FIGURE 1.

Overview of glycan-triggered immune responses during plant–filamentous pathogen interactions. (A) Filamentous pathogen cell walls are targeted by host-derived hydrolytic enzymes, as an innate defense response resulting in the release of glycan fragments (chitin, α- and β-glucans). (B) The hydrolyzed glycans are recognized as PAMPs by host pattern recognition receptors (PRRs) triggering innate immune response. (C) The pathogen secretes effector molecules that (D) suppress PTI defense responses by (E) converting immunogenic chitin to the less immunogenic chitosan (F) sequestering or masking the PAMPs released, to evade detection. (G) Remodeling of the cell wall components by the pathogen (e.g., accumulation of α-1,3-glucan) mitigates the effect of host-hydrolytic enzymes on the microbial cell wall glycans, thereby preventing hydrolysis. (H) Lastly, the pathogens may secrete certain effectors that directly inhibit host hydrolytic enzymes. (Adapted from Rovenich et al., 2016 and reproduced with permission from John Wiley and Sons).