Ammonium Transporter Keeps Plant-Fungal Exchange Going

A group of soil fungi classified as arbuscular myccorhizal fungi (AMF) gets sugars from plant roots in exchange for nutrients. AMF dies off if they cannot provide nutrients to the plant. A research team from Cornell University led by Professor Maria Harrison has identified the exact protein transporters needed to keep the exchange going. They found that while the plant prefers phosphate, under certain conditions, it appears that nitrogen will suffice, and a single transporter is required to tell the plant that it's getting nutrients.

Professor Harrison's research team interbred mutant Medicago truncatula plants that were missing certain phosphate or ammonium transporters to create double- and triple-mutants. By creating plants without necessary proteins to take in the nutrients, they can genetically simulate a shortage of AMF-delivered phosphate or nitrogen. They then grew these mutants with the fungi and looked for evidence of successful AM formation to find the vital transporters.

They identified AMT2;3, a critical ammonium transporter that can keep the symbiosis going. The researchers hypothesize that without this transporter or the critical phosphate transporters, sugars stop flowing to the fungus and consequently the symbiosis breaks down. The discovery of AMT2;3 improves the understanding of how plant and fungal partners regulate the symbiosis and how phosphate and nitrogen move through the system. These are both important components of fertilizers in agriculture, and in future applications.

For more details, read the news release from the Boyce Thompson Institute for Plant Research.