Xanthomonas Campestris Pv. Campestris (xanthomonas + campestri_pv._campestri)

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Selected Abstracts

Isolation and Characterization of a Porin-Like Outer Membrane Protein from Xanthomonas campestris pv. campestris

IUBMB LIFE, Issue 1 2002
Lingyun Wang
Abstract Xanthomonas campestris pv. campestris, a plant-associated pathogenic bacterium, is the causal agent of foliar spots and blights in crucifers. The major outer membrane protein, Omp37, of 37 kDa, has been identified, purified to homogeneity, and its characterization has also been carried out. Native Omp37 behaved as a trimer, as revealed by gel filtration and SDS-PAGE. FTIR measurements revealed a high ,-structure content. The pore-forming ability of the purified Omp37 was studied by the liposome swelling assay. Omp37, to our knowledge, is the first porin that has been isolated from Xanthomonas . This study clearly demonstrates that Omp37 is related to the family of trimeric bacterial porins. [source]

Co-regulation of Xanthomonas campestris virulence by quorum sensing and a novel two-component regulatory system RavS/RavR

Ya-Wen He
Summary Xanthomonas campestris pv. campestris (Xcc) is known to regulate virulence through a quorum-sensing mechanism. Detection of the quorum-sensing signal DSF by sensor RpfC leads to activation of the response regulator RpfG, which influences virulence by degrading cyclic-di-GMP and by subsequent increasing expression of the global regulator Clp. In this study, we show that mutation of a response regulator RavR containing the GGDEF,EAL domains decreases Xcc virulence factor production. The functionality of RavR is dependent on its EAL domain-associated cyclic-di-GMP phosphodiesterase activity. Deletion of a multidomain sensor gene ravS, which shares the same operon with ravR, results in similar phenotype changes as the ravR mutant. In addition, the sensor mutant phenotypes can be rescued by in trans expression of the response regulator, supporting the notion that RavS and RavR constitute a two-component regulatory system. Significantly, mutation of either the PAS domain or key residues of RavS implicated in sensing low-oxygen tension abrogates the sensor activity in virulence regulation. Moreover, similar to the DSF signalling system, RavS/RavR regulates virulence gene expression through the global regulator Clp. These results outline a co-regulation mechanism that allows Xcc to integrate population density and environmental cues to modulate virulence factor production and adaptation. [source]

Optimization of pathogenicity assays to study the Arabidopsis thaliana,Xanthomonas campestris pv. campestris pathosystem

SUMMARY The cruciferous weed Arabidopsis thaliana and the causal agent of black rot disease of Crucifers Xanthomonas campestris pv. campestris (Xcc) are both model organisms in plant pathology. Their interaction has been studied successfully in the past, but these investigations suffered from high variability. In the present study, we describe an improved Arabidopsis,Xcc pathosystem that is based on a wound inoculation procedure. We show that after wound inoculation, Xcc colonizes the vascular system of Arabidopsis leaves and causes typical black rot symptoms in a compatible interaction, while in an incompatible interaction bacterial multiplication is inhibited. The highly synchronous and reproducible symptom expression allowed the development of a disease scoring scheme that enabled us to analyse the effects of mutations in individual genes on plant resistance or on bacterial virulence in a simple and precise manner. This optimized Arabidopsis,Xcc pathosystem will be a robust tool for further genetic and post-genomic investigation of fundamental questions in plant pathology. [source]

The apo structure of sucrose hydrolase from Xanthomonas campestris pv. campestris shows an open active-site groove

Elise Champion
Glycoside hydrolase family 13 (GH-13) mainly contains starch-degrading or starch-modifying enzymes. Sucrose hydrolases utilize sucrose instead of amylose as the primary glucosyl donor. Here, the catalytic properties and X-ray structure of sucrose hydrolase from Xanthomonas campestris pv. campestris are reported. Sucrose hydrolysis catalyzed by the enzyme follows Michaelis,Menten kinetics, with a Km of 60.7,mM and a kcat of 21.7,s,1. The structure of the enzyme was solved at a resolution of 1.9, in the resting state with an empty active site. This represents the first apo structure from subfamily 4 of GH-13. Comparisons with structures of the highly similar sucrose hydrolase from X. axonopodis pv. glycines most notably showed that residues Arg516 and Asp138, which form a salt bridge in the X. axonopodis sucrose complex and define part of the subsite ,1 glucosyl-binding determinants, are not engaged in salt-bridge formation in the resting X. campestris enzyme. In the absence of the salt bridge an opening is created which gives access to subsite ,1 from the `nonreducing' end. Binding of the glucosyl moiety in subsite ,1 is therefore likely to induce changes in the conformation of the active-site cleft of the X. campestris enzyme. These changes lead to salt-bridge formation that shortens the groove. Additionally, this finding has implications for understanding the molecular mechanism of the closely related subfamily 4 glucosyl transferase amylosucrase, as it indicates that sucrose could enter the active site from the `nonreducing' end during the glucan-elongation cycle. [source]

Crystallization and preliminary X-ray diffraction characterization of an essential protein from Xanthomonas campestris that contains a noncanonical PilZ signature motif yet is critical for pathogenicity

Tso-Ning Li
Recent studies have identified c-di-GMP as a novel secondary messenger molecule that is heavily involved in regulating bacterial biofilm formation, motility, production of pathogenicity factors etc. PilZ domain-containing proteins have been suggested and subsequently proved to be the c-di-GMP receptor. However, considering the diverse biological functions exhibited by c-di-GMP, it may be that receptors other than the PilZ domain exist. An essential protein from the plant pathogen Xanthomonas campestris pv. campestris (Xcc) that contains a noncanonical PilZ signature motif yet is critical for Xcc pathogenicity has been cloned, purified and crystallized. Detailed characterization of this protein may reveal an alternative binding mode of c-di-GMP and allow a more thorough understanding of how c-di-GMP exhibits its diverse effects. [source]