title: Indole-3-acetaldoxime-derived compounds restrict root colonization in the beneficial interaction between Arabidopsis roots and the endophyte Piriformospora indica.
abstract: The growth-promoting and root-colonizing endophyte Piriformospora indica induces camalexin and the expression of CYP79B2, CYP79B3, CYP71A13, PAD3, and WRKY33 required for the synthesis of indole-3-acetaldoxime (IAOx)-derived compounds in the roots of Arabidopsis seedlings. Upregulation of the mRNA levels by P. indica requires cytoplasmic calcium elevation and mitogen-activated protein kinase 3 but not root-hair-deficient 2, radical oxygen production, or the 3-phosphoinositide-dependent kinase 1/oxidative signal-inducible 1 pathway. Because P. indica-mediated growth promotion is impaired in cyp79B2 cyp79B3 seedlings, while pad3 seedlings-which do not accumulate camalexin-still respond to the fungus, IAOx-derived compounds other than camalexin (e.g., indole glucosinolates) are required during early phases of the beneficial interaction. The roots of cyp79B2 cyp79B3 seedlings are more colonized than wild-type roots, and upregulation of the defense genes pathogenesis-related (PR)-1, PR-3, PDF1.2, phenylalanine ammonia lyase, and germin indicates that the mutant responds to the lack of IAOx-derived compounds by activating other defense processes. After 6 weeks on soil, defense genes are no longer upregulated in wild-type, cyp79B2 cyp79B3, and pad3 roots. This results in uncontrolled fungal growth in the mutant roots and reduced performance of the mutants. We propose that a long-term harmony between the two symbionts requires restriction of root colonization by IAOx-derived compounds.
authors.affiliation: Friedrich-Schiller-University, Jena, Germany.
authors.forename: Pyniarlang L
authors.initials: PL
authors.lastname: Nongbri
authors.forename: Joy Michal
authors.initials: JM
authors.lastname: Johnson
authors.forename: Irena
authors.initials: I
authors.lastname: Sherameti
authors.forename: Erich
authors.initials: E
authors.lastname: Glawischnig
authors.forename: Barbara Ann
authors.initials: BA
authors.lastname: Halkier
authors.forename: Ralf
authors.initials: R
authors.lastname: Oelmüller
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000382:microbiology*; D001487:Basidiomycota / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D007211:Indoles / Q000737:chemistry* / Q000494:pharmacology*; D010091:Oximes / Q000737:chemistry* / Q000494:pharmacology*; D018517:Plant Roots / Q000382:microbiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012988:Soil Microbiology; D013997:Time Factors
chemical_list: D007211:Indoles; D010091:Oximes; D012333:RNA, Messenger; C467098:indole-3-acetaldoxime