title: Expression profiling during arabidopsis/downy mildew interaction reveals a highly-expressed effector that attenuates responses to salicylic acid.
abstract: Plants have evolved strong innate immunity mechanisms, but successful pathogens evade or suppress plant immunity via effectors delivered into the plant cell. Hyaloperonospora arabidopsidis (Hpa) causes downy mildew on Arabidopsis thaliana, and a genome sequence is available for isolate Emoy2. Here, we exploit the availability of genome sequences for Hpa and Arabidopsis to measure gene-expression changes in both Hpa and Arabidopsis simultaneously during infection. Using a high-throughput cDNA tag sequencing method, we reveal expression patterns of Hpa predicted effectors and Arabidopsis genes in compatible and incompatible interactions, and promoter elements associated with Hpa genes expressed during infection. By resequencing Hpa isolate Waco9, we found it evades Arabidopsis resistance gene RPP1 through deletion of the cognate recognized effector ATR1. Arabidopsis salicylic acid (SA)-responsive genes including PR1 were activated not only at early time points in the incompatible interaction but also at late time points in the compatible interaction. By histochemical analysis, we found that Hpa suppresses SA-inducible PR1 expression, specifically in the haustoriated cells into which host-translocated effectors are delivered, but not in non-haustoriated adjacent cells. Finally, we found a highly-expressed Hpa effector candidate that suppresses responsiveness to SA. As this approach can be easily applied to host-pathogen interactions for which both host and pathogen genome sequences are available, this work opens the door towards transcriptome studies in infection biology that should help unravel pathogen infection strategies and the mechanisms by which host defense responses are overcome.
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom; Center for Sustainable Resource Science, RIKEN, Tsurumi, Yokohama, Kanagawa, Japan.
authors.forename: Shuta
authors.initials: S
authors.lastname: Asai
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Ghanasyam
authors.initials: G
authors.lastname: Rallapalli
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Sophie J M
authors.initials: SJ
authors.lastname: Piquerez
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Marie-Cécile
authors.initials: MC
authors.lastname: Caillaud
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Furzer
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Naveed
authors.initials: N
authors.lastname: Ishaque
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom; John Innes Centre, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Lennart
authors.initials: L
authors.lastname: Wirthmueller
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Georgina
authors.initials: G
authors.lastname: Fabro
authors.affiliation: Center for Sustainable Resource Science, RIKEN, Tsurumi, Yokohama, Kanagawa, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Shirasu
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Jonathan D G
authors.initials: JD
authors.lastname: Jones
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions / Q000187:drug effects / Q000276:immunology*; D009868:Oomycetes / Q000187:drug effects* / Q000235:genetics; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D057865:Plant Immunity / Q000276:immunology*; D020156:Salicylic Acid / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; D020156:Salicylic Acid