Dataset Information

Suppression of pathogen-inducible NO synthase (iNOS) activity in tomato increases susceptibility to Pseudomonas syringae.

ABSTRACT: Inducible NO synthase (iNOS) activity is induced upon pathogen inoculation in resistant, but not susceptible, tobacco and Arabidopsis plants. It was shown recently that a variant form of the Arabidopsis P protein (AtvarP) has iNOS activity. P protein is part of the glycine decarboxylase complex (GDC). It is unclear whether P protein also has iNOS activity and, if so, whether AtvarP, P, or both, play a role in plant defense. Here, we show that iNOS activity is induced in both resistant and susceptible tomato leaves upon inoculation with the Pseudomonas syringae pv. tomato strain DC3000. Virus-induced gene-silencing targeting LevarP, a putative tomato ortholog of AtvarP, led to complete suppression of DC3000-induced iNOS activation and an approximately 80% reduction in GDC activity; it also increased disease-symptom severity and DC3000 growth in both resistant and susceptible tomato. To determine whether enhanced susceptibility exhibited by LevarP-silenced, susceptible tomato was due to loss of (i) iNOS activity, (ii) GDC activity, or (iii) both, GDC activity was inhibited with or without concurrent suppression of iNOS. Treatment with methotrexate inhibited both iNOS and GDC activities and resulted in increased susceptibility, comparable with that observed in LevarP-silenced plants. When normal iNOS activity was maintained in the presence of methotrexate by the addition of tetrahydrobiopterin, there was no change in susceptibility, despite a dramatic reduction in GDC activity. Together, these results indicate that iNOS contributes to host defense response against DC3000.

SUBMITTER: Chandok MR

PROVIDER: S-EPMC419587 | biostudies-literature | 2004 May

REPOSITORIES: biostudies-literature

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Suppression of pathogen-inducible NO synthase (iNOS) activity in tomato increases susceptibility to Pseudomonas syringae.

Chandok Meena R MR Ekengren Sophia K SK Martin Gregory B GB Klessig Daniel F DF

Proceedings of the National Academy of Sciences of the United States of America 20040514 21

Inducible NO synthase (iNOS) activity is induced upon pathogen inoculation in resistant, but not susceptible, tobacco and Arabidopsis plants. It was shown recently that a variant form of the Arabidopsis P protein (AtvarP) has iNOS activity. P protein is part of the glycine decarboxylase complex (GDC). It is unclear whether P protein also has iNOS activity and, if so, whether AtvarP, P, or both, play a role in plant defense. Here, we show that iNOS activity is induced in both resistant and suscep ...[more]

PMID: 15146069

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Project description:UnlabelledThe bacterial plant pathogen Pseudomonas syringae causes disease in a wide range of plants. The associated decrease in crop yields results in economic losses and threatens global food security. Competition exists between the plant immune system and the pathogen, the basic principles of which can be applied to animal infection pathways. P. syringae uses a type III secretion system (T3SS) to deliver virulence factors into the plant that promote survival of the bacterium. The P. syringae T3SS is a product of the hypersensitive response and pathogenicity (hrp) and hypersensitive response and conserved (hrc) gene cluster, which is strictly controlled by the codependent enhancer-binding proteins HrpR and HrpS. Through a combination of bacterial gene regulation and phenotypic studies, plant infection assays, and plant hormone quantifications, we now report that Chp8 (i) is embedded in the Hrp regulon and expressed in response to plant signals and HrpRS, (ii) is a functional diguanylate cyclase, (iii) decreases the expression of the major pathogen-associated molecular pattern (PAMP) flagellin and increases extracellular polysaccharides (EPS), and (iv) impacts the salicylic acid/jasmonic acid hormonal immune response and disease progression. We propose that Chp8 expression dampens PAMP-triggered immunity during early plant infection.ImportanceThe global demand for food is projected to rise by 50% by 2030 and, as such, represents one of the major challenges of the 21st century, requiring improved crop management. Diseases caused by plant pathogens decrease crop yields, result in significant economic losses, and threaten global food security. Gaining mechanistic insights into the events at the plant-pathogen interface and employing this knowledge to make crops more resilient is one important strategy for improving crop management. Plant-pathogen interactions are characterized by the sophisticated interplay between plant immunity elicited upon pathogen recognition and immune evasion by the pathogen. Here, we identify Chp8 as a contributor to the major effort of the plant pathogen Pseudomonas syringae pv. tomato DC3000 to evade immune responses of the plant.

Dataset Information

Suppression of pathogen-inducible NO synthase (iNOS) activity in tomato increases susceptibility to Pseudomonas syringae.

Publications

Suppression of pathogen-inducible NO synthase (iNOS) activity in tomato increases susceptibility to Pseudomonas syringae.

Similar Datasets

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