Dikaryomycota Persistent dikaryon: cells with two haploid nuclei Regularly septate hyphae

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 G2S M

Dikaryomycota – two haploid nuclei

Nuclei: Haploid Dikaryotic Diploid

plasmogamy karyogamy

?

Dikaryons in fungi

• Only one cell – Zygomycetes

• Limited dikaryon – Ascomycetes

• Persistent dikaryon – Basidiomycetes

monokaryon

dikaryon

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 cycleAsexual cycle: haploid spores (n)+/– mating typesseptate hyphae (n)

Ascomycete life cycle, Raven 15-14

Asexual cycle: haploid spores (n)+/– mating typesseptate hyphae (n)

ascogonium trichogyne

antheridium

plasmogamy

Mating structures:

Trichogyne growth

Nuclear migration

Ascogonia and antheridia

An

As

T

Ascus development

crozier

karyogamy2n

meiosis I

meiosis II

mitosis(sp dep)

germination

Ascus formation

Crozier = hook

penultimate cell karyogamy

Meiosis andmitosis in developing ascus

Ascus development

meiosis I meiosis II mitosiskaryogamy

Ascomata: four types

PezizaMorchella

NeurosporaMagnaporthe

EmericellaErysiphe

Cochliobolus

Note ascus shape: elongate vs spherical

Elongate asci: 2 types

unitunicate bitunicateoperculum

pore

Cleistothecial asci

Asci and ascospores

Peziza

Eurotium

Otidea

Ascoma development

dikaryoticascogenous hyphae (n+n)

SterileHyphae (n)

croziersAscogonium

Ascogonium

apothecium

perithecium

Ascomycete fruiting bodies: ascomata

Mycosphaerella pseudothecia

Erysiphe graminis

HeterobasidiaHolobasidiaSynchronous spore formation Asynchronous spore formation

septa

sterigma

basidiospore

Nuclei migrate through the sterigma/spore junction

Mushroom life cycle 15-19

Basidiomata initiation is triggered by environmental conditions, including moisture

Dikaryotic hyphae

Mushroom development

Hymenium – fertile layer

Mushroom hymenium on: _____, _____, _____

Lactarius indigo

Gilled mushroomsAgaricales

Pores are lined with basidia

Fomes fomentarius

Hydnum repandum

Auriscalpium vulgare

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