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      The Evolution of Amastin Surface Glycoproteins in Trypanosomatid Parasites

      research-article
        *
      Molecular Biology and Evolution
      Oxford University Press
      amastin, Leishmania, evolution, phylogeny, comparative genomics

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          Abstract

          Amastin is a transmembrane glycoprotein found on the cell surfaces of trypanosomatid parasites. Encoded by a large, diverse gene family, amastin was initially described from the intracellular, amastigote stage of Trypanosoma cruzi and Leishmania donovani. Genome sequences have subsequently shown that the amastin repertoire is much larger in Leishmania relative to Trypanosoma. However, it is not known when this expansion occurred, whether it is associated with the origins of Leishmania and vertebrate parasitism itself, or prior to this. To examine the timing of amastin diversification, as well as the evolutionary mechanisms regulating gene repertoire and sequence diversity, this study sequenced the genomic regions containing amastin loci from two related insect parasites ( Leptomonas seymouri and Crithidia sp.) and estimated a phylogeny for these and other amastin sequences. The phylogeny shows that amastin includes four subfamilies with distinct genomic positions, secondary structures, and evolution, which were already differentiated in the ancestral trypanosomatid. Diversification in Leishmania was initiated from a single ancestral locus on chromosome 34, with rapid derivation of novel loci through transposition and accelerated sequence divergence. This is absent from related organisms showing that diversification occurred after the origin of Leishmania. These results describe a substantial elaboration of amastin repertoire directly associated with the origin of Leishmania, suggesting that some amastin genes evolved novel functions crucial to cell function in leishmanial parasites after the acquisition of a vertebrate host.

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          Most cited references50

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          MRBAYES: Bayesian inference of phylogenetic trees.

          The program MRBAYES performs Bayesian inference of phylogeny using a variant of Markov chain Monte Carlo. MRBAYES, including the source code, documentation, sample data files, and an executable, is available at http://brahms.biology.rochester.edu/software.html.
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            ProtTest: selection of best-fit models of protein evolution.

            Using an appropriate model of amino acid replacement is very important for the study of protein evolution and phylogenetic inference. We have built a tool for the selection of the best-fit model of evolution, among a set of candidate models, for a given protein sequence alignment. ProtTest is available under the GNU license from http://darwin.uvigo.es
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              The genome of the African trypanosome Trypanosoma brucei.

              African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. We present the sequence and analysis of the 11 megabase-sized chromosomes of Trypanosoma brucei. The 26-megabase genome contains 9068 predicted genes, including approximately 900 pseudogenes and approximately 1700 T. brucei-specific genes. Large subtelomeric arrays contain an archive of 806 variant surface glycoprotein (VSG) genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of T. brucei, T. cruzi, and Leishmania major reveals the least overall metabolic capability in T. brucei and the greatest in L. major. Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a number of novel potential drug targets have been identified.
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                Author and article information

                Journal
                Mol Biol Evol
                molbiolevol
                molbev
                Molecular Biology and Evolution
                Oxford University Press
                0737-4038
                1537-1719
                January 2010
                11 September 2009
                11 September 2009
                : 27
                : 1
                : 33-45
                Affiliations
                Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, CB10 1SA, United Kingdom
                Author notes
                [* ] Corresponding author: E-mail: aj4@ 123456sanger.ac.uk .

                Associate editor: Kenneth Wolfe

                Article
                10.1093/molbev/msp214
                2794310
                19748930
                36717df7-1f85-4ca3-b7c3-72dea04eb464
                © 2009 The Authors

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/2.5), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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                Categories
                Research Articles

                Molecular biology
                comparative genomics,amastin,evolution,leishmania,phylogeny
                Molecular biology
                comparative genomics, amastin, evolution, leishmania, phylogeny

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