Abstract
Two hallmark features of meiosis are i) the formation of crossovers (COs) between homologs and ii) the production of genetically-unique haploid spores that will fuse to restore the somatic ploidy level upon fertilization. In this study we analysed meiosis in haploid Arabidopsis thaliana plants and a range of haploid mutants to understand how meiosis progresses without a homolog. Extremely low chiasma frequency and very limited synapsis occurred in wild-type haploids. The resulting univalents segregated in two uneven groups at the first division, and sister chromatids segregated to opposite poles at the second division, leading to the production of unbalanced spores. DNA double-strand breaks that initiate meiotic recombination were formed, but in half the number compared to diploid meiosis. They were repaired in a RAD51- and REC8-dependent manner, but independently of DMC1, presumably using the sister chromatid as a template. Additionally, turning meiosis into mitosis (MiMe genotype) in haploids resulted in the production of balanced haploid gametes and restoration of fertility. The variability of the effect on meiosis of the absence of homologous chromosomes in different organisms is then discussed.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism
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Arabidopsis / genetics*
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Arabidopsis / metabolism
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism
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Chromosome Pairing / genetics
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Crossing Over, Genetic / genetics
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DNA Breaks, Double-Stranded*
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DNA Repair / genetics*
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Diploidy
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Fertility / genetics
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Haploidy*
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Indoles / chemistry
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Meiosis / genetics*
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Mitosis / genetics
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MutL Protein Homolog 1
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Mutation
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Pollen / genetics
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Pollen / metabolism
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Rad51 Recombinase / genetics
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Rad51 Recombinase / metabolism
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Rec A Recombinases / genetics
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Rec A Recombinases / metabolism
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Staining and Labeling / methods
Substances
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Arabidopsis Proteins
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Cell Cycle Proteins
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Indoles
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REC8 protein, Arabidopsis
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DAPI
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ATDMC1 protein, Arabidopsis
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ATRAD51 protein, Arabidopsis
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Rad51 Recombinase
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Rec A Recombinases
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Adenosine Triphosphatases
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MLH1 protein, Arabidopsis
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MutL Protein Homolog 1
Grants and funding
RM thanks INRA BAP department and the European Research Council (FP7 "Ideas" Specific programme ERC 2011 StG 281659 MeioSight ) for financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.