Abstract
The actin cytoskeleton has been implicated in plant defenses against pathogenic fungi and oomycetes with limited, indirect evidence. To date, there are no reports linking actin with resistance against phytopathogenic bacteria. The dynamic behavior of actin filaments is regulated by a diverse array of actin-binding proteins, among which is the Actin-Depolymerizing Factor (ADF) family of proteins. Here, we demonstrate that actin dynamics play a role in the activation of gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato. Using a reverse genetics approach, we explored the roles of Arabidopsis ADFs in plant defenses. AtADF4 was identified as being specifically required for resistance triggered by the effector AvrPphB but not AvrRpt2 or AvrB. Recombinant AtADF4 bound to monomeric actin (G-actin) with a marked preference for the ADP-loaded form and inhibited the rate of nucleotide exchange on G-actin, indicating that AtADF4 is a bona fide actin-depolymerizing factor. Exogenous application of the actin-disrupting agent cytochalasin D partially rescued the Atadf4 mutant in the AvrPphB-mediated hypersensitive response, demonstrating that AtADF4 mediates defense signaling through modification of the actin cytoskeleton. Unlike the mechanism by which the actin cytoskeleton confers resistance against fungi and oomycetes, AtADF4 is not involved in resistance against pathogen entry. Collectively, this study identifies AtADF4 as a novel component of the plant defense signaling pathway and provides strong evidence for actin dynamics as a primary component that orchestrates plant defenses against P. syringae.
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Claims 8
Claim · model-written summary
AtADF4 is specifically required for resistance triggered by the effector AvrPphB, but not by AvrRpt2 or AvrB.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Treatment
- inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomatoe0
- Interactor
- Pseudomonas syringae pv tomato
Pseudomonas syringaee0pathogen - Gene
- AtADF4e1
- Outcome
- resistance triggered by the effector AvrPphBe1
- Direction
- specifically requirede1
- Comparator
- AvrRpt2 or AvrBe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato”
e1“AtADF4 was identified as being specifically required for resistance triggered by the effector AvrPphB but not AvrRpt2 or AvrB”
Claim · model-written summary
Recombinant AtADF4 binds monomeric actin (G-actin), with a marked preference for the ADP-loaded form.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Gene
- AtADF4e2
- Outcome
- bound to monomeric actin (G-actin)e2
- Direction
- marked preferencee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato”
e2“Recombinant AtADF4 bound to monomeric actin (G-actin) with a marked preference for the ADP-loaded form”
Claim · model-written summary
AtADF4 inhibits the rate of nucleotide exchange on G-actin.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Gene
- AtADF4e2
- Outcome
- rate of nucleotide exchange on G-actine3
- Direction
- inhibitede3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato”
e2“Recombinant AtADF4 bound to monomeric actin (G-actin) with a marked preference for the ADP-loaded form”
e3“inhibited the rate of nucleotide exchange on G-actin”
Claim · model-written summary
Exogenous cytochalasin D partially rescued the Atadf4 mutant in the AvrPphB-mediated hypersensitive response.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- Atadf4 mutante4
- Treatment
- Exogenous application of the actin-disrupting agent cytochalasin De4
- Outcome
- AvrPphB-mediated hypersensitive responsee4
- Direction
- partially rescuede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato”
e4“Exogenous application of the actin-disrupting agent cytochalasin D partially rescued the Atadf4 mutant in the AvrPphB-mediated hypersensitive response”
Claim · model-written summary
AtADF4 mediates defense signalling through modification of the actin cytoskeleton.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Gene
- AtADF4e5
- Outcome
- defense signalinge5
- Qualifier
- through modification of the actin cytoskeletone5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato”
e5“AtADF4 mediates defense signaling through modification of the actin cytoskeleton”
Claim · model-written summary
AtADF4 is not involved in resistance against pathogen entry.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Gene
- AtADF4e6
- Outcome
- resistance against pathogen entrye6
- Direction
- not involvede6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato”
e6“AtADF4 is not involved in resistance against pathogen entry”
Claim · model-written summary
AtADF4 is identified as a novel component of the plant defence signalling pathway.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Gene
- AtADF4e7
- Outcome
- defense signaling pathwaye7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato”
e7“identifies AtADF4 as a novel component of the plant defense signaling pathway”
Claim · model-written summary
Actin dynamics are a primary component that orchestrates plant defences against P. syringae.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Interactor
- P. syringaePseudomonas syringaee1pathogen
- Outcome
- plant defensese1
- Qualifier
- actin dynamics as a primary componente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gene-for-gene resistance in Arabidopsis (Arabidopsis thaliana) following inoculation with the phytopathogenic bacterium Pseudomonas syringae pv tomato”
e1“actin dynamics as a primary component that orchestrates plant defenses against P. syringae”
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