title: Phosphatidylcholine synthesis is essential for HrpZ harpin secretion in plant pathogenic Pseudomonas syringae and non-pathogenic Pseudomonas sp. 593.
abstract: Pseudomonas syringae pv. syringae van Hall is important phytopathogenic bacterium of stone fruit trees, and able to elicit hypersensitive response (HR) in nonhost plants. The HrpZ, secreted via type III secretion system (T3SS) to the extracellular space of the plant, is a T3SS-dependent protein and a sole T3SS effector able to induce the host defense response outside host cells. We deleted the phosphatidylcholine synthase gene (pcs) of P. syringae pv. syringae van Hall CFCC 1336, and found that the 1336 pcs(-) mutant was unable to synthesize phosphatidylcholine and elicit a typical HR in soybean. Further studies showed that the 1336 pcs(-) mutant was unable to secrete HrpZ harpin but could express HrpZ protein in cytoplasm as effectively as the wild type. To confirm if phosphatidylcholine affects HrpZ harpin secretion, we introduced the hrpZ gene into the soil-dwelling bacterium Pseudomonas sp. 593 and the 593 pcs(-) mutant, which were unable to express HrpZ harpin and elicit HR in tobacco or soybean. Western blotting and HR assay showed that the 593H not only secreted HrpZ harpin but also caused a strong HR in tobacco and soybean. In contrast, the 593 pcs(-)H only expressed HrpZ protein in its cytoplasm at the wild type level, but did not secrete HrpZ harpin or elicit HR reaction. Our results demonstrate that phosphatidylcholine is essential for the secretion of HrpZ harpin in P. syringae pv. syringae van Hall and other Pseudomonas strains.
authors.affiliation: The Faculty of Life Science, Hubei University, China.
authors.forename: Min
authors.initials: M
authors.lastname: Xiong
authors.affiliation: The Faculty of Life Science, Hubei University, China.
authors.forename: Deliang
authors.initials: D
authors.lastname: Long
authors.affiliation: The Faculty of Life Science, Hubei University, China.
authors.forename: Huoguang
authors.initials: H
authors.lastname: He
authors.affiliation: The Faculty of Life Science, Hubei University, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.affiliation: The Faculty of Life Science, Hubei University, China.
authors.forename: Yadong
authors.initials: Y
authors.lastname: Li
authors.affiliation: The Faculty of Life Science, Hubei University, China. Electronic address: xgwang@hubu.edu.cn.
authors.forename: Xingguo
authors.initials: X
authors.lastname: Wang
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000096:biosynthesis* / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*; D021381:Protein Transport; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D044224:Pseudomonas syringae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D013025:Glycine max / Q000276:immunology / Q000382:microbiology; D014026:Nicotiana / Q000276:immunology / Q000382:microbiology; D017855:Transferases (Other Substituted Phosphate Groups) / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D010713:Phosphatidylcholines; C087295:HrpZ protein, Pseudomonas syringae; D017855:Transferases (Other Substituted Phosphate Groups); C483298:CDP-diacylglycerol choline O-phosphatidyltransferase
keywords: HrpZ harpin; Hypersensitive response; Phosphatidylcholine; Pseudomonas; Secretion