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