The sellckchem comparison of paralogous copies shows surprisingly high nucleic acid identity rates on average, 99% in cod ing regions, 98. 4% in untranslated regions, and 97. 8% in introns and intergenic regions. Interestingly, those values are homogeneous among all paralogous blocks, suggesting that all blocks were duplicated at the same time. Two hypotheses could explain the origin of these dupli cated blocks. Inhibitors,Modulators,Libraries First, the duplicates may have arisen from a whole genome duplication that took place recently and was followed by rapid genome rearrangements and losses of gene copies. The high homology between gene copies could also result from a high rate of homogenization through gene conversion Inhibitors,Modulators,Libraries driven by the high frequency of rearrange ments.

The frequent rearrangements in the Blastocystis lineage Inhibitors,Modulators,Libraries are probably also the reason why no extensive synteny could be detected between Blastocystis sp. and other stramenopiles. Second, the duplicates could also have occurred through segmental duplications, although the rela tively uniform divergence between copies is more symp tomatic of a single event and would imply a burst of segmental duplications during a short period or a very high rate of homogenization by recombination. The intri guing pattern of gene duplications, likely caused by the high rate of rearrangements in the Blastocystis genome, makes it impossible to determine which scenario is the most likely. It could be interesting to sequence other sub types to determine whether the high rate of recombina tion and the pattern of duplications observed in subtype 7 is a common feature within this lineage.

Endosymbiotic and horizontal gene transfers in Blastocystis sp Phylogenetic analyses revealed two genes Inhibitors,Modulators,Libraries of possible cyanobacterial origin in the genome of Blastocystis, those encoding phosphoglycerate kinase and 6 phosphogluconate dehydrogenase. Inhibitors,Modulators,Libraries It is important to notice that 6 phosphogluconate dehydrogenase encoding genes have been identified in non photosynthetic protists such as Heterolobosea. This was interpreted as secondary horizontal gene transfer from photosynthetic eukaryotes to Heterolobosea. The presence of plastids in various photosynthetic stra menopile lineages was interpreted as a secondary endosym biosis that occurred between a red algae and the ancestor of these groups.

By contrast, the evolutionary meaning of the lack of plastids in some heterotrophic stramenopile lineages is still under discussion does it indicate secondary losses of the plastid acquired by the ancestor of all stramenopiles Or does it reflect the fact that the secondary endosymbiosis at the selleckchem Ponatinib origin of stramenopile plastids did not occur in their common ancestor but after the divergence of heterotrophic lineages The presence of genes of cyanobacterial origin in Blastocystis supports the first hypothesis even if we can not rule out possible recent acquisitions of genes of chloroplastic origin from photo synthetic eukaryotes as in the case of Heterolobosea.