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Improving Phylogenetic Signals of Mitochondrial Genes Using a New Method of Codon Degeneration.

ABSTRACT: Recovering deep phylogeny is challenging with animal mitochondrial genes because of their rapid evolution. Codon degeneration decreases the phylogenetic noise and bias by aiming to achieve two objectives: (1) alleviate the bias associated with nucleotide composition, which may lead to homoplasy and long-branch attraction, and (2) reduce differences in the phylogenetic results between nucleotide-based and amino acid (AA)-based analyses. The discrepancy between nucleotide-based analysis and AA-based analysis is partially caused by some synonymous codons that differ more from each other at the nucleotide level than from some nonsynonymous codons, e.g., Leu codon TTR in the standard genetic code is more similar to Phe codon TTY than to synonymous CTN codons. Thus, nucleotide similarity conflicts with AA similarity. There are many such examples involving other codon families in various mitochondrial genetic codes. Proper codon degeneration will make synonymous codons more similar to each other at the nucleotide level than they are to nonsynonymous codons. Here, I illustrate a "principled" codon degeneration method that achieves these objectives. The method was applied to resolving the mammalian basal lineage and phylogenetic position of rheas among ratites. The codon degeneration method was implemented in the user-friendly and freely available DAMBE software for all known genetic codes (genetic codes 1 to 33).

SUBMITTER: Xia X

PROVIDER: S-EPMC7555918 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Improving Phylogenetic Signals of Mitochondrial Genes Using a New Method of Codon Degeneration.

Xia Xuhua X

Life (Basel, Switzerland) 20200830 9

Recovering deep phylogeny is challenging with animal mitochondrial genes because of their rapid evolution. Codon degeneration decreases the phylogenetic noise and bias by aiming to achieve two objectives: (1) alleviate the bias associated with nucleotide composition, which may lead to homoplasy and long-branch attraction, and (2) reduce differences in the phylogenetic results between nucleotide-based and amino acid (AA)-based analyses. The discrepancy between nucleotide-based analysis and AA-bas ...[more]

PMID: 32872619

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Project description:BackgroundCommon phylogenomic approaches for recovering phylogenies are often time-consuming and require annotations for orthologous gene relationships that are not always available. In contrast, alignment-free phylogenomic approaches typically use structure and oligomer frequencies to calculate pairwise distances between species. We have developed an approach to quickly calculate distances between species based on codon aversion.MethodsUtilizing a novel alignment-free character state, we present CAM, an alignment-free approach to recover phylogenies by comparing differences in codon aversion motifs (i.e., the set of unused codons within each gene) across all genes within a species. Synonymous codon usage is non-random and differs between organisms, between genes, and even within a single gene, and many genes do not use all possible codons. We report a comprehensive analysis of codon aversion within 229,742,339 genes from 23,428 species across all kingdoms of life, and we provide an alignment-free framework for its use in a phylogenetic construct. For each species, we first construct a set of codon aversion motifs spanning all genes within that species. We define the pairwise distance between two species, A and B, as one minus the number of shared codon aversion motifs divided by the total codon aversion motifs of the species, A or B, containing the fewest motifs. This approach allows us to calculate pairwise distances even when substantial differences in the number of genes or a high rate of divergence between species exists. Finally, we use neighbor-joining to recover phylogenies.ResultsUsing the Open Tree of Life and NCBI Taxonomy Database as expected phylogenies, our approach compares well, recovering phylogenies that largely match expected trees and are comparable to trees recovered using maximum likelihood and other alignment-free approaches. Our technique is much faster than maximum likelihood and similar in accuracy to other alignment-free approaches. Therefore, we propose that codon aversion be considered a phylogenetically conserved character that may be used in future phylogenomic studies.AvailabilityCAM, documentation, and test files are freely available on GitHub at https://github.com/ridgelab/cam.

Project description:BackgroundIn genus Rhinolophus, species in the Rhinolophus philippinensis and R. macrotis groups are unique because the horseshoe bats in these group have relatively low echolocation frequencies and flight speeds compared with other horseshoe bats with similar body size. The different characteristics among bat species suggest particular evolutionary processes may have occurred in this genus. To study the adaptive evidence in the mitochondrial genomes (mitogenomes) of rhinolophids, especially the mitogenomes of the species with low echolocation frequencies, we sequenced eight mitogenomes and used them for comparative studies of molecular phylogeny and adaptive evolution.ResultsPhylogenetic analysis using whole mitogenome sequences produced robust results and provided phylogenetic signals that were better than those obtained using single genes. The results supported the recent establishment of the separate macrotis group. The signals of adaptive evolution discovered in the Rhinolophus species were tested for some of the codons in two genes (ND2 and ND6) that encode NADH dehydrogenases in oxidative phosphorylation system complex I. These genes have a background of widespread purifying selection. Signals of relaxed purifying selection and positive selection were found in ND2 and ND6, respectively, based on codon models and physicochemical profiles of amino acid replacements. However, no pronounced overlap was found for non-synonymous sites in the mitogenomes of all the species with low echolocation frequencies. A signal of positive selection for ND5 was found in the branch-site model when R. philippinensis was set as the foreground branch.ConclusionsThe mitogenomes provided robust phylogenetic signals that were much more informative than the signals obtained using single mitochondrial genes. Two mitochondrial genes that encoding proteins in the oxidative phosphorylation system showed some evidence of adaptive evolution in genus Rhinolophus and the positive selection signals were tested for ND5 in R. philippinensis. These results indicate that mitochondrial protein-coding genes were targets of adaptive evolution during the evolution of Rhinolophus species, which might have contributed to a diverse range of acoustic adaptations in this genus.

Dataset Information

Improving Phylogenetic Signals of Mitochondrial Genes Using a New Method of Codon Degeneration.

Publications

Improving Phylogenetic Signals of Mitochondrial Genes Using a New Method of Codon Degeneration.

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