The majority of terrestrial plants rely on symbiotic relationships to obtain necessary nutrients. One of these relationships is between the roots of plants and arbuscular mycorrhizal fungi (see Parniske). Akiyama et al. isolated and identified the so-far elusive chemical that is the signal, called branching factor (BF), released by plants to attract the fungi. The compound was determined to be a strigolactone, which belongs to a class of sesquiterpene lactones that also serve as seed germination stimulants for parasitic weeds. Natural and synthetic strigolactones stimulated the formation of hyphal branches in an in vitro bioassay. Strigolactones are unstable compounds that are released by plants under conditions of low phosphate availability, which are the same conditions that allow parasitic weeds to prevail. The sharing of the signal for symbiotic root colonization by fungi with seed germination of parasitic weeds may lead to new strategies for managing beneficial symbiotic relationships and preventing the invasion by parasitic plants.
M. Parniske, Plant-fungal association: Cue for the branching connection. Nature 435, 750-751 (2005). [PubMed]
K. Akiyama, K.-i. Matsuzaki, H. Hayashi, Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi. Nature 435, 824-827 (2005). [PubMed]