Deciphering cell wall integrity signalling in Aspergillus fumigatus: identification and functional characterization of cell wall stress sensors and relevant Rho GTPases.
The fungal cell wall, a conserved and highly dynamic structure, is essential for virulence and viability of fungal pathogens and is an important antifungal drug target. The cell wall integrity (CWI) signalling pathway regulates shape and biosynthesis of the cell wall. In this work we identified, localized and functionally characterized four putative CWI stress sensors of Aspergillus fumigatus, an airborne opportunistic human pathogen and the cause of invasive aspergillosis. We show that Wsc1 is specifically required for resistance to echinocandin antifungals. MidA is specifically required for elevated temperature tolerance and resistance to the cell wall perturbing agents congo red and calcofluor white. Wsc1, Wsc3 and MidA additionally have overlapping functions and are redundantly required for radial growth and conidiation. We have also analysed the roles of three Rho GTPases that have been implicated in CWI signalling in other fungi. We show that Rho1 is essential and that conditional downregulation of rho1 or deletion of rho2 or rho4 results in severely impaired CWI. Our data indicate significant functional differences between the CWI stress sensors of yeasts and moulds.
Max von Pettenkofer-Institut, Ludwig-Maximilians-Universität, Pettenkoferstraße 9a, Munich, Germany.
Karl
K
Dichtl
Christoph
C
Helmschrott
Franziska
F
Dirr
Johannes
J
Wagener
D000935:Antifungal Agents / Q000494:pharmacology*; D001232:Aspergillus fumigatus / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity; D002473:Cell Wall / Q000187:drug effects* / Q000502:physiology; D025141:Drug Resistance, Fungal; D054714:Echinocandins / Q000494:pharmacology*; D005656:Fungal Proteins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D008826:Microbial Sensitivity Tests; D015398:Signal Transduction; D013312:Stress, Physiological; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
D000935:Antifungal Agents; D054714:Echinocandins; D005656:Fungal Proteins; D020741:rho GTP-Binding Proteins