Dikaryomycota
• Persistent
dikaryon: cells
with two haploid
nuclei
• Regularly septate
hyphae
Dikaryomycota – two haploid nuclei
Haploidy  nuclear condition, referring
to number of chromosome copies per
cell in G1
G1
S
G2
M
Dikaryomycota – two haploid nuclei
Nuclei: Haploid
Dikaryotic
plasmogamy
?
Diploid
karyogamy
Dikaryons in fungi
• Only one cell – Zygomycetes
• Limited dikaryon – Ascomycetes
• Persistent dikaryon – Basidiomycetes
dikaryon
monokaryon
Maintaining the dikaryon state
• Conjugate mitosis –
coordinated nuclear
division
• Typically at
“clamp connections” that
have specialized septa
Simple septum vs
Dolipore septum
Dikaryomycete classes based on
sexual sporulation
• Ascomycetes  in sacs
• Basidiomycetes  on stalks
Ascomycete life cycle
Asexual cycle:
haploid spores (n)
+/– mating types
septate hyphae (n)
Ascomycete life cycle, Raven 15-14
Asexual cycle:
haploid spores (n)
+/– mating types
septate hyphae (n)
Mating structures:
ascogonium
trichogyne
antheridium
plasmogamy
Trichogyne growth
Nuclear migration
Ascogonia and antheridia
T
An
As
Ascus development
germination
meiosis II
mitosis
(sp dep)
meiosis I
karyogamy
2n
crozier
Ascus formation
Crozier = hook
penultimate cell
 karyogamy
Meiosis and
mitosis in
developing
ascus
Ascus development
karyogamy
meiosis I
meiosis II
mitosis
Ascomata: four types
Peziza
Morchella
Emericella
Erysiphe
Neurospora
Magnaporthe
Cochliobolus
Note ascus
shape:
elongate vs
spherical
Elongate asci: 2 types
unitunicate
bitunicate
operculum
pore
Cleistothecial
asci
Asci and ascospores
Peziza
Eurotium
Otidea
Ascoma development
Ascogonium
croziers
dikaryotic
ascogenous
hyphae (n+n)
Sterile
Hyphae (n)
Ascogonium
Ascomycete fruiting bodies: ascomata
apothecium
perithecium
Mycosphaerella pseudothecia
Erysiphe graminis
Holobasidia
Synchronous spore formation
Heterobasidia
Asynchronous spore formation
basidiospore
sterigma
septa
Nuclei migrate through
the sterigma/spore junction
Mushroom life cycle 15-19
Dikaryotic hyphae
Basidiomata initiation is triggered by environmental
conditions, including moisture
Mushroom development
Hymenium – fertile layer
Mushroom hymenium on: _____, _____, _____
Gilled mushrooms
Agaricales
Lactarius
indigo
Pores are lined with basidia
Fomes fomentarius
Auriscalpium vulgare
Hydnum repandum
Deuteromycetes – life without sex
Deuteromycetes – life without sex
• Advantages
– speed (of reproduction, ~1 day)
– flexibility (can maintain a well-adapted
genome)
– can maintain (lethal?) mutations in
haploid nuclei, since hyphae are
multinucleate