Virulence traits and origin of potato soft-rot pathogens.

*<p>The potential of each strain to induce a tuber soft-rot was evaluated in potato host plant seven days after infection by intra-medulla injection.</p>#<p>The potential of each strain to induce a hypersensitive response (HR) was evaluated in tobacco non host plant 24 hours after leaves infiltration.</p><p>CFBP, Collection Française de Bactéries Phytopathogènes, Institut National de la Recherche Agronomique, Angers, France.</p

Bacterial QS signal producers or biosensors, and plasmids.

<p>Gm^r and Tet^r indicate resistance to gentamicin and tetracycline, respectively.</p><p>NAHSL, N-acyl homoserine lactones; AI-2, Autoinducer-2; HHQ, 4-hydroxy-2-heptylquinoline; PQS, Pseudomonas quinolone signal.</p

Characterization of signaling molecules produced by potato soft-rot pathogens.

*<p>Production of different N-acyl homoserine lactones (NAHSL) was determined by thin-layer chromatography (TLC) and HPLC-MS/MS. For quantification, NAHSL were extracted from PGA minimal medium culture at late exponential phase (optimal production).</p>#<p>Autoinducer-2 (AI-2) activity was determined using biosensor <i>V. harveyi</i> BB170.</p>°<p>Production of 4-hydroxy-2-heptylquinoline (HHQ) and Pseudomonas quinolone signal (PQS) were determined by TLC.</p>†<p>Production of indole-3-acetic acid (IAA), indole-3-propionic acid (IPA), indole-3-butyric acid (IBA) and kynurenic acid (KA) were determined by HPLC-UV. For quantification, indolic compounds were extracted from M9 minimal medium supplemented with l-tryptophan culture at stationary growth phase (optimal production).</p>§<p>Production of γ-amino butyric acid (GABA) was determined by ELISA test.(+) positive detection by the biosensor; (−) not detected or below threshold.</p

Kinetics of IAA-like production measured in the supernatant of potato soft-rot <i>Dickeya</i> spp.

<p>Indolic compounds were quantified by a colorimetric method with Salkowski's reagent. Bacterial growth was monitored by measuring optical density (OD) at 580 nm. For each point, at least 3 independent cultures in M9 minimal medium supplemented with l-tryptophan (500 µg/ml) were analyzed, with standard deviation shown.</p

Kinetics of <i>metK</i>, <i>luxI</i>, <i>luxS</i> and <i>iaaM</i> gene expression involved in AI-1, AI-2 and IAA production by <i>D. chrysanthemi</i> strain CFBP 2048^T.

<p>AI-1 and AI-2 biosynthetic pathways are described in the legend to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035176#pone-0035176-g003" target="_blank">Fig. 3</a>. A third signal, the indole-3-acetic acid (IAA) is synthesized by the indole-3-acetamine (IAM) pathway, in which l-tryptophan is first converted to IAM by the key enzyme of this pathway, the IaaM tryptophan-2-monooxygenase. IAM is then converted to IAA by IaaM hydrolase <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035176#pone.0035176-Yang1" target="_blank">[36]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035176#pone.0035176-Spaepen1" target="_blank">[54]</a>. Abundances of <i>metK</i> (checkered bars), <i>luxI</i> (white bars), <i>luxS</i> (black bars) and <i>iaaM</i> (grey bars) mRNAs were determined by RT-PCR experiments on RNA extracts from cells grown in PGA minimal medium (<b>A</b>) or M9 minimal medium supplemented with l-tryptophan (500 µg/ml) (<b>B</b>) and harvested at mid-exponential phase (<b>1</b>), late exponential phase (<b>2</b>), during the transition from exponential to stationary phases (<b>3</b>) or early stationary growth phase (<b>4</b>) followed by electrophoresis on 1% (m/v) agarose gels. Results were expressed as a ratio: synthase transcripts vs. 16S transcripts. The corresponding kinetics of AI-1 and AI-2 activities and IAA production in the supernatant of potato soft-rot <i>Dickeya</i> strain are shown at the top.</p