Effect of Iron Concentration on the Growth Rate of
            <i>Pseudomonas syringae</i>
            and the Expression of Virulence Factors in
            <i>hrp</i>
            -Inducing Minimal Medium

Kim, Beum Jun; Park, Joon Ho; Park, Tai Hyun; Bronstein, Philip A.; Schneider, David J.; Cartinhour, Samuel; Shuler, Michael L.

doi:10.1128/aem.02738-08

Cited by 48 publications

(42 citation statements)

References 25 publications

(35 reference statements)

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“…It was expected that abundant iron would repress high-affinity iron scavenging, but the induction of virulence genes was surprising. In a follow-up study, Kim et al found that expression of virulence factors in hrp-inducing minimal medium was limited by iron availability and that higher iron to well above 10 M continued to induce higher virulence gene expression (32,33). Taken together, these results indicate not only that the environment in which DC3000 causes disease is relatively iron rich, but also that iron-as opposed to the lack of it-may act as a signal for DC3000 pathogenesis.…”

mentioning

confidence: 53%

The Phytopathogen Pseudomonas syringae pv. tomato DC3000 Has Three High-Affinity Iron-Scavenging Systems Functional under Iron Limitation Conditions but Dispensable for Pathogenesis

Jones

Wildermuth

2011

J Bacteriol

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High-affinity iron scavenging through the use of siderophores is a well-established virulence determinant in mammalian pathogenesis. However, few examples have been reported for plant pathogens. Here, we use a genetic approach to investigate the role of siderophores in Pseudomonas syringae pv. tomato DC3000 (DC3000) virulence in tomato. DC3000, an agronomically important pathogen, has two known siderophores for highaffinity iron scavenging, yersiniabactin and pyoverdin, and we uncover a third siderophore, citrate, required for growth when iron is limiting. Though growth of a DC3000 triple mutant unable to either synthesize or import these siderophores is severely restricted in iron-limited culture, it is fully pathogenic. One explanation for this phenotype is that the DC3000 triple mutant is able to directly pirate plant iron compounds such as heme/hemin or iron-nicotianamine, and our data indicate that DC3000 can import iron-nicotianamine with high affinity. However, an alternative explanation, supported by data from others, is that the pathogenic environment of DC3000 (i.e., leaf apoplast) is not iron limited but is iron replete, with available iron of >1 M. Growth of the triple mutant in culture is restored to wild-type levels by supplementation with a variety of iron chelates at >1 M, including iron(III) dicitrate, a dominant chelate of the leaf apoplast. This suggests that lower-affinity iron import would be sufficient for DC3000 iron nutrition in planta and is in sharp contrast to the high-affinity iron-scavenging mechanisms required in mammalian pathogenesis.Pathogenic microorganisms must acquire all critical nutrients from the host environment in order to survive. Iron nutrition in particular presents a fundamental challenge due to its extremely low solubility in aerobic environments at moderate pHs (ϳ10 Ϫ9 M) and further host limitation of available free iron (e.g., ϳ10Ϫ18 M in mammalian fluids [22,44]). Most bacteria require much higher levels (i.e., 10 Ϫ6 to 10 Ϫ7 M of bioavailable iron) for optimal growth (24) and therefore must solve an iron supply problem for survival. There is abundant evidence that competition for iron is a key virulence determinant in mammalian pathosystems. Iron in human serum is predominantly complexed with transferrin protein (pFe ϭ 10 22 M [1]) and is therefore limited from invading pathogens. The human immune system can limit iron further through release of the iron-binding protein lactoferrin at the site of infection (57). Evading these defenses, several mammalian pathogens pirate host-synthesized heme for iron nutrition directly from host fluids (20). Alternatively, pathogenic bacteria can scavenge iron from host fluids using very high-affinity iron carriers termed siderophores that can effectively compete with host iron chelates for iron. Siderophores are low-molecular-weight compounds that are synthesized, exported from the bacterial cell, and then imported once bound to iron (43). As this strategy carries metabolic costs associated with siderophore synthesis and transp...

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confidence: 53%

The Phytopathogen Pseudomonas syringae pv. tomato DC3000 Has Three High-Affinity Iron-Scavenging Systems Functional under Iron Limitation Conditions but Dispensable for Pathogenesis

Jones

Wildermuth

2011

J Bacteriol

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“…The time points chosen for virulence gene expression are based on published reports (Vasil and Ochsner, 1999;Kim et al, 2009).…”

Section: Bacterial and Fungal Growth Conditions And Disease Assaysmentioning

confidence: 99%

“…The direct effect of IAA-Asp on the growth and expression of virulence genes of Pst DC3000 in vitro was studied as previously described (Vasil and Ochsner, 1999;Kim et al, 2009). The time points chosen for virulence gene expression are based on published reports (Vasil and Ochsner, 1999;Kim et al, 2009).…”

Section: Bacterial and Fungal Growth Conditions And Disease Assaysmentioning

confidence: 99%

The Conjugated Auxin Indole-3-Acetic Acid–Aspartic Acid Promotes Plant Disease Development

et al. 2012

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“…To measure PME activity, plants were inoculated with bacteria or mock (5 mM MgSO 4 ) and three leaves from one plant were collected at the indicated time points per biological replicate. To measure PME activity in culture grown bacteria, Pma ES4326 was grown overnight at room temperature in either King's B or hypersensitive response and pathogenicityinducing minimal medium (Kim et al, 2009) using 0.2% Fru as a carbon source.…”

Section: Pathogen Strains Growth Conditions and Pathogen Growth Assaysmentioning

confidence: 99%

Arabidopsis PECTIN METHYLESTERASEs Contribute to Immunity against Pseudomonas syringae

et al. 2013

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Pectins, major components of dicot cell walls, are synthesized in a heavily methylesterified form in the Golgi and are partially deesterified by pectin methylesterases (PMEs) upon export to the cell wall. PME activity is important for the virulence of the necrotrophic fungal pathogen Botrytis cinerea. Here, the roles of Arabidopsis PMEs in pattern-triggered immunity and immune responses to the necrotrophic fungus Alternaria brassicicola and the bacterial hemibiotroph Pseudomonas syringae pv maculicola ES4326 (Pma ES4326) were studied. Plant PME activity increased during pattern-triggered immunity and after inoculation with either pathogen. The increase of PME activity in response to pathogen treatment was concomitant with a decrease in pectin methylesterification. The pathogen-induced PME activity did not require salicylic acid or ethylene signaling, but was dependent on jasmonic acid signaling. In the case of induction by A. brassicicola, the ethylene response factor, but not the MYC2 branch of jasmonic acid signaling, contributed to induction of PME activity, whereas in the case of induction by Pma ES4326, both branches contributed. There are 66 PME genes in Arabidopsis, suggesting extensive genetic redundancy. Nevertheless, selected pme single, double, triple and quadruple mutants allowed significantly more growth of Pma ES4326 than wild-type plants, indicating a role of PMEs in resistance to this pathogen. No decreases in total PME activity were detected in these pme mutants, suggesting that the determinant of immunity is not total PME activity; rather, it is some specific effect of PMEs such as changes in the pattern of pectin methylesterification.The plant cell wall determines cell shape, facilitates cell-cell interaction, and provides mechanical strength to plant cells. De Bary (1886) first observed that a plant pathogen, Sclerotina sclerotiorum, degraded host cell walls during infection. Later, it was concluded that plant cell walls act as preformed structural barriers against pathogen entry, because it was noticed that many plant pathogens produced various types of cell wall-degrading enzymes and that some of those were required for optimal infection of host plants (Albersheim et al., 1969).Arabidopsis mesophyll cells are surrounded by primary cell walls consisting of three major components: cellulose, hemicelluloses, and pectins. Pectins make up approximately 50% of Arabidopsis leaf cell walls (Zablackis et al., 1995;Harholt et al., 2010). They are complex GalA-containing polysaccharides composed of homogalacturonan (HG), rhamnogalacturonan I and II, and xylogalacturonan (Mohnen, 2008). HG is typically the most abundant polysaccharide, constituting approximately 65% of the pectin (Mohnen, 2008;Harholt et al., 2010). HG is a linear homopolymer of 1,4-linked GalA and is synthesized in the Golgi in a highly methylesterified form (Caffall and Mohnen, 2009). Pectin methylesterases (PMEs) demethylesterify HG in the apoplast (Mohnen, 2008;Harholt et al., 2010). Demethylesterification of pectin is considered t...

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Effect of Iron Concentration on the Growth Rate of Pseudomonas syringae and the Expression of Virulence Factors in hrp -Inducing Minimal Medium

Cited by 48 publications

References 25 publications

The Phytopathogen Pseudomonas syringae pv. tomato DC3000 Has Three High-Affinity Iron-Scavenging Systems Functional under Iron Limitation Conditions but Dispensable for Pathogenesis

The Phytopathogen Pseudomonas syringae pv. tomato DC3000 Has Three High-Affinity Iron-Scavenging Systems Functional under Iron Limitation Conditions but Dispensable for Pathogenesis

The Conjugated Auxin Indole-3-Acetic Acid–Aspartic Acid Promotes Plant Disease Development

Arabidopsis PECTIN METHYLESTERASEs Contribute to Immunity against Pseudomonas syringae

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