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.

scholarly journals Oleanolic Acid Induces the Type III Secretion System of Ralstonia solanacearum

2015 ◽  
Vol 6 ◽  
Author(s):  
Dousheng Wu ◽  
Wei Ding ◽  
Yong Zhang ◽  
Xuejiao Liu ◽  
Liang Yang
Keyword(s):  
Oleanolic Acid ◽  
Ralstonia Solanacearum ◽  
Type Iii Secretion ◽  
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 Two Type III Secretion System Effectors from Ralstonia solanacearum GMI1000 Determine Host-Range Specificity on Tobacco

2009 ◽  
Vol 22 (5) ◽  
pp. 538-550 ◽  
Author(s):  
Marie Poueymiro ◽  
Sébastien Cunnac ◽  
Patrick Barberis ◽  
Laurent Deslandes ◽  
Nemo Peeters ◽  
...  
Keyword(s):  
Host Range ◽  
Ralstonia Solanacearum ◽  
Type Iii Secretion ◽  
Tandem Repeats ◽  
Hypervariable Region ◽  
Type Iii Secretion System ◽  
Defense Responses ◽  
Secretion System ◽  
Tobacco Plants ◽  
Type Iii

The model pathogen Ralstonia solanacearum GMI1000 is the causal agent of the bacterial wilt disease that attacks many solanaceous plants and other hosts but not tobacco (Nicotiana spp.). We found that two type III secretion system effector genes, avrA and popP1, are limiting the host range of strain GMI1000 on at least three tobacco species (N. tabacum, N. benthamiana, and N. glutinosa). Both effectors elicit the hypersensitive response (HR) on these tobacco species, although in different manners; AvrA is the major determinant recognized by N. tabacum and N. benthamiana, while PopP1 appears to be the major HR elicitor on N. glutinosa. Only the double inactivation of the avrA and popP1 genes allowed GMI1000 to wilt tobacco plants, thus showing that GMI1000 intrinsically possesses the functions necessary to wilt tobacco plants. A focused analysis on AvrA revealed that the first 58 N-terminal amino acids are sufficient to direct its injection into plant cells. We identified a hypervariable region in avrA, which contains variable numbers of tandem repeats (VNTR), each composed of 12 base pairs. We show that an 18–amino acid region in which the VNTR insertion occurs is an important domain involved in HR elicitation on N. benthamiana. avrA appears to be the target of various DNA insertions or mobile elements that probably allow R. solanacearum to evade the recognition and defense responses of tobacco.

scholarly journals Involvement of a PadR regulator PrhP on virulence of Ralstonia solanacearum by controlling detoxification of phenolic acids and type III secretion system

2019 ◽  
Vol 20 (11) ◽  
pp. 1477-1490 ◽  
Author(s):  
Yong Zhang ◽  
Weiqi Zhang ◽  
Liangliang Han ◽  
Jing Li ◽  
Xiaojun Shi ◽  
...  
Keyword(s):  
Phenolic Acids ◽  
Ralstonia Solanacearum ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Type Iii

scholarly journals Functional Characterization of RsRsgA for Ribosome Biosynthesis and Expression of the Type III Secretion System in Ralstonia solanacearum

2020 ◽  
Vol 33 (7) ◽  
pp. 972-981
Author(s):  
Jiaman Li ◽  
Liangliang Han ◽  
Nan Chen ◽  
Chao Zhu ◽  
Yuwei Gao ◽  
...  
Keyword(s):  
Ralstonia Solanacearum ◽  
Type Iii Secretion ◽  
Functional Characterization ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
In Planta ◽  
Tobacco Leaves ◽  
Type Iii ◽  
30S Subunit ◽  
Ribosome Biosynthesis

RsgA plays an important role in maturation of 30S subunit in many bacteria that assists in the release of RbfA from the 30S subunit during a late stage of ribosome biosynthesis. Here, we genetically characterized functional roles of RsgA in Ralstonia solanacearum, hereafter designated RsRsgA. Deletion of R. solanacearum rsgA or rbfA resulted in distinct deficiency of 16S ribosomal RNA, significantly slowed growth in broth medium, and diminished growth in nutrient-limited medium, which are similar as phenotypes of rsgA mutants and rbfA mutants of Escherichia coli and other bacteria. Our gene-expression studies revealed that RsRsgA is important for expression of genes encoding the type III secretion system (T3SS) (a pathogenicity determinant of R. solanacearum) both in vitro and in planta. Compared with the wild-type R. solanacearum strain, proliferation of the rsgA and rbfA mutants in tobacco leaves was significantly impaired, while they failed to migrate into tobacco xylem vessels from infiltrated leaves, and hence, these two mutants failed to cause any bacterial wilt disease in tobacco plants. It was further revealed that rsgA expression was highly enhanced under nutrient-limited conditions compared with that in broth medium and RsRsgA affects T3SS expression through the PrhN-PrhG-HrpB pathway. Moreover, expression of a subset of type III effectors was substantially impaired in the rsgA mutant, some of which are responsible for R. solanacearum GMI1000 elicitation of a hypersensitive response (HR) in tobacco leaves, while RsRsgA is not required for HR elicitation of GMI1000 in tobacco leaves. All these results provide novel insights into understanding various biological functions of RsgA proteins and complex regulation on the T3SS in R. solanacearum.

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