title: RacA-Mediated ROS Signaling Is Required for Polarized Cell Differentiation in Conidiogenesis of Aspergillus fumigatus.
abstract: Conidiophore development of fungi belonging to the genus Aspergillus involves dynamic changes in cellular polarity and morphogenesis. Synchronized differentiation of phialides from the subtending conidiophore vesicle is a good example of the transition from isotropic to multi-directional polarized growth. Here we report a small GTPase, RacA, which is essential for reactive oxygen species (ROS) production in the vesicle as well as differentiation of phialides in Aspergillus fumigatus. We found that wild type A. fumigatus accumulates ROS in these conidiophore vesicles and that null mutants of racA did not, resulting in the termination of conidiophore development in this early vesicle stage. Further, we found that stress conditions resulting in atypical ROS accumulation coincide with partial recovery of phialide emergence but not subsequent apical dominance of the phialides in the racA null mutant, suggesting alternative means of ROS generation for the former process that are lacking in the latter. Elongation of phialides was also suppressed by inhibition of NADPH-oxidase activity. Our findings provide not only insights into role of ROS in fungal cell polarity and morphogenesis but also an improved model for the developmental regulatory pathway of conidiogenesis in A. fumigatus.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Oklahoma, United States of America.
authors.forename: Myoung-Hwan
authors.initials: MH
authors.lastname: Chi
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Oklahoma, United States of America.
authors.forename: Kelly D
authors.initials: KD
authors.lastname: Craven
mesh_terms: D001232:Aspergillus fumigatus / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D016764:Cell Polarity / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005656:Fungal Proteins / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal; D005809:Genes, Regulator; D008954:Models, Biological; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010641:Phenotype; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013172:Spores, Fungal / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D017382:Reactive Oxygen Species; D019255:NADPH Oxidases