title: Infection of Arabidopsis thaliana by Phytophthora parasitica and identification of variation in host specificity.
abstract: Oomycete pathogens cause severe damage to a wide range of agriculturally important crops and natural ecosystems. They represent a unique group of plant pathogens that are evolutionarily distant from true fungi. In this study, we established a new plant-oomycete pathosystem in which the broad host range pathogen Phytophthora parasitica was demonstrated to be capable of interacting compatibly with the model plant Arabidopsis thaliana. Water-soaked lesions developed on leaves within 3 days and numerous sporangia formed within 5 days post-inoculation of P. parasitica zoospores. Cytological characterization showed that P. parasitica developed appressoria-like swellings and penetrated epidermal cells directly and preferably at the junction between anticlinal host cell walls. Multiple haustoria-like structures formed in both epidermal cells and mesophyll cells 1 day post-inoculation of zoospores. Pathogenicity assays of 25 A. thaliana ecotypes with six P. parasitica strains indicated the presence of a natural variation in host specificity between A. thaliana and P. parasitica. Most ecotypes were highly susceptible to P. parasitica strains Pp014, Pp016 and Pp025, but resistant to strains Pp008 and Pp009, with the frequent appearance of cell wall deposition and active defence response-based cell necrosis. Gene expression and comparative transcriptomic analysis further confirmed the compatible interaction by the identification of up-regulated genes in A. thaliana which were characteristic of biotic stress. The established A. thaliana-P. parasitica pathosystem expands the model systems investigating oomycete-plant interactions, and will facilitate a full understanding of Phytophthora biology and pathology.
authors.affiliation: College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Yuling
authors.initials: Y
authors.lastname: Meng
authors.forename: Meng
authors.initials: M
authors.lastname: Zhang
authors.forename: Xinmeng
authors.initials: X
authors.lastname: Tong
authors.forename: Qinhu
authors.initials: Q
authors.lastname: Wang
authors.forename: Yinyin
authors.initials: Y
authors.lastname: Sun
authors.forename: Junli
authors.initials: J
authors.lastname: Quan
authors.forename: Francine
authors.initials: F
authors.lastname: Govers
authors.forename: Weixing
authors.initials: W
authors.lastname: Shan
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000469:parasitology* / Q000648:ultrastructure; D015169:Colony Count, Microbial; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D058507:Host Specificity / Q000235:genetics; D010838:Phytophthora / Q000166:cytology / Q000502:physiology*; D010935:Plant Diseases / Q000469:parasitology*; D018515:Plant Leaves / Q000469:parasitology / Q000648:ultrastructure; D018517:Plant Roots / Q000166:cytology / Q000469:parasitology; D015854:Up-Regulation / Q000235:genetics