scholarly journals HrpB4 from Xanthomonas campestris pv. vesicatoria acts similarly to SctK proteins and promotes the docking of the predicted sorting platform to the type III secretion system

2021 ◽  
Author(s):  
Christian Otten ◽  
Daniela Büttner
Keyword(s):  
Type Iii Secretion ◽  
Xanthomonas Campestris ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Type Iii

scholarly journals The Type III Secretion System of Xanthomonas fuscans subsp. fuscans Is Involved in the Phyllosphere Colonization Process and in Transmission to Seeds of Susceptible Beans

2008 ◽  
Vol 74 (9) ◽  
pp. 2669-2678 ◽  
Author(s):  
A. Darsonval ◽  
A. Darrasse ◽  
D. Meyer ◽  
M. Demarty ◽  
K. Durand ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Xanthomonas Campestris ◽  
Pathogenic Bacteria ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Regulatory Genes ◽  
Population Densities ◽  
Host Colonization ◽  
Plant Pathogenic Bacteria ◽  
Type Iii

ABSTRACT Understanding the survival, multiplication, and transmission to seeds of plant pathogenic bacteria is central to study their pathogenesis. We hypothesized that the type III secretion system (T3SS), encoded by hrp genes, could have a role in host colonization by plant pathogenic bacteria. The seed-borne pathogen Xanthomonas fuscans subsp. fuscans causes common bacterial blight of bean (Phaseolus vulgaris). Directed mutagenesis in strain CFBP4834-R of X. fuscans subsp. fuscans and bacterial population density monitoring on bean leaves showed that strains with mutations in the hrp regulatory genes, hrpG and hrpX, were impaired in their phyllospheric growth, as in the null interaction with Escherichia coli C600 and bean. In the compatible interaction, CFBP4834-R reached high phyllospheric population densities and was transmitted to seeds at high frequencies with high densities. Strains with mutations in structural hrp genes maintained the same constant epiphytic population densities (1 × 105 CFU g−1 of fresh weight) as in the incompatible interaction with Xanthomonas campestris pv. campestris ATCC 33913 and the bean. Low frequencies of transmission to seeds and low bacterial concentrations were recorded for CFBP4834-R hrp mutants and for ATCC 33913, whereas E. coli C600 was not transmitted. Moreover, unlike the wild-type strain, strains with mutations in hrp genes were not transmitted to seeds by vascular pathway. Transmission to seeds by floral structures remained possible for both. This study revealed the involvement of the X. fuscans subsp. fuscans T3SS in phyllospheric multiplication and systemic colonization of bean, leading to transmission to seeds. Our findings suggest a major contribution of hrp regulatory genes in host colonization processes.

scholarly journals Characterization of the cis-Acting Regulatory Element Controlling HrpB-Mediated Activation of the Type III Secretion System and Effector Genes in Ralstonia solanacearum

2004 ◽  
Vol 186 (8) ◽  
pp. 2309-2318 ◽  
Author(s):  
Sébastien Cunnac ◽  
Christian Boucher ◽  
Stéphane Genin
Keyword(s):  
Ralstonia Solanacearum ◽  
Type Iii Secretion ◽  
Xanthomonas Campestris ◽  
Consensus Sequence ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Site Directed Mutagenesis ◽  
Critical Parameters ◽  
Type Iii ◽  
Regulated Promoters

ABSTRACT The ability of Ralstonia solanacearum to cause disease on plants depends on its type III secretion system (TTSS) encoded by hrp genes. The expression of hrp genes and known TTSS substrates is coordinately regulated by HrpB, a member of the AraC family of transcriptional regulators. Two HrpB-regulated promoters (hrpY and popABC) were characterized by deletion analysis, and the HrpB-dependent activation of these promoters was found to be conferred by a 25-nucleotide DNA element, the hrp II box (TTCGn16TTCG), which is present in other hrp promoters. The hrp II box element is an imperfect plant inducible promoter box, an element which was originally found in hrp promoters of Xanthomonas campestris (S. Fenselau and U. Bonas, Mol. Plant-Microbe Interact. 8:845-854, 1995) but which was not characterized at the molecular level. Site-directed mutagenesis showed that the hrp II box is essential for hrpY promoter activation in vivo. Functional analysis of the hrp II box element identified critical parameters that are required for HrpB-dependent activity. Further mapping analyses of several other hrpB-dependent promoters also indicated that the position of the hrp II box is conserved, at −70 to −47 bp from the transcriptional start. As a first step toward identifying novel TTSS effectors, we used the hrp II box consensus sequence to search for potential HrpB-regulated promoters in the complete genome sequence of R. solanacearum strain GMI1000. Among the 114 genes identified, a subset of promoters was found to have a structural relationship with hrp promoters, thus providing a pool of candidate genes encoding TTSS effectors.

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