Arbuscular mycorrhiza symbioses between most land plants and fungi of the glomeromycota improve plant performance because the fungi deliver mineral nutrients to their hosts. In return, the fungi receive photosynthetically fixed carbon. It has long been believed that the fungi are only fed with carbohydrates but we and others have recently discovered that plants serve their symbionts also with lipids and that fungal development and growth depends on this lipid source. Root colonization by arbuscular mycorrhiza fungi involves distinct developmental steps that are largely under plant control and can be genetically separated by plant mutants. These steps include fascinating plant cell rearrangements that precede differentiation of fungal hyphae into particular shapes inside these plant cells. In my research group, we use a combination of genetic, physiological, biochemical and cell biological approaches to uncover and understand the plant molecular mechanisms, which regulate and execute these plant cell rearrangements for fungal accommodation. Plants regulate the extend of colonization according to their physiological state. For example, at high phosphate levels or insufficient light availability, root colonization is suppressed. It is our long-term goal to unravel the molecular mechanisms, which interconnect plant physiology with arbuscular mycorrhiza development, to understand how plants orchestrate AM symbiosis with their physiological needs under changing environmental conditions. My presentation will focus on our recent progress in understanding the role of plant hormone signaling and transcriptional regulation in arbuscular mycorrhiza development and function.
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