title: abaA controls phialide differentiation in Aspergillus nidulans.
abstract: Aspergillus nidulans is an ascomycetous fungus that reproduces asexually by forming multicellular conidiophores and uninucleate spores called conidia. Loss of function mutations in the abacus A (abaA) regulatory locus result in formation of aberrant conidiophores that fail to produce conidia. Wild-type conidiophores form two tiers of sterigmata. The first tier, metulae, divide to produce the second tier, phialides. Phialides are sporogenous cells that produce conidia through a specialized apical budding process. We have examined conidiophore development in an abaA- strain at the ultrastructural level. The results showed that in the mutant metulae produce supernumerary tiers of cells with metula-like, rather than phialide-like, properties. Temperature shift experiments with an abaA14ts strain demonstrated that abaA+ function induced phialide formation by the aberrant abacus cells and was continuously required for maintenance of phialide function. In the absence of abaA+ activity, metulae simply proliferated and later developmental steps never occurred. We conclude that abaA+ directs the differentiation of phialides and is continuously required for maintenance of their function.
authors: Department of Plant Pathology, University of Georgia, Athens 30602.
authors: T C
authors: TC
authors: Sewall
authors: C W
authors: CW
authors: Mims
authors: W E
authors: WE
authors: Timberlake
mesh_terms: D001233:Aspergillus nidulans / Q000166:cytology / Q000235:genetics*; D002454:Cell Differentiation; D005800:Genes, Fungal; D008854:Microscopy, Electron; D013172:Spores, Fungal / Q000166:cytology