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167 results for “Sequence Evolution”
Data from: Mixture models of nucleotide sequence evolution that account for heterogeneity in the substitution process across sites and across lineages
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Data from: High-throughput sequencing of transposable element insertions suggests adaptive evolution of the invasive Asian Tiger Mosquito towards temperate environments
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Data from: Phylogenetic inferences using nuclear ribosomal ITS and chloroplast sequences provide insights into the biogeographic origins, diversification timescales and trait evolution of Rubus in the Japanese Archipelago
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Data from: The importance of being genomic: non-coding and coding sequences suggest different models of toxin multi-gene family evolution
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Data from: Dealing with the adaptive immune system during de novo evolution of genes from intergenic sequences
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Sequence-capture phylogenomics of true spiders reveals convergent evolution of respiratory systems
<p>The common ancestor of spiders likely used silk to line burrows or make simple webs, with specialized spinning organs and aerial webs originating with the evolution of the megadiverse "true spiders" (Araneomorphae). The base of the araneomorph tree also concentrates the greatest number of changes in respiratory structures, a character system whose evolution is still poorly understood, and that might be related to the evolution of silk glands. Emphasizing a dense sampling of multiple araneomorph lineages where tracheal systems likely originated, we gathered genomic-scale data and reconstructed a phylogeny of true spiders. This robust phylogenomic framework was used to conduct maximum likelihood and Bayesian character evolution analyses for respiratory systems, silk glands, and aerial webs, based on a combination of original and published data. Our results indicate that in true spiders, posterior book lungs were transformed into morphologically similar tracheal systems six times independently, after the evolution of novel silk gland systems and the origin of aerial webs. From these comparative data we put forth a novel hypothesis that early-diverging web building spiders were faced with new energetic demands for spinning, which prompted the evolution of similar tracheal systems via convergence; we also propose tests of predictions derived from this hypothesis.</p>
Evolution of conserved noncoding sequences in Arabidopsis thaliana
<p>Recent pangenome studies have revealed that a large fraction (>20%) of the gene content within a species exhibits presence-absence variation (PAV). However, coding regions alone provide an incomplete assessment of functional genomic sequence variation at the species level. Little to no attention has been paid to noncoding regulatory regions in pangenome studies, though these sequences directly modulate gene expression and phenotype. To uncover regulatory genetic variation, we generated chromosome-scale genome assemblies for thirty Arabidopsis thaliana accessions from multiple distinct habitats and characterized species level variation in Conserved Noncoding Sequences (CNS). Our analyses uncovered not only evidence for PAV and Positional Variation (PosV) but that diversity in CNS is non-random, with variants shared across different accessions. Using evolutionary analyses and chromatin accessibility data, we provide further evidence supporting conserved and variable CNS roles in gene regulation. Characterizing species-level diversity in all functional genomic sequences may later uncover previously unknown mechanistic links between genotype and phenotype.<span> </span></p>
Data from: Lineage-specific sequence evolution and exon edge conservation partially explain the relationship of evolutionary rate and expression level in A. thaliana
Rapidly evolving proteins can aid the identification of genes underlying phenotypic adaptation across taxa, but functional and structural elements of genes can also affect evolutionary rates. In plants, the 'edges' of exons, flanking intron junctions, are known to contain splice enhancers and to have a higher degree of conservation compared to the remainder of the coding region. However, the extent to which these regions may be masking indicators of positive selection or account for the relationship between dN/dS and other genomic parameters is unclear. We investigate the effects of exon edge conservation on the relationship of dN/dS to various sequence characteristics and gene expression parameters in the model plant Arabidopsis thaliana. We also obtain lineage-specific dN/dS estimates, making use of the recently sequenced genome of Thellungiella parvula, the second closest sequenced relative after the sister species Arabidopsis lyrata. Overall, we find that the effect of exon edge conservation, as well as the use of lineage-specific substitution estimates, upon dN/dS ratios partly explains the relationship between the rates of protein evolution and expression level. Furthermore, the removal of exon edges shifts dN/dS estimates upwards, increasing the proportion of genes potentially under adaptive selection. We conclude that lineage-specific substitutions and exon edge conservation have an important effect on dN/dS ratios and should be considered when assessing their relationship with other genomic parameters..
Data from: Genome sequence of Striga asiatica provides insight into the evolution of plant parasitism
Parasitic plants in the genus Striga, commonly known as witchweeds, cause major crop losses in sub-Saharan Africa and pose a threat to agriculture worldwide. An understanding of Striga parasite biology, which could lead to agricultural solutions, has been hampered by the lack of genome information. Here we report the draft genome sequence of Striga asiatica with 34,577 predicted protein-coding genes, which reflects gene family contractions and expansions that are consistent with a three-phase model of parasitic plant genome evolution. Striga seeds germinate in response to host-derived strigolactones (SLs) and then develop a specialised penetration structure, the haustorium, to invade the host root. A family of SL receptors has undergone a striking expansion, suggesting a molecular basis for the evolution of broad host range among Striga spp. We found that genes involved in lateral root development in non-parasitic model species are coordinately induced during haustorium development in Striga, suggesting a pathway that was partly co-opted during the evolution of the haustorium. In addition, we found evidence for horizontal transfer of host genes as well as retrotransposons, indicating gene flow to S. asiatica from hosts. Our results provide valuable insights into the evolution of parasitism and a key resource for the future development of Striga control strategies.
Data from: Targeted sequencing of venom genes from cone snail genomes improves understanding of conotoxin molecular evolution
To expand our capacity to discover venom sequences from the genomes of venomous organisms, we applied targeted sequencing techniques to selectively recover venom gene superfamilies and non-toxin loci from the genomes of 32 cone snail species (family, Conidae), a diverse group of marine gastropods that capture their prey using a cocktail of neurotoxic peptides (conotoxins). We were able to successfully recover conotoxin gene superfamilies across all species with high confidence (> 100X coverage) and used these data to provide new insights into conotoxin evolution. First, we found that conotoxin gene superfamilies are composed of 1-6 exons and are typically short in length (mean = ~85bp). Second, we expanded our understanding of the following genetic features of conotoxin evolution: (a) positive selection, where exons coding the mature toxin region were often three times more divergent than their adjacent noncoding regions, (b) expression regulation, with comparisons to transcriptome data showing that cone snails only express a fraction of the genes available in their genome (24%-63%), and (c) extensive gene turnover, where Conidae species varied from 120-859 conotoxin gene copies. Finally, using comparative phylogenetic methods, we found that while diet specificity did not predict patterns of conotoxin evolution, dietary breadth was positively correlated with total conotoxin gene diversity. Overall, the targeted sequencing technique demonstrated here has the potential to radically increase the pace at which venom gene families are sequenced and studied, reshaping our ability to understand the impact of genetic changes on ecologically relevant phenotypes and subsequent diversification.
Data from: A branch-heterogeneous model of protein evolution for efficient inference of ancestral sequences
Most models of nucleotide or amino acid substitution used in phylogenetic studies assume that the evolutionary process has been homogeneous across lineages and that composition of nucleotides or amino acids has remained the same throughout the tree. These oversimplified assumptions are refuted by the observation that compositional variability characterizes extant biological sequences. Branch-heterogeneous models of protein evolution that account for compositional variability have been developed, but are not yet in common use because of the large number of parameters required, leading to high computational costs and potential overparameterization. Here, we present a new branch-nonhomogeneous and nonstationary model of protein evolution that captures more accurately the high complexity of sequence evolution. This model, henceforth called Correspondence and likelihood analysis (COaLA), makes use of a correspondence analysis to reduce the number of parameters to be optimized through maximum likelihood, focusing on most of the compositional variation observed in the data. The model was thoroughly tested on both simulated and biological data sets to show its high performance in terms of data fitting and CPU time. COaLA efficiently estimates ancestral amino acid frequencies and sequences, making it relevant for studies aiming at reconstructing and resurrecting ancestral amino acid sequences. Finally, we applied COaLA on a concatenate of universal amino acid sequences to confirm previous results obtained with a nonhomogeneous Bayesian model regarding the early pattern of adaptation to optimal growth temperature, supporting the mesophilic nature of the Last Universal Common Ancestor.
Data from: Integrating sequence evolution into probabilistic orthology analysis
Orthology analysis, that is, finding out whether a pair of homologous genes are orthologs — stemming from a speciation — or paralogs — stemming from a gene duplication - is of central importance in computational biology, genome annotation, and phylogenetic inference. In particular, an orthologous relationship makes functional equivalence of the two genes highly likely. A major approach to orthology analysis is to reconcile a gene tree to the corresponding species tree, (most commonly performed using the most parsimonious reconciliation, MPR). However, most such phylogenetic orthology methods infer the gene tree without considering the constraints implied by the species tree and, perhaps even more importantly, only allow the gene sequences to influence the orthology analysis through the a priori reconstructed gene tree. We propose a sound, comprehensive Bayesian Markov chain Monte Carlo-based method, DLRSOrthology, to compute orthology probabilities. It efficiently sums over the possible gene trees and jointly takes into account the current gene tree, all possible reconciliations to the species tree, and the, typically strong, signal conveyed by the sequences. We compare our method with PrIME-GEM, a probabilistic orthology approach built on a probabilistic duplication-loss model, and MRBAYESMPR, a probabilistic orthology approach that is based on conventional Bayesian inference coupled with MPR. We find that DLRSOrthology outperforms these competing approaches on synthetic data as well as on biological data sets and is robust to incomplete taxon sampling artifacts.
Data from: Chloroplast phylogenomic data from the green algal order Sphaeropleales (Chlorophyceae, Chlorophyta) reveal complex patterns of sequence evolution
Chloroplast sequence data are widely used to infer phylogenies of plants and algae. With the increasing availability of complete chloroplast genome sequences, the opportunity arises to resolve ancient divergences that were heretofore problematic. On the flip side, properly analyzing large multi-gene data sets can be a major challenge, as these data may be riddled with systematic biases and conflicting signals. Our study contributes new data from nine complete and four fragmentary chloroplast genome sequences across the green algal order Sphaeropleales. Our phylogenetic analyses of a 56-gene data set show that analyzing these data on a nucleotide level yields a well-supported phylogeny – yet one that is quite different from a corresponding amino acid analysis. We offer some possible explanations for this conflict through a range of analyses of modified data sets. In addition, we characterize the newly sequenced genomes in terms of their structure and content, thereby further contributing to the knowledge of chloroplast genome evolution.
Data from: Mode and tempo of sequence and floral evolution within the Anserineae
The Chenopodiaceae Tribe Anserineae Dumort was proposed to include the genus Spinacia and the genus Blitum. In addition to the recent domestication of Spinacia, the tribe demonstrates extensive evolution within its floral development. We test whether the development of dioecy, monoecy, and protogyny is reflected differentially among floral developmental versus non-floral developmental genes, and whether recent domestication leaves traces in the phylogenetic relationship within the genus Spinacia. The phylogenetic predictions consistently support the sister relationship of Spinacia sp. to a Blitum clade consisting of Blitum bonus-henricus, Blitum virgatum, and Blitum nuttallianum. Relative rates tests indicate a generally faster rate of nucleotide substitutions within Spinacia. Tests of selection indicate that there is generally purifying selection acting on the sequences. In addition, insertion/deletion (indel) events occur more prominently within the Spinacia clade and occur in both coding and intron regions. The phylogenetic relationships within this tribe calls into question the hypothesis that dioecy in Spinacia evolved from a monoecious grade. The evidence for purifying selection in Spinacia suggests that the increased nucleotide substitution rates are not driving protein evolution, in contrast to evidence of protein sequence and structure evolution driven by indels. There is no footprint of domestication on sequence evolution, and we cannot detect phylogenetic signals that would support separation of the Spinacia accessions into three distinct taxa.
Data from: Elucidating the functional evolution of heat sensors among Xenopus species adapted to different thermal niches by ancestral sequence reconstruction
Ambient temperature fluctuations are detected via the thermosensory system which allows animals to seek preferable thermal conditions or escape from harmful temperatures. Evolutionary changes in thermal perception have thus potentially played crucial roles in niche selection. The genus Xenopus (clawed frog) is suitable for investigating the relationship between thermal perception and niche selection due to their diverse latitudinal and altitudinal distributions. Here we performed comparative analyses of the neuronal heat sensors TRPV1 and TRPA1 among closely related Xenopus species (X. borealis, X. muelleri, X. laevis, and X. tropicalis) to elucidate their functional evolution and to assess whether their functional differences correlate with thermal niche selection among the species. Comparison of TRPV1 among four extant Xenopus species and reconstruction of the ancestral TRPV1 revealed that TRPV1 responses to repeated heat stimulation were specifically altered in the lineage leading to X. tropicalis which inhabits warmer niches. Moreover, the thermal sensitivity of TRPA1 was lower in X. tropicalis than the other species, although the thermal sensitivity of TRPV1 and TRPA1 was not always lower in species that inhabit warmer niches than the species inhabit cooler niches. However, a clear correlation was found in species differences in TRPA1 activity. Heat-evoked activity of TRPA1 in X. borealis and X. laevis, which are adapted to cooler niches, was significantly higher than in X. tropicalis and X. muelleri which are adapted to warmer niches. These findings suggest that the functional properties of heat sensors changed during Xenopus evolution, potentially altering the preferred temperature ranges among species.
Data from: Complex models of sequence evolution require accurate estimators as exemplified with the invariable site plus Gamma model
The invariable site plus Γ model is widely used to model rate heterogeneity among alignment sites in maximum likelihood and Bayesian phylogenetic analyses. The proof that the invariable site plus continuous Γ model is identifiable (model parameters can be inferred correctly given enough data) has increased the creditability of its application to phylogeny reconstruction. However, most phylogenetic software implement the invariable site plus discrete Γ model, whose identifiability is likely but unproven. How well the parameters of the invariable site plus discrete Γ model are estimated is still disputed. Especially the correlation of the fraction of invariable sites with the fractions of sites with a slow evolutionary rate is discussed as being problematic. We show that optimization heuristics as implemented in frequently used phylogenetic software cannot always reliably estimate the shape parameter, the proportion of invariable sites and the tree length. Here, we propose an improved optimization heuristic that accurately estimates the three parameters. While research efforts mainly focus on tree search methods, our results signify the equal importance of verifying and developing effective estimation methods for complex models of sequence evolution.
Data from: The Solanum commersonii genome sequence provides insights into adaptation to stress conditions and genome evolution of wild potato relatives
Here, we report the draft genome sequence of Solanum commersonii, which consists of ∼830 megabases with an N50 of 44,303 bp anchored to 12 chromosomes, using the potato (Solanum tuberosum) genome sequence as a reference. Compared with potato, S. commersonii shows a striking reduction in heterozygosity (1.5% versus 53 to 59%), and differences in genome sizes were mainly due to variations in intergenic sequence length. Gene annotation by ab initio prediction supported by RNA-seq data produced a catalog of 1703 predicted microRNAs, 18,882 long noncoding RNAs of which 20% are shown to target cold-responsive genes, and 39,290 protein-coding genes with a significant repertoire of nonredundant nucleotide binding site-encoding genes and 126 cold-related genes that are lacking in S. tuberosum. Phylogenetic analyses indicate that domesticated potato and S. commersonii lineages diverged ∼2.3 million years ago. Three duplication periods corresponding to genome enrichment for particular gene families related to response to salt stress, water transport, growth, and defense response were discovered. The draft genome sequence of S. commersonii substantially increases our understanding of the domesticated germplasm, facilitating translation of acquired knowledge into advances in crop stability in light of global climate and environmental changes.
Complementary evolution of coding and noncoding sequence underlies mammalian hairlessness
<p><span>Body hair is a defining mammalian characteristic, but several mammals, such as whales, naked mole-rats, and humans, have notably less hair than others. To find the genetic basis of reduced hair quantity, we used our evolutionary-rates-based method, RERconverge, to identify coding and noncoding sequences that evolve at significantly different rates in so-called hairless mammals compared to hairy mammals. Using RERconverge, we performed an unbiased, genome-wide scan over 62 mammal species using 19,149 genes and 343,598 conserved noncoding regions to find genetic elements that evolve at significantly different rates in hairless mammals compared to hairy mammals. We show that these rate shifts resulted from relaxation of evolutionary constraint on hair-related sequences in hairless species. In addition to detecting known and potential novel hair-related genes, we also discovered hundreds of putative hair-related regulatory elements. Computational investigation revealed that genes and their associated noncoding regions show different evolutionary patterns and influence different aspects of hair growth and development. Many genes under accelerated evolution are associated with the structure of the hair shaft itself, while evolutionary rate shifts in noncoding regions also included the dermal papilla and matrix regions of the hair follicle that contribute to hair growth and cycling. Genes that were top-ranked for coding sequence acceleration included known hair and skin genes KRT2, KRT35, PKP1, and PTPRM that surprisingly showed no signals of evolutionary rate shifts in nearby noncoding regions. Conversely, accelerated noncoding regions are most strongly enriched near regulatory hair-related genes and microRNAs, such as mir205, ELF3, and FOXC1, that themselves do not show rate shifts in their protein-coding sequences. Such dichotomy highlights the interplay between the evolution of protein sequence and regulatory sequence to contribute to the emergence of a convergent phenotype.</span></p>
Figure 2 from: Shah AA, Ahmad M, Ul-Haq T (2018) Deciphering conserved identical sequences of mature miRNAs among six members of great apes. Zoosystematics and Evolution 94(2): 401-408. https://doi.org/10.3897/zse.94.28099
Figure 2 Represents evolutionary relationships of taxa for Gorillagorilla. The optimal tree with the sum of branch length = 0.40606061 is shown. The analysis involved 12 nucleotide sequences.
Figure 4 from: Shah AA, Ahmad M, Ul-Haq T (2018) Deciphering conserved identical sequences of mature miRNAs among six members of great apes. Zoosystematics and Evolution 94(2): 401-408. https://doi.org/10.3897/zse.94.28099
Figure 4 Represents evolutionary relationships of taxa for Pantroglodytes. The optimal tree with the sum of branch length = 0.71717172 is shown. The analysis involved 7 nucleotide sequences.
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ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
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