Discussion

DNA replication is an essential process in all eukaryotes initiated from sites termed origins of replication. Recent studies in the kinetoplastid species Leishmania and Trypanosoma brucei have revealed striking differences in the process of DNA replication between the largely syntenic genomes. The genome of Leishmania parasites is able to adapt efficiently in different life cycle stages and in response to changing environmental factors. Genome plasticity and tolerance of pervasive mosaic aneuploidy are established features of the Leishmania genome, although the underlying mechanism allowing this behaviour is not clear. We have used genomics approaches to investigate the adaptation of Leishmania mexicana from a mouse infection in serial passage conditions by sequencing DNA samples at regular intervals. We assess chromosome and gene copy number variation, the presence and absence of SNPs and structural variants and the potential relationship between aneuploidy and DNA replication from a single origin. We observe a correlation between chromosome length and relative fold change throughout passage indicating a potential limit to the extent of replication completed by a single origin in fast-replicating cells in serial passage conditions.