Fungi

2. Fungi Chapter 31

3. Fungi Characteristics • Despite their diversity fungi share some key traits: • Fungi are heterotrophs but do not ingest their food • Fungi secrete exoenzymes into their surroundings which break down molecules and then the fungi absorbs the remaining smaller compounds • This mode of nutrition is related to the diverse lifestyles exhibited by fungi: • Decomposers, Parasites, Mutualistic symbionts

4. Reproductive structure.The mushroom produces tiny cells called spores. Hyphae. The mushroom and its subterranean mycelium are a continuous network of hyphae. Spore-producing structures 20 m Mycelium Body Structure

5. Nematode Hyphae 25 m (a) Hyphae adapted for trapping and killing prey Plant cell wall Fungal hypha Plant cell Plant cell plasma membrane Haustorium (b) Haustoria Specialized Hyphae • Some unique fungi have specialized hyphae that allow them to penetrate the tissues of their host • Mycorrhizae are mutually beneficial relationships between fungi and plant roots

6. Reproduction in Fungi • Fungi propagate themselves • By producing vast numbers of spores, either sexually or asexually • Spores can be carried long distances • Only if they land in an acceptable area will they germinate and produce new mycelia

7. Key Heterokaryotic stage Haploid (n) Heterokaryotic (unfused nuclei from different parents) PLASMOGAMY (fusion of cytoplasm) Diploid (2n) KARYOGAMY (fusion of nuclei) Spore-producing structures Zygote SEXUAL REPRODUCTION Spores ASEXUAL REPRODUCTION Mycelium MEIOSIS GERMINATION GERMINATION Spore-producing structures Spores Life Cycle of Fungi

8. Sexual Reproduction • The sexual life cycle involves • Cell fusion, plasmogamy • Nuclear fusion, karyogamy • An intervening heterokaryotic stage • Occurs between plasmogamy and karyogamy in which cells have haploid nuclei from two parents • Sometimes can be dikaryotic and have two different, separate nuclei • The diploid phase following karyogamy • Is short-lived and undergoes meiosis, producing haploid spores

9. 3 2 Diploid nuclei Sporesreleased 1 Fruiting body(mushroom) Meiosis Fusion of haploid nuclei Haploidnucleus DIPLOID Spore HAPLOID DIKARYOTIC 4 Germination of sporesand growth of mycelia 6 Growth ofdikaryotic mycelium 5 Fusion of two hyphaeof compatible mating types Sexual Reproduction

10. Parent cell Bud Asexual Reproduction • Many fungi that can reproduce asexually • Grow as mold, sometimes on fruit, bread, and other foods • Clones are produced by mitotic production of spores • Other asexual fungi are yeasts • Which produce by simple cell division

11. Types of Fungi

12. Arbuscular mycorrhizal fungi Club fungi Zygote fungi Sac fungi Chytrids Zygomycota Ascomycota Basidiomycota Glomeromycota Chytridiomycota The Phylogeny of Fungi • Fungi can be placed into five major phyla based on morphological and molecular findings

13. Hyphae Chytrids • Phylum Chytridiomycota • Are found in freshwater and terrestrial habitats • Can be saprobic or parasitic • Unique to other fungi in having flagellated spores called zoospores

14. Zygomycetes • Considerable diversity of life histories • Include fast-growing molds, parasites, and commensal symbionts • Are named for their sexually produced zygosporangia • Where karyogamy and meiosis occur

15. Zygomycetes • Some zygomycetes, such as Pilobolus • Can actually “aim” their sporangia toward conditions with good food sources • Zygosporangia are resistant to freezing and drying • Are capable of persisting through unfavorable conditions • Can undergo meiosis when conditions improve

16. Ascomycetes • Found in marine, freshwater, and terrestrial habitats • Defined by the production of sexual spores in saclike asci, which are contained in fruiting bodies called ascocarps • Commonly called sac fungi • Vary in size and complexity

17. (a)The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus. (b) The edible ascocarp of Morchella esculenta, the succulent morel, is often found under trees in orchards. 10 m (c)Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open. (d)Neurospora crassa feeds asa mold on bread and other food (SEM). Ascomycetes

18. Neurospora can reproduce sexually by producing specialized hyphae. Conidia of the opposite mating type fuse to these hyphae. Ascomycete mycelia can also reproduce asexually by producing haploid conidia. Key Conidia;mating type () 1 7 Haploid (n) Dikaryotic (n n) Diploid (2n) Dispersal Germination Matingtype () ASEXUALREPRODUCTION Mycelium PLASMOGAMY A dikaryotic ascus develops. 2 Ascus(dikaryotic) Ascogonium Mycelia Conidiophore Dikaryotichyphae SEXUALREPRODUCTION KARYOGAMY Germination Karyogamy occurs within theascus, producing adiploid nucleus. Dispersal Diploid nucleus(zygote) 3 Eightascospores Asci Fourhaploidnuclei MEIOSIS Ascocarp The diploid nucleusdivides by meiosis, yieldingfour haploid nuclei. Each haploid nucleus dividesonce by mitosis, yielding eightnuclei. Cell walls develop aroundthe nuclei, forming ascospores (LM). 4 5 • Ascomycetes reproduce • Asexually by producing asexual spores called conidia

19. Basidiomycetes • Mushrooms, shelf fungi, and some mycorrhizae and molds • Some nasty plant parasites, rusts and smuts • Are defined by a clublike structure called a basidium, a transient diploid stage in the life cycle • Club fungus • Important decomposers of • wood and other plant material

20. (b) Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat (a) Fly agaric (Amanita muscaria), acommon species in conifer forests in the northern hemisphere (d) Puffballs emitting spores (c) Shelf fungi, important decomposers of wood Basidiomycetes

21. A dikaryotic mycelium forms, growing faster then, and ultimately crowding out, the haploid parental mycelia. 2 Two haploid mycelia of different mating typesundergo plasmogamy. 1 Environmental cues such as rain ortemperature changes induce the dikaryoticmycelium to formcompact masses thatdevelop intobasidiocarps(mushrooms, in thiscase). Dikaryoticmycelium 3 PLASMOGAMY In a suitableenvironment, thebasidiospores germinate andgrow intoshort-livedhaploid mycelia. Matingtype () 8 Matingtype () Haploidmycelia Gills linedwith basidia SEXUALREPRODUCTION Basidiocarp(dikaryotic) Dispersalandgermination When mature,the basidiosporesare ejected, fallfrom the cap, andare dispersed bythe wind. 7 Basidiospores Basidia(dikaryotic) Basidium withfour appendages Basidium containingfour haploid nuclei Basidium The basidiocarpgills are lined withterminal dikaryoticcells called basidia. 4 KARYOGAMY MEIOSIS Each diploid nucleus yields four haploid nuclei. Each basidiumgrows four appendages, and one haploid nucleusenters each appendage and develops into a basidiospore (SEM). 6 Key Diploidnuclei Karyogamy in the basidia produces diploidnuclei, which thenundergo meiosis. Haploid (n) 5 Basidiospore Dikaryotic (n n) 1 m Diploid (2n) Basidiomycetes

22. Ascocarp of fungus Soredia Fungal hyphae Algal layer Algal cell Fungal hyphae Lichens • The ultimate symbiosis • Algae and fungus • The fungal component of a lichen • Is most often an ascomycete • Algae or cyanobacteria • Occupy an inner layer below the lichen surface