Roberts, Nicola Yvette (2010)
Ph.D. thesis, University of Birmingham.
During meiosis, homologous chromosomes pair and become connected by formation of the synaptonemal complex. Recombination is initiated by DNA double strand breaks (DSBs), formed by the protein SPO11-1. In Arabidopsis, ~10% of DSBs are repaired as crossovers, which are reciprocal exchanges of DNA between homologues. These physical connections ensure the correct segregation of chromosomes and generate genetic diversity. The remainder are processed as non-crossovers, important for pairing and synapsis. How these processes are integrated and controlled remains poorly understood. Telomeres are thought to play a role in pairing of homologues. The role of telomeres was investigated in Arabidopsis by treatment with colchicine, a microtubule-depolymerising drug, known to disrupt telomere clustering and pairing in rye. A mutant deficient for the telomerase reverse transcriptase TERT was studied, in which telomeres were severely shortened and showed reduced fertility. To track the movement of telomeres during meiosis the telomere binding proteins POT1a and POT1b were chosen for antibody production. Telomeres were found to be dispensable for pairing and synapsis. SPO11-1 RNA interference lines with varying reductions in DSBs were analysed, to investigate how reducing DSBs affects pairing, synapsis, and the crossover/non-crossover decision. Chromosomes showed autonomous crossover control. The synaptonemal-complex was shown to be important in preventing non-homologous interactions.
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