Iavicoli, Annalisa Boutet, Emmanuel Buchala, Antony J. Métraux, Jean-Pierre 2003 Root inoculation of <i>Arabidopsis thaliana</i> ecotype Columbia with <i>Pseudomonas fluorescens</i> CHA0r partially protected leaves from the oomycete <i>Peronospora parasitica</i>. The molecular determinants of <i>Pseudomonas fluorescens</i> CHA0r for this induced systemic resistance (ISR) were investigated, using mutants derived from strain CHA0: CHA400 (pyoverdine deficient), CHA805 (exoprotease deficient), CHA77 (HCN deficient), CHA660 (pyoluteorin deficient), CHA631 (2,4-diacetylphloroglucinol [DAPG] deficient), and CHA89 (HCN, DAPG- and pyoluteorin deficient). Only mutations interfering with DAPG production led to a significant decrease in ISR to <i>Peronospora parasitica</i>. Thus, DAPG production in <i>Pseudomonas fluorescens</i> is required for the induction of ISR to <i>Peronospora parasitica. </i>DAPG is known for its antibiotic activity; however, our data indicate that one action of DAPG could be due to an effect on the physiology of the plant. DAPG at 10 to 100 µM applied to roots of <i>Arabidopsis</i> mimicked the ISR effect. CHA0r-mediated ISR was also tested in various <i>Arabidopsis</i> mutants and transgenic plants: NahG (transgenic line degrading salicylic acid [SA]), <i>sid2-1</i> (nonproducing SA), <i>npr1-1</i> (nonexpressing NPR1 protein), <i>jar1-1</i> (insensitive to jasmonic acid and methyl jasmonic acid), <i>ein2-1</i> (insensitive to ethylene), <i>etr1-1</i> (insensitive to ethylene), <i>eir1-1</i> (insensitive to ethylene in roots), and <i>pad2-1</i> (phytoalexin deficient). Only <i>jar1-1, eir1-1</i>, and <i>npr1-1</i> mutants were unable to undergo ISR. Sensitivity to jasmonic acid and functional NPR1 and EIR1 proteins were required for full expression of CHA0r-mediated ISR. The requirements for ISR observed in this study in <i>Peronospora parasitica </i>induced by<i> Pseudomonas fluorescens</i> CHA0r only partially overlap with those published so far for <i>Peronospora parasitica</i>, indicating a great degree of flexibility in the molecular processes leading to ISR. application/pdf https://folia.unifr.ch/global/documents/300055 https://folia.unifr.ch/documents/300055/files/1_metraux_isr.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1094/MPMI.2003.16.10.851 info:eu-repo/semantics/openAccess License undefined Molecular Plant-Microbe Interactions. - 2003, vol. 16, no. 10, p. 851-858 info:eu-repo/classification/udc/57 Induced Systemic Resistance in Arabidopsis thaliana in Response to Root Inoculation with Pseudomonas fluorescens CHA0 http://purl.org/coar/resource_type/c_6501