<i>Arabidopsis</i> cell wall composition determines disease resistance specificity and fitness.

Abstract

Plant cell walls are complex structures subject to dynamic remodeling in response to developmental and environmental cues and play essential functions in disease resistance responses. We tested the specific contribution of plant cell walls to immunity by determining the susceptibility of a set of <i>Arabidopsis</i> cell wall mutants (<i>cwm</i>) to pathogens with different parasitic styles: a vascular bacterium, a necrotrophic fungus, and a biotrophic oomycete. Remarkably, most <i>cwm</i> mutants tested (29/34; 85.3%) showed alterations in their resistance responses to at least one of these pathogens in comparison to wild-type plants, illustrating the relevance of wall composition in determining disease-resistance phenotypes. We found that the enhanced resistance of <i>cwm</i> plants to the necrotrophic and vascular pathogens negatively impacted <i>cwm</i> fitness traits, such as biomass and seed yield. Enhanced resistance of <i>cwm</i> plants is not only mediated by canonical immune pathways, like those modulated by phytohormones or microbe-associated molecular patterns, which are not deregulated in the <i>cwm</i> tested. Pectin-enriched wall fractions isolated from <i>cwm</i> plants triggered immune responses in wild-type plants, suggesting that wall-mediated defensive pathways might contribute to <i>cwm</i> resistance. Cell walls of <i>cwm</i> plants show a high diversity of composition alterations as revealed by glycome profiling that detect specific wall carbohydrate moieties. Mathematical analysis of glycome profiling data identified correlations between the amounts of specific wall carbohydrate moieties and disease resistance phenotypes of <i>cwm</i> plants. These data support the relevant and specific function of plant wall composition in plant immune response modulation and in balancing disease resistance/development trade-offs.