Linear β-1,2-glucans trigger immune hallmarks and disease resistance in plants

Immune responses in plants are triggered by molecular patterns or elicitors, recognized by plant pattern recognition receptors (PRRs). Such molecular patterns arise from host-pathogen interactions and the response cascade activated after their perception is known as pattern-triggered immunity (PTI). Glucans have emerged as key players in PTI, but certain glucans ability to stimulate defensive responses in plants remains understudied. This work focused on identifying novel glucan oligosaccharides acting as molecular patterns. The ability of various microorganism-derived glucans to prompt PTI responses was tested, revealing that specific microbial-derived glucans, such as short linear {beta}-1,2-glucans, trigger this response in plants by increasing reactive oxygen species (ROS) production, MAP kinase phosphorylation, and differential expression of defence-related genes in Arabidopsis thaliana. Pretreatments with {beta}-1,2-glucan trisaccharide (B2G3) improved Arabidopsis defence against bacterial and fungal infections in a hypersusceptible genotype. The knowledge generated was then transferred to the monocotyledonous model species maize and wheat, confirming that these plants also respond to {beta}-1,2-glucans, with increased ROS production and improved protection against fungal infections following B2G3 pretreatments. In summary, as with other {beta}-glucans, plants perceive {beta}-1,2-glucans as warning signals and stimulate defence responses against phytopathogens. HighlightsWe describe a new group of glycans present in the extracellular matrices of some plant-interacting microorganisms that are sensed by host surveillance systems and enhance the plants natural resistance to disease.