Type III Secretion Contributes to the Pathogenesis of the Soft-Rot Pathogen <i>Erwinia carotovora</i>: Partial Characterization of the <i>hrp</i> Gene Cluster

Rantakari, Anssi; Virtaharju, O.; Vähämiko, Sanna; Taira, Suvi; Palva, E. Tapio; Saarilahti, Hannu T.; Romantschuk, Martin

doi:10.1094/mpmi.2001.14.8.962

Cited by 73 publications

(82 citation statements)

References 37 publications

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“…The hrp box was originally defined as GGAACC-N 15 or 16 -CCA CNNA in P. syrinage (Xiao and Hutcheson 1994). The hrp box has been found in the 59-flanking regions of many TTSS-related genes in a broad range of plant pathogens, allowing some redundancies (Arnold et al 2001;Rantakari et al 2001). In P. viridiflava, we identified 12 hrp boxes in the T-PAI and 9 in the S-PAI (supplemental Table 2 at http:/ /www.genetics.org/supplemental/).…”

Section: Discussionmentioning

confidence: 99%

Molecular Evolution of Pathogenicity-Island Genes in Pseudomonas viridiflava

et al. 2007

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The bacterial pathogen Pseudomonas viridiflava possesses two pathogenicity islands (PAIs) that share many gene homologs, but are structurally and phenotypically differentiated (T-PAI and S-PAI). These PAIs are paralogous, but only one is present in each isolate. While this dual presence/absence polymorphism has been shown to be maintained by balancing selection, little is known about the molecular evolution of individual genes on the PAIs. Here we investigate genetic variation of 12 PAI gene loci (7 on T-PAI and 5 on S-PAI) in 96 worldwide isolates of P. viridiflava. These genes include avirulence genes (hopPsyA and avrE ), their putative chaperones (shcA and avrF ), and genes encoding the type III outer proteins (hrpA, hrpZ, and hrpW ). Average nucleotide diversities in these genes (p ¼ 0.004-0.020) were close to those in the genetic background. Large numbers of recombination events were found within PAIs and a sign of positive selection was detected in avrE. These results suggest that the PAI genes are evolving relatively freely from each other on the PAIs, rather than as a single unit under balancing selection. Evolutionarily stable PAIs may be preferable in this species because preexisting genetic variation enables P. viridiflava to respond rapidly to natural selection.

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Section: Discussionmentioning

confidence: 99%

Molecular Evolution of Pathogenicity-Island Genes in Pseudomonas viridiflava

et al. 2007

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“…dspA is dependent on HrpL for expression and is required for virulence (58). In addition to E. amylovora, several other members of the Erwinia genus carry hrpL and other hrp genes, including the tumorigenic pathogen Erwinia herbicola (149,155,156) and the soft-rot pathogens Erwinia carotovora (24,125,180) and Erwinia chrysanthemi (6). The hrp-encoded type III secretion system is thus a common virulence mechanism among plant pathogens and is widespread among several types of pathogens, including tumorigenic, macerating, and soft-rot-causing species.…”

Section: Hrplmentioning

confidence: 99%

Alternative Sigma Factors and Their Roles in Bacterial Virulence

Kazmierczak

Wiedmann

Boor

2005

Microbiol Mol Biol Rev

318

317

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SUMMARY Sigma factors provide promoter recognition specificity to RNA polymerase holoenzyme, contribute to DNA strand separation, and then dissociate from the core enzyme following transcription initiation. As the regulon of a single sigma factor can be composed of hundreds of genes, sigma factors can provide effective mechanisms for simultaneously regulating expression of large numbers of prokaryotic genes. One newly emerging field is identification of the specific roles of alternative sigma factors in regulating expression of virulence genes and virulence-associated genes in bacterial pathogens. Virulence genes encode proteins whose functions are essential for the bacterium to effectively establish an infection in a host organism. In contrast, virulence-associated genes can contribute to bacterial survival in the environment and therefore may enhance the capacity of the bacterium to spread to new individuals or to survive passage through a host organism. As alternative sigma factors have been shown to regulate expression of both virulence and virulence-associated genes, these proteins can contribute both directly and indirectly to bacterial virulence. Sigma factors are classified into two structurally unrelated families, the σ70 and the σ54 families. The σ70 family includes primary sigma factors (e.g., Bacillus subtilis σA) as well as related alternative sigma factors; σ54 forms a distinct subfamily of sigma factors referred to as σN in almost all species for which these proteins have been characterized to date. We present several examples of alternative sigma factors that have been shown to contribute to virulence in at least one organism. For each sigma factor, when applicable, examples are drawn from multiple species.

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“…carotovora strain SCC1 (Rantakari et al, 2001) was propagated in Luria medium (Miller, 1972) at 28°C. An overnight culture was centrifuged for 7 min (6,500g), the pellet resuspended in 1 mL of 0.9% NaCl, and diluted to the appropriate concentration.…”

Section: Pathogen Strains and Plant Stress Treatmentsmentioning

confidence: 99%

EARLY RESPONSIVE TO DEHYDRATION 15, a Negative Regulator of Abscisic Acid Responses in Arabidopsis

et al. 2006

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EARLY RESPONSIVE TO DEHYDRATION 15 (ERD15) is rapidly induced in response to various abiotic and biotic stress stimuli in Arabidopsis (Arabidopsis thaliana). Modulation of ERD15 levels by overexpression or RNAi silencing altered the responsiveness of the transgenic plants to the phytohormone abscisic acid (ABA). Overexpression of ERD15 reduced the ABA sensitivity of Arabidopsis manifested in decreased drought tolerance and in impaired ability of the plants to increase their freezing tolerance in response to this hormone. In contrast, RNAi silencing of ERD15 resulted in plants that were hypersensitive to ABA and showed improved tolerance to both drought and freezing, as well as impaired seed germination in the presence of ABA. The modulation of ERD15 levels not only affected abiotic stress tolerance but also disease resistance: ERD15 overexpression plants showed improved resistance to the bacterial necrotroph Erwinia carotovora subsp. carotovora accompanied with enhanced induction of marker genes for systemic acquired resistance. We propose that ERD15 is a novel mediator of stress-related ABA signaling in Arabidopsis.

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Type III Secretion Contributes to the Pathogenesis of the Soft-Rot Pathogen Erwinia carotovora: Partial Characterization of the hrp Gene Cluster

Cited by 73 publications

References 37 publications

Molecular Evolution of Pathogenicity-Island Genes in Pseudomonas viridiflava

Molecular Evolution of Pathogenicity-Island Genes in Pseudomonas viridiflava

Alternative Sigma Factors and Their Roles in Bacterial Virulence

EARLY RESPONSIVE TO DEHYDRATION 15, a Negative Regulator of Abscisic Acid Responses in Arabidopsis

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