HrpZ harpins from different Pseudomonas syringae pathovars differ in molecular interactions and in induction of anion channel responses in Arabidopsis thaliana suspension cells

• Published in: Plant physiology and biochemistry 2012-02, Vol.51, p.168-174
• Main Authors: Haapalainen, M., Dauphin, A., Li, C.-M., Bailly, G., Tran, D., Briand, J., Bouteau, F., Taira, S.
• Format: Article
• Language: English
• Subjects: Alleles; Anion currents; Arabidopsis - cytology; Arabidopsis - microbiology; Arabidopsis - physiology; Arabidopsis cells; Arabidopsis thaliana; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Bacterial plant pathogens; bacteriophages; Biological and medical sciences; Cell Death; Cells, Cultured; Electrophysiological Phenomena; Fundamental and applied biological sciences. Psychology; Harpins; host specificity; Host-Pathogen Interactions; Host-specific interactions; KORC; Lycopersicon esculentum; Mutation; pathogens; Peptide Library; Peptide-binding; peptides; Phytopathology. Animal pests. Plant and forest protection; Plant Cells - metabolism; Plant Cells - microbiology; Plant physiology and development; potassium channels; Potassium Channels - metabolism; Protein Binding; Pseudomonas syringae; Pseudomonas syringae - genetics; Pseudomonas syringae - pathogenicity; secretion; Species Specificity; Substrate Specificity; Time Factors; tomatoes
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2011.10.022

HrpZ, a type three secretion system helper protein from the plant-pathogen Pseudomonas syringae, can be recognized by many plants as a defence elicitor. Responses of Arabidopsis thaliana suspension cells to different HrpZ variants were studied by electrophysiological methods and cell death assay. Purified HrpZ originating from a compatible pathogen P. syringae pv. tomato DC3000 (HrpZ Pto) and incompatible P. syringae pv. phaseolicola (HrpZ Pph) both promoted Arabidopsis cell death. As an early response, both HrpZ variants induced an increase in time dependent K + outward rectifying current. In contrast, the effects of HrpZ proteins on anion currents were different: HrpZ Pph had no effect, and HrpZ Pto induced an anion current increase. This suggests that the observed responses of the K + channels and anion channels resulted from different and separable interactions and that the interaction implied in anion current modulation is host-specific. HrpZ Pto and HrpZ Pph also had a different sequence preference in phage display screen for peptide-binding. These peptides presumably represent a part of a putative target protein in the host, and HrpZ proteins of different P. syringae pathovars might have different binding specificities to match the allelic variation between plant species. Supporting the idea that the peptide-binding region of HrpZ is important for interactions with host cell components, we found that a mutation in that region changed the anion channel response of Arabidopsis cells. ► Responses of Arabidopsis suspension cells to different variants of HrpZ harpin. ► HrpZ from compatible (Pto) and incompatible (Pph) strains of Pseudomonas syringae. ► HrpZ(Pto) induced an anion current increase while HrpZ(Pph) did not. ► A mutation in HrpZ(Pto) peptide-binding region changed the anion channel response. ► HrpZ(Pto) and HrpZ(Pph) have different sequence preferences for peptide-binding.