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Recombination Restriction, Degenerat...

Beaudry, Felix.

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Recombination Restriction, Degeneration and Population Divergence on Plant Sex Chromosomes.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Recombination Restriction, Degeneration and Population Divergence on Plant Sex Chromosomes./
Author:	Beaudry, Felix.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
Description:	244 p.
Notes:	Source: Dissertations Abstracts International, Volume: 82-01, Section: B.
Contained By:	Dissertations Abstracts International82-01B.
Subject:	Genetics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27741497
ISBN:	9798662392762

Recombination Restriction, Degeneration and Population Divergence on Plant Sex Chromosomes.
Beaudry, Felix.

Recombination Restriction, Degeneration and Population Divergence on Plant Sex Chromosomes. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 244 p.

Source: Dissertations Abstracts International, Volume: 82-01, Section: B.

Thesis (Ph.D.)--University of Toronto (Canada), 2020.

This item must not be sold to any third party vendors.

This dissertation investigates patterns of sex chromosome evolution in the dioecious plant Rumex hastatulus, an annual species with two distinct largely allopatric sex chromosome cytotypes (females XX and males XY or XYY). My thesis addresses three general observations often associated with sex chromosome evolution, which are summarized in Chapter 1: i) the degeneration of the Y chromosome, ii) the lower rates of recombination between the X and Y chromosomes compared with the rest of the genome, and iii) the finding that sex chromosomes contribute disproportionately to population genetic divergence. In Chapter 2, I demonstrate that in R. hastatulus the loss of gene expression precedes gene deletion from the Y, suggesting that the loss of constraint allowed by lowered expression is a prerequisite for gene loss on the Y chromosome. In Chapter 3, I show that pollen-expressed genes are significantly less likely to be lost from the Y chromosome during degeneration with important implications for selection during the haploid phase of the life cycle. In Chapter 4, construction of a linkage map revealed that the sex chromosomes probably arose in a pericentromeric region and population-level analyses estimated very low rates of recombination across this region prior to sex chromosome evolution. These findings are consistent with the hypothesis that low rates of recombination predate the origin of sex chromosomes and likely facilitated their evolution. In Chapter 5, my studies of demographic history revealed that during a historic period of reduced gene flow between the cytotypes of R. hastatulus, both the X and Y played a more significant role in genetic divergence than autosomes. My demographic modelling also suggests an X-A fusion event occurred at roughly the same time as the loss of gene flow between the cytotypes. Finally, in Chapter 6, I detect reduced gene flow around the fused region of the X chromosome in R. hastatulus and show biased segregation of the fused X in an F2 cross implicating the presence of a selfish transmission advantage. My thesis research highlights that even in plants, where sex chromosomes are rare, the sex chromosomes are of outsized evolutionary importance in species that bear them.

ISBN: 9798662392762Subjects--Topical Terms:

530508
Genetics.
Subjects--Index Terms:

Haploid selection

Recombination Restriction, Degeneration and Population Divergence on Plant Sex Chromosomes.
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300 $a 244 p.
500 $a Source: Dissertations Abstracts International, Volume: 82-01, Section: B.
500 $a Advisor: Wright, Stephen I.
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506 $a This item must not be sold to any third party vendors.
520 $a This dissertation investigates patterns of sex chromosome evolution in the dioecious plant Rumex hastatulus, an annual species with two distinct largely allopatric sex chromosome cytotypes (females XX and males XY or XYY). My thesis addresses three general observations often associated with sex chromosome evolution, which are summarized in Chapter 1: i) the degeneration of the Y chromosome, ii) the lower rates of recombination between the X and Y chromosomes compared with the rest of the genome, and iii) the finding that sex chromosomes contribute disproportionately to population genetic divergence. In Chapter 2, I demonstrate that in R. hastatulus the loss of gene expression precedes gene deletion from the Y, suggesting that the loss of constraint allowed by lowered expression is a prerequisite for gene loss on the Y chromosome. In Chapter 3, I show that pollen-expressed genes are significantly less likely to be lost from the Y chromosome during degeneration with important implications for selection during the haploid phase of the life cycle. In Chapter 4, construction of a linkage map revealed that the sex chromosomes probably arose in a pericentromeric region and population-level analyses estimated very low rates of recombination across this region prior to sex chromosome evolution. These findings are consistent with the hypothesis that low rates of recombination predate the origin of sex chromosomes and likely facilitated their evolution. In Chapter 5, my studies of demographic history revealed that during a historic period of reduced gene flow between the cytotypes of R. hastatulus, both the X and Y played a more significant role in genetic divergence than autosomes. My demographic modelling also suggests an X-A fusion event occurred at roughly the same time as the loss of gene flow between the cytotypes. Finally, in Chapter 6, I detect reduced gene flow around the fused region of the X chromosome in R. hastatulus and show biased segregation of the fused X in an F2 cross implicating the presence of a selfish transmission advantage. My thesis research highlights that even in plants, where sex chromosomes are rare, the sex chromosomes are of outsized evolutionary importance in species that bear them.
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