Molecular and cellular aspects of the arbuscular mycorrhizal symbiosis

Arbuscular mycorrhizae are symbiotic associations formed between a wide ran ge of plant species including angiosperms, gymnosperms, pteridophytes, and some bryophytes, and a limited range of fungi belonging to a single order, the Glomales. The symbiosis develops in the plant roots where the fungus co lonizes the apoplast and cells of the cortex to access carbon supplied by t he plant. The fungal contribution to the symbiosis is complex, but a major aspect includes the transfer of mineral nutrients, particularly phosphate f rom the soil to the plant. Development of this highly compatible associatio n requires the coordinate molecular and cellular differentiation of both sy mbionts to form specialized interfaces over which bi-directional nutrient t ransfer occurs. Recent insights into the molecular events underlying these aspects of the symbiosis are discussed.