Sensing host and environmental cues by fungal GPCRs

G protein-coupled receptors (GPCRs) represent the largest superfamily of cell surface membrane receptors in eukaryotes. Unlike plants, fungi do not have receptor kinases or receptor-like kinases. Instead, GPCRs play critical roles in fungi to sense signals crucial for their survival and interspecies interactions to activate downstream cAMP and mitogen-activated protein kinase pathways via heterotrimeric G proteins. Some fungal GPCRs have relatively conserved roles in nutrient sensing and pheromone recognition to facilitate growth and sexual reproduction. For fungal pathogens with expanded families of classical or fungal-specific GPCRs, including those with the CFEM (common in fungal extracellular membrane) domain, distinctive GPCRs are involved in recognizing different signals from their hosts and surroundings. Although only a few ligands recognized by fungal GPCRs have been identified, recent studies have advanced our knowledge of GPCR biology in plant pathogenic and nematode-trapping fungi.