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opencc-zeroDec 2010View details →

Data from: The timing of eukaryotic evolution: Does a relaxed molecular clock reconcile proteins and fossils?

The use of nucleotide and amino acid sequences allows improved understanding of the timing of evolutionary events of life on earth. Molecular estimates of divergence times are, however, controversial and are generally much more ancient than suggested by the fossil record. The limited number of genes and species explored and pervasive variations in evolutionary rates are the most likely sources of such discrepancies. Here we compared concatenated amino acid sequences of 129 proteins from 36 eukaryotes to determine the divergence times of several major clades, including animals, fungi, plants, and various protists. Due to significant variations in their evolutionary rates, and to handle the uncertainty of the fossil record, we used a Bayesian relaxed molecular clock simultaneously calibrated by six paleontological constraints. We show that, according to 95% credibility intervals, the eukaryotic kingdoms diversified 950–1,259 million years ago (Mya), animals diverged from choanoflagellates 761–957 Mya, and the debated age of the split between protostomes and deuterostomes occurred 642–761 Mya. The divergence times appeared to be robust with respect to prior assumptions and paleontological calibrations. Interestingly, these relaxed clock time estimates are much more recent than those obtained under the assumption of a global molecular clock, yet bilaterian diversification appears to be ≈100 million years more ancient than the Cambrian boundary.

opencc-zeroApr 2024View details →

Data from: The evolution of protein-coding gene structure in eukaryotes

Introns are highly prevalent in most eukaryotic genomes. Despite the accumulating evidence for benefits conferred by the possession of introns, their specific roles and functions, as well as the processes shaping their evolution, are still only partially understood. Here we explore the evolution of the eukaryotic gene intron-exon structure by focusing on several key features such as the intron length, the number of introns, and the intron-to-exon ratio of protein-coding genes. We utilize whole genome data from 590 species covering the main eukaryotic taxonomic groups and analyze them within a statistical phylogenetic framework. We found that the basic gene structure differs markedly among the main eukaryotic phyla, with animals, and particularly chordates, displaying intron-rich genes, compared to plants and fungi. Reconstruction of gene structure evolution suggests that these differences had evolved prior to the divergence of the phyla, and have remained mostly conserved within groups. We revisit the previously reported association between the genome size and the mean intron length, and report that the correlation patterns differ considerably among phyla. Our findings suggest that the evolution of introns may be affected by different processes across the eukaryotic tree. The substantial diversity in gene structures may indicate that introns play different molecular and evolutionary roles in different organisms.

Figure 5 in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 5. Gene family and time-calibrated evolution analyses of 28 litostomateans and two spirotricheans. Ages are given as million years ago (Mya). Calibrated nodes are indicated with a star. Numbers asser "+" and "-" represent the expanded or contracted gene families in each branch* respectively. MRCA* the most recent common ancestor; H* subclass Haptoria; R* subclass Rhynchostomatia; º* subclass ºrichostomatia; CZ* Cenozoic; MZ* Mesozoic; NP* Neoproterozoic; PZ* Palaeozoic.

Figure 6 in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 6. Heatmap showing the bias of stop codon usage among 28 litostomatean ciliates. H* subclass Haptoria; R* subclass Rhynchostomatia; º* subclass ºrichostomatia.

Figure 3. Phylogenomic tree estimated from a in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 3. Phylogenomic tree estimated from a concatenated dataset of 1680 orthogroups of 28 litostomateans and two spirotricheans

Figure 3. Phylogenomic tree estimated from a in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 3. Phylogenomic tree estimated from a concatenated dataset of 1680 orthogroups of 28 litostomateans and two spirotricheans by maximum likelihood (ML) and Bayesian inference (BI) methods. Sequences from the present study are in bold. Ŋe numbers at the nodes are the bootstrap values of ML out of 1000 pseudoreplicates and the posterior probability of Bayesian analysis* respectively. Ŋe black dots represent full support values both in the ML and in the BI trees. º* subclass ºrichostomatia; H* subclass Haptoria; R* subclass Rhynchostomatia.

Figure 2 in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 2. Comparative analysis of 28 litostomatean ciliates. A* UpSet plot of shared orthogroups among the three litostomatean subclasses. B* GO enrichment analysis of conserved orthogroups in Litostomatea. C* heatmap showing the number of shared genes among 28 litostomatean ciliates. º* subclass ºrichostomatia; H* subclass Haptoria; R* subclass Rhynchostomatia.

Figure 7 in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 7. Ŋe length distribution (A–C) and motif (C–E) of the introns detected in Monodinium sp.* Myriokaryon sp.* and Apodileptus visscheri.

Figure 1 in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 1. Maps showing the location of the sampling sites and photomicrographs showing the in vivo morphology of the 14 litostomatean ciliates for which omics' data were newly obtained.

Figure 4 in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 4. Carbohydrate-Active Enzymes Database (CAZy) annotation results of 28 litostomatean ciliates. A* comparison of the number of CAZymes in 28 litostomatean ciliates. B* CAZy function classification diagrams of three newly sequenced litostomateans (Didinium sp.1* Myriokaryon sp.* and Apodileptus visscheri). º* subclass ºrichostomatia; H* subclass Haptoria; R* subclass Rhynchostomatia.

Figure 2 in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 2. Comparative analysis of 28 litostomatean ciliates. A* UpSet plot of shared orthogroups among the three litostomatean subclasses. B*

publicFeb 2011View details →

Data from: The timing of eukaryotic evolution: Does a relaxed molecular clock reconcile proteins and fossils?

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publicApr 2024View details →

Data from: The evolution of protein-coding gene structure in eukaryotes

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Data from: Do saline taxa evolve faster? comparing relative rates of molecular evolution between freshwater and marine eukaryotes

The major branches of life diversified in the marine realm, and numerous taxa have since transitioned between marine and freshwaters. Previous studies have demonstrated higher rates of molecular evolution in crustaceans inhabiting continental saline habitats as compared with freshwaters, but it is unclear whether this trend is pervasive or whether it applies to the marine environment. We employ the phylogenetic comparative method to investigate relative molecular evolutionary rates between 148 pairs of marine or continental saline vs. freshwater lineages representing disparate eukaryote groups, including bony fish, elasmobranchs, cetaceans, crustaceans, mollusks, annelids, algae, and other eukaryotes, using available protein-coding and non-coding genes. Overall, we observed no consistent pattern in nucleotide substitution rates linked to habitat across all genes and taxa. However, we observed some trends of higher evolutionary rates within protein-coding genes in freshwater taxa—the comparisons mainly involving bony fish—compared with their marine relatives. The results suggest no systematic differences in substitution rate between marine and freshwater organisms.

opencc-zeroDec 2015View details →

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Ubiquity and evolution of structural maintenance of chromosomes (SMC) proteins in eukaryotes

Structural maintenance of chromosomes (SMC) protein complexes are common in Bacteria, Archaea, and Eukaryota. SMC proteins, together with the proteins related to SMC (SMC-related proteins), constitute a superfamily of ATPases. Bacteria/Archaea and Eukaryotes are distinctive from one another in terms of the repertory of SMC proteins. A single type of SMC protein is dimerized in the bacterial and archaeal complexes, whereas eukaryotes possess six distinct SMC subfamilies (SMC1-6), constituting three heterodimeric complexes, namely cohesin, condensin, and SMC5/6 complex. Thus, to bridge the homodimeric SMC complexes in Bacteria and Archaea to the heterodimeric SMC complexes in Eukaryota, we need to invoke multiple duplications of an SMC gene followed by functional divergence. However, to our knowledge, the evolution of the SMC proteins in Eukaryota had not been examined for more than a decade. In this study, we reexamined the ubiquity of SMC1-6 in phylogenetically diverse eukaryotes that cover the major eukaryotic taxonomic groups recognized to date and provide two novel insights into the SMC evolution in eukaryotes. First, multiple secondary losses of SMC5 and SMC6 occurred in the eukaryotic evolution. Second, the SMC proteins constituting cohesin and condensin (i.e., SMC1-4), and SMC5 and SMC6 were derived from closely related but distinct ancestral proteins. Based on the above-mentioned findings, we discuss how SMC1-6 have diverged from the archaeal homologs.

opencc-zeroDec 2021View details →

zenodo28/100

Figure 8 in Comparative genomics reveals the evolutionary history of the unicellular eukaryote class Litostomatea and its adaptive evolution based on biochemical metabolic capacity

Figure 8. RSCU of 14 newly sequenced litostomatean genomes/transcriptomes. Each codon is ploưed.