Abstract
Genetic experiments have indicated that succinoglycan (EPS I), the acidic Calcofluor-binding exopolysaccharide, of the nitrogen-fixing bacterium Rhizobium meliloti strain Rm1021 is required for nodule invasion and possibly for later events in nodule development on alfalfa and other hosts. Thirteenn exo loci on the second megaplasmid have been identified that are required for, or affect, the synthesis of EPS I. Mutations in certain of these loci completely abolish the production of EPS I and result in mutants that form empty Fix- nodules. We have identified two loci, exoR and exoS, that are involved in the regulation of EPS I synthesis in the free-living state. Certain exo mutations which completely abolish EPS I production are lethal in an exoR95 or exoS96 background. Histochemical analyses of the expression of exo genes during nodulation using exo::TnphoA fusions have indicated that the exo genes are expressed most strongly in the invasion zone. In addition, we have discovered that R. meliloti has a latent capacity to synthesize a second exopolysaccharide (EPS II) that can substitute for the role(s) of EPS I in nodulation of alfalfa but not of other hosts. Possible roles for exopolysaccharides in symbiosis are discussed. Evidence indicating that the R. meliloti exoD gene encodes a novel function needed for nodule invasion is summarized.
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References
Aman, P., M. McNeil, L.-E. Franzen, A. G. Darvill, and P. Albersheim. 1981. Structural elucidation, using HPLC-MS and GLC-MS, of the acidic polysaccharide secreted by Rhizobium meliloti strain 1021. Carbohydr. Res. 95:263–282
Darvill, A.G., P. A. Albersheim, P. Bucheli., S. Doares, N. Doubrava, S. Eberhard, D.J. Gollin, M. G. Hahn, V. Marfa-Riera, W. S. York, and D. Mohnen. 1989. Oligosaccharins — plant regulatory molecules. In “NATO ASI Series, Vol. H36, Signal Molecules in Plants and Plant-Microbe Interactions”, B. J. J. Lutgenberg (Ed.), Springer-Verlag, Berlin Heidelberg, pp 41–48.
Djordjevic, S., H. Chen, M. Batley, J. W. Redmond, and B. G. Rolfe, 1987. Nitrogen fixation ability of exopolysaccharide synthesis mutants of Rhizobium sp. strain NGR234 and Rhizobium trifol ii is restored by the addition of homologous exopolysaccharides. J. Bacteriol. 169:53–60.
Doherty, D., J. A. Leigh, J. Glazebrook, and G. C. Walker. 1988. Mutants of Rhizobium meliloti that overproduce its acidic Calcofluor-binding exoplysaccharide. J. Bacteriol. 170:4249–4256.
Finan, T. M., A. M. Hirsch, J. A. Leigh, E. Johanson, G. A. Kulda, S. Deegan, G. C. Walker, and E. R. Signer. 1985. Symbiotic mutants of Rhizobium meliloti that uncouple plant from bacterial differentiation. Cell 40:869–877.
Finan, T. M., B. Kunkel, G. F. De Vos, and E. R. Signer. 1986. Second symbiotic megaplasmid in Rhizobium meliloti carrying exopolysaccharide and thiamine synthesis genes. J. Bacteriol. 167:66–72.
Glazebrook J., and G. C. Walker. 1989. A novel exopolysaccharide can function in place of the Calcofluor-binding exopolysaccharide in nodulation of alfalfa by Rhizobium meliloti. Cell 56:661–672.
Her, G. R., J. Glazebrook, G. C. Walker, and V. N. Reinhold. 1990. Structural studies of a novel exopolysaccharide produced by a mutant of Rhizobium meliloti strain Rm1021. Carbohydr. Res. 198:305–312.
Kombrink E., M. Schroeder, and K. Hahlbrock. 1988. Several “pathogenesisrelated” proteins in potato are 1,3- ß-glucanases and chitinases. Proc. Natl. Acad. Sci. USA 85:782–786.
Lang-Unnasch, N., and F. M. Ausubel. 1985. Nodule-specific polypeptides from effective alfalfa nodules and from ineffective root nodules lacking nitrogenase. Plant Physiol. 77:833–839.
Leigh, J.A., and C. C. Lee. 1988. Characterization of polysaccharides of Rhizobium meliloti exo mutants that form ineffective nodules. J. Bacteriol. 170:3327–3332.
Leigh, J. A., J. W. Reed, J. F. Hanks, A. M. Hirsch, and G. C. Walker. 1987. Rhizobium meliloti mutants that fail to succinylate their Calcofluor-binding exopolysaccharide are defective in nodule invasion. Cell 51:579–587.
Leigh, J. A., E. R. Signer, and G. C. Walker. 1985. Exopolysaccharide-deficient mutants of Rhizobium meliloti that form ineffective nodules. Proc. Natl. Acad. S USA 82. 6231–6235
Long, S., S. McCune, and G. C. Walker. 1988. Symbiotic loci of Rhizobium meliloti identified by random TnphoA mutagenesis. J. Bacteriol. 170: 4257–4265.
Long, S., J. W. Reed, J. W. Himawan, and G. C. Walker. 1988. Genetic analysis of a cluster of genes required for the synthesis of the Calcofluor-binding exopolysaccharide of Rhizobium meliloti. J. Bacteriol. 170:4239–4248.
Manoil, C., and J. Beckwith. 1985. TnphoA: a transposon probe for protein export signals. Proc. Natl. Acad. Sci. USA 82:8129–8133.
Muller, P., M. Hynes, D. Kapp, K. Niehaus, and A. Puhler. 1988. Two classes of Rhizobium meliloti infection mutants differ in exopolysaccharide production and in coinoculation properties with nodulation mutants. Mol. Gen. Genet. 211:17–26.
Norris, J. H., L. A. Marcol, and A. M. Hirsch. 1988. Nodulin gene expression in effective alfalfa nodules and in nodules arrested at three different stages of development. Plant Physiol. 88:321–328.
Reed, J. W., and G. C. Walker. The exoD gene of Rhizobium meliloti encodes a novel function needed for alfalfa nodule invasion. Submitted.
Reuber, T.L., and G. C. Walker. Regulation of Rhizobium meliloti exo genes in free-living cells and in planta analyzed using TnphoA fusions. Submitted
Sutherland, I. W. 1982. Biosynthesis of microbial exopolysaccharides. Adv. Microbiol. Physiol. 23:79–150.
Tolmasky, M. E., R. J. Staneloni, R. A. Ugalde, and L. F. Leloir. 1980. Lipidbound sugars in Rhizobium meliloti. Arch. Biochem. & Biophys. 203:358–364.
Tolmasky, M. E., R. J. Staneloni, and L. F. Leloir. 1982. Lipid-bound saccharides in Rhizobium meliloti. J. Biol. Chem. 257:6751–6757.
Williams, M. N. V., R. I. Hollingsworth, S. Klein, and E. R. Signer. 1990. The symbiotic defect of Rhizobium meliloti is suppressed by lpsZ +, a gene involved in lipopolysaccharide biosynthesis. J. Bacteriol., 172:2622–2632.
Zhan, H., S. B. Levery, C. C. Lee, and J. A. Leigh. 1989. A second exopolysaccharide of Rhizobium meliloti strain SU47 that can function in root nodule invasion. Proc. Natl. Acad. Sci. USA 86:3055–3059.
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© 1991 Springer Science+Business Media Dordrecht
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Reuber, T.L., Reed, J.W., Glazebrook, J., Urzainqui, A., Walker, G.C. (1991). Analyses of the Roles of R.Meliloti Exopolysaccharides in Nodulation. In: Hennecke, H., Verma, D.P.S. (eds) Advances in Molecular Genetics of Plant-Microbe Interactions Vol. 1. Current Plant Science and Biotechnology in Agriculture, vol 10. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-7934-6_28
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DOI: https://doi.org/10.1007/978-94-015-7934-6_28
Publisher Name: Springer, Dordrecht
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