ABSTRACT
Filamentous fungi can sense useful resources and hazards in their environment and direct growth of their hyphae accordingly. Chemotropism ensures access to nutrients, contact with other individuals (e.g., for mating), and interaction with hosts in the case of pathogens. Previous studies have revealed a complex chemotropic sensing landscape during host-pathogen interactions, but the underlying molecular machinery remains poorly characterized. Here we studied mechanisms controlling directed hyphal growth of the important plant pathogenic fungus Verticillium dahliae towards different chemoattractants. We found that the homologs of the Rag GTPase Gtr1 and the GAP (GTPase-Activating Protein) Tsc2, an activator and a repressor of the TOR kinase respectively, which have not been analyzed in filamentous fungi before, play important roles in hyphal chemotropism towards nutrients, plant-derived signals, and synthetic α-pheromone from the plant pathogenic fungus Fusarium oxysporum. Furthermore, important roles of these regulators were identified in fungal development and pathogenicity. We also included in our study components of mitogen-activated protein kinase (MAPK) cascades and found that the MAPK Fus3 is required for chemotropism towards nutrients, while the G protein-coupled receptor (GPCR) Ste2 and MAPK Slt2 control chemosensing of plant-derived signals and α-pheromone. Our study establishes V. dahliae as a suitable model for the analysis of fungal chemotropism and discovers new components and mechanisms of chemotropic signaling, such as the TOR pathway, during growth and host-pathogen interactions of V. dahliae.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Email addresses: vasvagg{at}biol.uoa.gr (Vasileios Vangalis); markakis{at}elgo.iosv.gr (Emmanouil A. Markakis); m.knop{at}zmbh.uni-heidelberg.de (Michael Knop); ge2dipia{at}uco.es (Antonio Di Pietro); matypas{at}biol.uoa.gr (Milton A. Typas); i.papaioannou{at}zmbh.uni-heidelberg.de (Ioannis A. Papaioannou)