Effect of crude exudates of <i>R. irregularis</i> on seed viability of <i>O. cumana</i>.

<p>Seeds were stained with TTC and examined with a dissecting microscope. Data represent the average percentage of viable seeds. Five batches of approx. 100 seeds were used for each treatment. Means were compared using the Kruskal-Wallis test. No significant differences between treatments were found.</p

Response of <i>O. cumana</i> seeds to <i>R. irregularis</i> exudates and pure germination stimulants.

<p>AM ex corresponds to 1,000 spores per mL in 0.2% acetone. Control: solvent only (0.2% acetone). GR24 and DCL were used at a final concentration of 10⁻⁸ M in 0.2% acetone. Data represent the average germination rate of five batches of approx. 100 seeds, +/−s.e.m. Means were compared using the Kruskal-Wallis test. Different letters indicate significant differences (P<0.05).</p

Induction of <i>O. cumana</i> germination by root exudates and GR24.

<p>Seeds were treated with GR24, and/or root exudates of mycorrhizal or non-mycorrhizal plants. Control: solvent only (0.1% acetone). GR24∶10⁻⁸ M GR24 in 0.1% acetone. Non-Myc and Myc: root exudates of non-mycorrhizal and mycorrhizal plants, respectively. Data represent the average germination percentage of five batches of approx. 100 seeds, +/−s.e.m. Means were compared using the Kruskal-Wallis test; different letters indicate statistically significant differences (P<0.05).</p

Effect of mycorrhizal status on sunflower infestation by <i>O. cumana</i>.

<p>Sunflower plants were inoculated with <i>O. cumana</i> seeds, in the presence or absence of AM fungal spores. A- Photograph of <i>O. cumana</i> tubercles of different sizes observed on sunflower roots. At the time of harvest (five or six weeks post inoculation) almost all attached broomrapes were at the tubercle stage. B- Number of <i>O. cumana</i> tubercles. The results of six independent experiments (Exp1 to Exp6) are presented. Values represent the average number of <i>O. cumana</i> tubercles per plant, +/− s.e.m (n = 8 to 10 plants per condition for each experiment). The asterisks indicate a highly significant effect of mycorrhizal inoculation according to multi-way ANOVA (P = 0.008, see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049273#pone.0049273.s003" target="_blank">Table S1</a>).</p

Robust Method for Investigating Nitrogen Metabolism of ¹⁵N Labeled Amino Acids Using AccQ•Tag Ultra Performance Liquid Chromatography-Photodiode Array-Electrospray Ionization-Mass Spectrometry: Application to a Parasitic Plant–Plant Interaction

An AccQ•Tag ultra performance liquid chromatography-photodiode array-electrospray ionization-mass spectrometry (AccQ•Tag-UPLC-PDA-ESI-MS) method is presented here for the fast, robust, and sensitive quantification of ¹⁵N isotopologue enrichment of amino acids in biological samples, as for example in the special biotic interaction between the cultivated specie <i>Brassica napus</i> (rapeseed) and the parasitic weed <i>Phelipanche ramosa</i> (broomrape). This method was developed and validated using amino acid standard solutions containing ¹⁵N amino acid isotopologues and/or biological unlabeled extracts. Apparatus optimization, limits of detection and quantification, quantification reproducibility, and calculation method of ¹⁵N isotopologue enrichment are presented. Using this method, we could demonstrate that young parasite tubercles assimilate inorganic nitrogen as ¹⁵N-ammonium when supplied directly through batch incubation but not when supplied by translocation from host root phloem, contrary to ¹⁵N₂-glutamine. ¹⁵N₂-glutamine mobility from host roots to parasite tubercles followed by its low metabolism in tubercles suggests that the host-derived glutamine acts as an important nitrogen containing storage compound in the young tubercle of <i>Phelipanche ramosa</i>