Download FUNGI Five lineages of Fungi (Chytrids paraphyletic) II. Structure

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I. Mycology: Mushrooms, molds, and
yeasts. General Characteristics
FUNGI
•  Eukaryotes.
•  Predominant stage
haploid.
•  Both multicellular
(hyphae made up of
filaments) and
unicellular (yeasts).
•  Not photosynthetic, all
heterotrophic by
absorption.
Fruiting
body
Mycelium
•  Key points:
•  Heterotrophs that obtain nutrition by
absorption.
•  Shared common ancestor of animal-like
protists with Animalia.
•  Vital symbionts of plants.
•  Classification based on reproductive
modes.
Hyphae made up of filaments are organized into
mushroom body (mycelium and fruiting body)
• 
m
0
a
by
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Share common ancestor with
animals and some Protists (to
the exclusion of other Protista
and Plants).
Ancient, fossils associated with
earliest land plants, ca. 400mya.
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• 
Five lineages of Fungi
(Chytrids paraphyletic)
ya
I. Mycology: Mushrooms, molds, and
yeasts. Evolutionary History
–  Molecular data suggests the
split between the lineage
leading to fungi and the lineage
leading to animals occurred ca.
1 bya.
• 
Have diversified into five main
lineages
I. Mycology: Mushrooms, molds, and
yeasts. The Absorptive Mode of Nutrition
–  Most plants depend on mutualist relationship with fungi.
•  Vegetative (nonreproductive) body.
•  Basic units are hyphae
–  Filaments of cells with a wall
of chitin.
–  Septate cells (most
common)
–  Aseptate & coenocytic cells
•  Hyphae form interwoven mat
called the mycelium
–  10 cm3 of soil can contain 1
km of hyphae.
•  Haustoria are specialized
hyphae of parasitic fungi that
penetrate plant cells.
Mycelium
•  Enzymes decompose organic materials.
•  Saprobes decompose and absorb nutrients from
non-living organic matter.
•  Parasitic fungi absorb nutrients from cells of living
hosts, some are pathogenic.
•  Mutualistic fungi also absorb from host organism,
but reciprocate with beneficial functions, e.g. uptake
of nutrients, minerals.
II. Structure: The mycelium
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II. 
Structure: Reproductive
body
•  Varies with taxonomic
group
•  All reproduce by
haploid spores in
specialized structures
peculiar to each group.
•  Evolution of fungi
toward larger, more
specialized sporebearing structures.
II. Structure:
Other Life Styles
•  Molds: Rapidly growing
asexual stage.
–  May develop sexual
stage as fruiting body
distinctive of one of 5
phyla.
–  Some without known
sexual stage, called
imperfect fungi or
deuteromycetes.
–  Important molds, e.g.
Penicillium (penicillin,
cheese)
Zygomycete
Basidiomycete
Ascomycete
Mutualistic Symbioses
II. Structure:
Other Life Styles
II. Structure:
Other Life Styles
•  Mycorrhizae: “fungus roots”
•  Yeasts: Unicellular fungi in
liquids or moisture including
sap and animal tissue.
–  Important mutualism.
–  Increases surface area for absorption and exchange of
nutrients.
–  Important in global Phosphorus cycle.
–  Over 95% of plants have mycorrhizae.
–  Ectomycorrhizae: Hyphal sheath covers root and hartig
net surrounds individual plant root cells.
–  Asexual cell division, or
budding; but some sexual
ascomycetes and
basidiomycetes are yeasts.
–  Saccharomyces: baker’s
yeast, brewer’s yeast; active
metabolically, release CO2
causes dough to rise, also
ferments sugars to alcohol.
–  Candida: pathogenic yeast
(vaginal, oral).
•  Species of Zygomycetes, Ascomycetes, Basidiomycetes.
–  Arbuscular mycorrhizae: Hyphae enter plant cells via
invagination of plant cell membrane (do not enter
protoplast--the interior of the cell).
•  Only and all species of Glomeromycota.
Mutualistic Symbioses
Mutualistic Symbioses
II. Structure:
Other Life Styles
• 
Endophytes live within plant
tissues.
–  Provide fungi with protection,
nutrients, water.
–  May receive from fungi
chemical protection from
insects, protists, bacteria, other
fungi.
–  May receive ability to tolerate
stressful environmental
conditions.
–  Found in every plant studied to
date (do not know role of all).
–  Primarily Ascomyceta.
–  Taxol, effective anti-cancer
drug derived from endophyte of
the Pacific Yew.
II. Structure:
Other Life Styles
•  Lichens are mutualisms between
fungi and photosynthetic
organisms.
1. 
2. 
3. 
4. 
Green Algae
Cyanobacteria
Yellow-Green Algae†
Brown Alga (1 known case)†
•  Rarely three-fold: Fungus +
photosynthetic green alga +
nitrogen-fixing cyanobacteria.
•  Fungi provide mineral nutrients and
water, algae provide carbohydrates
via photosynthesis.
•  Ascomyceta (mostly),
Basidiomyceta (a few),
Glomeromyceta (1)
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Mutualistic Symbioses
II. Structure:
Other Life Styles
• 
• 
• 
Insect cultivation: Fungi are cultivated by
insects, provided with protection, fungi
break down cellulose in plant tissue.
Internal cultivation: Termites
External cultivation:
– 
– 
Leaf-cutter ants: cultivate underground fungus
gardens. Fungi break down cellulose in leaf
tissue, ants eat fungus.
Bark and ambrosia beetles: colonize new trees
and inoculate carved galleries with ascomycete
fungus. Fungi break down cellulose in wood,
beetles consume fungus.
III. Growth & Reproduction:
Generalized life cycle
1. 
2. 
3. 
4. 
5. 
Plasmogamy: fusion of
cytoplasm of haploid hyphae.
Dikaryon: cells with two
haploid unfused nuclei.
Karyogamy: fusion of nuclei,
diploid stage; followed
immediately by:
Meiosis in haploid spore
producing structures.
Spores are released as
haploid and germinate into
filaments.
A. Chytridiomycota (chytrids)
•  ~1,000 species,
paraphyletic.
•  Only fungi with flagellated
(spore) stage.
•  A link between ancestral
protists and true fungi?
•  Once excluded from Fungi,
but share biochemical
characters, cell walls of
chitin, absorptive mode of
nutrition.
•  Mainly aquatic saprobes,
some parasitic on plants and
animals.
III. Growth & Reproduction
•  Growth not in bulk, but by
proliferation of hyphae
growing into resource
(e.g. giant fairy ring)
•  Reproduction mostly
asexual by spores or
simple cloning, only
chytrids with flagellar
stage.
•  Spores dispersed by
wind, water, animals.
IV. Diversity
A.  Chytridiomycota (chytrids)
B.  Zygomycota (zygote fungi)
C.  Glomeromycota (arbuscular
mycorrhizae)
D.  Ascomycota (sac or cup fungi)
E.  Basidiomycota (club fungi)
B. Zygomycota (zygote fungi)
•  ~1,000 species
•  Terrestrial, soil, decaying
plant/animal tissue.
•  Mycorrhizae: mutualistic
association with plant
roots.
•  Hyphae coenocytic.
•  Zygosporangia are the
reproductive structures
that give the name.
•  E.g. Rhizopus stolonifer,
black bread mold.
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C. Glomeromycota
(arbuscular mycorrhizae)
•  160 species, once
considered
Ascomycota, but now
recognized as distinct.
•  Nearly all form
arbuscular
mycorrhizae with
plants--ecologically
important.
–  Ca. 90% of all plant
species have them as
mutualists!
D. Ascomycota (sac or cup fungi)
•  Include such tasties as truffles
and morels.
•  Unicellular to complex
multicellularity.
•  Some extreme plant pathogens;
other important saprobes.
•  Half symbiotic with Chlorophyta:
lichens.
•  Karyogamy in an ascocarp;
sexual spore in asci.
•  Asexual: spores (conidia) come
from specialized structures
(conidiophores), wind
dispersed.
E. Basidiomyceta (club fungi)
•  Include the commonly
encountered mushrooms, shelf
fungi, puffballs.
•  Basidium (“little pedestal”)
transient diploid stage.
•  Most important plant (wood)
decomposers.
•  Karyogamy in basidiocarp
(sexual); puff balls release
spores explosively.
•  Most complex of fungi: longlived dikaryotic mycelium.
•  Fairy rings; giant ring in
Michigan ~40 acres (!);
genetically uniform mycelium.
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