Lipopolysaccharide O-antigen molecular and supramolecular modifications of plant root microbiota are pivotal for host recognition

Lipopolysaccharides, the major outer membrane components of Gram-negative bacteria, are crucial actors of the host-microbial dialogue. They can contribute to the establishment of either symbiosis or bacterial virulence, depending on the bacterial lifestyle. Plant microbiota shows great complexity, promotes plant health and growth and assures protection from pathogens. How plants perceive LPS from plant-associated bacteria and discriminate between beneficial and pathogenic microbes is an open and urgent question. Here, we report on the structure, conformation, membrane properties and immune recognition of LPS isolated from the Arabidopsis thaliana root microbiota member Herbaspirillum sp. Root189. The LPS consists of an O-methylated and variously acetylated Drhamnose containing polysaccharide with a rather hydrophobic surface. Plant immunology studies in A. thaliana demonstrate that the native acetylated O-antigen shields the LPS from immune recognition whereas the O- deacylated one does not. These findings highlight the role of Herbaspirillum LPS within plant-microbial crosstalk, and how O-antigen modifications influence membrane properties and modulate LPS host recognition.

Automated summary

Lipopolysaccharides (LPS) are important outer membrane components of Gram-negative bacteria, playing a crucial role in host-microbial interactions. Understanding how plants perceive and distinguish LPS from beneficial and pathogenic bacteria is a pressing question. This study investigated the structure, membrane properties, and immune recognition of LPS isolated from the root microbiota member Herbaspirillum sp. Root189 in Arabidopsis thaliana, highlighting the role of LPS in plant-microbial crosstalk and the influence of O-antigen modifications on LPS host recognition.