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  • 1
    Electronic Resource
    Electronic Resource
    Changes in the glycosylation pattern at the reducing end of azorhizobial Nod factors affect nodulation efficiency (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 158 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The Nod factors of Azorhizobium caulinodans ORS571 are lipo-chitooligosaccharides that at the reducing end can be unsubstituted, substituted with a l-fucosyl group, with a d-arabinose, or with both groups at the same time. These lipo-chitooligosaccharides are the compounds produced by the bacteria during the signal exchange with their host plant at the onset of the nodulation process. By the use of wild-type and mutant strains, the role of the different Nod factor glycosylations on the nodulation behavior was checked. The mere presence of the d-arabinosyl group at the reducing end of the lipo-chitooligosaccharides resulted in a higher number of nodules on roots of Sesbania rostrata, whereas the presence or absence of l-fucose had no effect. The situation is the opposite in other tropical legumes that respond to A. caulinodans ORS571: the l-fucose is the major determinant of nodulation, whereas the presence of d-arabinose is less significant. By the use of a β-glucuronidase reporter fusion, A. caulinodans ORS571 was shown to colonize nodules or nodule-like tissues induced on cowpea and bean, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb12826.x
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  • 2
    Electronic Resource
    Electronic Resource
    Structural characterization of extracellular polysaccharides of Azorhizobium caulinodans and importance for nodule initiation on Sesbania rostrata (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 52 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: During lateral root base nodulation, the microsymbiont Azorhizobium caulinodans enters its host plant, Sesbania rostrata, via the formation of outer cortical infection pockets, a process that is characterized by a massive production of H2O2. Infection threads guide bacteria from infection pockets towards nodule primordia. Previously, two mutants were constructed that produce lipopolysaccharides (LPSs) similar to one another but different from the wild-type LPS, and that are affected in extracellular polysaccharide (EPS) production. Mutant ORS571-X15 was blocked at the infection pocket stage and unable to produce EPS. The other mutant, ORS571-oac2, was impaired in the release from infection threads and was surrounded by a thin layer of EPS in comparison to the wild-type strain that produced massive amounts of EPS. Structural characterization revealed that EPS purified from cultured and nodule bacteria was a linear homopolysaccharide of α-1,3-linked 4,6-O-(1-carboxyethylidene)-d-galactosyl residues. In situ H2O2 localization demonstrated that increased EPS production during early stages of invasion prevented the incorporation of H2O2 inside the bacteria, suggesting a role for EPS in protecting the microsymbiont against H2O2. In addition, ex planta assays confirmed a positive correlation between increased EPS production and enhanced protection against H2O2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.03989.x
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  • 3
    Electronic Resource
    Electronic Resource
    Role of nodl and nodj in lipo-chitooligosaccharide secretion in Azorhizobium caulinodans and Escherichia coli (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 20 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Lipo-chitooligosaccharide (LCO) Nod factors are produced and secreted by rhizobia and trigger nodule development in leguminous host plants. The products of the bacterial nodlJ genes are related to transporters of capsular polysaccharides and were proposed to be involved in LCO transport. We have studied nodlJ of Azorhizobium caulinodans ORS571 by analysis of cell-associated and secreted radioactively labelled Nod factors in wild-type ORS571, a nodJ mutant and a complemented strain. Secretion was strongly reduced in the nodJ mutant, and restored to wild-type levels after complementation. Constructs were made for expression of combinations of different nod genes in Escherichia coli DH5a. The strain DH5α(pUCNABCSU) synthesized LCOs, but they were only secreted when a plasmid containing both nodl and nodJ was supplied in trans, nodi or nodJ alone was not sufficient. In E. coli as well as in Azorhizobium, the nod/J-encoded transporter showed a specificity for more hydrophilic LCOs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02540.x
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  • 4
    Electronic Resource
    Electronic Resource
    Fucosylation and arabinosylation of Nod factors in Azorhizobium caulinodans: involvement of nolKnodZ as well as noeC and/or downstream genes (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 21 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The DNA region downstream of the nodABCSUIJ operon of Azorhizobium caulinodans was further characterized and two new genes, nodZ and noeC were identified in the same operon. The A. caulinodans wild-type strain produces a population of Nod factors that, at the reducing end, are either unmodified or carry a D-arabinosyl and/or an L-fucosyl branch. Nod factors produced by Tn5-insertion mutants in nodZnoeC, and the separate nolK locus, were analysed by thin-layer chromatography and mass spectrometry. Fucosylation of Nod factors depended on both nodZ and nolK. Arabinosylation depended on noeC and/or downstream genes. Protein extracts of A. caulinodans contained an enzymatic activity for fucose transfer from GDP-fucose to chitooligosaccharides and to Nod factors. By mutant analysis and expression of nodZ in Escherichia coli, the fucosyltransferase activity was ascribed to the protein encoded by nodZ. In addition, a Nod factor fucosyltransferase activity, independent of nodZ or other known nod genes, was detected in A. caulinodans. Finally, on the basis of sequence similarity of the nolK gene product, and mass spectrometric analysis of Nod factors produced by a nolK mutant, we propose that this gene is involved in the synthesis of GDP-fucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.6451366.x
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    Paper (German National Licenses)
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