How alkalinization drives fungal pathogenicity
During infection, fungal pathogens induce alkalinization of the surrounding host tissue through regulated release of ammonia and, in certain phytopathogens, by secreting small regulatory peptides that mimic plant RALFs (left panel). The resulting increase in extracellular pH activates the fungal IG MAPK cascade, likely via modulation of pHi, to trigger phosphorylation of the IG MAPK and morphogenetic transition towards infectious growth (right panel). Yellow color denotes acidic pH, while purple denotes neutral to alkaline pH. IG, invasive growth; MAPK, mitogen-activated protein kinase; pHi, intracellular pH; RALF, Rapid ALkalinizing Factor.