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Lecture: Growth and Development, Part B
BIOL 4848/6948 - Fall 2009
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BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Fungal Growth and Development
Biology of Fungi
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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
Tetrpolar compatibility - two mating type gene pairs of multiple idiomorphs
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Sexual Development (cont.) Mating type and
hormonal control Chytridiomycota
Allomyces is a homothallic fungus that produces separate male and female gametangia that release motile gametes Gametangia of Allomyces. Source: www.palaeos.com/
Fungi/Lists/Glossary/GlossaryG.html
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Sexual Development (cont.)
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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 Sirenin and carotenoid color produced in male
gametangia are produced from the same precursor, indicating mating type gene controls development of the sex organs
Lecture: Growth and Development, Part B
BIOL 4848/6948 - Fall 2009
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BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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 capatibility
Hormonal control in Achlya Female produces antheridiol
causing the male to increase production of cellulase which induces hyphal branching to increase
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Sexual Development (cont.) Hormonal control in Achlya
(cont.) Once triggered by
antheridiol, males release oogoniols that induce oogonia development
Eventually, male branches (antherida) fuse with oogonia
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Sexual Development (cont.)
Oogonium and antheridium of Achlya. Source: www.palaeos.com/Fungi/Lists/Glossary/GlossaryG.html
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Trisporic acid hormonal system in mating within the Zygomycota. Sources: www.palaeos.com/Fungi/Lists/Glossary/GlossaryG.html
and Deacon, 2006
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Lecture: Growth and Development, Part B
BIOL 4848/6948 - Fall 2009
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BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Mating type loci of Saccharomyces. Source: nitro.biosci.arizona.edu/courses/EEB320-2005/Lecture13/lecture13.html
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Diagram of life cycle of Saccharomyces. Source: nitro.biosci.arizona.edu/courses/EEB320-2005/Lecture13/lecture13.html
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
“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,
Lecture: Growth and Development, Part B
BIOL 4848/6948 - Fall 2009
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BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr. BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
Diagram of life cycle of Saccharomyces. Source: www.brooklyn.cuny.edu/bc/ahp/LAD/C9/C9_tetrads.html
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.
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