Publications (12)73.42 Total impact
-
Article: Pseudomonas syringae pv. syringae Uses Proteasome Inhibitor Syringolin A to Colonize from Wound Infection Sites.
[show abstract] [hide abstract]
ABSTRACT: Infection of plants by bacterial leaf pathogens at wound sites is common in nature. Plants defend wound sites to prevent pathogen invasion, but several pathogens can overcome spatial restriction and enter leaf tissues. The molecular mechanisms used by pathogens to suppress containment at wound infection sites are poorly understood. Here, we studied Pseudomonas syringae strains causing brown spot on bean and blossom blight on pear. These strains exist as epiphytes that can cause disease upon wounding caused by hail, sand storms and frost. We demonstrate that these strains overcome spatial restriction at wound sites by producing syringolin A (SylA), a small molecule proteasome inhibitor. Consequently, SylA-producing strains are able to escape from primary infection sites and colonize adjacent tissues along the vasculature. We found that SylA diffuses from the primary infection site and suppresses acquired resistance in adjacent tissues by blocking signaling by the stress hormone salicylic acid (SA). Thus, SylA diffusion creates a zone of SA-insensitive tissue that is prepared for subsequent colonization. In addition, SylA promotes bacterial motility and suppresses immune responses at the primary infection site. These local immune responses do not affect bacterial growth and were weak compared to effector-triggered immunity. Thus, SylA facilitates colonization from wounding sites by increasing bacterial motility and suppressing SA signaling in adjacent tissues.PLoS Pathogens 03/2013; 9(3):e1003281. · 9.13 Impact Factor -
Article: A role in immunity for Arabidopsis cysteine protease RD21, the ortholog of the tomato immune protease C14.
[show abstract] [hide abstract]
ABSTRACT: Secreted papain-like Cys proteases are important players in plant immunity. We previously reported that the C14 protease of tomato is targeted by cystatin-like EPIC proteins that are secreted by the oomycete pathogen Phytophthora infestans (Pinf) during infection. C14 has been under diversifying selection in wild potato species coevolving with Pinf and reduced C14 levels result in enhanced susceptibility for Pinf. Here, we investigated the role C14-EPIC-like interactions in the natural pathosystem of Arabidopsis with the oomycete pathogen Hyaloperonospora arabidopsidis (Hpa). In contrast to the Pinf-solanaceae pathosystem, the C14 orthologous protease of Arabidopsis, RD21, does not evolve under diversifying selection in Arabidopsis, and rd21 null mutants do not show phenotypes upon compatible and incompatible Hpa interactions, despite the evident lack of a major leaf protease. Hpa isolates express highly conserved EPIC-like proteins during infections, but it is unknown if these HpaEPICs can inhibit RD21 and one of these HpaEPICs even lacks the canonical cystatin motifs. The rd21 mutants are unaffected in compatible and incompatible interactions with Pseudomonas syringae pv. tomato, but are significantly more susceptible for the necrotrophic fungal pathogen Botrytis cinerea, demonstrating that RD21 provides immunity to a necrotrophic pathogen.PLoS ONE 01/2012; 7(1):e29317. · 4.09 Impact Factor -
Article: Post-translational regulation and trafficking of the granulin-containing protease RD21 of Arabidopsis thaliana.
[show abstract] [hide abstract]
ABSTRACT: RD21-like proteases are ubiquitous, plant-specific papain-like proteases typified by carrying a C-terminal granulin domain. RD21-like proteases are involved in immunity and associated with senescence and various types of biotic and abiotic stresses. Here, we interrogated Arabidopsis RD21 regulation and trafficking by site-directed mutagenesis, agroinfiltration, western blotting, protease activity profiling and protein degradation. Using an introduced N-glycan sensor, deglycosylation experiments and glyco-engineered N. benthamiana plants, we show that RD21 passes through the Golgi where it becomes fucosylated. Our studies demonstrate that RD21 is regulated at three post-translational levels. Prodomain removal is not blocked in the catalytic Cys mutant, indicating that RD21 is activated by a proteolytic cascade. However, RD21 activation in Arabidopsis does not require vacuolar processing enzymes (VPEs) or aleurain-like protease AALP. In contrast, granulin domain removal requires the catalytic Cys and His residues and is therefore autocatalytic. Furthermore, SDS can (re-)activate latent RD21 in Arabidopsis leaf extracts, indicating the existence of a third layer of post-translational regulation, possibly mediated by endogenous inhibitors. RD21 causes a dominant protease activity in Arabidopsis leaf extracts, responsible for SDS-induced proteome degradation.PLoS ONE 01/2012; 7(3):e32422. · 4.09 Impact Factor -
Article: Phytophthora infestans effector AVRblb2 prevents secretion of a plant immune protease at the haustorial interface.
[show abstract] [hide abstract]
ABSTRACT: In response to pathogen attack, plant cells secrete antimicrobial molecules at the site of infection. However, how plant pathogens interfere with defense-related focal secretion remains poorly known. Here we show that the host-translocated RXLR-type effector protein AVRblb2 of the Irish potato famine pathogen Phytophthora infestans focally accumulates around haustoria, specialized infection structures that form inside plant cells, and promotes virulence by interfering with the execution of host defenses. AVRblb2 significantly enhances susceptibility of host plants to P. infestans by targeting the host papain-like cysteine protease C14 and specifically preventing its secretion into the apoplast. Plants altered in C14 expression were significantly affected in susceptibility to P. infestans in a manner consistent with a positive role of C14 in plant immunity. Our findings point to a unique counterdefense strategy that plant pathogens use to neutralize secreted host defense proteases. Effectors, such as AVRblb2, can be used as molecular probes to dissect focal immune responses at pathogen penetration sites.Proceedings of the National Academy of Sciences 12/2011; 108(51):20832-7. · 9.68 Impact Factor -
Article: Autophagy differentially controls plant basal immunity to biotrophic and necrotrophic pathogens.
[show abstract] [hide abstract]
ABSTRACT: In plants, autophagy has been assigned 'pro-death' and 'pro-survival' roles in controlling programmed cell death associated with microbial effector-triggered immunity. The role of autophagy in basal immunity to virulent pathogens has not been addressed systematically, however. Using several autophagy-deficient (atg) genotypes, we determined the function of autophagy in basal plant immunity. Arabidopsis mutants lacking ATG5, ATG10 and ATG18a develop spreading necrosis upon infection with the necrotrophic fungal pathogen, Alternaria brassicicola, which is accompanied by the production of reactive oxygen intermediates and by enhanced hyphal growth. Likewise, treatment with the fungal toxin fumonisin B1 causes spreading lesion formation in atg mutant genotypes. We suggest that autophagy constitutes a 'pro-survival' mechanism that controls the containment of host tissue-destructive microbial infections. In contrast, atg plants do not show spreading necrosis, but exhibit marked resistance against the virulent biotrophic phytopathogen, Pseudomonas syringae pv. tomato. Inducible defenses associated with basal plant immunity, such as callose production or mitogen-activated protein kinase activation, were unaltered in atg genotypes. However, phytohormone analysis revealed that salicylic acid (SA) levels in non-infected and bacteria-infected atg plants were slightly higher than those in Col-0 plants, and were accompanied by elevated SA-dependent gene expression and camalexin production. This suggests that previously undetected moderate infection-induced rises in SA result in measurably enhanced bacterial resistance, and that autophagy negatively controls SA-dependent defenses and basal immunity to bacterial infection. We infer that the way in which autophagy contributes to plant immunity to different pathogens is mechanistically diverse, and thus resembles the complex role of this process in animal innate immunity.The Plant Journal 02/2011; 66(5):818-30. · 6.16 Impact Factor -
Article: An effector-targeted protease contributes to defense against Phytophthora infestans and is under diversifying selection in natural hosts.
[show abstract] [hide abstract]
ABSTRACT: Since the leaf apoplast is a primary habitat for many plant pathogens, apoplastic proteins are potent, ancient targets for apoplastic effectors secreted by plant pathogens. So far, however, only a few apoplastic effector targets have been identified and characterized. Here, we discovered that the papain-like cysteine protease C14 is a new common target of EPIC1 and EPIC2B, two apoplastic, cystatin-like proteins secreted by the potato (Solanum tuberosum) late blight pathogen Phytophthora infestans. C14 is a secreted protease of tomato (Solanum lycopersicum) and potato typified by a carboxyl-terminal granulin domain. The EPIC-C14 interaction occurs at a wide pH range and is stronger than the previously described interactions of EPICs with tomato defense proteases PIP1 and RCR3. The selectivity of the EPICs is also different when compared with the AVR2 effector of the fungal tomato pathogen Cladosporium fulvum, which targets PIP1 and RCR3, and only at apoplastic pH. Importantly, silencing of C14 increased susceptibility to P. infestans, demonstrating that this protease plays a role in pathogen defense. Although C14 is under conservative selection in tomato, it is under diversifying selection in wild potato species (Solanum demissum, Solanum verrucosum, and Solanum stoliniferum) that are the natural hosts of P. infestans. These data reveal a novel effector target in the apoplast that contributes to immunity and is under diversifying selection, but only in the natural host of the pathogen.Plant physiology 10/2010; 154(4):1794-804. · 6.53 Impact Factor -
Article: Proteasome activity profiling: a simple, robust and versatile method revealing subunit-selective inhibitors and cytoplasmic, defense-induced proteasome activities.
[show abstract] [hide abstract]
ABSTRACT: The proteasome plays essential roles in nearly all biological processes in plant defense and development, yet simple methods for displaying proteasome activities in extracts and living tissues are not available to plant science. Here, we introduce an easy and robust method to simultaneously display the activities of all three catalytic proteasome subunits in plant extracts or living plant tissues. The method is based on a membrane-permeable, small-molecule fluorescent probe that irreversibly reacts with the catalytic site of the proteasome catalytic subunits in an activity-dependent manner. Activities can be quantified from fluorescent protein gels and used to study proteasome activities in vitro and in vivo. We demonstrate that proteasome catalytic subunits can be selectively inhibited by aldehyde-based inhibitors, including the notorious caspase-3 inhibitor DEVD. Furthermore, we show that the proteasome activity, but not its abundance, is significantly increased in Arabidopsis upon treatment with benzothiadiazole (BTH). This upregulation of proteasome activity depends on NPR1, and occurs mostly in the cytoplasm. The simplicity, robustness and versatility of this method will make this method widely applicable in plant science.The Plant Journal 04/2010; 62(1):160-70. · 6.16 Impact Factor -
Chapter: Mining the active proteome in plant-pathogen interactions
01/2010; -
Article: Beta-lactone probes identify a papain-like peptide ligase in Arabidopsis thaliana.
[show abstract] [hide abstract]
ABSTRACT: New activity-based probes are essential for expanding studies on the hundreds of serine and cysteine proteases encoded by the genome of Arabidopsis thaliana. To monitor protease activities in plant extracts, we generated biotinylated peptides containing a beta-lactone reactive group. These probes cause strong labeling in leaf proteomes. Unexpectedly, labeling was detected at the N terminus of PsbP, nonproteolytic protein of photosystem II. Inhibitor studies and reverse genetics led to the discovery that this unusual modification is mediated by a single plant-specific, papain-like protease called RD21. In cellular extracts, RD21 accepts both beta-lactone probes and peptides as donor molecules and ligates them, probably through a thioester intermediate, to unmodified N termini of acceptor proteins.Nature Chemical Biology 09/2008; 4(9):557-63. · 14.69 Impact Factor -
Article: Fungal effector protein AVR2 targets diversifying defense-related cys proteases of tomato.
[show abstract] [hide abstract]
ABSTRACT: The interaction between the fungal pathogen Cladosporium fulvum and its host tomato (Solanum lycopersicum) is an ideal model to study suppression of extracellular host defenses by pathogens. Secretion of protease inhibitor AVR2 by C. fulvum during infection suggests that tomato papain-like cysteine proteases (PLCPs) are part of the tomato defense response. We show that the tomato apoplast contains a remarkable diversity of PLCP activities with seven PLCPs that fall into four different subfamilies. Of these PLCPs, transcription of only PIP1 and RCR3 is induced by treatment with benzothiadiazole, which triggers the salicylic acid-regulated defense pathway. Sequencing of PLCP alleles of tomato relatives revealed that only PIP1 and RCR3 are under strong diversifying selection, resulting in variant residues around the substrate binding groove. The doubled number of variant residues in RCR3 suggests that RCR3 is under additional adaptive selection, probably to prevent autoimmune responses. AVR2 selectively inhibits only PIP1 and RCR3, and one of the naturally occurring variant residues in RCR3 affects AVR2 inhibition. The higher accumulation of PIP1 protein levels compared with RCR3 indicates that PIP1 might be the real virulence target of AVR2 and that RCR3 acts as a decoy for AVR2 perception in plants carrying the Cf-2 resistance gene.The Plant Cell 05/2008; 20(4):1169-83. · 8.99 Impact Factor -
Article: Papain-like cysteine proteases: key players at molecular battlefields employed by both plants and their invaders.
[show abstract] [hide abstract]
ABSTRACT: Papain-like cysteine proteases (PLCPs) play crucial roles in plant-pathogen/pest interactions. During these parasitic interactions, PLCPs act on non-self substrates, provoking the selection of counteracting inhibitors and other means to evade proteolysis. We review examples of PLCPs acting on molecular battlefields in the extracellular space, plant cytoplasm and herbivore gut. Examples are maize Mir1 (Maize inbred resistance 1), tomato Rcr3 (Required for Cladosporium resistance-3), Pseudomonas AvrRpt2 and AurPphB, insect DvCAL1 (Diabrotica virgifera cathepsin L-like protease-1) and nematode MiCpl1 (Meloidogyne incognita cathepsin L-like protease 1). The data suggest that PLCPs cleave specific proteins and that their translocation, activation and inhibition of PLCPs are tightly regulated.Molecular Plant Pathology 02/2008; 9(1):119-25. · 3.90 Impact Factor -
Article: Fungal Effector Protein AVR2 Targets Diversifying Defense-Related Cys Proteases of Tomato
The Plant Cell, v.20, 1169-1183 (2008).
Top co-authors
Top Journals
Institutions
-
2008–2013
-
Max-Planck-Institut für Pflanzenzüchtungsforschung
Köln, North Rhine-Westphalia, Germany
-
