Assessment of phylo-functional coherence along the bacterial phylogeny and taxonomy.
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ABSTRACT:
SUBMITTER: Parras-Molto M
PROVIDER: S-EPMC8050241 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The evolutionary history of all life forms is usually represented as a vertical tree-like process. In prokaryotes, however, the vertical signal is partly obscured by the massive influence of horizontal gene transfer (HGT). The HGT creates widespread discordance between evolutionary histories of different genes as genomes become mosaics of gene histories. Thus, the Tree of Life (TOL) has been questioned as an appropriate representation of the evolution of prokaryotes. Nevertheless a common hypothesis is that prokaryotic evolution is primarily tree-like, and a routine effort is made to place new isolates in their appropriate location in the TOL. Moreover, it appears desirable to exploit non-tree-like evolutionary processes for the task of microbial classification. In this work, we present a novel technique that builds on the straightforward observation that gene order conservation ('synteny') decreases in time as a result of gene mobility. This is particularly true in prokaryotes, mainly due to HGT. Using a 'synteny index' (SI) that measures the average synteny between a pair of genomes, we developed the phylogenetic reconstruction tool 'Phylo SI'. Phylo SI offers several attractive properties such as easy bootstrapping, high sensitivity in cases where phylogenetic signal is weak and computational efficiency. Phylo SI was tested both on simulated data and on two bacterial data sets and compared with two well-established phylogenetic methods. Phylo SI is particularly efficient on short evolutionary distances where synteny footprints remain detectable, whereas the nucleotide substitution signal is too weak for reliable sequence-based phylogenetic reconstruction. The method is publicly available at http://research.haifa.ac.il/ssagi/software/PhyloSI.zip.
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Project description:BACKGROUND: Analysis of large-scale experimental datasets frequently produces one or more sets of proteins that are subsequently mined for functional interpretation and validation. To this end, a number of computational methods have been devised that rely on the analysis of functional annotations. Although current methods provide valuable information (e.g. significantly enriched annotations, pairwise functional similarities), they do not specifically measure the degree of homogeneity of a protein set. RESULTS: In this work we present a method that scores the degree of functional homogeneity, or coherence, of a set of proteins on the basis of the global similarity of their functional annotations. The method uses statistical hypothesis testing to assess the significance of the set in the context of the functional space of a reference set. As such, it can be used as a first step in the validation of sets expected to be homogeneous prior to further functional interpretation. CONCLUSION: We evaluate our method by analysing known biologically relevant sets as well as random ones. The known relevant sets comprise macromolecular complexes, cellular components and pathways described for Saccharomyces cerevisiae, which are mostly significantly coherent. Finally, we illustrate the usefulness of our approach for validating 'functional modules' obtained from computational analysis of protein-protein interaction networks. Matlab code and supplementary data are available at http://www.cnb.csic.es/~monica/coherence/
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Project description:Within the field of mycology, macrofungi have been relatively well-studied when compared to microfungi. However, the diversity and distribution of microfungi inhabiting woody material have not received the same degree of research attention, especially in relatively unexplored regions, such as Yunnan Province, China. To help address this knowledge gap, we collected and examined fungal specimens from different plants at various locations across Yunnan Province. Our investigation led to the discovery of four species that are clearly distinct from extant ones. These taxonomic novelties were recognized based on morphological comparisons coupled with phylogenetic analyses of multiple gene sequences (non-translated loci and protein-coding regions). The monotypic genus Neoheleiosa gen. nov. (type: N. lincangensis) is introduced in Monoblastiaceae (Monoblastiales) for a woody-based saprobic ascomycete that possesses globose to subglobose or obpyriform ascomata with centric or eccentric, papillate ostioles, an ascomatal wall with thin-walled cells of textura globulosa, cylindric, pedicellate asci with an ocular chamber, and 1-septate, brown, guttulate, longitudinally striated, bicellular ascospores. Neoheleiosa has a close phylogenetic affinity to Heleiosa, nevertheless, it is morphologically dissimilar by its peridium cells and ornamented ascospores. Acrocalymma hongheense and A. yuxiense are described and illustrated as new species in Acrocalymmaceae. Acrocalymma hongheense is introduced with sexual and asexual (coelomycetous) features. The sexual morph is characterized by globose to subglobose, ostiolate ascomata, a peridium with textura angularis cells, cylindric-clavate asci with a furcate to truncate pedicel and an ocular chamber, hyaline, fusiform, 1-septate ascospores which are surrounded by a thick, distinct sheath, and the asexual morph is featured by pycnidial conidiomata, subcylindrical, hyaline, smooth, annelledic, conidiogenous cells, hyaline, guttulate, subcylindrical, aseptate conidia with mucoid ooze at the apex and with a rounded hilum at the base. Acrocalymma yuxiense is phylogenetically distinct from other extant species of Acrocalymma and differs from other taxa in Acrocalymma in having conidia with three vertical eusepta. Magnibotryascoma kunmingense sp. nov. is accommodated in Teichosporaceae based on its coelomycetous asexual morph which is characterized by pycnidial, globose to subglobose, papillate conidiomata, enteroblastic, annelledic, discrete, cylindrical to oblong, hyaline conidiogenous cells arising from the inner layer of pycnidium wall, subglobose, oval, guttulate, pale brown and unicelled conidia.
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Project description:Relict species play an important role in understanding the biogeography of intercontinental disjunctions. Pterocarya (a relict genus) is the valuable model taxon for studying the biogeography of East Asian versus southern European/West Asian disjunct patterns. This disjunction has not been as well studied as others (e.g., between Eastern Asia and North America). Several phylogenetic studies on Pterocarya have been conducted, but none have provided a satisfactory phylogenetic resolution. Here, we report the first well-resolved phylogeny of Pterocarya using restriction site-associated DNA sequencing data based on the sampling of all taxa across the entire distribution area of the genus. Taxonomic treatments were also clarified by combining morphological traits. Furthermore, fossil-calibrated phylogeny was used to explore the biogeography of Pterocarya. Our results support the existence of two sections in Pterocarya, which is in accordance with morphological taxonomy. Section Platyptera comprises three species: P. rhoifolia, P. macroptera, and P. delavayi. Section Pterocarya also comprises three species: P. fraxinifolia, P. hupehensis, and P. stenoptera. The divergence between the two sections took place during the early Miocene (20.5 Ma). The formation of the Gobi Desert and climate cooling of northern Siberia in the Middle Miocene (15.7 Ma) might have caused the split of the continuous distribution of this genus and the formation of the East Asian versus southern European/West Asian disjunct pattern. Lastly, the divergence between P. hupehensis and P. stenoptera as well as between P. rhoifolia and P. macroptera/P. delavayi (10.0 Ma) supports the late Miocene diversification hypothesis in East Asia.
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Project description:The recently generated molecular phylogeny for the kingdom Fungi, on which a new classification scheme is based, still suffers from an under representation of numerous apparently asexual genera of microfungi. In an attempt to populate the Fungal Tree of Life, fresh samples of 10 obscure genera of hyphomycetes were collected. These fungi were subsequently established in culture, and subjected to DNA sequence analysis of the ITS and LSU nrRNA genes to resolve species and generic questions related to these obscure genera. Brycekendrickomyces (Herpotrichiellaceae) is introduced as a new genus similar to, but distinct from Haplographium and Lauriomyces. Chalastospora is shown to be a genus in the Pleosporales, with two new species, C. ellipsoidea and C. obclavata, to which Alternaria malorum is added as an additional taxon under its oldest epithet, C. gossypii. Cyphellophora eugeniae is newly described in Cyphellophora (Herpotrichiellaceae), and distinguished from other taxa in the genus. Dictyosporium is placed in the Pleosporales, with one new species, D. streliziae. The genus Edenia, which was recently introduced for a sterile endophytic fungus isolated in Mexico, is shown to be a hyphomycete (Pleosporales) forming a pyronellea-like synanamorph in culture. Thedgonia is shown not to represent an anamorph of Mycosphaerella, but to belong to the Helotiales. Trochophora, however, clustered basal to the Pseudocercospora complex in the Mycosphaerellaceae, as did Verrucisporota. Vonarxia, a rather forgotten genus of hyphomycetes, is shown to belong to the Herpotrichiellaceae and Xenostigmina is confirmed as synanamorph of Mycopappus, and is shown to be allied to Seifertia in the Pleosporales. Dichotomous keys are provided for species in the various genera treated. Furthermore, several families are shown to be polyphyletic within some orders, especially in the Capnodiales, Chaetothyriales and Pleosporales.
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