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Poster

Session: Session 1 Presenting Authors at Posters (Evens)

P-168 - Galactan content in plant cell walls connects carbohydrate starvation and penetration resistance against a fungal pathogen

Tuesday, July 15, 2025
09:55 - 11:30  
Location: Confex Hall 3
Microbial infection strategies (pathogens & non-pathogens)

Plant cell walls provide support to plant cells and delimit them against neighboring cells and their environment. Polysaccharides represent the main components of the wall and form a network that is dynamically modified during pathogen infections. Congruently, Arabidopsis mutants with impaired carbohydrate metabolism and altered cell wall composition are impaired in their penetration resistance against the hemibiotrophic fungal pathogen Colletotrichum higginsianum.



We hypothesized that carbohydrates are mobilized from the cell wall during periods of starvation and that the altered cell walls provide reduced protection against pathogen infection. Time-course analysis of cell wall composition demonstrated that galactose is reversibly released from leaf cell walls upon starvation through the activity of specific beta-galactosidase isoforms. Using a combination of transcript, metabolite and mutant analysis, we found that the sugar is recycled and re-used for primary metabolism. Instead, the synthesis of cell wall galactan via GALACTAN SYNTHASE1 (GALS1) is inhibited, leading to an increased entry rate of C. higginsianum. We show that overexpression of GALS1 prevents cell wall galactose depletion and is sufficient to prevent starvation-induced pathogen hypersusceptibility.



We suggest that the plant cell wall serves as a sugar resource during starvation conditions, leading to impaired penetration resistance and a growth-defense tradeoff.