Many plants form symbiotic relationships with mycorrhizal fungi. A much smaller group of plants, mostly the legumes, form symbiotic relationships with rhizobial bacteria. Op den Camp et al. (see the Perspective by Kereszt and Kondorosi) analyzed the molecular pathways underlying the early stages of mycorrhizal and rhizobial symbioses. The nonleguminous small tree Parasponia can form symbiotic relationships with rhizobia. Comparisons of the nodulation pathways in legumes with that in Parasponia suggest that the rhizobial pathway is derived from the mycorrhizal pathway.
R. Op den Camp, A. Streng, S. De Mita, Q. Cao, E. Polone, W. Liu, J. S. S. Ammiraju, D. Kudrna, R. Wing, A. Untergasser, T. Bisseling, R. Geurts, LysM-type mycorrhizal receptor recruited for rhizobium symbiosis in nonlegume Parasponia. Science 331, 909–912 (2011). [Abstract] [Full Text]