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BiologySylvia S. Mader
Michael Windelspecht
Chapter 22 Fungi Evolution and Diversity
Lecture Outline
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1
Outline
• 22.1 Evolution and Characteristics of Fungi• 22.2 Diversity of Fungi• 22.3 Symbiotic Relationships of Fungi
2
22.1 Evolution and Characteristics of Fungi
• The fungi contains over 80,000 species
• Mostly multicellular eukaryotes that share a common mode of nutrition– Heterotrophic
– Saprotrophs - Cells release digestive enzymes and then absorb resultant nutrient molecules
3
Evolution and Characteristics of Fungi
• Protists evolved some 1,500 BYA – Plants, animals, and fungi trace their ancestry
to protists– Molecular data tells us that animals and fungi
shared a common ancestor after plants evolved.
• Animals and fungi are more closely related to each other than either is to plants.
• A flagellated unicellular protist was most likely the common ancestor of fungi and animals
4
Evolution and Characteristics of Fungi
• Fungal anatomy doesn’t lend itself to becoming fossilized – Probably evolved a lot earlier than the earliest
known fungal fossil dated 450 MYA. – Mycorrhizae are evident in plant fossils
5
Evolutionary Relationships Among the Fungi
6A
lve
ola
tes
Do
man
Eu
kary
a
Rh
izar
ia
commonancestor ofeukaryotes
common ancestor Red algae
Chlorophytes
Land plants
Charophytes
Apicomplexans
Dinoflagellates
Ciliates
Brown algae
Golden brown algae
Diatoms
Water molds
Diplomonads
Parabasalids
Euglenoids
Kinetoplastids
Cellular slime molds
Plasmodial slime molds
Amoeboids
Animals
Choanoflagellates
Fungi
Radiolarians
Foraminiferans
Nucleariids
Arc
hae
pla
stid
sA
mo
ebo
zoa
ns
Ch
rom
alv
eola
tes
Exc
avat
es
Op
isth
oko
nts
Str
am
eno
ph
iles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Evolutionary Relationships Among the Fungi
7
commonancestor
common ancestor Basidiomycota(club fungi)
Ascomycota(sac fungi)
Glomeromycota(AM fungi)**
Zygomycota(zoospore fungi)
Chytridiomycota(zoospore fungi)
**AM fungi were once considered part of Zygomycota,but molecular data suggest they are a different phylum.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Evolutionary Relationships Among the Fungi
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Alv
eo
late
s
Do
man
Eu
kary
a
Rh
izar
ia
commonancestor ofeukaryotes
common ancestor Red algae
Chlorophytes
Land plants
Charophytes
Apicomplexans
Dinoflagellates
Ciliates
Brown algae
Golden brown algae
Diatoms
Water molds
Diplomonads
Parabasalids
Euglenoids
Kinetoplastids
Cellular slime molds
Plasmodial slime molds
Amoeboids
Animals
Choanoflagellates
Fungi
Radiolarians
Foraminiferans
Nucleariids
commonancestor
common ancestor Basidiomycota(club fungi)
Ascomycota(sac fungi)
Glomeromycota(AM fungi)**
Zygomycota(zoospore fungi)
Chytridiomycota(zoospore fungi)
**AM fungi were once considered part of Zygomycota,but molecular data suggest they are a different phylum.
Arc
hae
pla
stid
sA
mo
ebo
zoa
ns
Ch
rom
alv
eola
tes
Exc
avat
es
Op
isth
oko
nts
Str
am
eno
ph
iles
8
Evolution and Characteristics of Fungi
• Structure of Fungi– Body (thallus) of most fungi is multicellular
mycelium (yeasts are unicellular)• Consists of a vast network of thread-like hyphae
– Septate fungi have hyphae with cross walls– Nonseptate fungi are multinucleated– Hyphae grow at their tips
• Give the mycelium a large surface area per unit volume
– Cell walls of chitin, like insect exoskeletons– Excess food is stored as glycogen as in animals
9
Mycelia and Hyphae of Fungi
10
a. Fungal mycelia on a corn tortilla
b. Specialized fungal hyphae that bear spores
SEM 300
hypha
spore
Cell wall
nuclei
septum
Septate hyphac. Nonseptate hypha
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a: © Gary R. Robinson/Visuals Unlimited; b: © Dennis Kunkel/Visuals Unlimited
Evolution and Characteristics of Fungi
• Reproduction of Fungi
– Both sexual and asexual reproduction
– Sexual reproduction involves three stages:
• Haploid Hyphae
• Dikaryotic Stage
• Diploid Zygote
11
Evolution and Characteristics of Fungi
• During sexual reproduction, hyphae from two different mating types fuse– Hyphae that contain paired haploid nuclei are said to be
dikaryotic– Nuclear fusion produces a diploid nucleus, which produces
haploid spores by meiosis– Spores germinate directly into haploid hyphae without
embryological development
• Terrestrial fungi usually produce non-motile, windblown spores
• Asexual reproduction usually involves the production of windblown spores
• Unicellular yeasts reproduce asexually by budding
12
22.2 Diversity of Fungi
• R. H. Whittaker (1969) was the first to say– Fungi are separate group from protists, plants,
and animals– His reasoning was that fungi are the only type of
multicellular organism to be saprotrophic. • Some experts place fungi in the supergroup
Opisthokonta• fungal groups: chytrids, zygospore fungi, AM
fungi, sac fungi, and club fungi – Differentiated according to their life cycle and the
type of structure they use to produce spores.
13
Diversity of Fungi
• Chytrids (Chytridiomycota)– Include about 790 species of the simplest fungi. – Some are single cells; others form branched
nonseptate hyphae. – They are unique among fungi
• The only fungi to still have flagellated cells. – Characteristic of aquatic lifestyle, – Some also live in moist soil.
– They produce flagellated gametes and spores. – Most reproduce asexually through the production of
zoospores within a single cell. • The zoospores grow into new chytrids
14
Chytrids Parasitizing a Protist
15
hyphae
chytrid
20 m
algal cellwall
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© Dr. Hilda Canter-Lund
Diversity of Fungi
• Zygomycota
– Zygospore fungi
• Mainly saprotrophs decomposing animal and plant remains
• Black bread mold - Rhizopus stolonifer
16
Diversity of Fungi
• Rhizopus stononifer life cycle: – Hyphae of opposite mating types grow toward each other– Hyphae swell at tips; cross walls develop behind each end;
form gametangia– Gametangia merge resulting in a large multi-nucleate cell
• Nuclei of the two mating types pair and then fuse• A thick wall develops around the zygospore
– The zygospore becomes dormant for period– Sporangiophore(s) then sporangia develop, and spores are
released– Spores are dispersed by air currents; germinate into new
haploid mycelia
17
rhizoid
Black Bread Mold, Rhizopus stolonifer
18
NUCLEAR FUSION
3. Gametangia merge andnuclei pair, then fuse.
CYTOPLASMIC F
USION
2. Gametangia form at the end of each hypha. 5. Sporangiophores
develop, and spores are released from sporangium.
1. Hyphae of opposite mating types touch.
4. A thick wall develops around the cell.
Sexualreproduction
Asexualreproduction
+ mating type
– mating type
5 µm
sporangiophore
sporangium
Zygote
diploid (2n)
haploid (n)sporangium
rhizoid
spores (n)
spores (n)
germination of spores
zygospore germination
+ mating type– mating type
mycelium
MEIOSIS
50 µm
gametangia
thick-walledzygospore
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Diversity of Fungi
• Glomeromycota (AM fungi)– The arbuscular mycorrhizal (AM) fungi are a
relatively small group of about 160 species• Arbuscules are branching invaginations that the
fungus makes when it invades plant roots • Mycorrhizae are a mutualistic association of plants
and fungi
– They were classified as zygospore fungi for many years
• Now classified as a separate group based on molecular data.
19
Diversity of Fungi
• Sac Fungi– Phylum Ascomycota - about 50,000 species of sac fungi– Most are saprotrophs that digest resistant materials containing
cellulose, lignin, or collagen– Most are composed of septate hyphae– Neurospora was the experimental organism for the one-gene-
one-enzyme studies– Morels and truffles, famous gourmet delicacies revered
throughout the world– Sac fungi cause many plant diseases: powdery mildews; leaf
curl fungi; ergot of rye; chestnut blight and Dutch elm disease– Aspergillus and Candida cause serious human infections– Talaromyces (formerly Penicillium) is the source of penicillin
20
Diversity of Fungi
• Life cycle of Sac fungi– Asexual reproduction is the norm
• Yeast usually reproduce by budding– A small bulge forms on side of cell – Receives a nucleus and gets pinched off and becomes full
size– The other ascomycetes produce spores called conidia or
conidiospores– Vary in size and shape and may be multicellular– Conidia usually develop at the tips of aerial hyphae called
conidiophores • Conidiophores differ in appearance and are used for
identification of fungi• Spores are windblown• Conidia of Cladosporium cause allergies - concentrations of
more than 35,000 conidia/m3 over Leiden (Germany)
21
Asexual Reproduction in Sac Fungi
22
b.a.
conidiabuddingyeast cell
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(Both): © David M. Phillips/Visuals Unlimited
Diversity of Fungi
• Sexual reproduction in Sac fungi– Ascus refers to the fingerlike sac that
develops during sexual reproduction– Ascus may be surrounded and protected by
sterile hyphae within a fruiting body called an ascocarp
• In cup fungi, ascocarps are cup-shaped• In morels they are stalked and crowned by a pitted
bell-shaped ascocarp– Haploid hyphae fuse to make a diploid
nucleus– Meiosis followed by mitosis produces 8
ascospores23
Sexual Reproduction in Sac Fungi
24
meiosis
c. Peach leaf curl, Taphrina
ascospores
ascus
fungal hypha
a. Ascocarp of the cup fungus, Sarcoscypha b. Ascocarp of the morel, Morchella
ascospores
200 m
male organ
ridge of pit
pit asci
ascospores
female organ
dikaryotichyphae
nuclearfusionzygote
(2n)matureascus
+ mating type (n)spore
- mating type (n)spore
ridgeof pit
hollowcenter
uppersurfaceof leaf
asexuallyproduced
spore
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a(Top): © Walter H. Hodge/Peter Arnold, Inc.; b(Top left): © Corbis Royalty-Free; b(Top right): © James Richardson/Visuals Unlimited; c(Top): © Kingsley Stern
Diversity of Fungi
• Yeasts
– Yeasts can be both beneficial and harmful to humans.
• Saccharomyces cerevisiae are used to make beer and wine
• used in genetic engineering experiments
• Candida albicans is a yeast that causes fungal infections.
– Oral thrush is a Candida infection of the mouth, common in newborns and AIDS patients.
25
Diversity of Fungi
• Molds– Can be helpful to humans.
• Aspergillus is a group of green molds used to produce soy sauce by fermentation of soybeans.
• Aspergillus is used to produce citric and gallic acids
26
Diversity of Fungi
• Molds– Can be harmful to humans
• Aspergillus flavus secretes a toxin that acts as a carcinogen
• Stachybotrys chartarum produces a toxin leading to dermatitis, flu-like symptoms, fatigue, and immune system complications.
• Trichophyton causes athletes foot (a type of tineas)
• Histoplasma capsulatum leads to the “fungal flu” and causes systemic illness
27
Black Mold
28
conidiophore
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© SciMAT/Photo Researchers, Inc.
SEM 1,8003
Tineas
29
b.
a.
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a: © Dr. P. Marazzi/SPL/Photo Researchers, Inc.; b: © John Hadfield/SPL/Photo Researchers, Inc.
Deadly Fungi
• It is unwise for amateurs to collect mushrooms in the wild– Certain mushroom species are poisonous.
• The red and yellow Amanitas are especially dangerous.
• The death angel mushroom (Amanita phalloides), causes 90% of the fatalities attributed to mushroom poisoning.
– Not serious problems: Abdominal pain, vomiting, delirium, and hallucinations
– Serious problem: the poison inhibits RNA polymerase, leading to liver and kidney damage
30
Poisonous Mushroom, Amanita phalloides
31
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Ergot Infection of Rye, Caused by Claviceps purpurea
32
ergot
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© R. Calentine/Visuals Unlimited
Diversity of Fungi
• Club fungi– Phylum Basidomycota – 22,000 species– Familiar toadstools, mushrooms, bracket
fungi, puffballs, stinkhorns– Some are poisonous– Also plant diseases such as the smuts and
rusts– Mycelium composed of septate hyphae
33
Diversity of Fungi
• Club fungi
– Usually reproduce sexually
– Haploid hyphae fuse, forming a dikaryotic (n + n) mycelium
– Dikaryotic mycelium forms fruiting bodies called basidiocarps
• Contain club-shaped structures called a basidium
• Nuclear fusion followed by meiosis produces basidiospores
34
Club Fungi
6. Basidiospores are released.
basidiospore
nuclei
basidium
portion of gill
cap
gills
stalk
annulus
development of basidiocarp
zygote
basidiospores
5 m
diploid (2n)
haploid (n)
NUCLEAR FUSION
dikaryotic (n+n)
MEIOSIS
dikaryotic mycelium
Mature mushroom
basidium
2. Mycelium produces mushrooms (basidiocarps).
button stageof mushroom
1. Cytoplasmic fusion, resulting in dikaryotic mycelium.
CYTOPLASMIC FUSION
dikaryoticmycelium
haploidhyphae
7. Germination of spores results in haploid hyphae.
splittingof veil
3. Basidia form on gills of mushroom.
4. Nuclear fusion results in diploid nucleus.
5. Meiosis occurs and basidiospores are produced.
+
–
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© Biophoto Associates/Photo Researchers, Inc.35
Club Fungi
36
a. Fairy ring
b. Shelf fungus
c. Pore mushroom, Boletus d. Puffball, Calvatiga gigantea
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Diversity of Fungi
• Smuts and rusts are club fungi that parasitize cereal crops– Have great economic importance because of annual crop
losses• Do not form basidiocarps• Spores are small and numerous
• Life cycle of rusts often requires two different plant host species – One way to control rusts is to eradicate the alternate host– Wheat rust
• Controlled by breeding new resistant strains of wheat• Requires continuous development, because rust can mutate
37
Smuts & Rusts
38
a. Corn smut, Ustilago
b. Wheat rust, Puccinia
fungus
leaf
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22.3 Symbiotic Relationships of Fungi
• Lichens– Symbiotic association between a fungus and a
cyanobacterium or green alga• Specialized fungal hyphae penetrate the
photosynthetic symbiont• Nutrients are transferred directly to the fungus
– Possibly mutualistic, but the fungal symbiont is probably a parasite of photosynthetic symbiont
• The photosynthetic symbiont is independent• The fungal symbiont usually can’t grow alone
39
Symbiotic Relationships of Fungi
• Lichens– Three morphological types
• Compact crustose – often located on bare rocks or tree park
• Fruticose – shrublike• Foliose - leaflike
– Can live in areas of extreme conditions– Contribute to soil formation– Sensitive indicators of air pollution
40
Lichen Morphology
411mm
a. Crustose lichen, Xanthoria b. Fruticose lichen, Lobaria c. Foliose lichen, Xanthoparmelia
reproductive unit
fungal hyphae
sac fungireproductivecups
fungal hyphae
algal cell
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a: © Digital Vision/Getty Images; b: © Steven P. Lynch c: © Kerry T. Givens
Symbiotic Relationships of Fungi
• Mycorrhizae
– Mutualistic relationships between soil fungi and the roots of most plants
• Give plant greater absorptive surface
• Help plants acquire mineral nutrients in poor soil
– Fungal symbiont is usually a glomerulomycete or a sac fungus
• Hyphae may enter cortex of roots, but not the cytoplasm
– Ectomycorrhizae form a mantle that is exterior to the root, and they grow between cell walls
– Endomycorrhizae penetrate only the cell walls
– The earliest fossil plants have mycorrhizae associated with them
42
Plant Growth Experiment
43
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