A pathogen α-L-arabinofuranosidase degrades host-derived immunogenic oligosaccharides to suppress plant immunity

Plant cell wall fragments released during pathogen attack can act as signalling molecules that trigger immune responses. Successful pathogens have potentially evolved diverse strategies to evade host recognition, including minimizing the accumulation of cell wall-derived elicitors. However, the mechanisms underlying this process remain largely unknown. Here, we characterized Zt GH54, an α-L-arabinofuranosidase from the wheat pathogen Zymoseptoria tritici , that is essential for the acquisition of sugar nutrients from arabinan and arabinoxylan wall polysaccharides. Zt GH54 also hydrolyzes immunogenic oligosaccharides derived from arabinoxylan to prevent host recognition. Remarkably, this strategy is effective only in a subset of wheat cultivars, as the contribution of Zt GH54 to virulence is cultivar-dependent. While a Zt GH54 substrate is broadly recognized in wheat, one of the products generated by Zt GH54, xylotetraose, is recognized only by specific wheat cultivars, revealing natural variation in the perception of xylan-derived oligosaccharides. These findings establish Zt GH54 as a key virulence factor that simultaneously exploits cell wall host resources and suppresses wheat immunity through the precise hydrolysis of plant cell wall-derived signals.