Figure 1. Time course analysis of local and systemic changes in hormonal levels upon OG treatment in leaves or roots of tomato plants.Hormonal levels were quantified by UPLC-MS/MS at 1, 6 and 24 hours in tomato plants elicited with an OGs solution of 50 µg/mL. For leaf treatments (LT), the fourth true leaf was sprayed with the OGs solution and samples from the treated leaf (Local response-leaves-), upper leaf and roots (systemic response) were harvested at the different time points. For root treatments (RT) the OG solution was applied to roots and samples at the different time points were taken from roots (local response-roots-) and in the upper leaves for systemic responses (Systemic, RT). Hormone contents are shown in Sup Fig1a, b and c. Here, numbers represent fold induction in the hormone levels of treated vs control plants. Bold numbers indicate significant differences (t-test; p-value<0.05). Grey cells highlight significantly overaccumulated compounds.
Figure. 2. Impact of OG treatment on the leaf metabolic profiles a) sPLS-DA representation of ESI- and ESI+ signals obtained from a non-targeted analysis by UPLC-QTOF to monitor metabolomic changes 6 hours after OGs treatments. Three weeks old plants were treated in leaves or roots with a 50 µg/mL solution of OGs. Leaf samples were harvested 6 hours post treatment. Data points represent six biological replicates injected randomly into the UPLC-QTOF. The signals corresponding to different treatments were compared using the non-parametric Kruskal-Wallis test, and only data with a p-value<0.01 between groups was used for subsequent processing. b) Heatmap analysis of leaf metabolites responding to OGs. Signals from ESI+ and ESI- with p-value<0.01 were used to generate the heatmap analysis. The top 250 signals with the lowest p-value were selected to represent the heatmap. The relative amount of the metabolites was determined in all the samples by normalizing the chromatographic pick area of each compound with the dry weight of the corresponding sample. Local leaf responses were studied by comparing control-treated leaves (CT-TL) to OG-treated leaf (LT-TL). Systemic leaf responses were analysed comparing upper untreated leaves from water-treated plants as control (CT-SL) upper leaves from OGs treated plants in leaves (LT-SL) and to upper leaves from OGs treated plants in roots (RT-SL).
Figure 3: Impact of OG treatment on the root metabolic profilesa) sPLS-DA representation of ESI- and ESI+ signals obtained from a non-targeted analysis by UPLC-QTOF-MS to monitor metabolomic changes 6 hours after OGs treatments. Three weeks old plants were treated in leaves or roots with a solution of OGs 50 µg/mL. Root samples were harvested 6 hours post treatment. Data points represent six biological replicates injected randomly into the UPLC-QTOFMS. The signals corresponding to different treatments were compared using the non-parametric Kruskal-Wallis test, and only data with a p-value<0.01 between groups was used for subsequent processing. b) Heatmap analysis of root metabolites responding to OGs. Signals from ESI+ and ESI- with p-value<0.01 were used to generate the heatmap analysis. The top 100 signals with the lowest p-value were selected to represent the heatmap. The relative amount of the metabolites was determined in all the samples by normalizing the chromatographic pick area of each compound with the dry weight of the corresponding sample. Local root responses were studied comparing responses from control treated plants in roots (CT-Root) to OG treated roots (RT-roots). Systemic root responses were studied in roots of leaf treated plants (LT-Roots).
Figure 4. OG treatments induces systemic resistance against Botrytis cinerea . Three weeks old tomato plants were treated in roots with a 50 µg/mL OGs solution or in leaves with 50 µg/mL or 200 µg/mL OGs solution. Six hours after the treatment, plants were drop inoculated in upper or treated leaves with a Botrytis cinerea conidia suspension of 5x106 spore x mL-1. Lesion diameter was measured 5 days after inoculation. Data presented shows the average lesion diameter ±SE (n=10 plants). Asterisks indicate statistically significant differences compared to control plants (* water treated; t-test; p<0.05). Systemic leaf responses were analysed comparing upper untreated leaves from water-treated plants as control (CT-SL) to upper leaves from OGs- leaf treated plants (LT-SL) and to upper leaves from OGs-root treated plants in roots (RT-SL). Local leaf responses were studied by comparing water-treated leaves (CT-TL) to OGs treated leaf (LT-TL) at two different concentrations.
Figure 5. OG perception in leaves increases systemic leucyl aminopeptidase activity and β-1,3-glucanase GLUB gene expression.Leucyl aminopeptidase activity (JA-responsive protein) and quantitative RT-qPCR analysis of GLUB (coding for a pathogen inducible β-1,3-glucanase). Local responses were analysed in water-treated (CT-TL) or OG-treated leaves (LT-TL). Systemic responses were analysed comparing upper untreated leaves from water-treated plants as control (CT-SL) to upper leaves from OG-leaf treated plants (LT-SL) and to upper leaves from OG-root treated plants (RT-SL). Bars represent mean ± SD, n = 6 from six biological replicates. Asterisks indicate statistically significant differences compared to control plants (t-test; p-value<0.05).
Figure 6. Summary of the responses activated in tomato leaves and roots upon OG treatments. The model displays local and systemic tomato responses at the hormonal, enzymatic and metabolomic level depending on the organ of the perception. (a) Plant responses to OG treatment in leaves. Local responses in treated leaves and systemic responses in leaves and roots are shown. (b) Plant responses to OG application in roots. Local responses in roots and systemic response in leaves are shown.