chapter 31 fungi 生物醫學技環境生物學系 副教授 鄭智美. eukaryote supergroup...

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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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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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 )