title: Indole derivative production by the root endophyte Piriformospora indica is not required for growth promotion but for biotrophic colonization of barley roots.
abstract: Beneficial effects elicited by the root endophyte Piriformospora indica are widely known, but the mechanism by which these are achieved is still unclear. It is proposed that phytohormones produced by the fungal symbiont play a crucial role in the interaction with the plant roots. Biochemical analyses of the underlying biosynthetic pathways for auxin production have shown that, on tryptophan feeding, P. indica can produce the phytohormones indole-3-acetic acid (IAA) and indole-3-lactate (ILA) through the intermediate indole-3-pyruvic acid (IPA). Time course transcriptional analyses after exposure to tryptophan designated the piTam1 gene as a key player. A green fluorescence protein (GFP) reporter study and transcriptional analysis of colonized barley roots showed that piTam1 is induced during the biotrophic phase. Piriformospora indica strains in which the piTam1 gene was silenced via an RNA interference (RNAi) approach were compromised in IAA and ILA production and displayed reduced colonization of barley (Hordeum vulgare) roots in the biotrophic phase, but the elicitation of growth promotion was not affected compared with the wild-type situation. Our results suggest that IAA is involved in the establishment of biotrophy in P. indica-barley symbiosis and might represent a compatibility factor in this system.
authors.affiliation: Department of Organismic Interactions, Max Planck Institute for Terrestrial Microbiology, Karl von Frisch Str. 10, 35043, Marburg, Germany.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Hilbert
authors.affiliation: Department of Biology, Friedrich-Alexander University Erlangen-Nürnberg, Staudtstr. 5, 91058, Erlangen, Germany.
authors.forename: Lars M
authors.initials: LM
authors.lastname: Voll
authors.affiliation: Department of Organismic Interactions, Max Planck Institute for Terrestrial Microbiology, Karl von Frisch Str. 10, 35043, Marburg, Germany.
authors.forename: Yi
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Department of Biology, Friedrich-Alexander University Erlangen-Nürnberg, Staudtstr. 5, 91058, Erlangen, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Hofmann
authors.affiliation: Department of Mycology and Plant Pathology, Dr. YSP UHF, Nauni, Solan, HP, India.
authors.forename: Monica
authors.initials: M
authors.lastname: Sharma
authors.affiliation: Department of Organismic Interactions, Max Planck Institute for Terrestrial Microbiology, Karl von Frisch Str. 10, 35043, Marburg, Germany.
authors.forename: Alga
authors.initials: A
authors.lastname: Zuccaro
mesh_terms: D001487:Basidiomycota / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015169:Colony Count, Microbial; D060026:Endophytes / Q000187:drug effects / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D055785:Gene Knockdown Techniques; D005800:Genes, Fungal / Q000235:genetics; D001467:Hordeum / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism / Q000382:microbiology*; D007210:Indoleacetic Acids / Q000494:pharmacology; D007211:Indoles / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000187:drug effects; D010937:Plant Growth Regulators / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism / Q000382:microbiology*; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000382:microbiology; D013559:Symbiosis / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D014364:Tryptophan / Q000378:metabolism
chemical_list: D007210:Indoleacetic Acids; D007211:Indoles; D010937:Plant Growth Regulators; C024139:indole-3-lactic acid; C030737:indoleacetic acid; D014364:Tryptophan