lakes, and the sea.
Paradoxically, the researchers observed that when phosphorus levels in the soil are high, plants are less likely to collaborate with fungi, and they become worse at absorbing nutrients. Through experiments, they learned that a plant does not produce the CLE53 gene if it lacks phosphorus. However, when the phosphorus levels in a plant are high, or if the plant is already symbiotically involved with a fungus, CLE53 level increases.