Host Specificity ofRhizobium leguminosarumis Determined by the Hydrophobicity of Highly Unsaturated Fatty Acyl Moieties of the Nodulation Factors

1995 ◽  
Vol 8 (1) ◽  
pp. 155 ◽  
Author(s):  
Herman P Spaink
Keyword(s):  
Host Specificity ◽  
Fatty Acyl ◽  
Nodulation Factors

A central domain of Rhizobium NodE protein mediates host specificity by determining the hydrophobicity of fatty acyl moieties of nodulation factors

1995 ◽  
Vol 16 (6) ◽  
pp. 1123-1136 ◽  
Author(s):  
Guido V. Bloemberg ◽  
Eric Kamst ◽  
Marga Harteveld ◽  
Koen M. G. M. Drift ◽  
Johan Haverkamp ◽  
...  
Keyword(s):  
Host Specificity ◽  
Fatty Acyl ◽  
Central Domain ◽  
Nodulation Factors

scholarly journals Competitive Nodulation Blocking of cv. Afghanistan Pea Is Related to High Levels of Nodulation Factors Made by Some Strains of Rhizobium leguminosarum bv. viciae

2002 ◽  
Vol 15 (1) ◽  
pp. 60-68 ◽  
Author(s):  
Bridget Hogg ◽  
Andrea E. Davies ◽  
Karen E. Wilson ◽  
Ton Bisseling ◽  
J. Allan Downie
Keyword(s):  
Gene Expression ◽  
Host Specificity ◽  
Rhizobium Leguminosarum ◽  
Gene Region ◽  
Nod Factors ◽  
Nod Factor ◽  
Present Evidence ◽  
Factor Production ◽  
Nodulation Factors ◽  
Nod Gene Expression

Cultivar Afghanistan peas are resistant to nodulation by many strains of Rhizobium leguminosarum bv. viciae but are nodulated by strain TOM, which carries the host specificity gene nodX. Some strains that lack nodX can inhibit nodulation of cv. Afghanistan by strain TOM. We present evidence that this “competitive nodulation-blocking” (Cnb) phenotype may result from high levels of Nod factors inhibiting nodulation of cv. Afghanistan peas. The TOM nod gene region (including nodX) is cloned on pIJ1095, and strains (including TOM itself) carrying pIJ1095 nodulate cv. Afghanistan peas very poorly but can nodulate other varieties normally. The presence of pIJ1095, which causes increased levels of Nod factor production, correlates with Cnb. Nodulation of cv. Afghanistan by TOM is also inhibited by a cloned nodD gene that increases nod gene expression and Nod factor production. Nodulation of cv. Afghanistan can be stimulated if nodD on pIJ1095 is mutated, thus severely reducing the level of Nod factor produced. Repression of nod gene expression by nolR eliminates the Cnb phenotype and can stimulate nodulation of cv. Afghanistan. Addition of Nod factors to cv. Afghanistan roots strongly inhibits nodulation. The Cnb+ strains and added Nod factors inhibit infection thread initiation by strain TOM. The sym2A allele determines resistance of cv. Afghanistan to nodulation by strains of R. leguminosarum bv. viciae lacking nodX. We tested whether sym2A is involved in Cnb by using a pea line carrying the sym2A region introgressed from cv. Afghanistan; nodulation in the introgressed line was inhibited by Cnb+ strains. Therefore, the sym2A region has an effect on Cnb, although another locus (or loci) may contribute to the stronger Cnb seen in cv. Afghanistan.

Microstructural morphology of sphingolipid dispersions as investigated by freeze-fracture EM

1995 ◽  
Vol 53 ◽  
pp. 944-945
Author(s):  
Vitthal S. Kulkarni ◽  
Wayne H. Anderson ◽  
Rhoderick E. Brown
Keyword(s):  
Acyl Chain ◽  
Biological Significance ◽  
Freeze Fracture ◽  
Fatty Acyl ◽  
Fatty Acyl Moiety ◽  
Aqueous Dispersions ◽  
Head Groups ◽  
Lipid Species ◽  
Microstructural Morphology ◽  
Layer Chromatography

The biological significance of the sphingomyelins (SM) and monoglycosylated sphingolipids like galactosylceramides (GalCer) are well documented Our recent investigation showed tubular bilayers in the aqueous dispersions of N-nervonoyl GalCer [N-(24:lΔ15,cls) GalCer] (a major fatty acyl moiety of natural GalCer). To determine the influence of lipid head groups on the resulting mesophasic morphology, we investigated microstructural self-assemblies of N-nervonoyl-SM [N-(24:1 Δ15,cls) SM; the second most abundant sphingomyelin in mammalian cell membranes], 1- palmitoyl-2-nervonoyl phosphatidylcholine [PNPC] (the lipid species with the same acyl chain configuration as in N-(24: 1) GalCer) and also compared it with egg-SM by freeze-fracture EM.Procedures for synthesizing and purifying N-(24:1) GalCer, N-(24:1) SM, and PNPC have been reported . Egg-SM was purchased from Avanti Polar Lipids, Alabaster AL. All lipids were >99% pure as checked by thin layer chromatography. Lipid dispersions were prepared by hydrating dry lipid with phosphate buffer (pH 6.6) at 80-90°C (3-5 min), vigorously vortexing (1 min) and repeating this procedure for three times prior to three freeze-thaw cycles.

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