1. Biology Sylvia S. Mader Michael Windelspecht
Chapter 22
Fungi Evolution and Diversity
Lecture Outline
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2. Outline 22.1 Evolution and Characteristics of Fungi
22.2 Diversity of Fungi
22.3 Symbiotic Relationships of Fungi

3. 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

4. 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

5. 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

6. Evolutionary Relationships Among the Fungi
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common ancestor
Red algae
Chlorophytes
Archaeplastids
Land plants
Charophytes
Apicomplexans
Dinoflagellates
Alveolates
Ciliates
Chromalveolates
Brown algae
Golden brown algae
Stramenophiles
Diatoms
Water molds
Diplomonads
Doman Eukarya
common
ancestor of
eukaryotes
Parabasalids
Excavates
Euglenoids
Kinetoplastids
Cellular slime molds
Plasmodial slime molds
Amoebozoans
Amoeboids
Animals
Choanoflagellates
Opisthokonts
Fungi
Nucleariids
Foraminiferans
Rhizaria
Radiolarians

7. Evolutionary Relationships Among the Fungi
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common ancestor
Basidiomycota
(club fungi)
Ascomycota
(sac fungi)
Glomeromycota
(AM fungi)**
Zygomycota
(zoospore fungi)
common
ancestor
Chytridiomycota
(zoospore fungi)
**AM fungi were once considered part of Zygomycota,
but molecular data suggest they are a different phylum. 7

8. Evolutionary Relationships Among the Fungi
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common ancestor
Red algae
Chlorophytes
Archaeplastids
Land plants
Charophytes
Apicomplexans
Dinoflagellates
Alveolates
Ciliates
Chromalveolates
Brown algae
Golden brown algae
Stramenophiles
Diatoms
Water molds
common ancestor
Basidiomycota
(club fungi)
Diplomonads
Doman Eukarya
Excavates
Ascomycota
(sac fungi)
common
ancestor of
eukaryotes
Parabasalids
Euglenoids
Glomeromycota
(AM fungi)**
Kinetoplastids
Cellular slime molds
Zygomycota
(zoospore fungi)
common
ancestor
Plasmodial slime molds
Amoebozoans
Amoeboids
Chytridiomycota
(zoospore fungi)
Animals
**AM fungi were once considered part of Zygomycota,
but molecular data suggest they are a different phylum.
Choanoflagellates
Opisthokonts
Fungi
Nucleariids
Foraminiferans 8
Rhizaria
Radiolarians

9. 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

10. Mycelia and Hyphae of Fungi
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a. Fungal mycelia on a corn tortilla
hypha
spore
Cell wall
nuclei
septum
SEM 300´
b. Specialized fungal hyphae that bear spores
c. Nonseptate hypha
Septate hypha
a: © Gary R. Robinson/Visuals Unlimited; b: © Dennis Kunkel/Visuals Unlimited

11. Evolution and Characteristics of Fungi
Reproduction of Fungi
Both sexual and asexual reproduction
Sexual reproduction involves three stages:
Haploid Hyphae
Dikaryotic Stage
Diploid Zygote

12. 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

13. 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.

14. 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

15. Chytrids Parasitizing a Protist
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algal cell
wall
hyphae
chytrid
20 mm
© Dr. Hilda Canter-Lund

16. Diversity of Fungi Zygomycota Zygospore fungi
Mainly saprotrophs decomposing animal and plant remains
Black bread mold - Rhizopus stolonifer

17. 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

18. Black Bread Mold, Rhizopus stolonifer
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Zygote
thick-walled zygospore
50 µm
3. Gametangia merge and nuclei pair, then fuse.
NUCLEAR FUSION
4. A thick wall develops around the cell.
gametangia
diploid (2n)
Sexual reproduction
MEIOSIS
2. Gametangia form at the end of each hypha.
sporangium
haploid (n)
spores (n)
5. Sporangiophores develop, and spores are released from sporangium.
– mating type
+ mating type
1. Hyphae of opposite mating types touch.
CYTOPLASMIC FUSION
zygospore germination
sporangium
spores (n)
germination of spores
sporangiophore
5 µm
Asexual reproduction
– mating type
+ mating type
rhizoid
rhizoid
mycelium
Bottom left: © James W. Richardson/Visuals Unlimited; Top right: © David M. Phillips/Visuals Unlimited

19. 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.

20. 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

21. 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)

22. Asexual Reproduction in Sac Fungi
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conidia
budding
yeast cell a. b.
(Both): © David M. Phillips/Visuals Unlimited

23. 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 ascospores

24. Sexual Reproduction in Sac Fungi
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ascospores
nuclear
fusion
zygote
(2n)
pit
ridge
of pit
200 mm
asci
meiosis
mature
ascus
ascospores
asexually
produced
spore
ascus
ridge of pit
upper
surface
of leaf
ascospores
dikaryotic
hyphae
fungal hypha
hollow
center
+ mating type (n)
spore
male organ
female organ
- mating type (n)
spore
a. Ascocarp of the cup fungus, Sarcoscypha
b. Ascocarp of the morel, Morchella
c. Peach leaf curl, Taphrina
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

25. 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.

26. 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

27. 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

28. © SciMAT/Photo Researchers, Inc.
Black Mold
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conidiophore
SEM 1,8003´
© SciMAT/Photo Researchers, Inc.

29. Tineas
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a: © Dr. P. Marazzi/SPL/Photo Researchers, Inc.; b: © John Hadfield/SPL/Photo Researchers, Inc.

30. 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

31. Poisonous Mushroom, Amanita phalloides
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© Patrick Endres/Visuals Unlimited

32. Ergot Infection of Rye, Caused by Claviceps purpurea
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ergot
© R. Calentine/Visuals Unlimited

33. 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

34. 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

35. © Biophoto Associates/Photo Researchers, Inc.
Club Fungi
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Mature mushroom
3. Basidia form on gills
of mushroom.
cap
annulus
portion of gill
gills
2. Mycelium produces
mushrooms (basidiocarps).
stalk
splitting
of veil
button stage
of mushroom
basidium
dikaryotic mycelium
nuclei
development of basidiocarp
NUCLEAR FUSION
1. Cytoplasmic fusion, resulting
in dikaryotic mycelium.
zygote
dikaryotic (n+n)
dikaryotic
mycelium
CYTOPLASMIC FUSION
diploid (2n)
4. Nuclear fusion results
in diploid nucleus.
haploid
hyphae
haploid (n) + –
MEIOSIS
7. Germination of spores
results in haploid hyphae.
5 mm
basidiospore
basidium
5. Meiosis occurs
and basidiospores
are produced.
basidiospores
6. Basidiospores are released.
© Biophoto Associates/Photo Researchers, Inc.

36. Club Fungi a. Fairy ring b. Shelf fungus c. Pore mushroom, Boletus
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a. Fairy ring
b. Shelf fungus
c. Pore mushroom, Boletus
d. Puffball, Calvatiga gigantea
a: © Glenn Oliver/Visuals Unlimited; b: © imagebroker/Alamy RF; c: © M. Eichelberger/Visuals Unlimited; d: © L. West/Photo Researchers, Inc.

37. 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

38. a: © Steven P. Lynch; b: © Arthur M. Siegelman/Visuals Unlimited
Smuts & Rusts
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a. Corn smut, Ustilago
fungus
leaf
b. Wheat rust, Puccinia
a: © Steven P. Lynch; b: © Arthur M. Siegelman/Visuals Unlimited

39. 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

40. 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

41. Lichen Morphology algal cell reproductive unit fungal hyphae
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algal cell
reproductive unit
fungal hyphae
fungal hyphae
sac fungi
reproductive
cups
1mm
a. Crustose lichen, Xanthoria
b. Fruticose lichen, Lobaria
c. Foliose lichen, Xanthoparmelia
a: © Digital Vision/Getty Images; b: © Steven P. Lynch c: © Kerry T. Givens

42. 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

43. Plant Growth Experiment
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© R. Roncadori/Visuals Unlimited