title: The inter-kingdom volatile signal indole promotes root development by interfering with auxin signalling.
abstract: Recently, emission of volatile organic compounds (VOCs) has emerged as a mode of communication between bacteria and plants. Although some bacterial VOCs that promote plant growth have been identified, their underlying mechanism of action is unknown. Here we demonstrate that indole, which was identified using a screen for Arabidopsis growth promotion by VOCs from soil-borne bacteria, is a potent plant-growth modulator. Its prominent role in increasing the plant secondary root network is mediated by interfering with the auxin-signalling machinery. Using auxin reporter lines and classic auxin physiological and transport assays we show that the indole signal invades the plant body, reaches zones of auxin activity and acts in a polar auxin transport-dependent bimodal mechanism to trigger differential cellular auxin responses. Our results suggest that indole, beyond its importance as a bacterial signal molecule, can serve as a remote messenger to manipulate plant growth and development.
authors.affiliation: Department of Microbiology, Institute of Plant Biology, University of Zurich, Zurich, Switzerland; Institute for Sustainability Sciences, Agroscope, Zurich, Switzerland.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Bailly
authors.forename: Ulrike
authors.initials: U
authors.lastname: Groenhagen
authors.forename: Stefan
authors.initials: S
authors.lastname: Schulz
authors.forename: Markus
authors.initials: M
authors.lastname: Geisler
authors.forename: Leo
authors.initials: L
authors.lastname: Eberl
authors.forename: Laure
authors.initials: L
authors.lastname: Weisskopf
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D004926:Escherichia coli / Q000378:metabolism; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism* / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014364:Tryptophan / Q000378:metabolism; D055549:Volatile Organic Compounds / Q000378:metabolism / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D044783:F-Box Proteins; D007210:Indoleacetic Acids; D007211:Indoles; D011956:Receptors, Cell Surface; C501405:TIR1 protein, Arabidopsis; D055549:Volatile Organic Compounds; C030737:indoleacetic acid; D014364:Tryptophan
keywords: Arabidopsis thaliana; Escherichia coli; auxin signalling; plant-growth-promoting rhizobacteria; plant-microbe interaction; root development; volatile organic compounds