title: Plant-derived auxin plays an accessory role in symptom development upon Rhodococcus fascians infection.
abstract: The biotrophic phytopathogen Rhodococcus fascians has a profound impact on plant development, mainly through its principal virulence factors, a mix of synergistically acting cytokinins that induce shoot formation. Expression profiling of marker genes for several auxin biosynthesis routes and mutant analysis demonstrated that the bacterial cytokinins stimulate the auxin biosynthesis of plants via specific targeting of the indole-3-pyruvic acid (IPA) pathway, resulting in enhanced auxin signaling in infected tissues. The double mutant tryptophan aminotransferase 1-1 tryptophan aminotransferase related 2-1 (taa1-1 tar2-1) of Arabidopsis (Arabidopsis thaliana), in which the IPA pathway is defective, displayed a decreased responsiveness towards R. fascians infection, although bacterial colonization and virulence gene expression were not impaired. These observations implied that plant-derived auxin was employed to reinforce symptom formation. Furthermore, the increased auxin production and, possibly, the accumulating bacterial cytokinins in infected plants modified the polar auxin transport so that new auxin maxima were repetitively established and distributed, a process that is imperative for symptom onset and maintenance. Based on these findings, we extend our model of the mode of action of bacterial and plant signals during the interaction between R. fascians and Arabidopsis.
authors.affiliation: Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Stes
authors.forename: Els
authors.initials: E
authors.lastname: Prinsen
authors.forename: Marcelle
authors.initials: M
authors.lastname: Holsters
authors.forename: Danny
authors.initials: D
authors.lastname: Vereecke
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D001692:Biological Transport; D003583:Cytokinins / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D054884:Host-Pathogen Interactions; D007210:Indoleacetic Acids / Q000032:analysis / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D035261:Plant Components, Aerial / Q000235:genetics / Q000254:growth & development / Q000382:microbiology / Q000502:physiology; D010935:Plant Diseases / Q000382:microbiology*; D010937:Plant Growth Regulators / Q000032:analysis / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000382:microbiology / Q000502:physiology; D018749:RNA, Plant / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012240:Rhodococcus / Q000254:growth & development / Q000472:pathogenicity*; D015398:Signal Transduction / Q000187:drug effects; D051279:Tryptophan Transaminase / Q000235:genetics; D014774:Virulence / Q000187:drug effects
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D007211:Indoles; D010937:Plant Growth Regulators; D018749:RNA, Plant; C008122:indol-3-yl pyruvic acid; D051279:Tryptophan Transaminase