It has been hypothesized that both fungi and bacteria interacting with plant roots do so using similar genetic mechanisms. It has already been shown that rhizobial bacteria – particularly the nitrogen fixing microbes associated with leguminous plants – produce lipochitooligosaccharide (LCO) signals used in the communication with host plants. The authors of this study discovered that the fungus Glomus intraradices, like the nitrogen-fixing bacteria, secretes an array of sulfated and non-sulfated simple LCOs which stimulated the formation of arbuscular mycorrhizae in disparately related plants, such as Medicago (Fabaceae), Daucus carota (Wild Carrot; Apiaceae), and Tagetes patula (French Marigold; Asteraceae). These compounds were found in Glomus intraradices both interacting with plant roots and in free-living resting spores in the soil.
http://cymeandcystidium.com/2011/02/23/135/