title: Bacteria establish an aqueous living space in plants crucial for virulence.
abstract: High humidity has a strong influence on the development of numerous diseases affecting the above-ground parts of plants (the phyllosphere) in crop fields and natural ecosystems, but the molecular basis of this humidity effect is not understood. Previous studies have emphasized immune suppression as a key step in bacterial pathogenesis. Here we show that humidity-dependent, pathogen-driven establishment of an aqueous intercellular space (apoplast) is another important step in bacterial infection of the phyllosphere. Bacterial effectors, such as Pseudomonas syringae HopM1, induce establishment of the aqueous apoplast and are sufficient to transform non-pathogenic P. syringae strains into virulent pathogens in immunodeficient Arabidopsis thaliana under high humidity. Arabidopsis quadruple mutants simultaneously defective in a host target (AtMIN7) of HopM1 and in pattern-triggered immunity could not only be used to reconstitute the basic features of bacterial infection, but also exhibited humidity-dependent dyshomeostasis of the endophytic commensal bacterial community in the phyllosphere. These results highlight a new conceptual framework for understanding diverse phyllosphere-bacterial interactions.
authors.affiliation: Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Xiu-Fang
authors.initials: XF
authors.lastname: Xin
authors.affiliation: Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Kinya
authors.initials: K
authors.lastname: Nomura
authors.affiliation: Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.|Howard Hughes Medical Institute-Gordon and Betty Moore Foundation, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Kyaw
authors.initials: K
authors.lastname: Aung
authors.affiliation: Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: André C
authors.initials: AC
authors.lastname: Velásquez
authors.affiliation: Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Yao
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Freddy
authors.initials: F
authors.lastname: Boutrot
authors.affiliation: Department of Botany and Plant Pathology and Center for Genome Research and Biocomputing, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Jeff H
authors.initials: JH
authors.lastname: Chang
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Cyril
authors.initials: C
authors.lastname: Zipfel
authors.affiliation: Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.|Howard Hughes Medical Institute-Gordon and Betty Moore Foundation, Michigan State University, East Lansing, Michigan 48824, USA.|Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA.|Plant Resilience Institute, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Sheng Yang
authors.initials: SY
authors.lastname: He
mesh_terms: D017360:Arabidopsis / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D006706:Homeostasis; D054884:Host-Pathogen Interactions; D006813:Humidity; D007108:Immune Tolerance; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*; D057865:Plant Immunity; D018515:Plant Leaves / Q000276:immunology / Q000382:microbiology*; D044224:Pseudomonas syringae / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000472:pathogenicity*; D013559:Symbiosis; D014774:Virulence / Q000276:immunology; D014867:Water / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C512008:At3g43300 protein, Arabidopsis; D001426:Bacterial Proteins; D020662:Guanine Nucleotide Exchange Factors; D014867:Water