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  • 1
    Electronic Resource
    Electronic Resource
    Structural identification of metabolites produced by the NodB and NodC proteins of Rhizobium leguminosarum (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 13 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Rhizobium nodulation genes nodABC are involved in the synthesis of lipo-chitin oligosac-charides. We have analysed the metabolites which are produced in vivo and in vitro by Rhizobium strains which express the single nodA, nodB and nodC genes or combinations of the three. In vivo radioactive labelling experiments, in which D-[1-14C]-glucosamine was used as a precursor, followed by mass spectrometric analysis of the purified radiolabelled metabolic products, showed that Rhizobium strains that only express the combination of the nodB and nodC genes do not produce lipo-chitin oligosaccharides but instead produce chitin oligomers (mainly pentamers) which are devoid of the N-acetyl group on the non-reducing terminal sugar residue (designated NodBC metabolites). Using the same procedure we have shown that when the nodL gene is expressed in addition to the nodBC genes the majority of metabolites contain an additional O-acetyl substituent on the non-reducing terminal sugar residue (designated NodBCL metabolites). The NodBC and NodBCL metabolites purified after in vivo labelling were compared with the radiolabelled metabolites produced in vitro by Rhizobium bacterial cell lysates to which UDP-N-acetyl-D-[U-14C]-glucosamine was added using thin-layer chromatography. The results show that the lysates of strains which expressed the nodBC or nodBCL genes can also produce NodBC and NodBCL metabolites. The same results were obtained when the NodB and NodC proteins were produced separately in two different strains. On the basis of these and other recent results, we propose that NodB is a chitin oilgosaccharide deacetylase, NodC an N-acetylglucosaminyltransferase and, by default, NodA is involved in lipie attachment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00474.x
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  • 2
    Electronic Resource
    Electronic Resource
    Rhizobium nodulation protein NodA is a host-specific determinant of the transfer of fatty acids in Nod factor biosynthesis (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 44-51 
    Details
    ISSN: 1617-4623
    Keywords: Key words Rhizobium ; Nodulation ; Nod factors ; Acyl transfer ; nodA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In the biosynthesis of lipochitin oligosaccharides (LCOs) the Rhizobium nodulation protein NodA plays an essential role in the transfer of an acyl chain to the chitin oligosaccharide acceptor molecule. The presence of nodA in the nodABCIJ operon makes genetic studies difficult to interpret. In order to be able to investigate the biological and biochemical functions of NodA, we have constructed a test system in which the nodA, nodB and nodC genes are separately present on different plasmids. Efficient nodulation was only obtained if nodC was present on a low-copy-number vector. Our results confirm the notion that nodA of Rhizobium leguminosarum biovar viciae is essential for nodulation on Vicia. Surprisingly, replacement of R. l. bv. viciae nodA by that of Bradyrhizobium sp. ANU289 results in a nodulation-minus phenotype on Vicia. Further analysis revealed that the Bradyrhizobium sp. ANU289 NodA is active in the biosynthesis of LCOs, but is unable to direct the transfer of the R. l. bv. viciae nodFE-dependent multi-unsaturated fatty acid to the chitin oligosaccharide acceptor. These results lead to the conclusion that the original notion that nodA is a common nod gene should be revised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02174343
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  • 3
    Electronic Resource
    Electronic Resource
    Additional nodulation genes on the Sym plasmid of Rhizobium leguminosarum biovar viciae (1989)
    Springer
    Plant molecular biology 13 (1989), S. 163-174 
    Details
    ISSN: 1573-5028
    Keywords: Rhizobium leguminosarum biovar viciae ; nodulation genes ; nodL ; transcription unit ; infection thread
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A Rhizobium leguminosarum biovar viciae strain lacking a 40 kb DNA region of the Sym plasmid pRL1IJ to the left (3′ side) of gene nodE failed to nodulate Vicia sativa plants. Therefore this DNA region was investigated for the presence of additional nodulation genes. Complementation experiments indicated that the DNA region to the left (3′ side) of nodE is functionally homologous between R. leguminosarum bv. viciae and R. leguminosarum bv. trifolii. In this DNA region, three nodulation genes were identified, nodT, nodM and nodL. TnphoA insertions in the nodT gene, about 4.5 kb to the left of nodE, lead to a delay in nodulation on Trifolium subterraneum, but not on V. sativa plants. TnphoA insertions in gene nodM have no detectable influence on nodulation. Finally, TnphoA insertions in the nodL gene affected nodulation so that only rarely nodules were induced on the inoculated plants. The nucleotide sequence of this gene is presented. On the basis of the sequence a membrane integrated protein is predicted with a molecular weight of 20.1 kDa. Microscopical analysis of the infection process by nodL mutants indicate a role for nodL in maintaining the stability of the infection thread. Experiments using transcriptional lacZ fusions suggest that nodL belongs to the same transcriptional unit as nodF,E. Very low expression of nodL seems to be sufficient for biological activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016135
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  • 4
    Electronic Resource
    Electronic Resource
    Role of rhizobial lipo-oligosacharides in root nodule formation on leguminous plants (1994)
    Springer
    Plant and soil 161 (1994), S. 81-89 
    Details
    ISSN: 1573-5036
    Keywords: fatty acid ; nod genes ; phospholipid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During recent years signals leading to the early stages of nodulation of legumes by rhizobia have been identified. Plant flavonoids induce rhizobialnod genes that are essential for nodulation. Most of thenod gene products are involved in the biosynthesis of lipo-oligosaccharide molecules. The commonnodABC genes are minimally required for the synthesis of all lipo-oligosaccharides. Host-specificnod gene products in a givenRhizobium species are responsible for synthesis or addition of various moieties to those basic lipo-oligosaccharide molecules. For example, inR. leguminosarum, thenodFEL operon is involved in the production of lipo-oligosaccharide signals that mediate host specificity. AnodFE-determined highly unsaturated fatty acid (trans-2, trans-4, trans-6, cis-11-octadecatetraenoic acid) is essential for inducing nodule meristems and pre-infection thread structures on the host plantVicia sativa. Lipo-oligosaccharides also trigger autoregulation of nodulation in pea and, if applied in excessive amounts to a legume, can prevent nodulation and thereby might play a role in competition. During our studies on the biosynthesis of lipo-oligosaccharides, we discovered that, besides the lipo-oligosaccharides, other metabolites are synthesizedde novo after induction of thenod genes. These novel metabolites appeared to be phospholipids, containing either one of the three fatty acids which are made by the action of NodFE inR. leguminosarum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02183087
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