Abstract
The importance of pattern-triggered immunity (PTI) in plant defense has been clearly established through genetic studies of mutants lacking functional pattern recognition receptors (PRRs) and signaling components downstream of PRR activation. Despite extensive knowledge of PRR-mediated signaling responses to pathogen-associated molecular patterns (PAMPs), little is known about which of these responses, if any, are directly responsible for limiting bacterial growth. In this work, we established a protocol for coculturing the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and Arabidopsis suspension cells. The system closely mirrors infection processes that occur in leaves, with bacteria relying on the type III secretion system (T3SS) for maximal growth and PAMP-induced plant defenses effectively limiting bacterial growth. To demonstrate the utility of this system, we investigated the molecular basis of PAMP-induced growth inhibition and discovered that T3SS-associated genes are inhibited when DC3000 is cocultured with PAMP-treated plant suspension cells. To determine the underlying mechanism of decreased T3SS gene expression, we performed metabolomics and biochemical analyses of suspension cell exudates and identified 14 metabolites that significantly increased or decreased following PAMP treatment. Citric acid, a known inducer of T3SS gene expression in DC3000, was among several organic acids decreased in exudates from PAMP-treated plant cells. Exogenous addition of citric acid increased T3SS gene expression and partially recovered growth of DC3000 in the presence of PAMP-treated cells, indicating that a portion of PAMP-induced defense in this system is decreased extracellular release of this metabolite. We envision that the well-defined infection conditions of this coculture system will be valuable for quantitative studies of type III effector delivery by P. syringae. Furthermore, this system provides a unique ‘top-down’ approach to unravel the molecular basis of PTI against P. syringae.
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Claims 9
Claim · model-written summary
The coculture system mirrored leaf infection, including T3SS dependence for maximal bacterial growth.
- Taxon
- Arabidopsis
Arabidopsist0 - Outcome
- maximal growthe0
- Comparator
- infection processes that occur in leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The system closely mirrors infection processes that occur in leaves, with bacteria relying on the type III secretion system (T3SS) for maximal growth”
t0“Arabidopsis”
Claim · model-written summary
PAMP induced plant defenses limited bacterial growth in the coculture system.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- PAMP-induced plant defensese0
- Interactor
- bacteriale0pathogen
- Outcome
- bacterial growthe0
- Direction
- limitinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PAMP-induced plant defenses effectively limiting bacterial growth”
t0“Arabidopsis”
Claim · model-written summary
T3SS-associated genes were inhibited during coculture with PAMP-treated plant cells.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- PAMP-treated plant suspension cellse0
- Interactor
- DC3000e0pathogen
- Outcome
- T3SS-associated genese0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“T3SS-associated genes are inhibited when DC3000 is cocultured with PAMP-treated plant suspension cells”
t0“Arabidopsis”
Claim · model-written summary
Fourteen exudate metabolites significantly increased or decreased after PAMP treatment.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- PAMP treatmente0
- Outcome
- metabolitese0
- Direction
- increased or decreasede0
- Value
- 14 metabolitese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“identified 14 metabolites that significantly increased or decreased following PAMP treatment”
t0“Arabidopsis”
Claim · model-written summary
Citric acid decreased in exudates from PAMP-treated plant cells.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- PAMP-treated plant cellse0
- Interactor
- DC3000e0pathogen
- Outcome
- Citric acide0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Citric acid, a known inducer of T3SS gene expression in DC3000, was among several organic acids decreased in exudates from PAMP-treated plant cells”
t0“Arabidopsis”
Claim · model-written summary
Other organic acids decreased in exudates from PAMP-treated plant cells.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- PAMP-treated plant cellse0
- Interactor
- DC3000e0pathogen
- Outcome
- organic acidse0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Citric acid, a known inducer of T3SS gene expression in DC3000, was among several organic acids decreased in exudates from PAMP-treated plant cells”
t0“Arabidopsis”
Claim · model-written summary
Exogenous citric acid increased DC3000 T3SS gene expression in the presence of PAMP-treated cells.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- Exogenous addition of citric acide0
- Interactor
- DC3000e0pathogen
- Outcome
- T3SS gene expressione0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous addition of citric acid increased T3SS gene expression and partially recovered growth of DC3000 in the presence of PAMP-treated cells”
t0“Arabidopsis”
Claim · model-written summary
Exogenous citric acid partially recovered DC3000 growth in the presence of PAMP-treated cells.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- Exogenous addition of citric acide0
- Interactor
- DC3000e0pathogen
- Outcome
- growth of DC3000e0
- Direction
- partially recoverede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous addition of citric acid increased T3SS gene expression and partially recovered growth of DC3000 in the presence of PAMP-treated cells”
t0“Arabidopsis”
Claim · model-written summary
Reduced extracellular citric acid release accounts for a portion of PAMP-induced defense in this system.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- PAMP-induced defensee0
- Qualifier
- decreased extracellular release of this metabolitee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“indicating that a portion of PAMP-induced defense in this system is decreased extracellular release of this metabolite”
t0“Arabidopsis”
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See all 24 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.