The role of extracellular polysaccharides as virulence factors for phytopathogenic pseudomonads and xanthomonads

Rudolph, K.; Groß, Michael; Ebrahim‐Nesbat, F.; Nöllenburg, Matthias; Zomorodian, Alim; Wydra, Kerstin; Neugebauer, Michael; Hettwer, Ursula; El-Shouny, Wagih A.; Sonnenberg, Bernd; Klement, Z.

doi:10.1007/978-94-011-0746-4_25

Cited by 32 publications

(33 citation statements)

References 40 publications

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“…This result demonstrated that P. syringae AlgT has a significant impact on in planta growth and virulence while alginate production only seems to be of marginal importance. This contradicts results of some other studies where alginate production had been associated with epiphytic fitness, virulence and symptom development (Fett & Dunn, 1989;Gross & Rudolph, 1987b;Osman et al, 1986;Rudolph et al, 1994;Yu et al, 1999). However, in support of our findings, Beattie & Lindow (1994) identified P. syringae mutants that were EPS-deficient in culture but were indistinguishable from their parental strain with respect to their epiphytic growth and survival.…”

Section: Discussioncontrasting

confidence: 91%

“…syringae alginate production has been associated with increased epiphytic fitness, virulence, resistance to desiccation and toxic molecules, dissemination in planta (Rudolph et al, 1994;Yu et al, 1999) and the induction of water-soaked lesions on infected leaves (Fett & Dunn, 1989). A positive correlation between virulence of P. syringae and the quantity of alginate produced in planta has been demonstrated (Gross & Rudolph, 1987b;Osman et al, 1986).…”

Section: Introductionmentioning

confidence: 99%

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The alternative sigma factor AlgT, but not alginate synthesis, promotes in planta multiplication of Pseudomonas syringae pv. glycinea

2008

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The alternative sigma factor AlgT, but not alginate synthesis, promotes in planta multiplication of Pseudomonas syringae pv. glycinea The phytopathogen Pseudomonas syringae pv. glycinea produces the exopolysaccharide (EPS) alginate, which is thought to function in epiphytic fitness and virulence. A key regulator for alginate biosynthesis in Pseudomonas aeruginosa and P. syringae is the alternative sigma factor AlgT (s 22 ). In this study, the contribution of alginate synthesis and AlgT to in planta epiphytic fitness and virulence of P. syringae was examined. Alginate biosynthesis mutants were generated for the P. syringae pv. glycinea strains PG4180 and PG4180.muc, representing a comprehensive set of alginate-and AlgT-positive or -negative derivatives. Analysis of in vitro and in planta phenotypes revealed that AlgT strongly promoted in planta growth, survival and symptom development, but decreased the ability to grow in vitro. In contrast, alginate biosynthesis had only marginal impact. Quantitative in vitro and in planta gene expression analyses for alginate biosynthesis and algT were carried out at two temperatures in AlgT-negative and -positive backgrounds. algT as well as algD gene expression was AlgT-dependent, plant-inducible and temperature-dependent, with higher expression at 18 compared to 28 6C; however, no temperature dependence was observed in vitro. Our data suggest that AlgT may act as a global regulator for virulence and in planta fitness traits of P. syringae independent of its role in EPS biosynthesis.

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Section: Discussioncontrasting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

The alternative sigma factor AlgT, but not alginate synthesis, promotes in planta multiplication of Pseudomonas syringae pv. glycinea

2008

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“…Alginate production had previously been associated with several fitness traits in the plant-microbe interaction (17,58,69). Herein, we evaluated the impact of a functional algT gene on in vitro and in planta growth.…”

Section: Vol 188 2006mentioning

confidence: 99%

“…Previous studies on EPS produced by P. syringae indicated that alginate was the major exopolysaccharide produced in planta (17). Alginate production has been associated with increased epiphytic fitness, resistance to desiccation and toxic molecules, the induction of water-soaked lesions, and the colonization and/or dissemination of P. syringae in planta (17,58,69). A direct correlation between virulence of P. syringae and the quantity of alginate produced in planta has been demonstrated (24,49).…”

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confidence: 96%

The algT Gene of Pseudomonas syringae pv. glycinea andNew Insights into the Transcriptional Organization of the algT-muc Gene Cluster

et al. 2006

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The phytopathogenic bacterium Pseudomonas syringae pv. glycinea infects soybean plants and causes bacterial blight. In addition to P. syringae, the human pathogen Pseudomonas aeruginosa and the soil bacterium Azotobacter vinelandii produce the exopolysaccharide alginate, a copolymer of D-mannuronic and L-guluronic acids. Alginate production in P. syringae has been associated with increased fitness and virulence in planta. Alginate biosynthesis is tightly controlled by proteins encoded by the algT-muc regulatory gene cluster in P. aeruginosa and A. vinelandii. These genes encode the alternative sigma factor AlgT ( 22 ), its anti-sigma factors MucA and MucB, MucC, a protein with a controversial function that is absent in P. syringae, and MucD, a periplasmic serine protease and homolog of HtrA in Escherichia coli. We compared an alginate-deficient algT mutant of P. syringae pv. glycinea with an alginate-producing derivative in which algT is intact. The alginateproducing derivative grew significantly slower in vitro growth but showed increased epiphytic fitness and better symptom development in planta. Evaluation of expression levels for algT, mucA, mucB, mucD, and algD, which encodes an alginate biosynthesis gene, showed that mucD transcription is not dependent on AlgT in P. syringae in vitro. Promoter mapping using primer extension experiments confirmed this finding. Results of reverse transcription-PCR demonstrated that algT, mucA, and mucB are cotranscribed as an operon in P. syringae. Northern blot analysis revealed that mucD was expressed as a 1.75-kb monocistronic mRNA in P. syringae.

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“…syringae causes disease in many plant species and produces the exopolysaccharide alginate, a linear polymer of O-acetylated ␤-1,4-linked D-mannuronic and L-guluronic residues (7, 11). Alginate functions as a virulence factor in P. syringae and also enhances epiphytic fitness, resistance to desiccation, and tolerance to toxic molecules (22,29). …”

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confidence: 99%

Characterization of Alginate Lyase from Pseudomonas syringae pv. syringae

et al. 2000

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The gene encoding alginate lyase (algL) in Pseudomonas syringae pv. syringae was cloned, sequenced, and overexpressed in Escherichia coli. Alginate lyase activity was optimal when the pH was 7.0 and when assays were conducted at 42°C in the presence of 0.2 M NaCl. In substrate specificity studies, AlgL from P. syringae showed a preference for deacetylated polymannuronic acid. Sequence alignment with other alginate lyases revealed conserved regions within AlgL likely to be important for the structure and/or function of the enzyme. Sitedirected mutagenesis of histidine and tryptophan residues at positions 204 and 207, respectively, indicated that these amino acids are critical for lyase activity.Pseudomonas syringae pv. syringae causes disease in many plant species and produces the exopolysaccharide alginate, a linear polymer of O-acetylated ␤-1,4-linked D-mannuronic and L-guluronic residues (7, 11). Alginate functions as a virulence factor in P. syringae and also enhances epiphytic fitness, resistance to desiccation, and tolerance to toxic molecules (22,29).

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The role of extracellular polysaccharides as virulence factors for phytopathogenic pseudomonads and xanthomonads

Cited by 32 publications

References 40 publications

The alternative sigma factor AlgT, but not alginate synthesis, promotes in planta multiplication of Pseudomonas syringae pv. glycinea

The alternative sigma factor AlgT, but not alginate synthesis, promotes in planta multiplication of Pseudomonas syringae pv. glycinea

The algT Gene of Pseudomonas syringae pv. glycinea andNew Insights into the Transcriptional Organization of the algT-muc Gene Cluster

Characterization of Alginate Lyase from Pseudomonas syringae pv. syringae

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