Abstract
Arbuscular mycorrhizal (AM) fungi form mutualistic association with the roots of more than 80% of all terrestrial plant species. The plant-AM fungus interaction is initiated by mutual signal exchange during preinfection stages. Host roots release a signal called "branching factor" that induces host recognition response characterized by extensive hyphal branching in AM fungi. Branching factor is found to be a lipophilic compound less than 500 Da, but its chemical structure has not been published yet. AM fungi have long been postulated to produce a signal called "Myc factor" during preinfection stages. Recently, the first experimental evidence was obtained by Becard and co-workers for the existence of a diffusible fungal signal inducing symbiosis-specific MtENOD11 expression. We are now trying to isolate and identify these plant and fungal signaling molecules using Lotus japonicus and Gigaspora margarita as a model organism.
