Transcriptional profile of Pseudomonas syringae pv. phaseolicola NPS3121 in response to tissue extracts from a susceptible Phaseolus vulgarisL. cultivar

Morales, Alejandro; Torre-Zavala, Susana De la; Ibarra-Laclette, Enrique; Hernández-Flores, José Luis; Jofre-Garfías, A.E.; Martı́nez-Antonio, Agustino; Alvarez‐Morales, Ariel

doi:10.1186/1471-2180-9-257

Cited by 31 publications

(28 citation statements)

References 65 publications

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“…This suggests that despite the presence of nitrate there is an abundance of amino acids on the leaf surface. Additionally, assessment of the transcriptome of P. syringae within bean pods, in macerated beans, and in apoplastic fluids found that a nitrate reductase was expressed only in cells grown in apoplastic fluid and not under the other conditions (31). Given that we find that nasB is expressed only in a small subpopulation of cells of P. syringae on leaves (Fig.…”

Section: Discussionmentioning

confidence: 97%

Contribution of Nitrate Assimilation to the Fitness of Pseudomonas syringae pv. syringae B728a on Plants

Parangan-Smith

Lindow

2013

Appl Environ Microbiol

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The ability of Pseudomonas syringae pv. syringae to use nitrate as a nitrogen source in culture and on leaves was assessed. Substantial amounts of leaf surface nitrate were detected directly and by use of a bioreporter of nitrate on bean plants grown with a variety of nitrogen sources. While a nitrate reductase mutant, P. syringae ⌬nasB, exhibited greatly reduced growth in culture with nitrate as the sole nitrogen source, it exhibited population sizes similar to those of the wild-type strain on leaves. However, the growth of the ⌬nasB mutant was much less than that of the wild-type strain when cultured in bean leaf washings supplemented with glucose, suggesting that P. syringae experiences primarily carbon-limited and only secondarily nitrogenlimited growth on bean leaves. Only a small proportion of the cells of a green fluorescent protein (GFP)-based P. syringae nitrate reductase bioreporter, LK2(pOTNas4), exhibited fluorescence on leaves. This suggests that only a subset of cells experience high nitrate levels or that nitrate assimilation is repressed by the presence of ammonium or other nitrogenous compounds in many leaf locations. While only a subpopulation of P. syringae consumes nitrate at a given time on the leaves, the ability of those cells to consume this resource would be strongly beneficial to those cells, especially in environments in which nitrate is the most abundant form of nitrogen. N itrate assimilation is a central metabolic process that contributes to bacterial growth in a variety of habitats such as the ocean (1), rhizosphere (2), and soils (3). While there are numerous studies of bacterial nitrate assimilation in such locations, very little is known about the importance of bacterial nitrate assimilation in other habitats such as the aerial portions of plants known as the phyllosphere. The phyllosphere is considered to be a relatively stressful habitat due to nutrient limitation, desiccation stress, low and variable water availability, and high fluxes of UV radiation; nonetheless, it is colonized by specialized microbes (4). The fitness of epiphytic bacteria is associated with their ability to tolerate or avoid these various stresses and to utilize the limited nutrients available to them on leaves.Various studies have suggested that the phyllosphere is generally a nutrient-limited habitat. A wide variety of both inorganic and organic compounds are found on a given plant species. Amino acids, organic acids, and carbohydrates were detected in all of the species tested, although the quantity and abundance of a given compound varied from species to species (5, 6). Inorganic nitrogen is also found on the surface of plants, but its form has generally not been determined. Many factors, such as leaf age and the hydrophobic properties of the leaf, affect the amount and composition of leaf leachates. Younger leaves are typically more hydrophobic than older leaves, and their thicker cuticle restricts nutrient flux. Leaves that are more wettable, such as those of beans (Phaseolus vulgaris), experience m...

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Section: Discussionmentioning

confidence: 97%

Contribution of Nitrate Assimilation to the Fitness of Pseudomonas syringae pv. syringae B728a on Plants

Parangan-Smith

Lindow

2013

Appl Environ Microbiol

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“…As in B728a, gabP in P. syringae pv. phaseolicola was induced by apoplastic fluid from bean leaves (24). This induction likely reflects the availability of plant-derived GABA.…”

Section: P Syringae Traits Strongly Favored In the Apoplast Include mentioning

confidence: 92%

Transcriptional responses of Pseudomonas syringae to growth in epiphytic versus apoplastic leaf sites

Yu¹,

Lund

Scott

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

201

268

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Some strains of the foliar pathogen Pseudomonas syringae are adapted for growth and survival on leaf surfaces and in the leaf interior. Global transcriptome profiling was used to evaluate if these two habitats offer distinct environments for bacteria and thus present distinct driving forces for adaptation. The transcript profiles of Pseudomonas syringae pv. syringae B728a support a model in which leaf surface, or epiphytic, sites specifically favor flagellar motility, swarming motility based on 3-(3-hydroxyalkanoyloxy)alkanoic acid surfactant production, chemosensing, and chemotaxis, indicating active relocation primarily on the leaf surface. Epiphytic sites also promote high transcript levels for phenylalanine degradation, which may help counteract phenylpropanoidbased defenses before leaf entry. In contrast, intercellular, or apoplastic, sites favor the high-level expression of genes for GABA metabolism (degradation of these genes would attenuate GABA repression of virulence) and the synthesis of phytotoxins, two additional secondary metabolites, and syringolin A. These findings support roles for these compounds in virulence, including a role for syringolin A in suppressing defense responses beyond stomatal closure. A comparison of the transcriptomes from in planta cells and from cells exposed to osmotic stress, oxidative stress, and iron and nitrogen limitation indicated that water availability, in particular, was limited in both leaf habitats but was more severely limited in the apoplast than on the leaf surface under the conditions tested. These findings contribute to a coherent model of the adaptations of this widespread bacterial phytopathogen to distinct habitats within its host.endophyte | epiphyte | phyllosphere

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“…P. syringae is likely to experience iron limitation on the surface of the leaf, where it is in competition with other epiphytes producing siderophores with binding affinities higher than those produced by DC3000 (16); however, once DC3000 has entered the apoplast it will likely be presented with an environment richer in iron (22). We expect that the role that Fur plays in virulence will be shown to be different between P. aeruginosa and DC3000.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Fur Regulon in Pseudomonas syringae pv. tomato DC3000

et al. 2011

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The plant pathogen Pseudomonas syringae pv. tomato DC3000 (DC3000) is found in a wide variety of environments and must monitor and respond to various environmental signals such as the availability of iron, an essential element for bacterial growth. An important regulator of iron homeostasis is Fur (ferric uptake regulator), and here we present the first study of the Fur regulon in DC3000. Using chromatin immunoprecipitation followed by massively parallel sequencing (ChIP-seq), 312 chromosomal regions were highly enriched by coimmunoprecipitation with a C-terminally tagged Fur protein. Integration of these data with previous microarray and global transcriptome analyses allowed us to expand the putative DC3000 Fur regulon to include genes both repressed and activated in the presence of bioavailable iron. Using nonradioactive DNase I footprinting, we confirmed Fur binding in 41 regions, including upstream of 11 iron-repressed genes and the iron-activated genes encoding two bacterioferritins (PSPTO_0653 and PSPTO_4160), a ParA protein (PSPTO_0855), and a two-component system (TCS) (PSPTO_3382 to PSPTO_3380).

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Transcriptional profile of Pseudomonas syringae pv. phaseolicola NPS3121 in response to tissue extracts from a susceptible Phaseolus vulgarisL. cultivar

Cited by 31 publications

References 65 publications

Contribution of Nitrate Assimilation to the Fitness of Pseudomonas syringae pv. syringae B728a on Plants

Contribution of Nitrate Assimilation to the Fitness of Pseudomonas syringae pv. syringae B728a on Plants

Transcriptional responses of Pseudomonas syringae to growth in epiphytic versus apoplastic leaf sites

Characterization of the Fur Regulon in Pseudomonas syringae pv. tomato DC3000

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