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Comparison of Characteristics of the nodX Genes from Various Rhizobium leguminosarum Strains

¹Institute of Molecular Plant Sciences, Clusius Laboratory, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands; ²All-Russia Research Institute for Agricultural Microbiology, Podbelsky shosee 3, 189620 St. Petersburg, Pushkin 8, Russia; ³Department of Mass Spectrometry, Bijvoet Center for Biomolecular Research, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands; ⁴PMI Group, Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra ACT 2601, Australia

We have analyzed the nucleotide sequences of the nodX genes from two strains of Rhizobium leguminosarum bv. viciae able to nodulate Afghan peas (strains A1 and Himalaya) and from two strains of R. leguminosarum bv. trifolii (ANU843 and CSF). The nodX genes of strains A1 and ANU843 were shown to be functional for the induction of nodules on Afghan peas. To analyze the cause of phenotypic differences of strain A1 and strain TOM we have studied the composition of the lipochitin-oligosaccharides (LCOs) produced by strain A1 after induction by the flavonoid naringenin or various pea root exudates. The structural analysis of the LCOs by mass spectrometry revealed that strain A1 synthesizes a family of at least 23 different LCOs. The use of exudates instead of naringenin resulted only in quantitative differences in the ratios of various LCOs produced.