Breaking linkage between mating compatibility factors: Tetrapolarity in Microbotryum

Linkage of genes determining separate self-incompatibility mechanisms is a general expectation of sexual eukaryotes that helps to resolve conflicts between reproductive assurance and recombination. However, in some organisms, multiple loci are required to be heterozygous in offspring while segregati...

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Bibliographic Details
Published inEvolution Vol. 69; no. 10; pp. 2561 - 2572
Main Authors Hood, Michael E., Scott, Molly, Hwang, Mindy
Format Journal Article
LanguageEnglish
Published United States Blackwell Publishing Ltd 01.10.2015
Society for the Study of Evolution
Oxford University Press
Subjects
Alleles
Automixis
Basidiomycetes
Basidiomycota
Basidiomycota - genetics
Biological Evolution
Biological taxonomies
bipolarity
Breeding
Chromosomes
Chromosomes, Fungal - genetics
Eukaryotes
Evolution
Fungi
Genes
Genes, Mating Type, Fungal
Genetic Linkage
Genetic loci
Genome, Fungal
Haploidy
Life cycles
mating type
Meiosis
Phylogeny
self-incompatibility
sex chromosomes
self-incompatibility
bipolarity
mating type
sex chromosomes
Automixis
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Summary:Linkage of genes determining separate self-incompatibility mechanisms is a general expectation of sexual eukaryotes that helps to resolve conflicts between reproductive assurance and recombination. However, in some organisms, multiple loci are required to be heterozygous in offspring while segregating independently in meiosis. This condition, termed "tetrapolarity" in basidiomycete fungi, originated in the ancestor to that phylum, and there have been multiple reports of subsequent transitions to "bipolarity" (i.e., linkage of separate mating factors). In the genus Microbotryum, we present the first report of the breaking of linkage between two haploid self-incompatibility factors and derivation of a tetrapolar breeding system. This breaking of linkage is associated with major alteration of genome structure, with the compatibility factors residing on separate mating-type chromosome pairs, reduced in size but retaining the structural dimorphism characteristic for regions of recombination suppression. The challenge to reproductive assurance from unlinked compatibility factors may be overcome by the automictic mating system in Microbotryum (i.e., mating among products of the same meiosis). As a curious outcome, this linkage transition and its effects upon outcrossing compatibility rates may reinforce automixis as a mating system. These observations contribute to understanding mating systems and linkage as fundamental principles of sexual life cycles, with potential impacts on conventional wisdom regarding mating-type evolution.
Bibliography:ark:/67375/WNG-ST9MDJBG-3
ArticleID:EVO12765
istex:1C472BEBE1021D3B01B7734FA97AAF0061BA6A30
Figure S1. Meiosis and automixis (intratetrad mating) in Microbotryum saponariae. Figure S2.  Germination by Microbotryum and formation of the linear meiotic tetrad. Figure S3. An example of a quantitative PCR profile for the nine chromosome-specific DNA samples taken from the a2 electrophoretic karyotype of Microbotryum lagerheimii for amplification of the mating type pheromone receptor (PR) locus. Figure S4. Electrophoretic karyotypes of Microbotryum species showing the position of identified chromosomes carrying the mating type pheromone receptor (PR) locus. Figure S5.  Mating type homeodomain (HD) allele-specific PCR products from the four haploids in a linear meiotic tetrad of Microbotryum saponariae. Table S1. Microbotryum collection details. Table S2. Crossing matrix design for testing mating type HD compatibility in Microbotryum saponariae. Table S3. Optical map data for mating-type chromosomes of Microbotryum saponariae.
ObjectType-Article-1
SourceType-Scholarly Journals-1
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content type line 23
ISSN:0014-3820
1558-5646
DOI:10.1111/evo.12765