P-365 - O-antigen modification alters Pseudomonas fluorescens mediated protection against plant pathogens

Wednesday, July 16, 2025

13:30 - 15:15

Location: Confex Hall 3

Plant microbiota functions and intermicrobial interactions

Presenting Author(s)

AG

Alexandra D. Gates, PhD

Postdoctoral Researcher
University of Pittsburgh
Pittsburgh, Pennsylvania, United States

Author(s)

YL

Yang Liu

University of British Columbia
Vancouver, British Columbia, Canada
ZL

Zhexian Liu

University of British Columbia
Vancouver, British Columbia, Canada
QD

Quinn Duque

University of Pittsburgh
Pittsburgh, Pennsylvania, United States
MC

Melissa Chen

University of British Columbia
Vancouver, British Columbia, Canada
CH

Corri Hamilton

Asst. Professor
University of Missouri
Columbia, Missouri, United States
GO

George O'Toole

Dartmouth
Hanover, New Hampshire, United States
CH

Cara Haney

University of Pittsburgh
Pittsburgh, Pennsylvania, United States

Microbiomes confer crucial benefits to their hosts including protection against pathogens, which could potentially prevent and treat pathogen infection. However, the underlying mechanisms remain poorly understood. To examine the genetic basis of pathogen protection, we make use of a reductionist host-pathogen-microbiome model consisting of Arabidopsis thaliana (Arabidopsis) and the commensal Pseudomonas fluorescens WCS365 that protects Arabidopsis from disease caused by pathogenic Pseudomonas fluorescens N2C3. In this system, WCS365 outcompetes N2C3 in planta. To identify novel genes involved in plant protection, we performed a high-throughput in planta screen of a WCS365 biofilm transposon mutant library and identified mutants that no longer protect. These genes include wbpA, wpbD, and wzt, O-antigen biosynthesis genes, and clpP, a serine protease. While WCS365 clpP::Tn5 no longer outcompeted N2C3, transposon mutations in O-antigen genes led to coexistence with N2C3. Moreover, we found these mutants lost plant protection against the pathogen Pseudomonas fuscovaginae SE-1, suggesting mechanistic overlap in protection. Our results indicate novel roles for O-antigen modification and a serine protease in commensalism and microbiome function. Further investigation into these genes will uncover the mechanisms of pathogen protection in WCS365. As microbiome manipulation could prevent and treat disease, elucidating these mechanisms is essential for food security and human health.