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Poster

Session: Session 2 Presenting Authors at Posters (Odds)

P-439 - Infection of Alfalfa cotyledons by an incompatible but not compatible species of Colletotrichum induces formation of paramural bodies and secretion of extracellular vesicles

Wednesday, July 16, 2025
13:30 - 15:15  
Location: Confex Hall 3
Spatial & temporal resolution of the interaction interface

    Presenting Author(s)

  • SG

    Suchismita Ghosh (she/her/hers)

    Post Doctoral Research Associate
    Washington University St. Louis
    St. Louis, MO, USA

    • Author(s)

  • KR

    Kamesh Regmi

    Assistant Professor
    Kenyon College
    Gambier, Ohio, United States

  • BS

    Barry Stein

    Assistant Scientist
    Indiana University Bloomington
    bloomington, Indiana, United States

  • JC

    Jun Chen

    Assistant Scientist
    Indiana Univeristy Bloomington
    Bloomington, Indiana, United States

  • RO

    Richard J. O'Connell

    Scientific Advisor of IMAFUN
    Université Paris-Saclay, INRAE, UR BIOGER
    Palaiseau, Ile-de-France, France

  • RI

    Roger W. Innes, PhD (he/him/his)

    Distinguished Professor
    Indiana University Bloomington
    Bloomington, Indiana, United States

Colletotrichum is a hemibiotrophic fungus, with a biotrophic phase invading host cells followed by a deadly necrotrophic phase. We used Serial Block Face Scanning Electron Microscopy (SBF-SEM) to compare the subcellular responses of Medicago sativa (alfalfa) to infection by the adapted pathogen Colletotrichum destructivum and the non-adapted pathogen C. higginsianum. Serial SEM images were assembled into 3D models of the infection site using the software IMOD.  These models revealed that alfalfa cotyledons infected with compatible C. destructivum undergo massive cellular changes allowing extensive fungal hyphal growth. In contrast, infection with incompatible C. higginsianum revealed not only fewer successful penetration events, but frequent formation of papillary-like structures beneath attempted fungal penetration sites. Incompatible interaction sites also displayed unique vesicular-like structures known as paramural bodies that fused with the cell membrane. We hypothesized that these paramural bodies may be a source of extracellular vesicles. Consistent with this, alfalfa leaves infected with incompatible C. higginsianum released more extracellular vesicles than leaves infected with compatible C. destructivum. Together, these results suggest that extracellular vesicles contribute to immunity during pathogen attack in alfalfa.