Conserved linkage groups associated with large-scale chromosomal rearrangements between Old World and New World Leishmania genomes

Genomic rearrangements in trypanosomatids: an alternative to the "one gene" evolutionary hypotheses?

“…Considering the importance of the rearranged genes, functional consequences might be expected through (i) gene dosage (Ashburner 1989), (ii) deletion of unique interspersed genes (Bourke et al 1996), and (iii) effect on intergenic regulatory sequences (Ramamoorthy et al 1995); (3) fusion/fission events are responsible for the most significant size-differences. For instance in Leishmania, there is a difference of about 1,200 kb between the 8/29 fused chromosome of NWL and the individual chromosome 8 of OWL and NWV (as calculated from data of Britto et al 1998). In contrast to previous mechanisms, fusion/ fission is not characterised by stepwise size-variation.…”

“…Phylogenetic reconstruction based on glucose transporters was in agreement with the monophyly of genus Trypanosoma and the early separation of T. vivax from the other Salivarian trypanosomes. Another example concerns the α-and β-tubulin genes which are linked and organised in alternated tandem repeats in T. cruzi (Maingon et al 1988, Cano et al 1995 and T. brucei (Tomashow et al 1983), while they are unlinked in Leishmania and Sauroleishmania (Dujardin 1995, Wincker et al 1996, Britto et al 1998 Wincker et al 1996, Britto et al 1998, and (ii) 4 chromosomes (1,8,21, and 32 in subgenus Viannia, or NWV; Dujardin 1995, Britto et al 1998. As globins in mammals (Dover et al 1982, Jeffreys 1982, it is likely that tubulin genes arose from a single copy gene that duplicated, diverged towards α-and β-tubulin genes, and then began to spread differentially among the genome of the different trypanosomatids.…”

“…This approach infers that chromosome size-polymorphism is reflecting gene rearrangements and it allows to explore the whole nuclear genome. Within genus Leishmania and within T. cruzi, there is conservation of most linkage groups (Henriksson et al 1995, Wincker et al 1996, Britto et al 1998, and chromosome-specific probes are available for identifying homologous chromosomes. This allowed to visualise chromosome-size differences, the extent of which varies according to the underlying mechanisms, their frequency and possibly their functional consequences.…”

Adaptive mechanisms in pathogens: universal aneuploidy in Leishmania

“…Old World Leishmania species (L. donovani/infantum, L. major, and L. tarentolae) have 36 chromosomes, whereas 35 are present in L. braziliensis, and 34 in L. mexicana, as result of unique chromosome fusion events [15,[18][19][20]. Gene content and synteny are remarkably well conserved across the species in comparison to other microbes, despite an estimated divergence time of 20-100 million years [15].…”

Cross-species genetic exchange between visceral and cutaneous strains of Leishmania in the sand fly vector

“…The Leishmania genome is organized in 36 chromosomes for the Old World species, such as L. major, L. donovani, and Leishmania infantum, and in 35 and 34 for the New World species Leishmania braziliensis and Leishmania mexicana, respectively (4,5). Although approximately a diploid organism, aneuploidy, including mosaic aneuploidy, is now known to be widespread (6-10); we refer to the nearly diploid state as "2n" here.…”