Arabidopsis Actin-Depolymerizing Factor AtADF4 Mediates Defense Signal Transduction Triggered by thePseudomonas syringaeEffector AvrPphB
Open Access
- 3 April 2009
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 150 (2), 815-824
- https://doi.org/10.1104/pp.109.137604
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.Keywords
This publication has 56 references indexed in Scilit:
- Depolymerization of the actin cytoskeleton induces defense responses in tobacco plantsJournal of General Plant Pathology, 2007
- Identification ofArabidopsisCyclase-associated Protein 1 as the First Nucleotide Exchange Factor for Plant ActinMolecular Biology of the Cell, 2007
- Barley MLO Modulates Actin-Dependent and Actin-Independent Antifungal Defense Pathways at the Cell PeripheryPlant Physiology, 2007
- A Novel Role for the TIR Domain in Association with Pathogen-Derived ElicitorsPLoS Biology, 2007
- Indirect activation of a plant nucleotide binding site–leucine-rich repeat protein by a bacterial proteaseProceedings of the National Academy of Sciences, 2007
- The plant immune systemNature, 2006
- Loss of actin cytoskeletal function and EDS1 activity, in combination, severely compromises non‐host resistance in Arabidopsis against wheat powdery mildewThe Plant Journal, 2003
- GFP‐tagging of cell components reveals the dynamics of subcellular re‐organization in response to infection of Arabidopsis by oomycete pathogensThe Plant Journal, 2003
- RIN4 Interacts with Pseudomonas syringae Type III Effector Molecules and Is Required for RPM1-Mediated Resistance in ArabidopsisCell, 2002
- Changes in the cytoskeleton accompanying infection‐induced nuclear movements and the hypersensitive response in plant cells invaded by rust fungiThe Plant Journal, 1998