Biology of Fungi - Homothallic or heterothallic ²-carotene to a prohormone Prohormoneis...

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Transcript of Biology of Fungi - Homothallic or heterothallic ²-carotene to a prohormone Prohormoneis...

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

BIOL 319

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

BIOL 319

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

BIOL 319

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

BIOL 319

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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

BIOL 319

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 -

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

BIOL 319

2

Lecture: Growth and Development, Part 3B BIOL 319 - Spring 2017

Sexual Development (cont.)

Ascomycota Typically two mating types a cells and cells Best characterized system is that of Saccharomyces

Mating is controlled by the MAT gene locus of

flanked by two other loci, MATa and MAT 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

BIOL 319) BIOL 319

Diagram of life cycle of Saccharomyces. Source: nitro.biosci.arizona.edu/

courses/EEB320-2005/Lecture13/lecture13.html BIOL 319

Sexual Development (cont.)

Ascomycota (cont.) MAT are responsible for producing:

Peptide hormones a-factor and -factor

Hormone receptors Cell surface agglutinins

cells constitutively release -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 319

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,

BIOL 319 3

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

BIOL 319

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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