FIGURE 5.

Illustration of the influence of Mannitol and Mannitol dehydrogenase in mediating plant defense responses. (A) Recognition of fungal PAMPs in the host apoplastic space triggers PTI mediated oxidative burst which is characterized by the activation of a membrane-bound NADPH oxidase, leading to the generation of reactive oxygen species (ROS) superoxide (∙O_2-), which is subsequently converted into hydrogen peroxide (H₂O₂) and hydroxyl radical (∙OH). (B) The filamentous pathogens secrete mannitol in response to mannitol dehydrogenase oxidative burst to mitigate host mediated oxidative burst through the formation of a protective shield around the fungal structures. (C) Several plants have been seen to secrete a mannitol catabolic enzyme, mannitol dehydrogenase (MTD) that can metabolize the fungal mannitol, thereby restoring the ROS-mediated responses and including antimicrobial effects (Adapted from Patel and Williamson, 2016 and reproduced with permission from Elsevier).