Intermolecular Gene Conversion in halophilic Archaea.

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Gene conversion is defined as the non-reciprocal transfer of information from one DNA sequence to a homologous (but not identical) sequence. Gene conversion occurs in all three domains of life and also in viruses. Gene conversion is involved in many different processes, from DNA repair at stalled replication forks to the generation of genetic diversity in meiosis. Gene conversion has mostly been studied in eukaryotes, and the studies with bacteria concentrated on intramolecular gene conversion, which results in concerted evolution of gene families or in antigenic variation. Intermolecular gene conversion between different genome copies of polyploid prokaryotes has hardly been studied. It can lead to the equalization of genome copies and represents an escape from Muller’s ratchet (a theory predicting that polyploid prokaryotes should not be able to exist). In the proposed project the haloarchaeon Haloferax volcanii will be used to study various aspects of intermolecular gene conversion for the equalization of genome copies. An experimental approach has been established that enables the quantitative analysis of unselected gene conversion events. The following objectives will be pursuit: 1) Characteristic features of unselected gene conversion will be analyzed, e.g. the influence of the extent of genome differences on gene conversion efficiencies; 2) The influence of external and environmental parameters on intermolecular gene conversion will be analyzed: 3) Proteins will be identified, which are involved in or essential for intermolecular gene conversion; and 4) Intermolecular gene conversion between genes of different species will be analyzed. Together, these approaches will lead to an unprecedented insight into intermolecular gene conversion for the equalization of genome copies in polyploid prokaryotes.