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Poster

Session: Session 1 Presenting Authors at Posters (Evens)

P-366 - Host unfolded protein response promotes transient transformation by Agrobacterium tumefaciens and regulates agrobacteria-modulated gene expression associated with abscisic acid signaling

Tuesday, July 15, 2025
09:55 - 11:30  
Location: Confex Hall 3
Subcellular dynamics and signaling in host-microbe interactions

    Presenting Author(s)

  • LB

    Lois M. Banta

    Professor
    Williams College
    Williamstown, Massachusetts, United States

    • Author(s)

  • AI

    Ashrita Iyengar

    Undergraduate student
    Williams College
    Williamstown, Massachusetts, United States

  • YI

    Yuu Ishikawa

    Undergraduate student
    Williams College
    Williamstown, Massachusetts, United States

  • LY

    Luke Young-Xu

    Undergraduate student
    Williams College
    Williamstown, Massachusetts, United States

  • LW

    Lili Winkelman

    Undergraduate student
    Williams College
    Williamstown, Massachusetts, United States

  • EL

    Edward Li

    Undergraduate student
    Williams College
    Williamstown, Massachusetts, United States

  • EK

    Elizabeth Kwon

    Undergraduate student
    Williams College
    Williamstown, Massachusetts, United States

  • EY

    Emily Yoon

    Undergraduate student
    Williams College
    Williamstown, Massachusetts, United States

  • MS

    Maxwell Song

    Undergraduate student
    Williams College
    Williamstown, Massachusetts, United States

The Unfolded Protein Response (UPR) is a protective mechanism employed by eukaryotic cells when misfolded proteins accumulate in the endoplasmic reticulum.  A collection of processes that work to relieve physiological demand and maintain cellular homeostasis, the UPR is a key component in host immune responses to microbial pathogen attack. Unexpectedly, we have found that transient transformation by Agrobacterium tumefaciens is enhanced, rather than attenuated, in Arabidopsis thaliana seedlings in which the UPR is active. Our experiments also revealed that A. tumefaciens infection impacts expression of genes related to abscisic acid (ABA) signaling; that pharmacological UPR induction modulates levels of those genes; and that Agrobacteria can strongly attenuate some of the UPR-related changes in gene expression.  The plant ribophorin ortholog HAP6 resides at the lumen-facing side of the ER membrane and interacts with ER-localized IOS1 to modulate host UPR and ABA signaling responses. HAP6 appears to promote ABA signaling, but limits induction of UPR marker genes, in response to A. tumefaciens. An ios1 mutant is more resistant to A. tumefaciens infection, suggesting that the bacterium may work through IOS1 to dampen host defenses.  Together, these data suggest that crosstalk between the UPR and ABA signaling, mediated at the level of host HAP6 (and potentially antagonism of HAP6 by IOS1) may be an important target of host manipulation by Agrobacterium.