Control of meiotic recombination during the diploidization of autopolyploids in Arabidopsis

Polyploids are organisms whose genomes consist of more than two complete sets of chromosomes. Polyploidization is a prominent process in the diversification of plant species and domestication of crops. Following polyploidy, one of the most important drawbacks is the impact of chromosome doubling on meiosis. Polyploids must develop strategies to control pairing preferences that result in disomic inheritance and proper segregation of genetic material during meiosis. Otherwise, the coexistence of more than two copies of the same (autopolyploids) or similar (allopolyploids) chromosome sets may lead to multivalent formation during the first meiotic division and subsequent fertility problems. The process by which polyploid lineages evolve into a diploid-like state where there is a prevention of multivalent associations favoring the formation of bivalents is known as cytological diploidization. In this context, the difference in genome composition in auto- and allopolyploids has important consequences, being more complex in the former ones. The genetic control of the diploidization process in autopolyploids is poorly known and no major locus involved in this process has been identified so far. The genus Arabidopsis constitutes a great model system for the analysis of both long- and short-term consequences of polyploidy. Natural autopolyploids are present within this genus but also can be easily obtained by a colchicine treatment. In this thesis, several approaches have been conducted to shed some light on the meiotic process in autopolyploids of Arabidopsis thaliana. The study has been possible after the development of an improved cytological protocol, including fluorescence in situ hybridization, to obtain high quality spreads of metaphase I chromosomes..