KINGDOM EUMYCOTA Phylum 3 - DIKARYOMYCOTA Subphylum ...

Key points:
-Corn smut is caused by Ustilago maydis
-A promycelium = a 4 celled smut basidium
-The monokaryon is a haploid saprophyte yeast
(yeast cells are here called sporidia).
-Not until mating and the formation of dikaryon
does this fungus become a obligate parasite on
corn. There are 2 mating type loci, each with
different “jobs”.
-Dimorphism means two forms: yeast + hyphae
-The haploid dikaryon is the obligate, biotrophic
parasitic phase. It is filamentous hyphae.
- To reproduce, a diploid forms that in turn
forms teliospores.
-Teliospores form basidia (= promycelia).
Switch from saprophytic growth by budding to
filamentous and pathogenic development
regulated by the multi-allelic b-mating type locus
that encodes 2 unrelated homeodomain proteins
bE and bW. The combination of the alleles forms
heterodimer that controls pathogenicity genes as
a transcriptional regulator.
- Bolker M. 2001. Microbiology 147:1395-1401.
- Steinberg, G. and Perez-Martin, J. (2008) Ustilago
maydis, a new fungal model system for cell biology.
Trends Cell Biol., 18, 61-67.