Symbiotic mutants of rhizobium meliloti that uncouple plant from bacterial differentiation

Finan, Turlough M.; Hirsch, Ann M.; Leigh, John A.; Johansen, Eric; Kuldau, Gretchen A.; Deegan, Sarah; Walker, Graham C.; Signer, Ethan R.

doi:10.1016/0092-8674(85)90346-0

Cited by 316 publications

(256 citation statements)

References 32 publications

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“…(7), Aeschynomene indica (3), A. americana (23), Neptunia plena (16), and N. oleracea (30). This mode of infection has also been described for alfalfa roots, which are normally infected through root hairs, following inoculation either with a strain of Agrobacterium tumefaciens carrying the symbiotic plasmid of Rhizobium meliloti (37) or with an exopolysaccharide-deficient mutant of R. meliloti (13). As such, it can be considered a "primitive" type of infection.…”

Section: Discussionmentioning

confidence: 99%

Root nodulation of Sesbania rostrata

et al. 1994

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The tropical legume Sesbania rostrata can be nodulated by Azorhizobium caulinodans on both its stem and its root system. Here we investigate in detail the process of root nodulation and show that nodules develop exclusively at the base of secondary roots. Intercellular infection leads to the formation of infection pockets, which then give rise to infection threads. Concomitantly with infection, cortical cells of the secondary roots dedifferentiate, forming a meristem which has an "open-basket" configuration and which surrounds the initial infection site. Bacteria are released from the tips of infection threads into plant cells via "infection droplets," each containing several bacteria. Initially, nodule differentiation is comparable to that of indeterminate nodules, with the youngest meristematic cells being located at the periphery and the nitrogen-fixing cells being located at the nodule center. Because of the peculiar form of the meristem, Sesbania root nodules develop uniformly around a central axis. Nitrogen fixation is detected as early as 3 days following inoculation, while the nodule meristem is still active. Two weeks after inoculation, meristematic activity ceases, and nodules then show the typical histology of determinate nodules. Thus, root nodule organogenesis in S. rostrata appears to be intermediate between indeterminate and determinate types.

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Section: Discussionmentioning

confidence: 99%

Root nodulation of Sesbania rostrata

et al. 1994

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“…Thirty plants were inoculated by this method. All plantlets formed exclusively ineffective nodules, which showed the typical empty nodule morphology (Finan et al, 1985;Leigh et al, 1987;Niehaus and Puhler, 1988;Muller et al, 1988). These results indicated that the nodulation mutant above the filter was unable to assist the infection mutant to invade alfalfa nodules.…”

Section: The Formation Of Alfalfa Nodules Infected By Lnf~epsã Nd Nodmentioning

confidence: 99%

“…infection mutants showed altered exopolysaccharide (EPS) production (Müller et al, 1988). Other researchers, therefore, name such mutants Exo mutants (Finan et al, 1985;Leigh et al, 1985;Long, McCune, and Walker, 1988). In infection mutants, the inability to synthesize EPS results from mutations on megaplasmid 2 (Finan et al, 1986;Hynes et al, 1986) or on the chromosome Finan et al, 1986).…”

Section: Introductionmentioning

confidence: 99%

“…The nodulation and host specificity genes have been identified and located on megaplasmid 1, the symbiotic plasmid of R. meliloti (Banfalvi et al, 1981;Rosenberg et al, 1981). In the second class are infection mutants (Inf-) that are capable of nodule formation, although the typical infection threads do not form (Finan et al, 1985;Leigh et al, 1987;Müller et al, 1988;Niehaus and Pühler, 1988;Putnoky et al, 1988). These nodules are termed empty nodules because the central nodule tissue is devoid of bacteroids.…”

Section: Introductionmentioning

confidence: 99%

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Cooperative Action of Rhizobium meliloti Nodulation and Infection Mutants during the Process of Forming Mixed Infected Alfalfa Nodules.

et al. 1990

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Alfalfa plants co-inoculated with Rhizobium meliloti nodulation (Nod-) and infection mutants deficient in exopolysaccharide production (Inf-EPS) formed mixed infected nodules that were capable of fixing atmospheric nitrogen. The formation of infected nodules was dependent on close contact between the inoculation partners. When the partners were separated by a filter, empt) Fix-nodules were formed, suggesting that infection thread formation in alfalfa is dependent on signals from the nodulation and infection genes. In rnixed infected nodules, both nodulation and infection mutants colonized the plant cells and differentiated into bacteroids. The formation of bacteroids was not dependent on cell-to-cell contact between the mutants. Immunogold/silver staining revealed that the ratio of the two mutants varied considerably in colonized plant cells following mixed inoculation. The introduction of an additional niflfix mutation into one of the inoculation partners did not abolish nitrogen fixation in mixed infected nodules. The expression of nif D::lacZ fusions additionally demonstrated that mutations in the nodulation and infection genes did not prevent the nif genes from being expressed in the mutant bacteroids.

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“…For several Rhizohium strains, a correlation has been established between LPS structure, resistance to bacteriophages and the ability to fix nitrogen in legume root nodules (Kleczkowska, 1950(Kleczkowska, , 1965Zaj?c & Lorkiewicz, 1983). Mutants with altered extracellular polysaccharide biosynthesis have also been reported to have altered capabilities for infection or symbiotic nitrogen fixation (Johansen et al, 1984;Finan et al, 1985).…”

Section: Introductionmentioning

confidence: 99%

Analysis of Lipopolysaccharide from Root Nodule Bacteroids of Rhizobium leguminosarum Using Monoclonal Antibodies

et al. 1986

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Monoclonal antibodies (McAb) that react with components of the bacteroid cell wall were isolated after immunization of rats with sonicated Rhizohium bacteroids from pea root nodules. More than 90% of the McAb reacted with lipopolysaccharides (LPS) from bacteroids and all of these cross-reacted with LPS from free-living cultures of the corresponding Rhizohium strains. Although LPS derived from free-living cultures of Rhizohium is very heterogeneous, detected as a ladder of immuno-staining bands after SDS-PAGE and electroblotting, the LPS from bacteroids is predominantly of the fast-migrating form. This observation suggests that LPS from bacteroids carries the core polysaccharide but lacks the repeating 0-antigen oligosaccharide substituents that are usually found in free-living cultures. Three classes of McAb differed in their specificity for different Rhizohium strains, and differences in antigenicity were also observed between bacteroid and free-living cultures of the same strain.

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Symbiotic mutants of rhizobium meliloti that uncouple plant from bacterial differentiation

Cited by 316 publications

References 32 publications

Root nodulation of Sesbania rostrata

Root nodulation of Sesbania rostrata

Cooperative Action of Rhizobium meliloti Nodulation and Infection Mutants during the Process of Forming Mixed Infected Alfalfa Nodules.

Analysis of Lipopolysaccharide from Root Nodule Bacteroids of Rhizobium leguminosarum Using Monoclonal Antibodies

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