How Nitrogen Fixation Depends on Calcium

Abstract

Leguminous plants form symbiotic relationships with rhizobial nitrogen-fixing bacteria and mycorrhizal fungi, which set up residence in nodules in the roots of host plants. Nodulation results from a signal transduction pathway induced in the roots of legumes by rhizobial signals called Nod factors. Two reports by Ané et al. and Lévy et al. define genes from the leguminous plant Medicago truncatula involved in the earliest steps of nodulation. One of the genes likely encodes a calcium- and calmodulin-dependent protein kinase, and the other a ligand-gated cation channel. Thus, calcium signaling appears to be critical for the establishment of a successful plant-microbe symbiosis. J.-M. Ané, G. B. Kiss, B. K. Riely, R. V. Penmetsa, G. E. D. Oldroyd, C. Ayax, J. Lévy, F. Debellé, J.-M. Baek, P. Kalo, C. Rosenberg, B. A. Roe, S. R. Long, J. Dénarié, D. R. Cook, Medicago truncatula DMI1 required for bacterial and fungal symbioses in legumes. Science 303 , 1364-1367 (2004). [Abstract] [Full Text] J. Lévy, C. Bres, R. Geurts, B. Chalhoub, O. Kulikova, G. Duc, E.-P. Journet, J.-M. Ané, E. Lauber, T. Bisseling, J. Dénarié, C. Rosenberg, F. Debellé, A putative Ca 2+ and calmodulin-dependent protein kinase required for bacterial and fungal symbioses. Science 303 , 1361-1364 (2004). [Abstract] [Full Text]