• Media type: E-Book
  • Title: ˜Theœ role of membrane nanodomains and the cell wall-plasma membrane-cytoskeleton continuum during symbiotic infection in Medicago truncatula
  • Contributor: Liang, Pengbo [Verfasser]; Ott, Thomas [Akademischer Betreuer]
  • Corporation: Albert-Ludwigs-Universität Freiburg, Fakultät für Biologie
  • Published: Freiburg: Universität2020
  • Extent: Online-Ressource
  • Language: English
  • DOI: 10.6094/UNIFR/167892
  • Identifier:
  • Keywords: Infection ; Medicago ; Cytoskeleton ; Continuity ; Multidisciplinary ; (local)doctoralThesis
  • Description: Abstract: Plant cell infections are tightly orchestrated by cell wall and plasma membrane signaling networks in conjunction with the dynamic rearrangement of the cytoskeleton in the cytosol. Several of the corresponding membrane proteins assemble as macromolecular complexes in nanodomains, which harbor numerous other proteins such as transmembrane cell surface receptors or scaffold proteins. Latter localize to the inner leaflet and contribute to the spatiotemporal dynamics and overall organization of these laterally immobile nandomains. However, the molecular mechanisms underlying dynamic transitions and their functional relevance remain elusive. This includes regulatory circuits controlling the stimulus-dependent lateral segregation of receptors into membrane nanodomains. By studying the legume model plant Medicago truncatula and its symbiont partner, Sinorhizobium meliloti, we have demonstrated that the scaffold protein FLOTILLIN 4 (FLOT4) forms the primary and indispensable core of a specific nanodomain in an actin-dependent manner. The ligand-induced remorin protein, SYMREM1, serves as a secondary molecular scaffold that is subsequently recruited into the domain and further stabilizes the entry receptor LYK3. Reciprocally, in symrem1 mutants the LYK3 receptor is destabilized and subsequently prone to endocytosis upon rhizobial inoculation, which results in the premature abortion of host cell infections. These data reveal that receptor recruitment into nanodomains is indispensable for their function during host cell infection. <br>Interestingly, the impairment of actin also results in the mis-localization of SYMREM1. As actin remodeling is critical for infection, we explored the molecular mechanism of actin remodeling at this infection stage. We identified and studied a formin protein (SYFO1) in M. truncatula that is induced during rhizobial infection. Phenotypical analysis of syfo1 mutants clearly indicates that the encoded protein is required for efficient rhizobial colonization of root hairs. SYFO1 itself is able to create a proteinaceous bridge between the cell wall and the polarized cytoskeleton. It binds to cell wall components via an extensin-like motif in its N-terminal segment, which is required for its function. On the cytoplasmic site of the plasma membrane, SYFO1 is associated with actin accumulations which supports the hypothesis that it contributes to cell polarization in vivo. The potential contribution of this polar establishment is further confirmed by the fact that cell shape changes can be induced in a ligand-dependent manner in root protoplasts expressing SYFO1. Therefore, we have provided evidence for a so far undescribed proteinaceous cell wall-plasma membrane-cytoskeleton continuum controlling rhizobial infections in M. truncatula
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