Fungi grow either as tubular, multinucleate hyphae or spherical, uninucleate yeasts. Much of the machinery required for polar growth is conserved between filamentous fungi and yeasts and some fungi switch between hyphal and yeast forms in response to changes in environmental conditions. Since hyphae are found in all fungal lineages and yeasts are generally in the most derived lineages, the common ancestor of all fungi is thought to have been hyphal. Saccharomyces cerevisiae strains generally grow as budding yeasts. However, under some conditions diploid strains become elongated, forming filamentous pseudohyphae and some haploid strains show filamentous haploid invasive growth. Septins were first discovered in S. cerevisiae where they form a scaffold that organizes the bud site and are a major component of the morphogenesis checkpoint that monitors bud shape and coordinates budding with nuclear division. Five of the S. cerevisiae septins (Cdc3, Cdc10, Cdc11, Cdc12 and Sep7) localize to the neck region between mother and daughter cells in yeast. The other two S. cerevisiae septins (Spr3 and Spr28) are sporulation specific. Cdc3, Cdc11 and Spr3 localize to the leading edge of membranes during formation of the four-spored ascus. AspC, one of five septins from the filamentous fungus Aspergillus nidulans, induces filaments and elongated asci containing up to twelve spores in S. cerevisiae. AspC-induced filaments differ from previously characterized S. cerevisiae pseudohyphal and haploid invasive filaments. AspC-induced filaments are noninvasive and form in both haploid and diploid strains. AspC is most homologous to the Cdc12 septin of S. cerevisiae. GFP-AspC localizes to the necks of both filaments and buds, while GFP-Cdc12 localizes only to the necks of buds. Our results suggest that AspC competes with Cdc12 for incorporation into the septin scaffold where it induces filamentous growth.
Fungal Genetics Reports (2009) Volume 56
Full conference title:
23rd Fungal Genetics Conference
- Fungal Genetics Conference 23rd (2002)