Fungi Notes - Chapter 31 PDF

2 Defining Fungi Mycologists believe there may be as many as 1.5 million fungal species Single-celled or multicellular Sexual or asexual Specialized to extract and absorb nutrients from surroundings Animal and fungi last shared a common ancestor 460 MYA FUNGI Chapter 31 1 Some debate on timing May h...

2 Defining Fungi Mycologists believe there may be as many as 1.5 million fungal species Single-celled or multicellular Sexual or asexual Specialized to extract and absorb nutrients from surroundings Animal and fungi last shared a common ancestor 460 MYA FUNGI Chapter 31 1 Some debate on timing May have 670 MYA ancestor 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 7 monophyletic phyla Microsporidia Blastocladiomycota Neocallismastigamycota Chytridiomycota Glomeromycota Basidiomycota Ascomycota 4 Microsporidia Blastocladiomycota Zygomycota Neocallimastigomycota Chytridiomycota Glomeromycota Basidiomycota Ascomycota a. c. 10 μm b. 500 μm 300 μm d. 300 μm e. 200 μm f. 300 μm g. h. Dikarya Fungi a: © Dr. Ronny Larsson; b: Contributed by Don Barr, Mycological Society of America; c: © Carolina Biological Supply Company/Phototake; d: Contributed by Don Barr, Mycological Society of America; e: © Dr. Yuuji Tsukii; f: © Yolande Dalpe, Agriculture and Agri-Food Canada; g: © inga spence/Alamy; h: © Michael & Patricia Fogden 1 polyphyletic Zygomycota 3 4 5 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6 General Biology of the Fungi Multicellular fungi consist of long, slender filaments called hyphae Some hyphae are continuous Others are divided by septa H yp h ae 10 μ m M yceliu m Cytoplasm flows throughout hyphae Allows rapid growth under good conditions (inset): © Micro Discovery/Corbis; (right): © Michael & Patricia Fogden/Corbis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dikaryotic cell Mycelium – mass of connected hyphae Fungal cell walls include chitin Septa with pores Nuclei Hypha Nuclei Pore Septum (right): © Garry T. Cole/ Biological Photo Service 5 Grows through and digests its substrate Also found in the hard shells (exoskeletons) of arthropods 0.2 !m 7 6 1 7 8 Fungi have an unusual Hyphae may have more than one nucleus Monokaryotic – 1 nucleus Dikaryotic – 2 nuclei mitosis Cell is not relevant unit of reproduction Nuclear envelope does not break down and re-form Instead, the spindle apparatus is formed within it Both genomes transcribed Sometimes many nuclei intermingle in the common cytoplasm of the fungal mycelium Heterokaryotic – nuclei from genetically distinct individuals Homokaryotic – nuclei are genetically similar to one another Fungi lack centrioles Spindle plaques regulate microtubule formation during mitosis 7 Yeasts Nuclear envelope remains intact; spindle microtubules form inside the nucleus between spindle pole bodies. A single kinetochore microtubule attaches to each chromosome and pulls each to a pole. Kinetochore microtubule Spindle pole body Polar microtubule 8 9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reproduction Nutrition Capable of both sexual and asexual reproduction Sexual reproduction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10 Fungal loop Nematode Fusion of two haploid hyphae of compatible mating types a. May form mushrooms or puffballs Spores are the most common means of reproduction among fungi May form from sexual or asexual processes Most are dispersed by wind 400 µm b. © Carolina Biological Supply Company/Phototake © L. West/ Photo Researchers, Inc. Obtain food by secreting digestive enzymes into surroundings Then absorb the organic molecules produced by this external digestion In some fungi, fusion immediately results in a diploid (2n) cell Others, have a dikaryon stage (1n + 1n) before parental nuclei form diploid nucleus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fungus 10 µm Great surface area-to-volume ratio Fungi can break down cellulose and lignin Decompose wood Some fungi are carnivorous © Eye of Science/Photo Researchers, Inc. Spores are the most common means of reproduction among fungi 9 10 – May form from sexual or asexual processes – Most are dispersed by wind 11 12 12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Microsporidia Obligate, intracellular, animal parasites Long thought to be protists Lack mitochondria Polar tube Spore Ancestors lost them A scom ycota B asidiom ycota G lom erom ycota C hytridiom ycota N eocallim astigom ycota Zygom ycota B lastocladiom ycota M icrosporidia Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 0.5 μm (left): © Daniel P. Fedorko Encephalitozoon cuniculi Commonly cause disease in immunosuppressed patients Infect hosts with their spores, which contain a polar tube Infects intestinal and neuronal cells, leading to diarrhea and neurodegenerative disease Fungi 11 12 2 13 14 Chytridiomycetes or chytrids Aquatic, flagellated fungi Zoospore Closely related to ancestral fungi Have motile zoospores Batrachochytrium dendrobatidis has been implicated in amphibian die-offs Blastocladiomycetes Ascomycota Basidiomycota Glomeromycota Chytridiomycota Zygomycota Microsporidia Blastocladiomycota Chytridiomycota Neocallimastigomycota Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Uniflagellated zoospores Allomyces example Water mold Haplodiplontic life cycle Female gametes secrete pheromone to attract male gametes Giant mitochondria in its zoospores Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fungi Contributed by Daniel Wubah, Mycological Society of America Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chytrid Zoospore Oedogonium filament Contributed by Daniel Wubah, Mycological Society of America Contributed by Don Barr, Mycological Society of America Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 17 13 14 Chytrid Oedogonium filament Contributed by Don Barr, Mycological Society of America 15 16 17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neocallimastigomycota Female gametangium Male gametangium MIT OSIS Young gametophyte (n) Haploid gametes (n) Mature gametophyte (n) Gametophyte (n) n Haploid zoospore (n) FERTILIZATION 2n Young sporophyte (2n) Diploid zoospores (2n) Asexual reproduction Asexual sporangium Sporophyte Mammal depends on fungi for sufficient calories Greatly reduced mitochondria lack cristae Zoospores have multiple flagella Horizontal gene transfer brought cellulase gene from bacteria into Neocallimastix genome Sporophyte(2n) Sporangium (2n) SIS MEIO Digest plant biomass in mammalian herbivore rumens Mature sporophyte (2n) Young sporophyte (2n) a. 100 !m b. a: © Carolina Biological Supply Company/Phototake 19 15 16 17 18 Zygomycota Sexual reproduction Fusion of gametangia Haploid nuclei fuse to form diploid zygote nuclei – karyogamy Develops into zygosporangium in which zygospore develops Meiosis occurs during germination of zygospore Zygomycetes are incredibly diverse Not monophyletic – still under research Include the common bread molds A few human pathogens Asexual reproduction more common Sporangiophores have sporangia that release spores Ascomycota Basidiomycota Releases haploid spores Glomeromycota Chytridiomycota N eocallim astigom ycota Zygomycota Blastocladiomycota Microsporidia Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fungi 17 18 3 19 20 Glomeromycota Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. GERMINATION Asexual reproduction Sporangium Sporangiophore – Mating strain + Mating strain 700 µm MEIOSIS No evidence of sexual reproduction Hypha (Meiosis occurs during germination) a. Glomeromycetes are a tiny group of fungi Form intracellular associations with plant roots called arbuscular mycorrhizae Rhizoid N IO AT IN RM GE Germinating zygosporangium Spores Spores (+) Cannot survive in absence of host plant (–) n 2n Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ascomycota Basidiomycota Glomeromycota Neocallimastigomycota Zygomycota b. Blastocladiomycota Microsporidia Zygosporangium FERTILIZATION Gametangia Chytridiomycota n+n Y AM OG RY KA a: © Carolina Biological Supply Company/Phototake Fungi 19 20 21 22 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Basidiomycota Basidiocarp Basidiomycetes are some of the most familiar fungi Mushrooms, toadstools, puffballs, shelf fungi, etc. Also important plant pathogens like rusts and smuts Named for basidium – club-shaped sexual reproductive structure Gills lined with basidia Basidium n+n Karyogamy occurs within basidia Only diploid cell in life cycle Basidiomycota KARYOGAMY 2n Zygote Basidium – Mating strain + Mating strain Ascomycota Glomeromycota Chytridiomycota Neocallimastigomycota Blastocladiomycota Zygomycota n Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Microsporidia Secondary mycelium (dikaryotic) a. Primary mycelium (monokaryotic) Basidiospores Sterigma b. Meiosis follows The four haploid products are incorporated into basidiospores a: © Alexandra Lowry/The National Audubon Society Collection/Photo Researchers, Inc. 27 Fungi 21 22 23 Contain about 75% of the known fungi Includes bread yeasts, common molds, cup fungi, truffles, and morels Serious plant pathogens – cause of chestnut blight and Dutch elm disease Penicillin-producing fungi are in the genus Penicillium Results in a monokaryotic mycelium, or primary mycelium Different mating types of monokaryotic hyphae may fuse Ascomycota Glomeromycota Basidiomycota Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Microsporidia Chytridiomycota Results in a dikaryotic mycelium, or secondary mycelium Heterokaryotic mycelium Basidiocarps (mushrooms) are formed entirely of secondary mycelium Neocallimastigomycota Zygomycota Ascomycota Spore germination leads to the production of monokaryotic hyphae Blastocladiomycota 24 Fungi 23 24 4 25 26 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Named for ascus – microscopic, saclike Conidia Asexual reproduction reproductive structure Karyogamy occurs within asci Each haploid nucleus divides once by mitosis Conidia GERMINATION Antheridium Only diploid nucleus of life cycle Ascogonium – Mating strain Asci differentiate in ascocarp Meiosis and mitosis follow, producing 8 Asexual reproduction is very common Conidia formed at the ends of modified hyphae called conidiophores Allow for the rapid colonization of a new food source Many conidia are multinucleate 25 RT IL IZ AT IO N n n+n 2n IO S IS O G AM Y ME RY haploid nuclei that become walled ascospores FE + Mating strain MITOSIS Young ascus Dikaryotic hyphae form From ascogonium KA Developing mycelium Ascospore Fully developed ascocarp composed of dikaryotic (ascogenic) hyphae and sterile hyphae (formation of young ascus) c. a: © Richard Kolar/Animals Animals; b: © Ed Reschke/Getty Images 26 27 28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Yeast Yeasts can ferment carbohydrates Break down glucose into ethanol and CO 2 Unicellular ascomycetes Used to make bread, beer, and wine Most Saccharomyces cerevisiae Fungi, together with bacteria, are the principal decomposers in the biosphere Break down cellulose and lignin from wood 5 !m © David Scharf/Photo Researchers, Inc. reproduce asexually by budding Yeasts can ferment carbohydrates Yeast is a long-standing model system for genetic – Break down glucose into ethanol and CO2 research Release carbon, nitrogen, and phosphorus – Used to make bread, beer, and wine First eukaryotes to–be manipulatedcerevisiae extensively Saccharomyces Saccharomyces cerevisiae first eukaryote to have genome sequenced Yeast two-hybrid system has been an important component of research on protein interactions 33 27 28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29 30 SCIENTIFIC THINKING Endophytic fungi Live in the intercellular spaces inside plants Italian rye Some parasitic, some grass is more commensalistic resistant to Some fungi protect their aphid feeding hosts from herbivores by in the producing toxins presence of endophytes Italian rye grass is more resistant to aphid feeding in the presence of endophytes Fungi symbioses Obligate symbiosis – essential for fungus survival Facultative symbiosis – nonessential Interactions Pathogen – pathogens harm host by causing disease Parasites cause harm to host (do not cause disease) Commensal relationships benefit one partner but does not harm the other Mutualistic relationships benefit both partners Hypothesis: Endophytic fungi can protect their host from herbivory. Prediction: There will be fewer aphids (Rhopalosiphum padi, an herbivore) on perennial ryegrass (Lolium perenne) infected with endophytic fungi than on uninfected ryegrass. Test: Place five adult aphids on each pot of 2-week-old grass plants with and without endophytic fungi. Place pots in perforated bags and grow for 36 days. Count the number of aphids in each pot. 5 aphids Fungal endophyte 5 aphids No endophyte Result: Significantly more aphids were found on the uninfected grass plants. Aphids after 36 days Ecology of Fungi Yeast Unicellular ascomycetes Most reproduce asexually by budding 140 120 100 80 60 40 20 0 Fungal Endophyte No Endophyte Conclusion: Endophytic fungi protect host plants from herbivory. Further Experiments: How do you think the fungi protect the plants from herbivory? If they secrete chemical toxins, could you use this basic experimental design to test specific fungal compounds? 38 (left): © Nigel Cattlin/Alamy; (right): © B. Borrell Casal/Frank Lane Picture Agency/Corbis 29 30 5 31 Lichens Symbiotic associations between a fungus and a photosynthetic partner a. Crustose Lichen b. c. a: © Ken Wagner/Phototake; b: © Robert & Jean Pollock/Visuals Unlimited; c: © Robert Lee/Photo Researchers, Inc. Algal cells Fungi in lichens are unable to grow normally without algae, or sometimes both Most are mutualistic Ascomycetes are found in all but about 20 of the 15,000 lichen species Foliose Lichen Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cyanobacteria, green 32 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fruticose Lichen their photosynthetic partners Fungi protect their partners from strong light and Fungal hyphae desiccation Lichens have invaded the harshest habitats Striking colors play a role in protecting photosynthetic 40 μm partner ©Ed Reschke Sensitive to pollutants 31 32 33 34 Arbuscular mycorrhizae Mycorrhizae Mutualistic relationships between fungi and plants Found on the roots of about 90% of all known vascular plant species Function as extensions of root system By far the most common Fungal partners are glomeromycetes No aboveground fruiting structures Potentially capable of increasing crop yields with lower phosphate and energy inputs Increase soil contact and absorption Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arbuscular Mycorrhizae Two principal types Arbuscular mycorrhizae Ectomycorrhizae 33 Root 5 µm a. © Eye of Science/Photo Researchers, Inc. Hyphae penetrate the root cell wall but not plant membranes 34 35 Ectomycorrhizae Most hosts are forest trees (pines, oaks) Fungal partners are mostly basidiomycetes 35 At least 5000 species of fungi are involved in ectomycorrhizal relationships 36 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ectomycorrhizae Animal mutual symbioses 50 µm b. © Dr. Gerald Van Dyke/Visuals Unlimited Ruminant animals host neocallimastigamycete fungi in their gut Leaf-cutter ants have domesticated fungi which they keep in underground gardens Ants provide fungi with leaves Hyphae surround but do not penetrate the root cells Fungi are food for the ants 36 6 37 38 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fungal Parasites and Pathogens Fungal species cause many diseases in plants Among most harmful pests of living plants Can also spoil harvested or stored food products a. b. 5 μm a: © Dayton W ild/Visuals Unlimited; b: © KAGE-Mikrofotografie Fungi may secrete substances making food Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. unpalatable, carcinogenic, or poisonous Fusarium – vomitoxin Aspergillus flavus – aflatoxin a. Courtesy of Ralph Williams/USDA Forest Service b.46 c. b: © agefotostock/SuperStock; c: USDA Forest Service Archive, USDA Forest Service, Bugwood.org 37 38 39 40 Batrachochytrium dendrobatidis causes chytridiomycosis Fungi also cause human and animal diseases Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Candida – thrush; vaginal infections Pneumocystis jiroveci – pneumonia in AIDS Athlete’s foot, ringworm, and nail fungus – Responsible for the worldwide decline in amphibian populations Fungal diseases are difficult to treat because of the close phylogenetic relationship between fungi and animals Chytrid 10 μm (left): © School of Biological Sciences, University of Canterbury, New Zealand; (inset): Courtesy of Dr. Peter Daszak 39 40 7