Form and function of arbuscular mycorrhiza symbiosis

Most land plants form symbioses with Glomeromycotina fungi to acquire mineral nutrients from the soil. This so-called arbuscular mycorrhiza (AM) symbiosis is evolutionarily ancient and found in the oldest fossils of land plants, sparking speculations about its importance in the colonization of the land by originally aquatic plants during evolution, at a time when plants had not yet evolved complex root systems for nutrient uptake. The fungi form extended hyphal networks in the soil to scavenge mineral nutrients. These are transported into the root and released via beautifully-shaped, highly branched hyphal structures, the arbuscules inside inner root cells. In return they receive up to 20% of photosynthetically fixed carbon from their host in the form of sugars and lipids. As a consequence, AM contributes significantly to plant nutrition and to global carbon cycles.

For symbiosis establishment, AM fungi colonize the root interior and the inside of plant cells. Symbiotic infection of single, already differentiated cells within the tissue context requires a poorly understood cellular remodeling program that is intertwined with mechanisms that control plant development and physiology. In my presentation, I will provide examples of how we investigate the molecular mechanisms underlying development and functioning of this fascinating symbiosis.