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Mating system evolution and self-incompatibility in the wild plant species Brassica cretica

Aaltonen, Kristina LU (2008)
Abstract
Compared to animals like ourselves, plants have a very flexible sexual life. Most plants are, for example, hermaphrodites with the potential capacity for reproduction by self-fertilization (or selfing). While selfing can provide several definite advantages for the individual plant, there is a downside; mainly the severe reduction in fitness due to inbreeding depression. To avoid the negative consequences of selfing, many hermaphrodite plant species have evolved an intricate self-recognition – or self-incompatibility (SI) – system that prevents fertilization by cognate pollen. SI is in the majority of cases genetically controlled by a narrowly delimited region of the genome, called the S locus. The S locus contains several tightly linked... (More)
Compared to animals like ourselves, plants have a very flexible sexual life. Most plants are, for example, hermaphrodites with the potential capacity for reproduction by self-fertilization (or selfing). While selfing can provide several definite advantages for the individual plant, there is a downside; mainly the severe reduction in fitness due to inbreeding depression. To avoid the negative consequences of selfing, many hermaphrodite plant species have evolved an intricate self-recognition – or self-incompatibility (SI) – system that prevents fertilization by cognate pollen. SI is in the majority of cases genetically controlled by a narrowly delimited region of the genome, called the S locus. The S locus contains several tightly linked genes, two of which – SRK and SCR – determine the pistil (female) and pollen (male) SI recognition type. One of the best-characterized SI systems is found in the Brassicaceae family, which includes the model plant Arabidopsis thaliana and a number of economically important crop species of the Brassica genus, e.g. rape seed, cabbage, and turnip.



For evolutionary biologists, SI have long been a prominent and fascinating example of Darwinian natural selection acting in a frequency-dependent manner, i.e. the rarer a genetic variant becomes, the more favoured by natural selection it is. For the S locus, this means that a very large number of variants – or haplotypes – are expected to be maintained in a population and that the DNA sequences of different haplotypes will be very divergent. However, until recently there has been a shortage of empirical studies from natural plant populations to test these, and other, theoretical predictions of S locus evolutionary dynamics.



In this thesis, I have produced the largest SRK and SCR DNA sequence data set from a wild Brassica species available to date. These data have allowed me to explore, in more detail than previously possible, the population genetic properties and the evolutionary history of the Brassica S locus. Moreover, accompanying studies of the pattern of inheritance of S locus variants and the occurrence of self-fertilization in natural B. cretica population have added novel information of great value to the understanding of how plants produce offspring in nature. (Less)
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author
supervisor
opponent
  • Prof. Dr. van Tienderen, Peter H., University of Amsterdam
organization
publishing date
type
Thesis
publication status
published
subject
keywords
mating system, Brassicaceae, Brassica cretica, recombination, frequency-dependent selection, evolution, population structure, segregation distortion, SCR, self-incompatibility, SRK
pages
142 pages
defense location
Genetikhusets föreläsningssal, Sölvegatan 29, Lund
defense date
2008-05-31 10:00
ISBN
978-91-85067-41-1
language
English
LU publication?
yes
id
60d4254f-c22a-44b1-90fc-c4b4425e91bb (old id 1148019)
date added to LUP
2008-05-07 09:00:00
date last changed
2016-09-19 08:45:20
@phdthesis{60d4254f-c22a-44b1-90fc-c4b4425e91bb,
  abstract     = {Compared to animals like ourselves, plants have a very flexible sexual life. Most plants are, for example, hermaphrodites with the potential capacity for reproduction by self-fertilization (or selfing). While selfing can provide several definite advantages for the individual plant, there is a downside; mainly the severe reduction in fitness due to inbreeding depression. To avoid the negative consequences of selfing, many hermaphrodite plant species have evolved an intricate self-recognition – or self-incompatibility (SI) – system that prevents fertilization by cognate pollen. SI is in the majority of cases genetically controlled by a narrowly delimited region of the genome, called the S locus. The S locus contains several tightly linked genes, two of which – SRK and SCR – determine the pistil (female) and pollen (male) SI recognition type. One of the best-characterized SI systems is found in the Brassicaceae family, which includes the model plant Arabidopsis thaliana and a number of economically important crop species of the Brassica genus, e.g. rape seed, cabbage, and turnip.<br/><br>
	<br/><br>
For evolutionary biologists, SI have long been a prominent and fascinating example of Darwinian natural selection acting in a frequency-dependent manner, i.e. the rarer a genetic variant becomes, the more favoured by natural selection it is. For the S locus, this means that a very large number of variants – or haplotypes – are expected to be maintained in a population and that the DNA sequences of different haplotypes will be very divergent. However, until recently there has been a shortage of empirical studies from natural plant populations to test these, and other, theoretical predictions of S locus evolutionary dynamics.<br/><br>
	<br/><br>
In this thesis, I have produced the largest SRK and SCR DNA sequence data set from a wild Brassica species available to date. These data have allowed me to explore, in more detail than previously possible, the population genetic properties and the evolutionary history of the Brassica S locus. Moreover, accompanying studies of the pattern of inheritance of S locus variants and the occurrence of self-fertilization in natural B. cretica population have added novel information of great value to the understanding of how plants produce offspring in nature.},
  author       = {Aaltonen, Kristina},
  isbn         = {978-91-85067-41-1},
  keyword      = {mating system,Brassicaceae,Brassica cretica,recombination,frequency-dependent selection,evolution,population structure,segregation distortion,SCR,self-incompatibility,SRK},
  language     = {eng},
  pages        = {142},
  school       = {Lund University},
  title        = {Mating system evolution and self-incompatibility in the wild plant species Brassica cretica},
  year         = {2008},
}