FIGURE 8.

A proposed schematic model of the CgMsb2, CgSho1, and CgMk1 cascades in Colletotrichum gloeosporioides and the reported functions of Msb2 and Sho1 homologues. (a) Conidia of C. gloeosporioides germinate on a host cuticle and subsequently go through surface recognition, downstream pathway activation, appressorium formation, and penetration and invasive growth. PC, plant cell; C, conidium; GT, germ tube; AP, appressorium; IH, infection hypha. (b) The putative cell surface sensors CgMsb2 and CgSho1 recognize a variety of host signals and activate the downstream CgMk1 MAPK pathway; CgSte50, CgSte11, and CgSte7 subsequently activate CgMk1 through phosphorylation to regulate growth under nitrogen‐limiting conditions, cellophane membrane penetration, appressorium formation, invasive growth, and pathogenicity. Moreover, CgSte50–Ste11–Ste7 may activate unidentified component(s) of the oxidative stress response in a CgMk1‐independent manner (Wang et al., 2021b). Solid and dashed arrows indicate the verified and putative connections, respectively. (c) The conserved and species‐specific functions of reported Msb2 and Sho1 homologues in pathogenicity, vegetative growth, appressorium formation, conidiation, oxidant adaptation, growth under nitrogen‐limiting conditions, penetration, cellophane membrane penetration, and Pmk1 activation. √ and × indicate the homologues that are important or dispensable for specific functions, respectively. NA, not applicable; N/S, not significant