Nodulation host specificity

Z. Banfalvi and A. Kondorosi, Production of root hair deformation factors by Rhizohium meliloti nodulation genes in Escherichia coli H.mD (NocM) is involved in the plant host-specific modification of the NodABS-factor. Plant Mol. Biol. 13 1 (1989). 

J. A. Downie, A. Economou, A. K. Scheu, A. W. B. John.son, J. L. Firmin, K. E. Wilson, M. T. Cubo, A. Mavridou, C. Marie, A. Davies and B. P. Surin, The Rhizohium legumino.sarum bv. viciae NodO protein compensates for the exported signal made by the host-specific nodulation genes. Nitrogen Fixation Achievements and... 

G. V. Bloembcrg, E. Kamst, M. Hartevcid, K. M. G. M. van der Drift, J. Haverkamp, J, E. Thomas-Oates, B. J. J. Lugtenberg, and H. P. Spaink. A central domain of Rhizobium NodE protein mediates host specificity by determining the hydropho-bicity of fatty acyl moieties of nodulation factors. Mol. Microbiol. I6 123 (1995). 

The fact that rhizobia can be aborted from infection threads shows (40) that a continuous declaration of identity is necessary throughout the travel, consisting in the exposure of specific surface EPS determinants, in the absence of which the transfer is interrupted. Host specificity between rhizobium and legumes is therefore played at two main levels a chitolipooligosaccharide password, acting at a distance, and an exopolysaccharide passport to be exhibited by the bearer in its trip to the awaiting nodule (40). 

Spaink, H.P. et al., Rhizobium nodulation gene nodD as a determinant of host specificity, Nature, 328, 337, 1987. 

Horvath B., Bachem, C.W.B., Schell, J. Kondorosi, A. (1987). Host-specific regulation of nodulation genes in Rhizobium is mediated by a plant-signal interacting with the nodD gene product. The EM BO Journal 6, 841-8. 

M-acetyl glucosamine chitin oligosaccharides (NA-COSs) play a crucial role in plant biotechnology, secondary metabolites production, plant resistance (chitin in cell walls), and symbiotic bacteria released in root nodules for nitrogen fixation (Asaoka 1996). It has an estabUshment of a host-specific symbiosis between legumes, and their rhizobia were determined in plants (Cohn et al. 1998). 

It is a characteristic of the rhizobium-legume symbiosis that the bacteria exhibit great specificity in their choice of host, indeed the genus Rhizobium is divided into species on the ability of the strain to form nodules in specific plant species (Table 6.1). Inter-species and inter-strain nodulation may occur, although often the nodules produced are atypical and fail to fix nitrogen effectively. 

The economic importance of nitrogen-fixation by leguminous plants has led to extensive study of the process of nodulation and in particular the nature of the host specificity of Rhizobium. Antiserum raised to clover tissue reacts with virulent strains of R. trifolii and to a lesser extent with avirulent strains of the same organism. If the antiserum is pretreated with avirulent cells a purified antibody, specific for the virulent strain, can be prepared. The purified antisera will bind to R. trifolii virulent strains and clover cells, but not to incompatible Rhizobium species. Immunofluorescence can be used to demonstrate that antisera raised against the capsular polysaccharide of R. trifolii binds to the surface of clover root cells, in particular to the tips of the root hairs. Chemical analysis of this capsule shows that it... 

Albrecht, C., Geurts, R. and Bisseling, T. (1999) Legume nodulation and mycorrhizae formation two extremes in host specificity meet. EMBO J. 

S. R. Long, In vitro sulfotransferase activity of NodH, a nodulation protein of Rhizobium meliloti required for host-specific nodulation. J. Bacterial 1995 177, 6237-6245. 

Initially, a single species of bacterium was thought to infect and induce nodules on all l umes. However, between 1930to 1940 several studies demonstrated that only certain strains of Rhizobium induce nodules on specific legume hosts. This specificity was the basis of the cross-inoculation concept of... 

The Rhizobium-legume symbiosis, an interaction between a prokaryote (Rhizobium) and a eukaryote (legume), requires a series of sequential induction and function of both bacterium-encoded (bac-teroidins) and host-encoded (nodulins) nodule-specific proteins. It has been shown that many plant (Peters et al., 1986 Firmin et al., 1986 Djordjevic et al., 1987 Sadowsky et al., 1988 see also Peters Verma,... 

Successful infection proceeds simultaneously with nodule morphogenesis triggered by the signal compounds produced by Rhizobium in response to its host, and leads to the release of bacteria from the infection threads into the cortical cells. Concomitantly, the bacteria are enveloped in a host-derived plasma membrane called the peribacteroid membrane (PBM) (Verma et al., 1978 Robertson et al., 1978). Both host- and bacterium-derived proteins are specifically targeted to this membrane (Fortin et al., 1985, 1987 Katinakis Verma, 1985 Katinakis et al., 1988), making it a unique subcellular compartment. 

For an effective symbiotic state, the plant and the microsymbiont must maintain a constant metabolic flow of carbon and nitrogen. While the bacteroids function as an engine for nitrogen fixation the fuel comes from the plant. Dicarboxylic acids are the primary carbon sources fed to the bacteroids by the plant. This unidirectional flow of carbon must be controlled by the PBM. Recently, several specific carbon and amino acid transport systems have been identified in the PBM using isolated peribac-teroid units (PBU Day et al., 1990). Thus, in order for the host plant to house endosymbiotic bacteria and support their metabolic needs, a number of nodulin genes must be induced to support the ontogeny and function of the nodules. 

Once an appropriate Rhizobium species infects the host plant roots, the plant responds by sequentially turning on a set of specific genes which are required for nodule formation and function. A number of nodule-specific... 

Ammonium, the primary product of nitrogen fixation, is transported to the host cell cytoplasm where it is assimilated into amides and, in some cases, further converted into ureides before being transported to the shoot. Since the physiological environment within the nodule is apparently different from the other parts of the plant, nodule-specific or nodule-abundant forms of several enzymes of the nitrogen and carbon assimilation pathways have evolved, and are induced to improve the efficiency of nitrogen and carbon metabolism in nodules. 

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