title: A Pseudomonas syringae type III effector suppresses cell wall-based extracellular defense in susceptible Arabidopsis plants.
abstract: Bacterial effector proteins secreted through the type III secretion system (TTSS) play a crucial role in causing plant and human diseases. Although the ability of type III effectors to trigger defense responses in resistant plants is well understood, the disease-promoting functions of type III effectors in susceptible plants are largely enigmatic. Previous microscopic studies suggest that in susceptible plants the TTSS of plant-pathogenic bacteria transports suppressors of a cell wall-based plant defense activated by the TTSS-defective hrp mutant bacteria. However, the identity of such suppressors has remained elusive. We discovered that the Pseudomonas syringae TTSS down-regulated the expression of a set of Arabidopsis genes encoding putatively secreted cell wall and defense proteins in a salicylic acid-independent manner. Transgenic expression of AvrPto repressed a similar set of host genes, compromised defense-related callose deposition in the host cell wall, and permitted substantial multiplication of an hrp mutant. AvrPto is therefore one of the long postulated suppressors of an salicylic acid-independent, cell wall-based defense that is aimed at hrp mutant bacteria.
authors.affiliation: Department of Energy Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Paula
authors.initials: P
authors.lastname: Hauck
authors.forename: Roger
authors.initials: R
authors.lastname: Thilmony
authors.forename: Sheng Yang
authors.initials: SY
authors.lastname: He
mesh_terms: D017360:Arabidopsis / Q000382:microbiology / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002473:Cell Wall / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D004198:Disease Susceptibility; D005030:Ethylenes / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D018506:Gene Expression Regulation, Plant; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000502:physiology; D010935:Plant Diseases / Q000382:microbiology*; D030821:Plants, Genetically Modified; D011549:Pseudomonas / Q000235:genetics / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology; D020156:Salicylic Acid / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C119963:EIN2 protein, Arabidopsis; D005030:Ethylenes; D011956:Receptors, Cell Surface; D014157:Transcription Factors; C081695:avrPto protein, Pseudomonas syringae; C060789:hrpS protein, Pseudomonas syringae; C077559:hrpH protein, Pseudomonas syringae; D003907:Dexamethasone; C036216:ethylene; D006899:Mixed Function Oxygenases; C022619:salicylate 1-monooxygenase; D020156:Salicylic Acid