LPMO-oxidized cellulose oligosaccharides evoke immunity in Arabidopsis conferring resistance towards necrotrophic fungus B. cinerea

Lytic Polysaccharide Monooxygenases (LPMOs) are powerful redox enzymes able to oxidatively cleave cellulose polymers. Widely conserved across biological kingdoms, LPMOs of the AA9 family are deployed by phytopathogens during necrotrophic attack of plant cell wall. In response, plants have evolved sophisticated mechanisms to sense cell wall damage and thus self-triggering Damage Triggered Immunity (DTI) responses. Here, we show that Arabidopsis plants exposed to LPMO products responds by activating the innate immunity ultimately leading to increased resistance to pathogenic fungus Botrytis cinerea. We demonstrated with microarray hybridization that plants undergo a deep transcriptional reprogramming upon elicitation with AA9 derived cellulose- or cello-oligosaccharides (AA9_COS). To decipher the specific effects of native and oxidized LPMO-generated cello-oligosaccharides, a pairwise comparison with cellobiose, the smallest non-oxidized unit constituting cellulose, is presented. Moreover, we identified two leucine-rich repeat receptor-like kinases, namely STRESS INDUCED FACTOR 2 and 4, playing a crucial role in signaling the AA9_COS-dependent responses such as camalexin production. We observed an increased production of ethylene, jasmonic and salicylic acid hormones, and finally deposition of callose in cell wall. Collectively, our data reveal that LPMOs might play a crucial role in plant-pathogen interactions.