Navegando por Palavras-chave "Hybrid strains"

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    Network genealogy of 195-bp satellite DNA supports the superimposed hybridization hypothesis of Trypanosoma cruzi evolutionary pattern
    (Elsevier B.V., 2010-07-01) Ienne, Susan; Pedroso, Aurelio; Ferreira, Renata Carmona [UNIFESP]; Briones, Marcelo R. S. [UNIFESP]; Zingales, Bianca; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)
    Trypanosoma cruzi is highly diverse genetically and has been partitioned into six discrete typing units (DTUs), recently re-named T. cruzi I-VI. Although T. cruzi reproduces predominantly by binary division, accumulating evidence indicates that particular DTUs are the result of hybridization events. Two major scenarios for the origin of the hybrid lineages have been proposed. It is accepted widely that the most heterozygous TcV and TcVI DTUs are the result of genetic exchange between TcII and TcIII strains. On the other hand, the participation of a TcI parental in the current genome structure of these hybrid strains is a matter of debate. Here, sequences of the T. cruzi-specific 195-bp satellite DNA of TcI, TcII, Tat, TcV, and TcVI strains have been used for inferring network genealogies. the resulting genealogy showed a high degree of reticulation, which is consistent with more than one event of hybridization between the Tc DTUs. the data also strongly suggest that Tat is a hybrid with two distinct sets of satellite sequences, and that genetic exchange between TcI and TcII parentals occurred within the pedigree of the TcV and TcVI DTUs. Although satellite DNAs belong to the fast-evolving portion of eukaryotic genomes, in >100 satellite units of nine T. cruzi strains we found regions that display 100% identity. No DTU-specific consensus motifs were identified, inferring species-wide conservation. (C) 2010 Elsevier B.V. All rights reserved.
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    Phylogenetic evidence based on Trypanosoma cruzi nuclear gene sequences and information entropy suggest that inter-strain intragenic recombination is a basic mechanism underlying the allele diversity of hybrid strains
    (Elsevier B.V., 2012-07-01) Ferreira, Renata Carmona [UNIFESP]; Briones, Marcelo Ribeiro da Silva [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The diversity of Trypanosoma cruzi is categorized into six discrete typing units (DTUs) T. cruzi I to VI. Several studies indicate that T. cruzi I and II are ancestors of T. cruzi which are considered products of independent hybridization events. the individual haplotypes or alleles of these hybrids cluster in three groups, either closer to T. cruzi I or T. cruzi II or forming a midpoint clade between T. cruzi I and II in network phylogenies. To understand the origins of these different sets of haplotypes and test the hypothesis of a direct correlation between high entropy and positive selection, we analyzed four nuclear protein coding genes. We show that hybrid strains contain haplotypes that are mosaics probably originated by intragenic recombination. Accordingly, in phylogenies, the hybrid haplotypes are closer to one or both parentals (T. cruzi I and II) depending on the proportion of parental sequences composing the mosaics. in addition, Shannon entropy, used to measure sequence diversity, is highly correlated with positive selection in the four genes here analyzed. Our data on recombination patterns also support the hypothesis of two hybridization events in the hybrid structures of T. cruzi Data presented and discussed here are consistent with a scenario where TcI and TcII are phylogenetically divergent forming a hybrid zone in between (T. cruzi III-VI). We predict that because of the quasi-random nature of T. cruzi I and II hybridization more DTUs, with different haplotype combinations, will be discovered in the hybrid zone. (C) 2012 Elsevier B.V. All rights reserved.