, Volume 175, Issue 4, pp 546–557 | Cite as

Feedback regulation of nodule formation in alfalfa

  • G. Caetano-Anollés
  • W. D. Bauer


When high dosages of wild-type Rhizobium meliloti RCR2011 were inoculated at two different times, 24 h apart, onto either the primary roots of alfalfa (Medicago sativa L.) seedlings or onto lateral roots on opposite sides of a split-root system, the number of nodules generated by the second inoculum was much smaller than the number generated by the first inoculum. These results provide evidence that alfalfa has an active, systemic mechanism for feedback control of nodulation. Non-nodulating mutants and delayed, weakly nodulating mutants did not elicit a discernable suppression of nodulation by subsequently inoculated wild-type cells. An appreciable number of Rhizobium infections thus seem required to elicit the suppressive response. Mutants in nodulation regions IIb and IIa nodulated extensively in the initially susceptible region of the root, but nodule initiation by these mutants was 100–1000 times less efficient, respectively, than the parent. Nodules formed by these mutants emerged 1 d later than normal. The IIb mutants elicited a relatively strong suppression of nodulation in younger parts of the root, but region-IIa mutants elicited only a weak response. These results indicate that elicitation of the regulatory response need not be proportional to nodule formation and imply that genes in region IIa play an important role in elicitation. At high dosages, the region-II mutants induced the development of thick, short roots in a considerably higher percentage of plants than the wild-type bacteria. Nodules generated by wild-type isolates and region-II mutants did not emerge in strict acropetal sequence, probably because some infections developed more slowly than others. Prior exposure of the root to non-nodulating mutants resulted in nodulation by the parent in regions of the root otherwise too mature to be susceptible, indicating that exposure to these mutants may affect the sequence of root development.

Key words

Feedback regulation (nodulation) Medicago Nodulation (efficiency, kinetics) Rhizobium (mutants) 



root tip


smallest emergent root hair


thick, short roots


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Allen, O.N., Allen, E.K. (1981) The Leguminosae, a source book of characteristics, uses and nodulation. University of Wisconsin Press, Madison, USAGoogle Scholar
  2. Bhuvaneswari, T.V., Bhagwat, A.A., Bauer, W.D. (1981) Transient susceptibility of root cells in four common legumes to nodulation by rhizobia. Plant Physiol. 68, 1114–1149Google Scholar
  3. Bhuvaneswari, T.V., Lesniak, A.P., Bauer, W.D. (1988) Efficiency of nodule initiation in cowpea and soybean. Plant Physiol. 86, 1210–1215Google Scholar
  4. Bhuvaneswari, T.V., Mills, K.K., Crist, D.K., Evans, W.R., Bauer, W.D. (1983) Effects of culture age on symbiotic infectivity of Rhizobium japonicum. J. Bacteriol. 153, 443–451Google Scholar
  5. Bhuvaneswari, T.V., Turgeon, G., Bauer, W.D. (1980) Early stages in the infection of soybean (Glycine max L. Merr.) by Rhizobium japonicum. I. Localization of infectible root cells. Plant Physiol. 66, 1027–1031Google Scholar
  6. Caetano-Anollés, G., Bauer, W.D. (1988) Enhanced nodule initiation on alfalfa by wild-type Rhizobium meliloti co-inoculated with nod gene mutants and other bacteria. Planta 174, 385–395Google Scholar
  7. Caetano-Anollés, G., Favelukes G. (1986) Host-symbiont specificity expressed during early adsorption of Rhizobium meliloti to the root surface of alfalfa. Appl. Environ. Microbiol. 52, 377–382Google Scholar
  8. Caetano-Anollés, G., Wall, L.G., DeMicheli, A.T., Macchi, E.M., Bauer, W.D., Favelukes, G. (1988) Role of motility and chemotaxis in efficiency of nodulation by Rhizobium meliloti. Plant Physiol 86, 1228–1235Google Scholar
  9. Calvert, H.E., Pence, M.K., Pierce, M., Malik, N.S.A., Bauer, W.D. (1984) Anatomical analysis of the development and distribution of Rhizobium infections in soybean roots. Can. J. Bot. 62, 2375–2384Google Scholar
  10. Carroll, B.J., McNeil, D.L., Gresshoff, P.M. (1985) Isolation and properties of soybean (Glycine max. (L) Merr.) mutants that nodulate in the presence of high nitrate concentrations. Proc. Natl. Acad. Sci. USA 82, 4162–4166Google Scholar
  11. Debellé, F., Rosenberg, C., Vasse, J., Maillet, F., Martinez, E., Dénarié, J., Truchet, G. (1986) Assignment of symbiotic development phenotypes to common and specific nodulation (nod) genetic loci of Rhizobium meliloti. J. Bacteriol. 168, 1075–1086Google Scholar
  12. Delves, A.C., Mathews, A., Day, D.A., Carter, A.S., Carroll, B.J., Gresshoff, P.M. (1986) Regulation of the soybean-Rhizobium symbiosis by shoot and root factors. Plant Physiol. 82, 588–590Google Scholar
  13. Dudley, M.E., Jacobs, T.W., Long, S.R. (1987) Microscopic studies of cell divisions induced in alfalfa roots by Rhizobium meliloti. Planta 171, 289–301Google Scholar
  14. Heron, D.S., Pueppke, S.G. (1987) Regulation of nodulation in the soybean-Rhizobium symbiosis. Strain and cultivar variability. Plant Physiol. 84, 1391–1396Google Scholar
  15. Hirsch, A.M., Long, S.R., Bang, M., Haskins, N., Ausubel, F.M. (1982) Structural studies of alfalfa roots infected with nodulation mutants of Rhizobium meliloti. J. Bacteriol. 151, 411–419Google Scholar
  16. Hoagland, D.R., Arnon, D.I. (1950) The water-culture method for growing plants without soil. Cal. Agric. Exp. Stat., Circ. No. 347 (rev. edn.)Google Scholar
  17. Jensen, H.L. (1942) Nitrogen fixation in leguminous plants. I. General characters of root nodule bacteria isolated from species of Medicago and Trifolium in Australia. Proc. Linn. Soc. N.S.W. 66, 98–108Google Scholar
  18. Kosslak, R.M., Bohlool, B.B. (1984) Suppression of nodule development of one side of a split-root system of soybeans caused by prior inoculation of the other side. Plant Physiol. 75, 125–130Google Scholar
  19. Meade, H.M., Long, S.R., Ruvkun, G.B., Brown, S.E., Ausubel, F.M. (1982) Physical and genetic characterization of symbiotic and auxotrophic mutants of Rhizobium meliloti induced by transposon mutagenesis. J. Bacteriol. 149, 114–122Google Scholar
  20. Peterson, M.A., Barnes, D.K. (1981) Inheritance of ineffective nodulation and non-nodulation traits in alfalfa. Crop Sci. 21, 611–616Google Scholar
  21. Pierce, M., Bauer, W.D. (1983) A rapid regulatory response governing nodulation in soybean. Plant Physiol. 73, 286–290Google Scholar
  22. Rosenberg, C., Boistard, P., Dénarié, J., Casse-Delbart, F. (1981) Genes controlling early and late functions in symbiosis are located on a megaplasmid in Rhizobium meliloti. Mol. Gen. Genet. 184, 326–333Google Scholar
  23. Sargent, L., Huang, S.Z., Rolfe, B.G., Djordjevic, M.A. (1987) Split-root assays using Trifolium subterraneum show that Rhizobium infection induces a systemic response that can inhibit nodulation of another invasive Rhizobium strain. Appl. Environ. Microbiol. 53, 1611–1619Google Scholar
  24. Takats, S.T. (1986) Suppression of nodulation in soybeans by superoptimal inoculation with Bradyrhizobium japonicum. Physiol. Plant. 66, 669–673Google Scholar
  25. Truchet, G., Debellé, F., Vasse, J., Terzaghi, B., Garnerone, A.M., Rosenberg, C., Batut, J., Maillet, F., Dénarié, J. (1985) Identification of a Rhizobium meliloti pSym 2011 region controlling the host specificity of root hair curling and nodulation. J. Bacteriol. 164, 1200–1210Google Scholar
  26. Truchet, G., Rosenberg, C., Vasse, J., Julliot, J.S., Camut, S., Dénarié, J. (1984) Transfer of Rhizobium meliloti pSym genes into Agrobacterium tumefaciens: host-specific nodulation by atypical infection. J. Bacteriol. 157, 134–142Google Scholar
  27. van Brussel, A.A.N., Tak, T., Wetselaar, A., Pees, E., Wijffelman, C.A. (1982) Small leguminosae as test plants for nodulation of Rhizobium leguminosarum and other Rhizobia and Agrobacteria harbouring a leguminosarum Sym-plasmid. Plant Sci. Lett. 27, 317–325Google Scholar
  28. van Brussel, A.A.N., Zaat, S.A.J., Canter Cremers, H.C.J., Wijffelman, C.A., Pees, E., Tak, T., Lugtenberg, B.J.J. (1986) Role of plant root exudate and Sym plasmid-localized nodulation genes in the synthesis by Rhizobium leguminosarum of Tsr factor, which causes thick and short roots on common vetch. J. Bacteriol. 165, 517–522Google Scholar

Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • G. Caetano-Anollés
    • 1
  • W. D. Bauer
    • 1
  1. 1.Department of AgronomyOhio State UniversityColumbusUSA

Personalised recommendations