Structure, function, and targeting of RTP1p, a protein delivered from rust haustoria into the host cell

Description

Bei der biotrophen Interaktion zwischen Rostpilzen und ihren Wirtspflanzen wurde ein neuartiger Transfer eines Proteins (RTP1p) von Haustorien in die Pflanzenzellen nachgewiesen. Nach regulärer Sekretion in die extrahaustoriale Matrix gelangt RTP1p in glykosylierter Form in das Zytoplasma und teilweise in den Kern der Wirtszelle. Die Glykosylierung erscheint notwendig für die Sekretion. Die Suche nach pflanzlichen Interaktionspartnern von RTP1p soll mittels Yeast-Two-Hybrid System, mit fluoreszenzmikroskopischen Methoden (FRET) und mit Hilfe von Suppressormutanten weitergeführt werden. Es wurde beobachtet, dass RTP1p in transformierten flanzenzellen einen vitalitätsreduzierenden Effekt hat. Dieser Effekt soll mittels Reportergen-Expression, Chlorophyllfluoreszenz, Pathogenabwehr und FRAP näher charakterisiert werden. RTP1p wurde auch in filamentartigen Strukturen nachgewiesen. Deren Vorhandensein in Einstülpungen der extrahaustoriellen Membran deutet darauf hin, dass der Transfer von RTP1p in das Zytoplasma über einen Endocytose-ähnlichen Mechanismus, unter Beteiligung zytoskelettaler Komponenten der Pflanzenzelle erfolgt. Dieses Modell soll überprüft werden.

Participants
  • Vögele, Ralf - Project leader
Institutions
  • Department of Biology
Publications
    Kemen, Eric; Kemen, Ariane Christiane; Rafiqi, Maryam; Hempel, Uta; Mendgen, Kurt; Hahn, Matthias; Voegele, Ralf T. (2005): Identification of a Protein from Rust Fungi Transferred from Haustoria into Infected Plant Cells Molecular Plant Microbe Interaction. 2005, 18(11), pp. 1130-1139. ISSN 0894-0282. Available under: doi: 10.1094/MPMI-18-1130

Identification of a Protein from Rust Fungi Transferred from Haustoria into Infected Plant Cells

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The formation of haustoria is one of the hallmarks of the interaction of obligate biotrophic fungi with their host plants. In addition to their role in nutrient uptake, it is hypothesized that haustoria are actively involved in establishing and maintaining the biotrophic relationship. We have identified a 24.3-kDa protein that exhibited a very unusual allocation. Rust transferred protein 1 from Uromyces fabae (Uf-RTP1p) was not only detected in the host parasite interface, the extrahaustorial matrix, but also inside infected plant cells by immunofluorescence and electron microscopy. Uf-RTP1p does not exhibit any similarity to sequences currently listed in the public databases. However, we identified a homolog of Uf-RTP1p in the related rust fungus Uromyces striatus (Us-RTP1p). The localization of Uf-RTP1p and Us-RTP1p inside infected plant cells was confirmed, using four independently raised polyclonal antibodies. Depending on the developmental stage of haustoria, Uf-RTP1p was found in increasing amounts in host cells, including the host nucleus. Putative nuclear localization signals (NLS) were found in the predicted RTP1p sequences. However, functional efficiency could only be verified for the Uf-RTP1p NLS by means of green fluorescent protein fusions in transformed tobacco protoplasts. Western blot analysis indicated that Uf-RTP1p and Us-RTP1p most likely enter the host cell as N-glycosylated proteins. However, the mechanism by which they cross the extrahaustorial membrane and accumulate in the host cytoplasm is unknown. The localization of RTP1p suggests that it might play an important role in the maintenance of the biotrophic interaction.

Origin (projects)

Funding sources
Name Finanzierungstyp Kategorie Project no.
Deutsche Forschungsgemeinschaft third-party funds research funding program 644/06
Further information
Period: since 30.04.2008