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Pseudomonas syringae infectivity correlates to altered transcript and metabolite levels of Arabidopsis Mediator mutants

ABSTRACT:

Rapid metabolic responses to pathogens are essential for plant survival and depend on numerous transcription factors. Mediator is the major transcriptional co-regulator for integration and transmission of signals from transcriptional regulators to RNA polymerase II. Using four Arabidopsis Mediator mutants, med16, med18, med25 and cdk8, we studied how differences in regulation of their transcript and metabolite levels correlate to their responses to Pseudomonas syringae infection. We found that med16 and cdk8 were susceptible, while med25 showed increased resistance. Glucosinolates, phytoalexins and carbohydrates were reduced already before infection in med16 and cdk8, but increased in med25, which also display increased benzenoids levels. Early after infection, wild type plants showed reduced glucosinolate and nucleoside levels, but increases in amino acids, benzeniods, oxylipins and the phytoalexin Camalexin. The Mediator mutants showed altered levels of these metabolites and in regulation of genes encoding key enzymes for their metabolism. At later stage, mutants displayed defective levels of specific amino acids, carbohydrates, lipids and jasmonates which correlates to their infection response phenotypes. Our results reveal that MED16, MED25 and CDK8 are required for a proper, coordinated transcriptional response of genes which encode enzymes involved in important metabolic pathways for Arabidopsis responses to Pseudomonas syringae infection.

INSTRUMENT(S): Liquid Chromatography MS - negative - reverse phase, Gas Chromatography MS - positive, Liquid Chromatography MS - positive - reverse phase

SUBMITTER: Stefan BjÃ¶rklund

PROVIDER: MTBLS8105 | MetaboLights | 1970-01-01

REPOSITORIES: MetaboLights

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Project description:Pseudomonas syringae pv. tomato DC3000 (Pst) is a virulent pathogen, which causes disease on tomato and Arabidopsis. The type III secretion system (TTSS) plays a key role in pathogenesis by translocating virulence effectors from the bacteria into the plant host cell, while the phytotoxin coronatine (COR) contributes to virulence and disease symptom development. Recent studies suggest that both the TTSS and and COR are involved in the suppression of host basal defenses. However, little is known about the interplay between the host gene expression associated with basal defenses and the virulence activities of the TTSS and COR during infection. The global effects of the TTSS and COR on host gene expression associated with other host cellular processes during bacterial infection are also not well characterized. In this study, we used the Affymetrix full genome chip to determine the Arabidopsis transcriptome associated with basal defense to Pst DC3000 hrp mutants and the human pathogenic bacterium Escherichia coli O157:H7. We then used Pst DC3000 virulence mutants to characterize Arabidopsis transcriptional responses to the action of hrp-regulated virulence factors (e.g., TTSS and COR) during bacterial infection. Additionally, we used bacterial fliC mutants to assess the role of the PAMP flagellin in induction of basal defense-associated transcriptional responses. In total, our global gene expression analysis identified more than 5000 Arabidopsis genes that are reproducibly regulated more than 2-fold in three independent biological replicates of at least one type of comparison. Regulation of these genes provides a molecular signature for Arabidopsis basal defense to plant and human pathogenic bacteria, and illustrates both common and distinct global virulence effects of the TTSS, COR, and possibly other hrp-regulated virulence factors during Pst DC3000 infection. Experimenter name = William Underwood; Experimenter phone = 517-353-9182; Experimenter fax = 517-353-9168; Experimenter address = Michigan State University; Experimenter address = 222 Plant Biology Building; Experimenter address = 178 Wilson R.d. Experimenter address = East Lansing, MI; Experimenter zip/postal_code = 48824; Experimenter country = USA Experiment Overall Design: 40 samples were used in this experiment

Project description:Pseudomonas syringae pv. tomato DC3000 (Pst) is a virulent pathogen, which causes disease on tomato and Arabidopsis. The type III secretion system (TTSS) plays a key role in pathogenesis by translocating virulence effectors from the bacteria into the plant host cell, while the phytotoxin coronatine (COR) contributes to virulence and disease symptom development. Recent studies suggest that both the TTSS and and COR are involved in the suppression of host basal defenses. However, little is known about the interplay between the host gene expression associated with basal defenses and the virulence activities of the TTSS and COR during infection. The global effects of the TTSS and COR on host gene expression associated with other host cellular processes during bacterial infection are also not well characterized. In this study, we used the Affymetrix full genome chip to determine the Arabidopsis transcriptome associated with basal defense to Pst DC3000 hrp mutants and the human pathogenic bacterium Escherichia coli O157:H7. We then used Pst DC3000 virulence mutants to characterize Arabidopsis transcriptional responses to the action of hrp-regulated virulence factors (e.g., TTSS and COR) during bacterial infection. Additionally, we used bacterial fliC mutants to assess the role of the PAMP flagellin in induction of basal defense-associated transcriptional responses. In total, our global gene expression analysis identified more than 5000 Arabidopsis genes that are reproducibly regulated more than 2-fold in three independent biological replicates of at least one type of comparison. Regulation of these genes provides a molecular signature for Arabidopsis basal defense to plant and human pathogenic bacteria, and illustrates both common and distinct global virulence effects of the TTSS, COR, and possibly other hrp-regulated virulence factors during Pst DC3000 infection. Experimenter name = William Underwood Experimenter phone = 517-353-9182 Experimenter fax = 517-353-9168 Experimenter address = Michigan State University Experimenter address = 222 Plant Biology Building Experimenter address = 178 Wilson R.d. Experimenter address = East Lansing, MI Experimenter zip/postal_code = 48824 Experimenter country = USA Keywords: pathogenicity_design

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Pseudomonas syringae infectivity correlates to altered transcript and metabolite levels of Arabidopsis Mediator mutants

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