chapter 31 fungi 生物醫學技環境生物學系 副教授 鄭智美. eukaryote supergroup...
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CHAPTER 31
Fungi
生物醫學技環境生物學系副教授鄭智美
Eukaryote supergroup Opisthokonta( 後鞭毛生物 )Certain closely related protistsKingdom FungiKingdom Animalia
Fungi arose from protists related to an amoeba that feeds by engulfing cells
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31.1 Evolutionary Relationship and distinctive Features of Fungi
Early diverging fungi include microsporidia微孢子蟲 and chytrids (Chytridiomycota壺菌門 )
Zygomycetes結合菌 – polyphyletic Arbuscular mycorrhizal fungi 樹枝狀体 (AM fungi)
(Glomeromycota)菌根菌 Sac fungi (Ascomycota)子囊菌 Club fungi (Basidiomycota)擔子菌
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Kingdom Fungi
Supergroup Opisthokonta
True hyphae/mycelium
Critical innovations
KEY
Septate hyphae, mated hyphaewith 2 types of nuclei, fruiting bodies
Beneficial associations withphotosynthetic organisms
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Fungi are closely related to animalsBoth heterotrophic – cannot produce their
own foodBoth use absorptive nutrition – secrete
enzymes and absorb resulting small organic molecules
Both store surplus food as the carbohydrate glycogen
31.1 Evolutionary Relationship and distinctive Features of Fungi
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Unique cell-wall chemistry
Fungal cells enclosed by tough cell walls composed of chitin
Cells cannot engulf food due to rigid cell walls Cell wall also restricts mobility of nonflagellate
cells
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Unique body form
Most have mycelia composed of hyphae 菌絲Most of the mycelium is diffuse and
inconspicuous Fruiting bodies子實體 are the visible
reproductive structuresMushrooms are one typeProduce spores孢子
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Different unmated myceliumUnmated mycelium
Fruiting bodyabove thesubstrate
Mated hyphae
Spores
Myceliumwithin substrate
(such as soil) Region where hyphae mate,forming a fruiting body
Fungal Morphology
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Distinctive growth processes
Mycelia can grow quickly when food is plentiful
Grow at the edges Narrow dimensions and extensive branching
provides high surface area for absorption Osmosis important in growth- entry of water
produces force for tip extension
WaterHyphae growth
(b) Mechanism of hyphal tip growth
0.3 µm
(a) Electron micrograph of a hyphal tip with numerous vesicles
Vesicle carryingdigestiveenzymes
Vesicle carrying cell-wallcomponents
Secreted digestiveenzymes
Small organicmolecules
Chitincell wall
Plasmamembrane
Golgiapparatus
Site of newcell-walldeposition
Hyphae tip growth and absorptive nutrition
Septate fungiSepta - Cross walls dividing cells of
myceliumEach cell has 1 or 2 nucleiNuclear division followed by cross-wall
formation11
(a) Septate hypha
Hyphae structure and nuclear division
Aseptate fungiNot partitioned into smaller cellsMultinucleateNuclei divide without cytokinesisCoenocytic
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(b) Aseptate hypha
Intranuclear spindle distinguishes fungal nuclear division from plants and animalsSpindle forms inside nucleus and nuclear
envelope does not break down In land plants and animals, the nuclear
envelope vesiculates during prometaphase and then re-forms at telophase
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EUKARYOTIC CELL, 2007, Vol. 6, No. 9p. 1521–1527
spindle pole bodies (blue)
NPC is composed of core Nups (green) and FG-repeat Nups (red),
mitotic entry
nuclear entry of tubulin
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G2, the spindle pole bodies (blue) nucleate microtubulesin the cytoplasm. The NPC is composed of core Nups (green) andFG-repeat Nups (red), which occupy the NPC central channel and restrictdiffusion. Upon mitotic entry, FG-repeat Nups disperse from the centralchannel, allowing nuclear entry of tubulin and thus spindle formation.Insets show a magnification of a single NPC. Note that the nuclear envelopemay prevent inappropriate microtubule connections between thespindle pole bodies and the chromosomes of the two nuclei which are inmitosis at the same time.
Natural mycelium may be irregular in shape In liquid culture it is sphericalOn agar it is more 2 dimensional
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Fungal shape shifting
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請問真菌是否與植物一樣具備由纖維素所構成的細胞壁 ( O or X )
Qiuz 1:
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Fungal asexual and sexual reproductionAsexual reproduction
Many fungi reproduce both sexually and asexually by spores
Many reproduce only asexually
Conidia – asexual spores at the tips of hyphae
Medically important fungi that reproduce primarily by asexual means include the athlete’s foot fungus (Epidermophyton floccosum) and the infectious yeast (Candida albicans)
Yeasts are fungi of various lineages that can occur as unicells; they reproduce by asexual budding
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Sexual reproduction
Involves union of gametes, zygote formation and meiosis
Gametes of most fungi are cells of hyphal branchesMating types differ biochemicallyHyphal branches fuse between compatible
mating types
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Celldivision
Hyphalbranches
of compatiblemating types
Dikaryoticmycelium
Spores
The reproduction cycle of many types of fungi
Most sexual organisms have plasmogamy (fusion of gametes’ cytoplasm) followed by karyogamy (fusion of gametes’ nuclei)
In fungi, after plasmogamy, nuclei may remain separate for a long timeMycelium is dikaryotic or heterokaryotic
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Mating process
Some fungi persist as dikaryons, producing
clones that can live for hundreds of years
Dikaryotic mycelia are functionally diploid
Eventually, dikaryotic mycelia produce fruiting
bodies, the next stage of reproduction
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Fruiting bodies子實體
Dikaryotic mycelium may produce a fleshy
fruiting body
All cells of the fruiting body are dikaryotic
When mature, the 2 nuclei in cells will fuse
Produces zygotes (only diploid stage)
Undergo meiosis to produce haploid spores
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Structure of fruiting bodies varies in ways that reflect adaptations for spore dispersal by wind, rain or animals.
Phallus impudicus鬼筆菌
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Many fungi produce substances in the fruiting body to deter consumption Toxins can cause liver failure requiring a transplant Hallucinogenic or psychoactive substances
Claviceps purpurea
麥角病
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Fungal ecology
Decomposer fungi are essential component’s
of the Earth’s ecosystems
Work with bacteria
Only certain bacteria and fungi can break down
cellulose
Release minerals to the soil and water
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Some fungi are predators trapping tiny soil nematodes
Arthrobotrys anchonia
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Fungal pathogens
5000 species cause serious crop diseases Rust spores can be spread
on the wind or by other means
Several human diseases Dermatophytes - athlete’s
foot, ringworm Pneomocystis carinii
pneumonia in AIDS
黑銹病
Dimorphic fungi
Live as spore-producing hyphae in the soil
Transform into pathogenic yeasts when mammals inhale
their wind-dispersed spores
Host body temperature triggers the change from hyphae to
yeast form
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Blastomyces dermititidiscauses blastomycosis
Coccidioides immitiscauses coccidiomycosis
Histiplasma capsulatumcauses histoplasmosis
hyhae
Human body temp
Yeast form
Histidine kinase
Dimorphic fungi
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Fungi form beneficial associations with other speciesFungal associations:
Beneficial associations with photosynthetic partners
Mycorhizzal fungi 菌根 Endophytes 體內寄生型 Lichens 地衣
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Mycorhizzae菌根 Association between the hyphae of certain fungi and the roots
of most seed plants
More than 80% of terrestrial plants have mycorrhizae
Plants receive increased supply of water and mineral nutrients
Fungi get organic food molecules from the plants
2 most common types are endomycorrhizae and
ectomycorrhizae
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EndomycorrhizaeFungal hyphae penetrate the spaces
between root cell walls and plasma membranes and grow along the outer surface of the plasma membrane
Arbuscular mycorrhizae (AM) form highly branched structures with high surface area
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EctomycorrhizaeCoat root surface and grow between
cells of rootsSome species of oak, beech, pine, and
spruce trees will not grow unless their ectomycorrhizal partners are also present
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(b) SEM of ectomycorrhizal hyphae (c) Hyphae invading intercellular spaces(a) Ectomycorrhizal fruiting body
Ectomycorrhizalhyphae coatinga root tip
Rootcells
Ectomycorrhizalhyphae
a: © Jacques Landry, Mycoquebec.org; b: © Courtesy of Larry Peterson and Hugues Massicotte
Gene Expression in Ectomycorrhizal Fungi Explains How They Live Both Independently and in Partnership with Plants
Laccaria bicolor雙色蠟蘑model organism
Mycelium grows well by itself and in symbiosis with tree roots
2008 genome study explained its characteristics
L. bicolor has a larger genome than nonmycorrhizal fungi –
suggests that symbiosis has accelerated evolution
High number of genes associated with plasma membrane transport
Lacks genetic capacity to break down cellulose and lignin
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Fungal endophytes
Live within the leaf and stem tissues of various types of
plants
Endophytes obtain organic food molecules from plants
In turn contribute toxins or antibiotics that deter
foraging animals, insect pests, and microbial pathogens
Plants with endophytes often grow better than plants of
the same species without endophytic fungi
Márquez and Associates Discovered That a Three-Partner Association Allows Plants to Cope with Heat Stress
Endophytic fungus Curvularia protuberata commonly lives within aboveground tissues of the grass Dichanthelium lanuginosum Unusual in its ability to grow on very hot soils
Alone, both die when temp reaches 38ºC Together, they can survive near 65ºC Curvularia thermal tolerance virus also involved Researchers determined that the virus infected Fungus (but not virus-free fungi) could also protect a
distantly related crop plant (tomato) from heat stress
(a) (b) (c)
Experimental level Conceptual level
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Brown, dead
Green, healthy
KEY
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GOAL To determine if a virus is essential to the protective role of endophytic fungi to host plants under heat stress.
KEY MATERIALS Curvularia thermal tolerance virus (CthTV), cultures of the endophytic fungus Curvularia protuberata infected with CthTV, C. protuberata cultures free of CthT V , and Dichanthelium lanuginosum plants.
Plant 25 replicate containers with D. lanuginosum lacking fungalsymbionts (a) or with C.protuberata endophytes that eitherdid (b) or did not (c) have virus.
(a) No fungus, no virus
(b) Fungus and virus
(c) Fungus, no virus
Compare the effects of virus onthe ability of the fungus to conferheat stress protection.
Expose plants to heat stresstreatment (up to 65°C) for 2weeks in a greenhouse.
Keep environmental conditionsconstant to reduce experimentalerro r .
Count the number of plants thatwere green (alive), yellow (dying),or brown (dead).
Assess plant survival in thepresence or absence of fungus and/or virus.
Yellow, dying
(a)No fungus,
no virus
(b)Fungus
and virus
(c)Fungus,no virus
THE DATA CONCLUSION A virus enhances the protective role of endophytic fungi in this grass species. The next step will be to try to determine just how the virus changes the fungus so that the fungus is able to protect the plant from heat stress.
SOURCE Márquez, Luis M. et al. 2007. A virus in a fungus in a plant: Three-way symbiosis required for thermal tolerance. Science 315:513–515.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(CthTV)+Endophyte Endophyte
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Lichens
Partnerships of particular fungi and certain photosynthetic green algae and/or cyanobacteria 藍綠菌
25,000 lichen species Not all descended from a common ancestor At least five separate fungal lineages
3 major forms – crustose( 殼狀 ), foliose( 葉狀 ), fruticose( 灌木狀 )
Photosynthetic partner provides organic food molecules and oxygen
Fungal partner provides carbon dioxide, water, and minerals
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Crustose lichen
Fruticose lichen
Foliose lichen
Microscopic view of a cross sectionof a lichen
Lichens reproduce Sexually with fungal partner producing fruiting
bodies and sexual spores 1/3 can only reproduce asexually using soredia
Small hyphal clumps surrounding a few algal cells
Clones
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Biotechnology applications
Fungi convert inexpensive organic compounds into citric acid, glycerol, and antibiotics
Distinctive flavor of blue cheese
Saccharomyces cerevisiae for bread, beer and wine
Replace chemical procedures that generate harmful waste products Wood pulp bleaching
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5 fungal kingdoms
Chytridiomycota 壺菌門 Zygomycota 結合菌 Glomeromycota菌根菌 Ascomycota子囊菌 Basidiomycota擔子菌
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Chytridiomycota
Simplest fungi Earliest fungal phylum Some are single, spherical cells that may produce hyphae Others are branched, aseptate hyphae Only fungi to produce flagellate cells – for spore or gamete
dispersal Live in water or moist soil Most decomposers, some parasites Not monophyletic
壺菌門
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Zygomycota
Mycelium mostly aseptate hyphae Produces asexual spores in sporangia Named for zygospore produced sexually Zygospore production begins with development of
gametangia Most are saprobes in soil Some are parasites Not monophyletic
結合菌
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Gametangium Zygospore
(b) Sexual reproduction
Fertilization
Crosswall
Aseptatehypha
ParentalhyphaeHypha
SporeMitosis Meiosis
Spores
Bread loaf
(a) Asexual reproduction
Aseptatehyphae
Asexualsporangia
a: © Peres/Custom Medical Stock Photo; b: © William E. Schadel/Biological Photo Service
Haploid
KEY
Diploid
Heterokaryotic
The asexual and sexual cycle of a zygomycetes, The black bread mold Rhizopus stolonifre
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Glomeromycota
Arbuscular mycorrhizal (AM) fungi 叢枝菌根 Aseptate hyphae Only asexual reproduction using unusually large
multinucleate spores Ability of early plants to live on land may have
depended on help from fungal associations
菌根菌
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Ascomycota
Hyphae subdivided into cells by septa with simple pores
Unique sporangia called asci Produce sexual spores called ascospores Asci produced on fruiting bodies called ascocarps Occur in terrestrial and aquatic habitats
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) Simple pore—ascomycetes
Pore
Septum
a: Micrograph courtesy of Timothy M Bourett, DuPont Crop Genetics, Wilmington, DE USA
子囊菌
子囊子囊孢子
子囊殼
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(b) Sexual reproduction of the ascomycete Aleuria aurantia
(a) Asexual reproductionAscus
Diploid nucleus
8 ascospores
Fruiting bodyHaploid
Diploid
Heterokaryotic
Mitosis
Ascocarp
Hyphalbranches
Dispersingspores
4 haploidnuclei
Dikaryoticmycelium
Meiosis
Fertilization
KEY
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Many decomposers and parasites
Chestnut blight 栗子病 Dutch elm disease荷蘭榆樹病 , apple scab蘋果斑點病
Truffles, morels Common lichen partner Many yeasts
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Basidiomycota
Hyphae subdivided into cells by septa with complex pores
Most recently evolved group of fungi along with Ascomycota
Important decomposers and mycorrhizal partners Produce mushrooms, puffballs, stinkhorns, shelf
fungi, rusts and smuts as fruiting bodies
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(b) Complex pore—basidiomycetes
Septum
Endoplasmicreticulum (ER)
© Charles Mims
擔子菌
Named for basidia that produce sexual spores called basidiospores擔孢子
Fruiting bodies called basidiocarps Clamp connections help distribute nuclei during cell
division Reproduce asexually by various types of spores
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Utilago maydis corn smut Shelf fungi
玉米黑穗菌
暗礁菌
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Diploid nucleus
Basidiospore
Basidiospores
Basidium
Haploid
Diploid
Heterokaryotic
KEY
Mitosis and cellgrowth in tip cell
Clampconnectionforms
NewseptumformsHyphal
branchcarries 1nucleus
Gill ofmushroom
Nucleardistributioncomplete
Basidium withhaploid nuclei
(left): © Biophoto Associates/Photo Researchers; (right): © Dr Jeremy Burgess/Photo Researchers
The sexual life cycle of the basidiomycetes fungus Corprinus disseminatus
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Qiuz 2:
金針菇為擔子菌 ( O or X )