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Concurrent Session

Session: Concurrent Session: Population Biology, Ecology & Genomics

An evolutionary and functional analysis of virulence gene promoters in Pseudomonas syringae.

Monday, July 14, 2025
11:30 - 11:40  
Location: Room P+Q

    Presenting Author(s)

  • RS

    Racquel A. Singh (she/her/hers)

    PhD Candidate
    Department of Cell and Systems Biology, University of Toronto
    Toronto, Ontario, Canada

    • Author(s)

  • TA

    Tamar V. Av-Shalom (she/her/hers)

    PhD Candidate
    Department of Cell and Systems Biology, University of Toronto
    Toronto, Ontario, Canada

  • BL

    Bradley Laflamme

    Department of Cell and Systems Biology, University of Toronto
    Toronto, Ontario, Canada

  • MD

    Marcus M. Dillon

    Department of Cell and Systems Biology, University of Toronto
    Mississauga, Ontario, Canada

  • RA

    Renan N. D. Almeida

    Department of Cell and Systems Biology, University of Toronto
    Sydney, New South Wales, Australia

  • DD

    Darrell Desveaux

    Professor
    Department of cell and Systems Biology, University of Toronto
    Toronto, Ontario, Canada

  • DG

    David S. Guttman

    Professor
    Department of Cell and Systems Biology, University of Toronto
    Toronto, Ontario, Canada

Abstract Text:

Phytopathogenic bacteria such as Pseudomonas syringae rely on type III secreted effector (T3E) proteins to infect a wide range of plants, including many significant crops. However, intracellular immune receptors in resistant plants can detect effectors and activate effector-triggered immunity (ETI). While effector diversification at the protein-coding level is well characterized, the role of regulatory sequence variation in immune evasion remains poorly understood. We hypothesize that P. syringae modulates T3E expression via sequence variation in T3E promoters (or “hrp box promoters”) to minimize immune activation. To test this, we identified and analyzed 9,578 promoters upstream of T3E genes across 494 diverse P. syringae genomes. Phylogenetic and motif analyses revealed 578 unique sequences with conserved core motifs and variable sites. To quantify functional variation, we constructed a library of over 160 promoter variants fused to GFP and optimized a high-throughput microplate assay to measure promoter activity. Our results suggest that specific polymorphisms in hrp box promoters significantly influence T3E expression levels. Ongoing work aims to computationally model T3E promoter activity and assess how promoter variation impacts host-microbe interactions in planta. These findings will expand our understanding of how changes in pathogen regulatory sequences influence disease outcomes and may reveal potential molecular targets for improved disease management in crops.