Abstract
The HrpZ gene product, harpin, is an export substrate of the type III secretion system of phytopathogenic Pseudomonas syringae. The role of this protein in pathogenesis is largely unknown. We previously determined that HrpZ binds to lipids and can form cation pores in synthetic lipid bilayers. Such pore-forming activity may allow nutrient release during bacterial colonisation of host plants. In addition. HrpZ is known to trigger plant defence responses in a variety of plants, such as tobacco. We have previously also characterised a binding site in tobacco plasma membranes that likely mediates HrpZ-induced defence responses. In order to reconcile these findings, we pose the question as to whether the activation of plant defence responses by HrpZ is mediated through a “classical” receptor perception mode or if plant membrane perturbation through the inherent pore-forming activity of HrpZ may induce defence responses. As defence in parsley cells can be induced both in a receptor-mediated manner or through ionophores these cells served as an ideal system for our analysis. We first performed ligand binding studies to characterise the presence of a binding site/receptor. We further digested HrpZ with endopeptidases and used subfragments of HrpZ to assess the elicitor-active domain of HrpZ. A C-terminal region of HrpZ appears to be sufficient to elicit plant defence responses. A novel assay involving dye-loaded liposomes was developed to validate previous electrophysiological findings on HrpZ-mediated cation pore formation. More importantly, this assay was used to establish if the elicitor-active C-terminal fragment of HrpZ could form pores. Our findings suggest that the structural requirements for ion pore formation and activation of plant defence responses by HrpZ are different. Thus, ion pore formation alone may not explain the activation of plant defence by HrpZ.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Alfano, J.R., Bauer, D.W., Milos, T.M., and Collmer, A., 1996, Analysis of the role of the Pseudomonas syringae pv. syringae HrpZ harpin in elicitation of the hypersensitive response in tobacco using functionally non-polar hrpZ deletion mutations, truncated HrpZ fragments, and hrmA mutations. Mol. Microbiol. 19: 715–728.
Bogdanove, A.J., Beer, S.V., Bonas, U., Boucher, C.A., Collmer, A., Coplin, D.L., Cornelis, G.R., Huang, H.C., Hutcheson, S.W., Panopoulos, N.J., and Van Gijsegem, F., 1996, Unified nomenclature for broadly conserved hrp genes of phytopathogenic bacteria. Mol. Microbiol. 20: 681–683.
Charkowski, A.O., Alfano, J.R., Preston, G., Yuan, J., He, S.Y., and Collmer, A., 1998, The Pseudomonas syringae pv. tomato HrpW protein has domains similar to harpins and pectate lyases and can elicit the plant hypersensitive response and bind to pectate. J. Bacteriol. 180: 5211–5217.
Galan, J.E., and Collmer, A., 1999, Type III secretion machines: Bacterial devices for protein delivery into host cells. Science 284: 1322–1328.
He, S.Y., Huang, H.-C., and Collmer, A., 1993, Pseudomonas syringae pv. Syringae harpinpss: a protein that is secreted by the hrp pathway and elicits the hypersensitive response in plants. Cell 73: 1255–1266.
Jabs, T., Tschöpe, M., Coiling, C., Hahlbrock, K., and Scheel, D., 1997, Elicitor-stimulated ion fluxes and 02 from the oxidative burst are essential components in triggering defense gene activation and phytoalexin synthesis in parsley. Proc. Natl. Acad. Sci. USA 94: 4800–4805.
Klüsener, B., and Weiler, E.W., 1999, Pore-forming properties of elicitors of plant defense reactions and cellulolytic enzymes. FEBS Lett. 459: 263–269.
Lee, J., Klessig, D.F., and Nürnberger, T., 2001a, A harpin binding site in tobacco plasma membranes mediates activation o the pathogenesis-related gene HIN1 independent of extracellular calcium but dependent on mitogen-activated protein kinase activity. Plant Cell 13: 1079–1093.
Lee, J., Klüsener, B., Tsiamis, G., Stevens, C., Neyt, C., Tampakaki, A.P., Panopoulos, N.J., Noller, J., Weiler, E.W., Cornelis, G.R., Mansfield, J.W., and Nürnberger, T., 2001b, HrpZpsph from the plant pathogen Pseudomonas syringae pv. phaseolicola binds to lipid bilayers and forms an ion-conducting pore in vitro. Proc. Natl. Acad. Sci. USA 98: 289–294.
Nürnberger, T., Nennstiel, D., Hahlbrock, K., and Scheel, D., 1995, Covalent cross-linking of the Phytophthora megasperma oligopeptide elicitor to its receptor in parsley membranes. Proc. Natl. Acad. Sci. USA 92: 2338–2342.
Nürnberger, T., Nennstiel, D., Jabs, T., Sacks, W.R., Hahlbrock, K., and Scheel, D., 1994, High affinity binding of a fungal oligopeptide elicitor to parsley plasma membranes triggers multiple defense responses. Cell 78: 449–460.
Preston, G., Huang, H.C., He, S.Y., and Collmer, A., 1995, The HrpZ proteins of Pseudomonas syringae pvs. syringae, glycinea, and tomato are encoded by an operon containing Yersinia ysc homologs and elicit the hypersensitive response in tomato but not soybean. Mol. Plant-Microbe Interact. 8: 717–732.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2003 Springer Science+Business Media Dordrecht
About this paper
Cite this paper
Lee, J., Nürnberger, T. (2003). Is Pore Formation Activity of HrpZ Required for Defence Activation in Plant Cells?. In: Iacobellis, N.S., et al. Pseudomonas syringae and related pathogens. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-0133-4_18
Download citation
DOI: https://doi.org/10.1007/978-94-017-0133-4_18
Publisher Name: Springer, Dordrecht
Print ISBN: 978-90-481-6267-3
Online ISBN: 978-94-017-0133-4
eBook Packages: Springer Book Archive