1,720,965 research outputs found
The Early Evolution of Tudor Genes in Holozoa and How Their Distribution Was Influenced by Life History Traits in Metazoa
Full text linkEarly metazoan evolution was characterized by the expansion of multiple gene families, such as the Tudor family, involved in novel multicellularity-related functions. In eukaryotes, Tudor genes (i.e. genes including at least one Tudor domain) are numerous, heterogeneous, and mostly associated with gene expression regulation. However, they underwent an animal-specific expansion, with novel elements almost exclusively involved in retrotransposon regulation through Piwi-interacting RNAs, as spatiotemporal regulators of the key-element Piwi, another previously considered animal-specific gene. Here, we used online-Available proteomes covering 25 major taxonomic groups to characterize the Tudor gene family at a holozoan-wide level, confirming the apomorphic metazoan expansion of Piwi-interacting RNA-related Tudor genes. However, we also annotated elements of the Piwi-interacting RNA pathway (Tudor and Piwi genes) in Ichthyosporea species, suggesting that elements of the Piwi-interacting RNA pathway were already present in the holozoan common ancestors. We observed an outstanding variability (34-fold) of Tudor gene number between and within metazoan phyla that could be associated with convergent genomic and phenotypic evolutions: expansions were usually sided by whole-genome duplications and/or life history traits such as parthenogenesis; reductions were mostly associated to overall phenotypic and genomic simplifications, like in almost all considered endoparasites. Lastly, we phylogenetically tested, and mostly (but not completely) confirmed, a previously proposed model for the evolution of the Tudor domain secondary structures
Germline-related molecular phenotype in Metazoa: conservation and innovation highlighted by comparative transcriptomics
Full text linkBACKGROUND: In Metazoa, the germline represents the cell lineage devoted to the transmission of genetic heredity across generations. Its functions intuitively evoke the crucial roles that it plays in organism development and species evolution, and its establishment is tightly tied to animal multicellularity itself. The molecular toolkit expressed in germ cells has a high degree of conservation between species, and it also shares many components with the molecular phenotype of some animal totipotent cell lineages, like planarian neoblasts and sponge archaeocytes. The present study stems from these observations and represents a transcriptome-wide comparative analysis between germline-related samples of 9 animal species (7 phyla), comprehending also totipotent lineages classically considered somatic. RESULTS: Differential expression analyses were performed for each species between germline-related and control somatic tissues. We then compared the different germline-related transcriptional profiles across the species without the need for an a priori set of genes. Through a phylostratigraphic analysis, we observed that the proportion of phylum- and Metazoa-specific genes among germline-related upregulated transcripts was lower than expected by chance for almost all species. Moreover, homologous genes related to proper DNA replication resulted the most common when comparing the considered species, while the regulation of transcription and post-transcriptional mechanisms appeared more variable, showing shared upregulated functions and domains, but very few homologous whole-length sequences. CONCLUSIONS: Our wide-scale comparative analysis mostly confirmed previous molecular characterizations of specific germline-related lineages. Additionally, we observed a consistent signal throughout the whole data set, therefore comprehending both canonically defined germline samples (germ cells), and totipotent cell lineages classically considered somatic (neoblasts and archaeocytes). The phylostratigraphic analysis supported the less probable involvement of novel molecular factors in the germline-related transcriptional phenotype and highlighted the early origin of such cell programming and its conservation throughout evolution. Moreover, the fact that the mostly shared molecular factors were involved in DNA replication and repair suggests how fidelity in genetic material inheritance is a strong and conserved driver of germline-related molecular phenotype, while transcriptional and post-transcriptional regulations appear differently tuned among the lineages. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13227-022-00207-3
The dynamics of mito-nuclear coevolution: A perspective from bivalve species with two different mechanisms of mitochondrial inheritance
No full textThe proteins involved in the main process of energy production of most eukaryotes (oxidative phosphorylation, OXPHOS) are encoded by either nuclear or mitochondrial genomes. The importance of mito‐nuclear interactions suggests that the two genomes might be under coevolution. While most eukaryotes are characterized by a strictly maternal inheritance (SMI) of mitochondria, some bivalves show doubly uniparental inheritance (DUI), where two distinct mitochondrial lineages coexist in the same individual, and the nuclear OXPHOS genes have to cofunction with genes produced by two different mitochondrial genomes. We took advantage of the natural heteroplasmy of a DUI species to get insights into the dynamics of mito‐nuclear coevolution. We used RNA‐seq to investigate transcription and rate of protein evolution of OXPHOS genes in two related bivalves: Ruditapes decussatus (Bivalvia, Veneridae), a species with SMI, and Ruditapes philippinarum (Bivalvia, Veneridae), a species with DUI. Surprisingly, our results are not consistent with most of the proposed hyphotheses about the mechanisms of mito‐nuclear coevolution. In particular, despite observing a rate of protein evolution of mitochondrial subunits an order of magnitude higher compared to that of most animal taxa investigated so far, we found no evidence for nuclear compensation. Moreover, we found no correlation between rate of protein evolution and transcription level in both nuclear and mitochondrial OXPHOS subunits. In this work, we report clear deviations from the expected results predicted by widely accepted hypotheses built around data obtained from a restricted representation of biodiversity. This should encourage further investigations based on broad comparative analyses encompassing usually overlooked non‐model species
Bivalve molluscs as model systems for studying mitochondrial biology
Full text linkThe class Bivalvia is a highly successful and ancient taxon including ∼25,000 living species. During their long evolutionary history bivalves adapted to a wide range of physicochemical conditions, habitats, biological interactions, and feeding habits. Bivalves can have strikingly different size, and despite their apparently simple body plan, they evolved very different shell shapes, and complex anatomic structures. One of the most striking features of this class of animals is their peculiar mitochondrial biology: some bivalves have facultatively anaerobic mitochondria that allow them to survive prolonged periods of anoxia/hypoxia. Moreover, more than 100 species have now been reported showing the only known evolutionarily stable exception to the strictly maternal inheritance of mitochondria in animals, named doubly uniparental inheritance. Mitochondrial activity is fundamental to eukaryotic life, and thanks to their diversity and uncommon features, bivalves represent a great model system to expand our knowledge about mitochondrial biology, so far limited to a few species. We highlight recent works studying mitochondrial biology in bivalves at either genomic or physiological level. A link between these two approaches is still missing, and we believe that an integrated approach and collaborative relationships are the only possible ways to be successful in such endeavour
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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