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The effect of branch lengths on phylogeny: an empirical study using highly conserved orthologs from mammalian genomes.

ABSTRACT: Phylogenetic analyses were applied to 269 families of putative orthologs represented by a single member in the genomes of human, mouse, dog, and chicken. Five methods were used: maximum parsimony (NP), neighbor-joining (NJ) with Poisson and Gamma distances; and maximum likelihood (ML) with JTT and JTT+gamma models. When applied to the concatenated sequence of all families, all methods strongly supported a tree in which mouse branched before human and dog. In analyses of individual families, the same topology was supported more than any other. Although there was evidence of an increased rate of amino acid replacement in the mouse lineage in comparison to the other two mammals, there was no evidence that support for the mouse's basal position was due to long-branch attraction; rather, this topology was seen in the families with the lowest rate variation among the three mammalian branches. In families with highly divergent mouse sequences, ML with both JTT and JTT+gamma and NJ with the gamma distance tended to support a topology in which the dog, rather than the mouse, branched first. Thus, in these data, a tendency of long and short branches to cluster together ("opposite-branch attraction") seemed to be more of a problem than long-branch attraction.

SUBMITTER: Hughes AL

PROVIDER: S-EPMC2756227 | biostudies-literature | 2007 Oct

REPOSITORIES: biostudies-literature

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The effect of branch lengths on phylogeny: an empirical study using highly conserved orthologs from mammalian genomes.

Hughes Austin L AL Friedman Robert R

Molecular phylogenetics and evolution 20070518 1

Phylogenetic analyses were applied to 269 families of putative orthologs represented by a single member in the genomes of human, mouse, dog, and chicken. Five methods were used: maximum parsimony (NP), neighbor-joining (NJ) with Poisson and Gamma distances; and maximum likelihood (ML) with JTT and JTT+gamma models. When applied to the concatenated sequence of all families, all methods strongly supported a tree in which mouse branched before human and dog. In analyses of individual families, the ...[more]

PMID: 17574446

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Project description:Recent advances in genome sequencing suggest a remarkable conservation in gene content of mammalian organisms. The similarity in gene repertoire present in different organisms has increased interest in studying regulatory mechanisms of gene expression aimed at elucidating the differences in phenotypes. In particular, a proximal promoter region contains a large number of regulatory elements that control the expression of its downstream gene. Although many studies have focused on identification of these elements, a broader picture on the complexity of transcriptional regulation of different biological processes has not been addressed in mammals. The regulatory complexity may strongly correlate with gene function, as different evolutionary forces must act on the regulatory systems under different biological conditions. We investigate this hypothesis by comparing the conservation of promoters upstream of genes classified in different functional categories.By conducting a rank correlation analysis between functional annotation and upstream sequence alignment scores obtained by human-mouse and human-dog comparison, we found a significantly greater conservation of the upstream sequence of genes involved in development, cell communication, neural functions and signaling processes than those involved in more basic processes shared with unicellular organisms such as metabolism and ribosomal function. This observation persists after controlling for G+C content. Considering conservation as a functional signature, we hypothesize a higher density of cis-regulatory elements upstream of genes participating in complex and adaptive processes.We identified a class of functions that are associated with either high or low promoter conservation in mammals. We detected a significant tendency that points to complex and adaptive processes were associated with higher promoter conservation, despite the fact that they have emerged relatively recently during evolution. We described and contrasted several hypotheses that provide a deeper insight into how transcriptional complexity might have been emerged during evolution.

Project description:BackgroundMost previous studies of morphological and molecular data have consistently supported the monophyly of the true water bugs (Hemiptera: Nepomorpha). An exception is a recent study by Hua et al. (BMC Evol Biol 9: 134, 2009) based on nine nepomorphan mitochondrial genomes. In the analysis of Hua et al. (BMC Evol Biol 9: 134, 2009), the water bugs in the group Pleoidea formed the sister group to a clade that consisted of Nepomorpha (the remaining true water bugs) + Leptopodomorpha (shore bugs) + Cimicomorpha (assassin bugs and relatives) + Pentatomomorpha (stink bugs and relatives), thereby suggesting that fully aquatic hemipterans evolved independently at least twice. Based on these results, Hua et al. (BMC Evol Biol 9: 134, 2009) elevated the Pleoidea to a new infraorder, the Plemorpha.ResultsOur reanalysis suggests that the lack of support for the monophyly of the true water bugs (including Pleoidea) by Hua et al. (BMC Evol Biol 9: 134, 2009) likely resulted from inadequate taxon sampling. In particular, long-branch attraction (LBA) between the distant outgroup taxa and Pleoidea, as well as LBA among taxa in the ingroup, made Nepomorpha appear to be polyphyletic. We used three complementary strategies to test and alleviate the effects of LBA: (1) the removal of distant outgroups from the analysis; (2) the addition of closely related outgroups; and (3) the addition of a mitochondrial genome from a second family of Pleoidea. We also performed likelihood-ratio tests to examine the support for monophyly of Nepomorpha with different combinations of taxa included in the analysis. Furthermore, we found that specimens of Helotrephes sp. were misidentified as Paraplea frontalis (Fieber, 1844) by Hua et al. (BMC Evol Biol 9: 134, 2009).ConclusionsAll analyses that included the addition of more taxa significantly and consistently supported the placement of Pleoidea within the Nepomorpha (i.e., supported the monophyly of the traditional true water bugs). Our analyses further support a close relationship between Notonectoidea and Pleoidea within Nepomorpha, and the superfamilies Nepoidea, Ochteroidea, Naucoroidea, and Pleoidea are resolved as monophyletic in all trees with strong support. Our results also confirmed that monophyly of Nepomorpha clearly is not refuted by the mitochondrial genome data.

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The effect of branch lengths on phylogeny: an empirical study using highly conserved orthologs from mammalian genomes.

Publications

The effect of branch lengths on phylogeny: an empirical study using highly conserved orthologs from mammalian genomes.

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