JXB Advance Access originally published online on September 10, 2004
Journal of Experimental Botany 2004 55(408):2635-2640; doi:10.1093/jxb/erh261
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RESEARCH PAPER |
Nod factor-treated Medicago truncatula roots and seeds show an increased number of nodules when inoculated with a limiting population of Sinorhizobium meliloti*

1Department of Agronomy and Soils, University of Puerto RicoMayagüez, PO Box 9030, Mayagüez, PR 00681-9030, USA
2Laboratoire des Interactions Plantes-Microorganismes, INRA/CNRS, Chemin de Borde-Rouge, BP 27, F-31326 Castanet-Tolosan, France
Present address and to whom correspondence should be sent: Biological Sciences Department, California State Polytechnic University, 3801 W. Temple Avenue, Pomona, CA 91768, USA. E-mail: gbrelles{at}csupomona.edu
Medicago truncatula is a model legume plant that interacts symbiotically with Sinorhizobium meliloti, the alfalfa symbiont. This process involves a molecular dialogue between the bacterium and the plant. Legume roots exude flavonoids that induce the expression of a set of rhizobial genes, the nod genes, which are essential for nodulation and determination of the host range. In turn, nod genes control the synthesis of lipo-chito-oligosaccharides (LCOs), Nod factors, which are bacteria-to-plant signal molecules mediating recognition and nodule organogenesis. M. truncatula roots or seeds have been treated with Nod factors and hydroponically growing seedlings have been inoculated with a limiting population of S. meliloti. It has been shown that submicromolar concentrations of Nod factors increase the number of nodules per plant on M. truncatula. Compared with roots, this increase is more noticeable when seeds are treated. M. truncatula seeds are receptive to submicromolar concentrations of Nod factors, suggesting the possibility of a high affinity LCO perception system in seeds or embryos as well.
Key words: Legume nodulation, Medicago truncatula, Nod factors, Sinorhizobium meliloti