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Transcript of Biology of Fungi - mycologysite.files.wordpress.com fileZygomycota Homothallic or heterothallic...
Lecture: Growth and Development, Part 3B
Biology of Fungi
Fungal Growth and Development
BIOL 319
Sexual Development (cont.)
Nature of sexuality Homothallic vs. heterothallic
Governed by mating type genes
(compatibility) Arrangement of mating types Bipolar compatibility - governed by a single gene
locus where one of a non-allelic pair of genes
(idiomorph) exists Tetrapolar compatibility - two mating type gene pairs
of multiple idiomorphs
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BIOL 319 - Spring 2017
Sexual Development
Sexual reproduction involves three
fundamental processes: Plasmogamy - fusion of haploid cells
Karyogamy - fusion of haploid nuclei
Meiosis - reduction division Two fundamental points of sexual
reproduction Nature of sexuality Serves as a survival mechanism
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Sexual Development (cont.) Mating type and
hormonal control
Chytridiomycota
Allomyces is a
homothallic fungus
that produces
separate male and
female gametangia
that release motile Gametangia of Allomyces. Source: www.palaeos.com/
gametes
Fungi/Lists/Glossary/GlossaryG.html
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Sexual Development (cont.)
BIOL 319
Sexual Development (cont.)
Mating type and hormonal control Chytridiomycota (cont.)
Females release a pheromone, serinin, that attracts
the male gametes Male gametes move along a concentration gradient
Serinin and carotenoid color produced in male
gametangia are produced from the same precursor,
indicating mating type gene controls development of
the sex organs
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Lecture: Growth and Development, Part 3B
Sexual Development (cont.)
Oomycota Homothallic or heterothallic, but in
most cases produces a colony
with both male and female sex
organs (antheridia and oogonia) Mating type genes control
compatibility Hormonal control in Achlya
Female produces antheridiol
causing the male to increase
production of cellulase which
induces hyphal branching to
increase
BIOL 319
BIOL 319 - Spring 2017
Sexual Development (cont.)
Once triggered by
antheridiol, males release
oogoniols that induce
oogonia development Eventually, male branches
(antherida) fuse with
oogonia
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Sexual Development (cont.)
Oogonium and antheridium of Achlya. Source:
www.palaeos.com/Fungi/Lists/Glossary/GlossaryG.html BIOL 319
Trisporic acid hormonal system in mating within the Zygomycota.
Sources: www.palaeos.com/Fungi/Lists/Glossary/GlossaryG.html
and Deacon, 2006 BIOL 319
Sexual Development (cont.)
Zygomycota Homothallic or heterothallic
Two mating type genes that govern conversion of β-
carotene to a prohormone Prohormone is eventually converted by mating-type
specific gene to trisporic acid Trisporic acid volatilizes and causes hyphae of
opposite mating type to grow towards one another
and fuse to form a zygospore BIOL 319
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Lecture: Growth and Development, Part 3B BIOL 319 - Spring 2017
Sexual Development (cont.)
Ascomycota Typically two mating types a cells and α cells Best characterized system is that of Saccharomyces
Mating is controlled by the MAT gene locus of
flanked by two other loci, MATa and MATα A copy of one loci is made and inserted into MAT
gene locus - this is now the mating type of the cell This copy can switch out after each new bud cell is
produced
Mating type loci of Saccharomyces. Source: nitro.biosci.arizona.edu/courses/ EEB320-2005/Lecture13/lecture13.html
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Diagram of life cycle of Saccharomyces. Source: nitro.biosci.arizona.edu/
courses/EEB320-2005/Lecture13/lecture13.html BIOL 319
Sexual Development (cont.)
Ascomycota (cont.) MATα are responsible for producing:
Peptide hormones a-factor and α-factor
Hormone receptors Cell surface agglutinins
α cells constitutively release α-factor that is
recognized by a receptor on a cells a cells cease growth and arrest at G1 phase of the
cell cycle, then release a-factor
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Sexual Development (cont.)
Ascomycota (cont.) Different mating types then form outgrowths
(“schmoo” cells) with strain specific agglutinins on
their surfaces Agglutinins cause cells to bind to one another, which
then leads to fusion (plasmogamy), followed by
karyogamy (diploid formation) Subsequent induction of meiosis produces four
ascospores BIOL 319
“Schmoo cell”, formation of zygotes via fusion of yeast cells,
and ascospores of Schizosaccharomyces. Sources:
www.biomade.nl/AmphipathicProteins.htm, www.jbc.org, www.visualsunlimited.com/browse/vu227/vu227486.html and,
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Lecture: Growth and Development, Part 3B BIOL 319 - Spring 2017
Diagram of life cycle of Saccharomyces. Source: www.brooklyn.cuny.edu/bc/ahp/LAD/C9/C9_tetrads.html
Sexual Development (cont.)
Basidiomycota Most are heterothallic having one or two mating type
loci (typically termed A and B) with mulitiple idiomorphs
at each locus (e.g., A1, A2, A3, etc.) Successful matings occur with different idiomorphs at
each locus (e.g., A1, B1 x A2, B2) Different pairings of idiomorphs have allowed a
dissection of the functions of the mating-type genes A locus - controls pairing and synchronous division
of nuclei and initiation of clamp formation B locus - controls septal dissolution, fusion of
clamp branches, and increased glucanase
activity BIOL 319
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Mating reactions between haploid isolates of Armillaria ostoyae (with bifactorial mating system): 1.
Incompatible mating (incompatibility factors A1B1 x A1B1). 2. hemicompatible I (incomp. factors A1B1
x A1B2). 3. hemicompatible II (incomp. factors A1B1 x A2B1). 4. compatible mating, resulting in diploid
mycelium (incomp. factors A1B1 x A2B2).Source: www.padil.gov.au/viewPest.aspx?id=518 BIOL 319
Species identification with the aid of mating test. 1. A. ostoyae haploid (lower) x A. borealis
haploid (intersterile – no reaction). 2. A. ostoyae diploid (lower) x A. borealis haploid (intersterile –
no reaction). 3. A. ostoyae haploid x A. ostoyae haploid (compatible – rapid diploidisation). 4. A.
ostoyae diploid (lower) x A. ostoyae haploid (intersterile – slow diploidisation of the haploid
tester) .Source: www.padil.gov.au/viewPest.aspx?id=518 BIOL 319
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