Long distance signaling during pathogen-induced systemic acquired resistance in plants: lipid requisites and their interface(s) with salicylates
Final Report Abstract
The study of the mobile signal in systemic acquired resistance (SAR) is an important area of plant disease resistance research. The project presented here investigated the signaling events leading to SAR in plants upon pathogen attack. For the systemic initiation of resistance a mobile signal is needed, which is produced at the site of infection and travels to the healthy uninfected parts of a plant. My research concentrated on the crosstalk between salicylates and lipid-based signaling, two signaling pathways leading lo SAR that were originally thought to act independently. We revealed that the lipid transport protein DIRl (defective in induced resistancel) that was previously shown to be involved in systemic signaling of SAR functions through the regulation of the accumulation and biosynthesis of methyl salicylate (MeSA) and salicylic acid (SA), two signaling molecules also known to be important for SAR signaling. A major problem of the project was the analysis of petiole exudates (PEX) from tobacco mosaic vims (TMV)-infected leaves. The aim was to find additional mobile signals for SAR in these PEX by 2-D NMR and bioassay-aided fractionation. This approach was technically challenging. During several optimization attempts of the bioassay it became clear that there might be a much stronger light-dependency for SAR to develop than originally expected. In the course of this struggle we also aimed to understand the controversial results concerning the relevance of MeSA for SAR development. In the end, one major finding of the presented work was that the length of light exposure after primary infection of plants determines the extent to which MeSA is required for SAR signaling and the overall strength of SAR. The findings of the project contribute significantly to the area of SAR research. We could show that the complexity of the signal leading to SAR is much higher than originally expected. Not only is SAR regulated by a much higher degree of signaling crosstalk, but there is also a stronger impact of environmental factors on SAR development itself and on the strength of the signaling crosstalk. The story of SAR signaling becomes more and more complex, as simple assumptions are falsified and more signals are identified. Caution is needed when single model systems are used and when experimental designs are chosen.
Publications
- (2011) Interconnection between methyl salicylate and lipid-based long-distance signaling during the development of systemic acquired resistance in Arabidopsis and tobacco. Plant Physiol. 155: 1762-1768
Po-Pu Liu, Caroline C. von Dahl, Sang-Wook Park, and Daniel F. Klessig
- (2011) The extent to which methyl salicylate is required for signaling systemic acquired resistance is dependent on exposure to light after infection. Plant Physiol
Po-Pu Liu, Caroline C. von Dahl, and Daniel F. Klessig
(See online at https://doi.org/10.1104/pp.111.187773)
