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Microbial Reproductive Modes Fungal Reproduction Week 12, PMB 220

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Presentation on theme: "Microbial Reproductive Modes Fungal Reproduction Week 12, PMB 220"— Presentation transcript:

1 Microbial Reproductive Modes Fungal Reproduction Week 12, PMB 220 J. Taylor

2 The cost of sex is two-fold.
Clonal progeny have twice as many parental genes.

3 The Value of Sex? The Red Queen Hypothesis.
"Now, here, you see, it takes all the running you can do, to keep in the same place." Lewis Carroll John Tenniel (illus) 1872.

4 The Value of Sex? Muller’s Ratchet H. Muller, 1964

5 Goddard, Godfray Burt. 2005 Nature 434:

6 Goddard, Godfray Burt Nature 434:636-40 2005

7 Harsh environment Goddard, Godfray Burt Nature 434:636-40 2005 Benign environment

8 Sex is nearly ubiquitous. Only the bdelloid rotifers have been
claimed to be an old asexual group. Aydin Örstan

9 Numbers of Species of Fungi
Ascomycota 32, % Lichenized fungi 13, % Basidiomycota 22, % Chytridiomycota % Zygomycota 1, % Mitosporic fungi 14, % Dictionary of the Fungi, Hawksworth et al. 1996

10 What is a species? How do they reproduce?

11 Determining the reproductive mode of Microbes:
Recombination v. clonality

12 Clonal: Association of Alleles.

13 Recombining: Lack of Association

14 Testing for reproductive mode.

15 Tree Length Test

16 Compter sex: Resampling
without replacement.

17 Tree Length Test

18 Index of Association

19 Distance matrix

20 IA

21 Gene Genealogy Concordance

22 Computer sex: Shuffling variable nucleotides among genes.

23 Aspergillus flavus

24 You have to know the species before you can study reproductive mode.

25 Example: Coccidioides immitis Vasso Koufopanou Austin Burt Mat Fisher

26 Distribution of Coccidioides immitis Rippon, 1988

27 Phylogenetic Species in C. immitis

28 Finding Single Nucleotide Polymorphisms
Agarose and SSCP gels of PCR products

29 Coccidioides immitis: multilocus genotypes
as single nucleotide polymorphisms (SNPs)

30 Parsimony analysis: Consensus of 62 most parsimonious trees.


32 Test of association of alleles: Index of Association

33 Phylogenetic Species in C. immitis

34 California Coccidioides Fisher et al. 2000

35 Likelihood ratio tests Kishino-Hasegawa Two different topologies
Shimodaira-Hasagawa Multiple topologies

36 Trebouxia and Letharia
Lichens Scott Kroken Trebouxia and Letharia

37 Letharia columbiana Question: Are there two species of Letharia, one sexual and the other not? Letharia vulpina

38 Letharia vulpina Letharia columbiana always produces soredia
apothecia are rare Letharia columbiana always produces apothecia sometimes produces isidia Are they a “species pair” and how do they reproduce?

39 Distribution of Letharia species
Xerox PARC map

40 Apothecia, filled with meiotic ascospores
Asexual Sexual Thomas Nash Apothecia, filled with meiotic ascospores Soredia, algal cells wrapped in hyphae

41 Kroken and Taylor. 2000. Mycologia 93:38-53
6 species suggested Kroken and Taylor Mycologia 93:38-53

42 Question: does the lichen outbreed or inbreed?

43 Paternity analysis of lichen apothecia
Fertilization Spermagonium-- produces spermatia Trichogyne-- fuses with spermatium Paternity analysis of lichen apothecia

44 Parent and progeny

45 Kroken and Taylor 2001 Fungal Genetics & Biology 34:83-92
Letharia “lupina” paternity analysis ‘lupina’ locus CS EarI ‘lupina’ ITS 1F/ 2 SacI Mom1 and 7 kids Mom2 and 6 kids Mom1 and 7 kids Mom2 and 6 kids All 36 apothecia in both species are the result of outcrossing Kroken and Taylor 2001 Fungal Genetics & Biology 34:83-92

46 Outbreeding and separate fertilizations

47 Högberg et al. 2002. Molecular Ecology 11:1191-1196
Dispersal of Letharia vulpina with its alga Xerox PARC map Högberg et al Molecular Ecology 11:

48 Recombining and Clonal in Letharia
North American sorediate Recombining: North American apotheciate Clonal: European and North African sorediate Letharia species


50 Daubin et al Science 301:

51 More polymorphism? Microsatellites or Short Tandem Repeats

52 Molecular markers- Microsatellites
Dinucleotide repeats randomly dispersed through the genome ctgcgtgtgacatACACACACACACACActgtatgtgatc Highly polymorphic and multialleleic due to polymerase slippage during strand replication Cocci_1 ctgcgtgtgacatACACACACACACACA ctgtatgt Cocci_2 ctgcgtgtgacatACACACACACACACACA------ctgtatgt Cocci_3 ctgcgtgtgacatACACACACACACACACACA----ctgtatgt Cocci_4 ctgcgtgtgacatACACACACACACACACACACACActgtatgt

53 Microsatellites

54 Microsatellite distance Flanking-sequence distance
These trees have the same topology (Kishino-Hasegawa test non-significant) THE MICROSATELLITE MARKERS ARE GOOD (Fisher et al. Mol. Biol. Evol. 2000)

55 Renaming the species California
- Coccidioides immitis Rixford and Gilchrist 1896 non-California - Coccidioides posadasii after Alejandro Posadas

56 All populations

57 Arizona

58 Texas/ South America

59 North America/ Mexico C. immitis ( ) and C. posadasii ( )
show isolation by distance... r = 0.694** r = 0.905

60 ...but NOT if South American isolates (all C. posadasii)
are included… r = 0.023 r = 0.694**

61 S. American isolates contain 6% of the variation found in N. America
28% of loci are in linkage disequlibrium (7% in N. America) This is a bottlenecked population …and is descended from the TEXAS population of Coccidioides posadasii

62 Genetic dating show that South American
populations were founded from those in North America between 9, ,000 BP (the Pleistocene)

63 Migration of Homo sapiens into South America by 10,000 BC
Jared Diamond ‘Guns, Germs and Steel’, 1997

64 How did non-CA C. immitis arrive in South America?
Host-pathogen dispersal: 9,000 year old bones of Bison antiquus from Nebraska contain C. immitis spherules. Demonstrates potential for long-distance dispersal with a host Human infections are viable for more than 12 years Ancient Amerindian middens contain high concentrations of C. immitis Documented invasion of South America by the Amerindians 12,500 yrs bp.

65 Does the present distribution of C. posadasii reflect the
co-dispersal of a host and its pathogen?

66 Recombining and Clonal in Coccidioides
Clonal (C. posadasii in Latin Amer?)


68 Daubin et al. 2003. Science 301:829-832 Fig 1

69 Daubin et al. 2003. Science 301: Fig 2

70 Daubin et al. 2003. Science 301: Fig 3

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