Arbuscular Mycorrhizal (AM) Symbiosis: A review of signalling and molecular aspects of root colonisation

Summary Mycorrhizal associations vary widely in structure and function, but the commonest interaction is the Arbuscular Mycorrhizal (AM) symbiosis which forms between the roots of over 80% of all terrestrial plant species and Zygomycete fungi of the Order Glomales. These are obligate symbionts which colonise plant root cells. This symbiosis confers benefits directly to the host plants through the acquisition of phosphate and other mineral nutrients from the soil by the fungus while the fungus receives a carbon source from the host. In addition, the symbiosis may also enhance the plants resistance to biotic and abiotic stresses. The beneficial effects of AM symbioses occur as a result of a complex molecular dialogue between the two symbiotic partners. Identifying the molecules and genes involved in the dialogue is necessary for a greater understanding of the symbiosis. This paper reviews the process of AM fungal colonisation of plant roots and the underlying molecular mechanisms associated with the formati...