MAT heterozygosity and the second sterility barrier in the reproductive isolation of Saccharomyces species
The genetic analysis of large numbers of Saccharomyces cerevisiae × S. uvarum (“cevarum”) and S. kudriavzevii × S. uvarum (“kudvarum”) hybrids in our previous studies revealed that these species are isolated by a postzygotic double-sterility barrier. We proposed a model in which the first barrier is...
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Published in | Current genetics Vol. 66; no. 5; pp. 957 - 969 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Berlin/Heidelberg
Springer Berlin Heidelberg
01.10.2020
Springer Nature B.V |
Subjects | |
Online Access | Get full text |
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Summary: | The genetic analysis of large numbers of
Saccharomyces cerevisiae
×
S. uvarum
(“cevarum”) and
S. kudriavzevii
×
S. uvarum
(“kudvarum”) hybrids in our previous studies revealed that these species are isolated by a postzygotic double-sterility barrier. We proposed a model in which the first barrier is due to the abruption of the meiotic process by the failure of the chromosomes of the subgenomes to pair (and recombine) in meiosis and the second barrier is assumed to be the result of the suppression of mating by allospecific
MAT
heterozygosity. While the former is analogous to the major mechanism of postzygotic reproductive isolation in plants and animals, the latter seems to be
Saccharomyces
specific. To bolster the assumed involvement of
MAT
in the second sterility barrier, we produced synthetic alloploid two-species cevarum and kudvarum hybrids with homo- and heterothallic backgrounds as well as three-species
S. cerevisiae
×
S. kudvarum
×
S. uvarum
(“cekudvarum”) hybrids by mass-mating and examined their
MAT
loci using species- and cassette-specific primer pairs. We found that the allospecific
MAT
heterozygosity repressed
MAT
switching and mating in the hybrids and in the viable but sterile spores produced by the cevarum hybrids that had increased (allotetraploid) genomes. The loss of heterozygosity by meiotic malsegregation of
MAT
-carrying chromosomes in the latter hybrids broke down the sterility barrier. The resulting spores nullisomic for the
S. uvarum
chromosome produced vegetative cells capable of
MAT
switching and conjugation, opening the way for GARMe (Genome Autoreduction in Meiosis), the process that leads to chimeric genomes. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Communicated by M. Kupiec. |
ISSN: | 0172-8083 1432-0983 |
DOI: | 10.1007/s00294-020-01080-0 |