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Detection and Visualization of the Major Acidic Exopolysaccharide of Ralstonia solanacearum and its Role in Tomato Root Infection and Vascular Colonization (1998)

Araud-Razou, Isabelle ; Vasse, Jacques ; Montrozier, Henry ; [et al.]

Springer

European journal of plant pathology 104 (1998), S. 795-809

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ISSN: 1573-8469

Keywords: bacterial wilt ; microscopy

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Exopolysaccharides play an important role in the pathogenicity of Ralstonia solanacearum. We compared in vitro and in planta exopolysaccharide production of the pathogenic strain AW1 with that of three related mutant strains impaired in both their exopolysaccharide production and aggressiveness on tomato. The distinction between the two hexosamine-rich exopolysaccharides, namely the N-acetyl-glucosaminorhamnan and the major N-acetyl-galactosamine-containing acidic polymer was emphasized. The major acidic polymer was identified specifically by electron microscopy using glutaraldehyde/ruthenium red/uranyl acetate staining, by immunofluorescence using specific monoclonal antibodies and correlated to an appropriate biochemical analysis. The two mutant strains AW1-1 and AW-19A were totally devoid of any production of the major exopolysaccharide in vitro or in planta whatever the technique used. Infection and vascular colonization of tomato roots by the pathogenic strain were also compared to those of the mutant strains by light microscopy. Pathogenicity on tomato was assessed by root infection without any artificial injury. Light microscopy showed that the two mutant strains AW1-1 and AW-19A were poorly infective and unable to invade xylem vessels, while they induced defence mechanisms in root tissues and appeared aggregated or degenerated within cortical infection pockets. These two mutant strains were non-pathogenic or weakly aggressive, respectively. In contrast, the pathogenic strain AW1 and the hypoaggressive AW1-41 strains, which produce large amounts of the major acidic exopolysaccharide in planta, were both infective and invasive, and tomato root tissues exhibited only limited defence reactions. Thus, the major acidic exopolysaccharide produced by Ralstonia solanacearum is involved in root infection and vascular colonization, though its precise role is still unknown.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008690712318

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Agglutination ofRhizobium japonicum 3I1b110 by soybean lectin (1983)

Truchet, Georges L. ; Dazzo, Frank B. ; Vasse, Jacques

Springer

Plant and soil 75 (1983), S. 265-268

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ISSN: 1573-5036

Keywords: Agglutination ; Lectins ; Rhizobium japonicum ; Soybean

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary Conditions leading to agglutination ofRhizobium japonicum 3I1b110 with soybean seed lectin were examined. Ability of cells to be agglutinated was transient and was optimal for cultures grown for 4–5 days on yeast extract mannitol plates. Similar lectin-binding results were obtained with cells from the same cultures using fluorescence microscopy with fluorescein isothiocyanate-labelled lectin. These results revise the previous model for soybean lectin-R. japonicum interactions, since it was based on the inability of soybean lectin to agglutinate these bacteria.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02375571

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Interactions between bacterial diazotrophs and non-legume dicots: Arabidopsis thaliana as a model plant (1997)

Gough, Clare ; Vasse, Jacques ; Galera, Christine ; [et al.]

Springer

Plant and soil 194 (1997), S. 123-130

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ISSN: 1573-5036

Keywords: Arabidopsis thaliana ; Azorhizobium caulinodans ; flavonoids ; lateral root crack ; nod genes ; rhizobia

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract When interactions between diazotrophic bacteria and non-legume plants are studied within the context of trying to extend biological nitrogen fixation to non-legume crops, an important first step is to establish reproducible internal colonization at high frequency of these plants. Using Azorhizobium caulinodans ORS571 (which induces stem and root nodules on the tropical legume Sesbania rostrata), tagged with a constitutively expressed lacZ reporter gene, we have studied the possibilities of internal colonization of the root system of the model dicot Arabidopsis thaliana. ORS571 was found to be able to enter A. thaliana roots after first colonizing lateral root cracks (LRCs), at the points of emergence of lateral roots. Cytological studies showed that after LRC colonization, bacteria moved into the intercellular space between the cortical and endodermal cell layers of roots. In our experimental conditions, this LRC and intercellular colonization are reproducible and occur at high frequency, although the level of colonization at each site is low. The flavonoids naringenin and daidzein, at low concentrations, were found to significantly stimulate (at the p=0.01 level) the frequency of LRC and intercellular colonization of A. thaliana roots by A. caulinodans. The role in colonization of the structural nodABC genes, as well as the regulatory gene nodD, was studied and it was found that both colonization and flavonoid stimulation of colonization are nod gene-independent. These systems should now enable the various genetic and physiological factors which are limiting both for rhizobial colonization and for endophytic nitrogen fixation in non-legumes, to be investigated. In particular, the use of A. thaliana, which has many advantages over other plants for molecular genetic studies, to study interactions between diazotrophic bacteria and non-legume dicots, should provide the means of identifying and understanding the mechanisms by which plant genes are involved in these interactions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004235919993

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