1,022 research outputs found

    Skeletal Rigidity of Phylogenetic Trees

    Full text link
    Motivated by geometric origami and the straight skeleton construction, we outline a map between spaces of phylogenetic trees and spaces of planar polygons. The limitations of this map is studied through explicit examples, culminating in proving a structural rigidity result.Comment: 17 pages, 12 figure

    Characterization of translationally controlled tumour protein from the sea anemone Anemonia viridis and transcriptome wide identification of cnidarian homologues

    Get PDF
    Gene family encoding translationally controlled tumour protein (TCTP) is defined as highly conserved among organisms; however, there is limited knowledge of non-bilateria. In this study, the first TCTP homologue from anthozoan was characterised in the Mediterranean Sea anemone, Anemonia viridis. The release of the genome sequence of Acropora digitifera, Exaiptasia pallida, Nematostella vectensis and Hydra vulgaris enabled a comprehensive study of the molecular evolution of TCTP family among cnidarians. A comparison among TCTP members from Cnidaria and Bilateria showed conserved intron exon organization, evolutionary conserved TCTP signatures and 3D protein structure. The pattern of mRNA expression profile was also defined in A. viridis. These analyses revealed a constitutive mRNA expression especially in tissues with active proliferation. Additionally, the transcriptional profile of A. viridis TCTP (AvTCTP) after challenges with different abiotic/biotic stresses showed induction by extreme temperatures, heavy metals exposure and immune stimulation. These results suggest the involvement of AvTCTP in the sea anemone defensome taking part in environmental stress and immune responses

    Buildings, spiders, and geometric Satake

    Full text link
    Let G be a simple algebraic group. Labelled trivalent graphs called webs can be used to product invariants in tensor products of minuscule representations. For each web, we construct a configuration space of points in the affine Grassmannian. Via the geometric Satake correspondence, we relate these configuration spaces to the invariant vectors coming from webs. In the case G = SL(3), non-elliptic webs yield a basis for the invariant spaces. The non-elliptic condition, which is equivalent to the condition that the dual diskoid of the web is CAT(0), is explained by the fact that affine buildings are CAT(0).Comment: 49 pages; revised and to appear in Compositio Mathematic

    Assessing Arboreal Adaptations of Bird Antecedents: Testing the Ecological Setting of the Origin of the Avian Flight Stroke

    Get PDF
    The origin of avian flight is a classic macroevolutionary transition with research spanning over a century. Two competing models explaining this locomotory transition have been discussed for decades: ground up versus trees down. Although it is impossible to directly test either of these theories, it is possible to test one of the requirements for the trees-down model, that of an arboreal paravian. We test for arboreality in non-avian theropods and early birds with comparisons to extant avian, mammalian, and reptilian scansors and climbers using a comprehensive set of morphological characters. Non-avian theropods, including the small, feathered deinonychosaurs, and Archaeopteryx, consistently and significantly cluster with fully terrestrial extant mammals and ground-based birds, such as ratites. Basal birds, more advanced than Archaeopteryx, cluster with extant perching ground-foraging birds. Evolutionary trends immediately prior to the origin of birds indicate skeletal adaptations opposite that expected for arboreal climbers. Results reject an arboreal capacity for the avian stem lineage, thus lending no support for the trees-down model. Support for a fully terrestrial ecology and origin of the avian flight stroke has broad implications for the origin of powered flight for this clade. A terrestrial origin for the avian flight stroke challenges the need for an intermediate gliding phase, presents the best resolved series of the evolution of vertebrate powered flight, and may differ fundamentally from the origin of bat and pterosaur flight, whose antecedents have been postulated to have been arboreal and gliding

    Identification of the molecular basis of the lacrimo-auriculo-dento-digital (LADD) syndrome

    Get PDF
    Lacrimo-auriculo-dento-digital (LADD) syndrome, also known as Levy-Hollister syndrome, is a rare autosomal dominant developmental disorder, mainly characterized by abnormalities of the lacrimal system and salivary glands, ears and hearing, teeth and distal limb development. Besides these cardinal features, facial dysmorphism and malformations of the kidney and the respiratory system have been reported. In this study, the LADD1 locus was mapped to chromosome 10q26 by genome wide linkage analysis using the Affymetrix GeneChip 10K array in three large LADD families. In all three LADD families and in one sporadic case, heterozygous missense mutations were found in exon 16 of the gene encoding the fibroblast-growth-factor-receptor 2 (FGFR2). After exclusion of the FGFR2 locus by haplotype analysis in two additional LADD families, one missense mutation was identified in FGFR3 and one mutation was found in the fibroblast-growth-factor 10 (FGF10), a known ligand of FGFR2 [Rohmann et al., 2006]. The functional properties of FGF10 LADD and FGFR2 LADD mutants were analyzed and compared to the activities of their normal counterparts. Protein expression in BL21 cells and binding studies showed that each of the three analyzed FGF10 mutations demonstrated severely impaired activity by different mechanisms. Transient and stable expression studies exhibited that the FGFR2 mutations possess a reduced autophosphorylation and a weaker tyrosine kinase activity. Mutations also lead to diminished phosphorylation activity in FGFR2-mediated substrates (e. g. FRS2 and Shc) and to a decreased downstream signaling pathway, as shown by MAPK activity. While tested FGF10 LADD mutations caused haploinsufficiency, the FGFR2 LADD mutants could exert a dominant-negative effect on normal FGFR2 protein [Shams and Rohmann et al., 2007]. An in vitro kinase assay and crystallization of both, FGFR2 WT and the p.A628T missense mutation in the catalytic part of the tyrosine kinase domain, demonstrated that the A628T LADD mutation disrupts the catalytic activity due to conformational changes, leading to LADD syndrome. In addition, the newly described crystal structure of FGFR2 in comparison to FGFR1 revealed that the FGFR2 utilizes a less stringent mode of autoinhibition [Lew, Bae and Rohmann et al., 2007]

    Potential for Powered Flight Neared by Most Close Avialan Relatives, but Few Crossed Its Thresholds

    Get PDF
    Uncertainties in the phylogeny of birds (Avialae) and their closest relatives have impeded deeper understanding of early theropod flight. To help address this, we produced an updated evolutionary hypothesis through an automated analysis of the Theropod Working Group (TWiG) coelurosaurian phylogenetic data matrix. Our larger, more resolved, and better-evaluated TWiG-based hypothesis supports the grouping of dromaeosaurids + troodontids (Deinonychosauria) as the sister taxon to birds (Paraves) and the recovery of Anchiornithinae as the earliest diverging birds. Although the phylogeny will continue developing, our current results provide a pertinent opportunity to evaluate what we know about early theropod flight. With our results and available data for vaned feathered pennaraptorans, we estimate the potential for powered flight among early birds and their closest relatives. We did this by using an ancestral state reconstruction analysis calculating maximum and minimum estimates of two proxies of powered flight potential—wing loading and specific lift. These results confirm powered flight potential in early birds but its rarity among the ancestors of the closest avialan relatives (select unenlagiine and microraptorine dromaeosaurids). For the first time, we find a broad range of these ancestors neared the wing loading and specific lift thresholds indicative of powered flight potential. This suggests there was greater experimentation with wing-assisted locomotion before theropod flight evolved than previously appreciated. This study adds invaluable support for multiple origins of powered flight potential in theropods (≥3 times), which we now know was from ancestors already nearing associated thresholds, and provides a framework for its further study. Video Abstract: [Figure presented] Pei et al. use an updated phylogeny of early birds and their closest relatives to reconstruct powered flight potential, showing it evolved at least three times. Many ancestors of the closest bird relatives neared thresholds of powered flight potential, suggesting broad experimentation with wing-assisted locomotion before theropod flight evolved.Fil: Pei, Rui. Institute Of Vertebrate Paleontology And Paleoanthropology Chinese Academy Of Sciences; ChinaFil: Pittman, Michael B.. The University Of Hong Kong; Hong KongFil: Goloboff, Pablo Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Dececchi, T. Alexander. Mount Marty College; Estados UnidosFil: Habib, Michael B.. Natural History Museum Of Los Angeles County; Estados UnidosFil: Kaye, Thomas G.. Foundation For Scientific Advancement; Estados UnidosFil: Larsson, Hans C. E.. Mcgill University; CanadáFil: Norell, Mark A.. American Museum of Natural History; Estados UnidosFil: Brusatte, Stephen L.. University of Edinburgh; Reino UnidoFil: Xu, Xing. Institute Of Vertebrate Paleontology And Paleoanthropology Chinese Academy Of Sciences; Chin

    Integument-based inferences on the swimming ability and prey hunting strategy of the bigeye thresher shark, Alopias superciliosus (Lamniformes: Alopiidae)

    Get PDF
    Alopias is a group of lamniform sharks characterized by a highly elongate caudal fin with three known extant species: A. pelagicus (pelagic thresher shark), A. superciliosus (bigeye thresher shark), and A. vulpinus (common thresher shark). Alopias pelagicus and A. vulpinus are considered fast swimmers and use their caudal fin to hunt for small schooling fish by stunning them, but the feeding behavior has never been directly observed for A. superciliosus. Under the ecomorphological framework, I examined the following four integumentary variables of selected fast swimming (e.g., A. pelagicus, A. vulpinus, and Lamna) and slow swimming (e.g., Mitsukurina and Megachasma) lamniform sharks to determine whether A. superciliosus is a fast swimmer or a slow swimmer: 1) dermis thickness, 2) average interkeel distances of scales, 3) scale density, and 4) scale shape. My integumentary data indicate that A. superciliosus is a slow swimming lamniform, but it likely employs a simple laterally directed tail slap to capture its prey. Its thick dermis layer on the body indicates its extreme body bending capability, perhaps to maximize the strike power of the caudal fin in order to compensate its slow swimming. Overall, my study points to an interpretation that A. superciliosus is an ambush predator, rather than an active prey-pursuing hunter. When my scale density and average interkeel distance data are mapped on to previously published molecular- and morphology-based phylogenetic trees, slow swimming is found to be a plesiomorphic condition in Lamniformes, where the evolution of fast swimming through lamniform phylogeny is more parsimonious in the morphology-based tree than the molecular-based tree. My work is the most extensive comparative study of the morphology and variation of integumentary structures, especially placoid scales, conducted so far for Lamniformes
    • …
    corecore