Funktionelle Charakterisierung konservierter putativer Effektorproteine in Sebacinales
Zell- und Entwicklungsbiologie der Pflanzen
Zusammenfassung der Projektergebnisse
To establish an integrated and holistic view of the metabolic interplay between plants and their microbes it is of paramount importance to investigate the mechanisms by which plant-associated microbes manipulate plant derived metabolites and how plant metabolism is linked to immunity. The study of apoplastic communication and metabolic fluxes during microbial colonization is an emerging research field which is still understudied. The recent improvements in LC–MS/MS and functional analysis of effector proteins made it now possible to identify and characterize microbial proteins in this compartment. During root colonization, plants and microbes secrete a number of proteins that are important for the outcome of the interaction. Although most of the work published focused on the interaction of microbial effectors with host proteins, we showed that the manipulation of plant derived metabolites in the apoplast by microbes plays an important role that should be addressed also in future studies. In this DFG funded project we combined bioinformatics and proteomics approaches to select putative compatibility factors from the apoplast. We identified several putative effectors from the root endophyte Serendipita indica (syn. Piriformospora indica) and characterized four secreted proteins with functions in: 1. manipulation of host immunity; 2. fungal cell wall reinforcement and modelling; 3. modification of apoplastic metabolism and 4. host cell death. We could show that the presence of two in planta-induced beta-glucan-binding fungal lectins that reinforce the fungal cell wall and protect the fungus from recognition by the plant immune system, implies that this neglected fungal cell wall component plays an important role during host colonization. We demonstrated that these lectins can be used as molecular probes to detect fungal derived betaglucan in different plant tissues. We additionally showed that during root colonization of barley and Arabidopsis by the beneficial fungal endophyte Serendipita indica (syn. Piriformospora indica) an accumulation of eATP in the apoplast occurs at early colonization stages but not during the cell death associated phase. The Arabidopsis dorn1-eATP receptor mutant line is better colonized by S. indica than the control line, especially at early time points, suggesting that eATP perception is important in root-fungus interactions. Proteome analysis identified the fungal derived ecto-5'-nucleotidase (E5´NT) in the plant root apoplast which was consistently found at all three symbiotic stages analyzed. Functional characterization of the substrate specificity of SiE5´NT shows that this fungal enzyme hydrolyzes different nucleotides extracellularly. A. thaliana SiE5´NT expressing lines are better colonized compared to the control lines, accumulate significantly less eATP upon fungal challenge and have lower expression levels for plant defense genes. In conclusion, our DFG funded work demonstrate that eATP perception plays an important role in plant-fungus interaction in the roots and that fungi have an intrinsic mechanism to counteract bioactive extracellular nucleotides-mediated host signaling.
Projektbezogene Publikationen (Auswahl)
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2016. The fungalspecific β-glucan binding lectin FGB1 alters cell wall composition and prevents glucan-triggered immunity in plants. Nature Communications
Wawra S, Fesel P, Widmer H, Leson L, Nostadt R, Langen G, Zuccaro A
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2019. FGB1 and WSC3 are in planta-induced beta-glucan-binding fungal lectins with different functions. New Phytologist
Wawra S, Fesel P, Widmer H, Neumann U, Lahrmann U, Becker S, Hehemann JH, Langen G, Zuccaro A
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2019. Serendipita indica E5NT modulates extracellular nucleotide levels in the plant apoplast and affects fungal colonization. 2019. EMBO reports
Nizam S, Qiang X, Wawra S, Nostadt R, Getzke F, Schwanke F, Dreyer I, Langen G, Zuccaro A.
