Figure 7.

Role of the extracellular matrix in the innate immunity of multicellular red (A) and brown (B) algae. Drawings adapted from in [136] and updated based on evidence provided by the authors of [7,139,140,149,152,161]. Note that the basic principles of innate immunity are shared by brown and red algae (as well as by plants and animals): recognition by Pattern Recognition Receptors (PPRs) of pathogen-derived PAMPs or cell-wall derived DAMPs triggers signaling cascades that activate defense and detoxification responses. Red (A) and brown algae (B) differ by the nature of their DAMPs and PPRs, highlighted in red and brown, respectively. In the ECM per se the main defense responses deal with ECM remodeling (thickening, strengthening) and the secretion of chemicals and enzymes that target the pathogen, eventually leading to the containment of non-adapted pathogens. Abbreviations: PAMPs, pathogen associated molecular patterns; DAMPs, Damage associated molecular patterns; PUFAs, poly unsaturated fatty acids; MAP Kinase, mitogen activated protein kinase; LOX, lipoxygenase; vHPO, vanadium-dependent haloperoxidase; IoH, hypoiodous acid; vBPO, vanadium-dependent bromoperoxidase; BrOH, hypobromous acid; ROS, reactive oxygen species. Org. organic compound. HSPs, heat shock proteins; G6PD, glucose-6-phospate-dehydrogenase; GST, Glutathion-S-transferase; SOD, superoxide dismutase; PKS, polyketate synthase; MC5E, mannuronan C5 epimerase, GHs, glycoside hydrolases.