jump to searchjump to navigationjump to content

Publications - Stress and Develop Biology

Sort by: Year Type of publication

Displaying results 1 to 4 of 4.

Publications

Engelhardt, S.; Lee, J.; Gäbler, Y.; Kemmerling, B.; Haapalainen, M.-L.; Li, C.-M.; Wei, Z.; Keller, H.; Joosten, M.; Taira, S.; Nürnberger, T.; Separable roles of the Pseudomonas syringae pv. phaseolicola accessory protein HrpZ1 in ion-conducting pore formation and activation of plant immunity Plant J. 57, 706-717, (2009) DOI: 10.1111/j.1365-313X.2008.03723.x

The HrpZ1 gene product from phytopathogenic Pseudomonas syringae is secreted in a type‐III secretion system‐dependent manner during plant infection. The ability of HrpZ1 to form ion‐conducting pores is proposed to contribute to bacterial effector delivery into host cells, or may facilitate the nutrition of bacteria in the apoplast. Furthermore, HrpZ1 is reminiscent of a pathogen‐associated molecular pattern (PAMP) that triggers immunity‐associated responses in a variety of plants. Here, we provide evidence that the ion pore formation and immune activation activities of HrpZ1 have different structure requirements. All HrpZ1 orthologous proteins tested possess pore formation activities, but some of these proteins fail to trigger plant defense‐associated responses. In addition, a C‐terminal fragment of HrpZ1 retains the ability to activate plant immunity, whereas ion pore formation requires intact HrpZ1. Random insertion mutagenesis of HrpZ1 further revealed the C terminus to be important for the PAMP activity of the protein. HrpZ1 binds to plant membranes with high affinity and specificity, suggesting that the activation of plant immunity‐associated responses by HrpZ1 is receptor‐mediated. Our data are consistent with dual roles of HrpZ1 as a virulence factor affecting host membrane integrity, and as a microbial pattern governing the activation of plant immunity during infection.
Publications

Gust, A. A.; Biswas, R.; Lenz, H. D.; Rauhut, T.; Ranf, S.; Kemmerling, B.; Götz, F.; Glawischnig, E.; Lee, J.; Felix, G.; Nürnberger, T.; Bacteria-derived Peptidoglycans Constitute Pathogen-associated Molecular Patterns Triggering Innate Immunity in Arabidopsis J. Biol. Chem. 282, 32338-32348, (2007) DOI: 10.1074/jbc.M704886200

Pathogen-associated molecular pattern (PAMP)-triggered immunity constitutes the primary plant immune response that has evolved to recognize invariant structures of microbial surfaces. Here we show that Gram-positive bacteria-derived peptidoglycan (PGN) constitutes a novel PAMP of immune responses in Arabidopsis thaliana. Treatment with PGN from Staphylococcus aureus results in the activation of plant responses, such as medium alkalinization, elevation of cytoplasmic calcium concentrations, nitric oxide, and camalexin production and the post-translational induction of MAPK activities. Microarray analysis performed with RNA prepared from PGN-treated Arabidopsis leaves revealed enhanced transcript levels for 236 genes, many of which are also altered upon administration of flagellin. Comparison of cellular responses after treatment with bacteria-derived PGN and structurally related fungal chitin indicated that both PAMPs are perceived via different perception systems. PGN-mediated immune stimulation in Arabidopsis is based upon recognition of the PGN sugar backbone, while muramyl dipeptide, which is inactive in this plant, triggers immunity-associated responses in animals. PGN adds to the list of PAMPs that induce innate immune programs in both plants and animals. However, we propose that PGN perception systems arose independently in both lineages and are the result of convergent evolution.
Publications

Qutob, D.; Kemmerling, B.; Brunner, F.; Küfner, I.; Engelhardt, S.; Gust, A. A.; Luberacki, B.; Seitz, H. U.; Stahl, D.; Rauhut, T.; Glawischnig, E.; Schween, G.; Lacombe, B.; Watanabe, N.; Lam, E.; Schlichting, R.; Scheel, D.; Nau, K.; Dodt, G.; Hubert, D.; Gijzen, M.; Nürnberger, T.; Phytotoxicity and Innate Immune Responses Induced by Nep1-Like Proteins Plant Cell 18, 3721-3744, (2006) DOI: 10.1105/tpc.106.044180

We show that oomycete-derived Nep1 (for necrosis and ethylene-inducing peptide1)–like proteins (NLPs) trigger a comprehensive immune response in Arabidopsis thaliana, comprising posttranslational activation of mitogen-activated protein kinase activity, deposition of callose, production of nitric oxide, reactive oxygen intermediates, ethylene, and the phytoalexin camalexin, as well as cell death. Transcript profiling experiments revealed that NLPs trigger extensive reprogramming of the Arabidopsis transcriptome closely resembling that evoked by bacteria-derived flagellin. NLP-induced cell death is an active, light-dependent process requiring HSP90 but not caspase activity, salicylic acid, jasmonic acid, ethylene, or functional SGT1a/SGT1b. Studies on animal, yeast, moss, and plant cells revealed that sensitivity to NLPs is not a general characteristic of phospholipid bilayer systems but appears to be restricted to dicot plants. NLP-induced cell death does not require an intact plant cell wall, and ectopic expression of NLP in dicot plants resulted in cell death only when the protein was delivered to the apoplast. Our findings strongly suggest that NLP-induced necrosis requires interaction with a target site that is unique to the extracytoplasmic side of dicot plant plasma membranes. We propose that NLPs play dual roles in plant pathogen interactions as toxin-like virulence factors and as triggers of plant innate immune responses.
Publications

Consonni, C.; Humphry, M. E.; Hartmann, H. A.; Livaja, M.; Durner, J.; Westphal, L.; Vogel, J.; Lipka, V.; Kemmerling, B.; Schulze-Lefert, P.; Somerville, S. C.; Panstruga, R.; Conserved requirement for a plant host cell protein in powdery mildew pathogenesis Nat. Genet. 38, 716-720, (2006) DOI: 10.1038/ng1806

In the fungal phylum Ascomycota, the ability to cause disease in plants and animals has been gained and lost repeatedly during phylogenesis1. In monocotyledonous barley, loss-of-function mlo alleles result in effective immunity against the Ascomycete Blumeria graminis f. sp. hordei, the causal agent of powdery mildew disease2,3. However, mlo-based disease resistance has been considered a barley-specific phenomenon to date. Here, we demonstrate a conserved requirement for MLO proteins in powdery mildew pathogenesis in the dicotyledonous plant species Arabidopsis thaliana. Epistasis analysis showed that mlo resistance in A. thaliana does not involve the signaling molecules ethylene, jasmonic acid or salicylic acid, but requires a syntaxin, glycosyl hydrolase and ABC transporter4,5,6. These findings imply that a common host cell entry mechanism of powdery mildew fungi evolved once and at least 200 million years ago, suggesting that within the Erysiphales (powdery mildews) the ability to cause disease has been a stable trait throughout phylogenesis.
IPB Mainnav Search