Toward a comprehensive model for induced endoreduplication

Both the biological significance and the molecular mechanism of endoreduplication (END) have been debated for a long time by cytogeneticists and researchers into cell cycle enzymology and dynamics alike. Mainly due to the fact that a wide variety of agents have been reported as able to induce endoreduplication and the diversity of cell types where it has been described, until now no clear or unique mechanism of induction of this phenomenon, rare in animals but otherwise quite common in plants, has been proposed. DNA topoisomerase II (topo II), plays a major role in mitotic chromosome segregation after DNA replication. The classical topo II poisons act by stabilizing the enzyme in the so-called cleavable complex and result in DNA damage as well as END, while the true catalytic inhibitors, which are not cleavable-complex-stabilizers, do induce END without concomitant DNA and chromosome damage. Taking into account these observations on the induction of END by drugs that interfere with topo II, together with our recently obtained evidence that the nature of DNA plays an important role for chromosome segregation [Cortes, F., Pastor, N., Mateos, S., Dominguez, I., 2003. The nature of DNA plays a role in chromosome segregation: endoreduplication in halogen-substituted chromosomes. DNA Repair 2, 719-726.], a straightforward model is proposed in which the different mechanisms leading to induced END are considered.     

Toward a global phylogeny of the Brassicaceae

The Brassicaceae is a large plant family (338 genera and 3,700 species) of major scientific and economic importance. The taxonomy of this group has been plagued by convergent evolution in nearly every morphological feature used to define tribes and genera. Phylogenetic analysis of 746 nrDNA internal transcribed spacer (ITS) sequences, representing 24 of the 25 currently recognized tribes, 146 genera, and 461 species of Brassicaceae, produced the most comprehensive, single-locus-based phylogenetic analysis of the family published to date. Novel approaches to nrDNA ITS analysis and extensive taxonomic sampling offered a test of monophyly for a large complement of the currently recognized tribes and genera of Brassicaceae. In the most comprehensive analysis, tribes Alysseae, Anchonieae plus Hesperideae, Boechereae, Cardamineae, Eutremeae, Halimolobeae, Iberideae, Noccaeeae, Physarieae, Schizopetaleae, Smelowskieae, and Thlaspideae were all monophyletic. Several broadly defined genera (e.g., Draba and Smelowskia) were supported as monophyletic, whereas others (e.g., Sisymbrium and Alyssum) were clearly polyphyletic. Analyses of ITS data identified several problematic sequences attributable to errors in sample identification or database submission. Results from parsimony ratchet and Bayesian analyses recovered little support for the backbone of the phylogeny, suggesting that many lineages of Brassicaceae have undergone rapid radiations that may ultimately be difficult to resolve with any single locus. However, the development of a preliminary supermatrix including the combination of 10 loci for 65 species provides an initial estimate of intertribal relations and suggests that broad application of such a method will provide greater understanding of relationships in the family.     

A supermatrix approach provides a comprehensive genus-level phylogeny for Gentianales

Gentianales consist of Apocynaceae, Gelsemiaceae, Gentianaceae, Loganiaceae, and Rubiaceae, of which the majority are woody plants in tropical and subtropical areas. Despite extensive efforts in reconstructing the phylogeny of Gentianales based on molecular data, some interfamily and intrafamily relationships remain uncertain. We reconstructed the genus-level phylogeny of Gentianales based on the supermatrix of eight plastid markers (rbcL, matK, atpB, ndhF, rpl16, rps16, thetrnL-trnF region, and atpB-rbcL spacer) and one mitochondrial gene (matR) using maximum likelihood. The major clades and their relationships retrieved in the present study concur with those of previous studies. All of the five families of Gentianales are monophyletic with strong support. We resolved Rubiaceae as sister to the remaining families in Gentianales and showed support for the sister relationship between Loganiaceae and Apocynaceae. Our results provide new insights into relationships among intrafamilial clades. For example, within Rubiaceae we found that Craterispermeae were sister to Morindeae + (Palicoureeae + Psychotrieae) and that Theligoneae were sister to Putorieae. Within Gentianaceae, our phylogeny revealed that Gentianeae were sister to Helieae and Potalieae, and subtribe Lisianthiinae were sister to Potaliinae and Faroinae. Within Loganiaceae, we found Neuburgia as sister to Spigelieae. Within Apocynaceae, our results supported Amsonieae as sister to Melodineae, and Hunterieae as sister to a clade comprising Plumerieae + (Carisseae + APSA). We also confirmed the monophyly of Perplocoideae and the relationships among Baisseeae + (Secamonoideae + Asclepiadoideae).     

A web-database of mammalian morphology and a reanalysis of placental phylogeny

Background  

Recent publications concerning the interordinal phylogeny of placental mammals have converged on a common signal, consisting of four major radiations with some ambiguity regarding the placental root. The DNA data with which these relationships have been reconstructed are easily accessible from public databases; access to morphological characters is much more difficult. Here, I present a graphical web-database of morphological characters focusing on placental mammals, in tandem with a combined-data phylogenetic analysis of placental mammal phylogeny.     

Using inter-SINE-PCR to study mammalian phylogeny

Results of the use of the fingerprinting method related to short interspersed elements (SINEs), inter-SINE-PCR, in the study of phylogenetic and taxonomic relationship in mammals from orders Chiroptera (family Vespertilionidae) and Lipotyphla (family Erinaceidae) are reported. The inter-SINE-PCR method is based on the amplification of fragments situated between copies of SINEs, which are short retroposons spaced 100 to 1000 bp apart. Specifically selected primers were used, which are complementary to consensus sequences of two short retroposons: the mammalian interspersed repeat (MIR), which is typical of all mammals and some other vertebrates, was used in the cases of bats and Erinaceidae, and the ERI-1 element recently isolated from the genome of the Daurian hedgehog was used in the case of Erinaceidae. The results support the current view on phylogenetic relationship between hedgehogs belonging to genera Erinaceus, Hemiechinus, and Paraechinus (but not the genus Atelerix). In bats, the phylogenetic reconstruction revealed a statistically valid topology only at lower taxonomic levels, whereas the topology for the genus and supragenus ranks was unresolved and fan-shaped. The benefits and limitations of the inter-SINE-PCR method are discussed.     

Toward a phylogeny and biogeography of Diaphanosoma (Crustacea: Cladocera)

Aquatic Ecology - Diaphanosoma s.l., with 40+? described species, is the largest genus of the Sididae and the Ctenopoda, similar in many ways to the anomopod genus Daphnia. Here, we offer a c...     

Data incongruence and the problem of avian louse phylogeny

Smith, V. S., Page, R. D. M. & Johnson, K. P. (2004). Data incongruence and the problem of avian louse phylogeny. — Zoologica Scripta, 33 , 239 –259.
Recent studies based on different types of data (i.e. morphological and molecular) have supported conflicting phylogenies for the genera of avian feather lice (Ischnocera: Phthiraptera). We analyse new and published data from morphology and from mitochondrial (12S rRNA and COI) and nuclear (EF1-α) genes to explore the sources of this incongruence and explain these conflicts. Character convergence, multiple substitutions at high divergences, and ancient radiation over a short period of time have contributed to the problem of resolving louse phylogeny with the data currently available. We show that apparent incongruence between the molecular datasets is largely attributable to rate variation and nonstationarity of base composition. In contrast, highly significant character incongruence leads to topological incongruence between the molecular and morphological data. We consider ways in which biases in the sequence data could be misleading, using several maximum likelihood models and LogDet corrections. The hierarchical structure of the data is explored using likelihood mapping and SplitsTree methods. Ultimately, we concede there is strong discordance between the molecular and morphological data and apply the conditional combination approach in this case. We conclude that higher level phylogenetic relationships within avian Ischnocera remain extremely problematic. However, consensus between datasets is beginning to converge on a stable phylogeny for avian lice, at and below the familial rank.     

Sponge-specific clusters revisited: a comprehensive phylogeny of sponge-associated microorganisms

Marine sponges often contain diverse and abundant communities of microorganisms including bacteria, archaea and eukaryotic microbes. Numerous 16S rRNA-based studies have identified putative 'sponge-specific' microbes that are apparently absent from seawater and other (non-sponge) marine habitats. With more than 7500 sponge-derived rRNA sequences (from clone, isolate and denaturing gradient gel electrophoresis data) now publicly available, we sought to determine whether the current notion of sponge-specific sequence clusters remains valid. Comprehensive phylogenetic analyses were performed on the 7546 sponge-derived 16S and 18S rRNA sequences that were publicly available in early 2010. Overall, 27% of all sequences fell into monophyletic, sponge-specific sequence clusters. Such clusters were particularly well represented among the Chloroflexi, Cyanobacteria, 'Poribacteria', Betaproteobacteria and Acidobacteria, and in total were identified in at least 14 bacterial phyla, as well as the Archaea and fungi. The largest sponge-specific cluster, representing the cyanobacterium 'Synechococcus spongiarum', contained 245 sequences from 40 sponge species. These results strongly support the existence of sponge-specific microbes and provide a suitable framework for future studies of rare and abundant sponge symbionts, both of which can now be studied using next-generation sequencing technologies.     

Compositional properties of coding sequences and mammalian phylogeny

The compositional distributions of large DNA fragments reflect those of the isochores that make up vertebrate genomes and can provide novel phylogenetic insights in the case of mammalian genomes (see Sabeur et al. 1993). This approach has been complemented here by an analysis of the compositional patterns of coding sequences and their codon positions (which also reflect the isochore pattern) and by a comparison of the base compositions of codon positions from homologous genes in a number of pairs of species. The results obtained using these two approaches support the existence of a general compositional pattern for mammalian genomes and of a distinct pattern for Myomorpha. The other two “special” patterns identified in a megachiropteran and in pangolin could not be tested here. Presented at the NATO Advanced Research Workshop onGenome Organization and Evolution, Spetsai, Greece, 16–22 September 1992     

Toward a comprehensive and systematic methylome signature in colorectal cancers

CpG Island Methylator Phenotype (CIMP) is one of the underlying mechanisms in colorectal cancer (CRC). This study aimed to define a methylome signature in CRC through a methylation microarray analysis and a compilation of promising CIMP markers from the literature. Illumina HumanMethylation27 (IHM27) array data was generated and analyzed based on statistical differences in methylation data (1st approach) or based on overall differences in methylation percentages using lower 95% CI (2nd approach). Pyrosequencing was performed for the validation of nine genes. A meta-analysis was used to identify CIMP and non-CIMP markers that were hypermethylated in CRC but did not yet make it to the CIMP genes’ list. Our 1st approach for array data analysis demonstrated the limitations in selecting genes for further validation, highlighting the need for the 2nd bioinformatics approach to adequately select genes with differential aberrant methylation. A more comprehensive list, which included non-CIMP genes, such as APC, EVL, CD109, PTEN, TWIST1, DCC, PTPRD, SFRP1, ICAM5, RASSF1A, EYA4, 30ST2, LAMA1, KCNQ5, ADHEF1, and TFPI2, was established. Array data are useful to categorize and cluster colonic lesions based on their global methylation profiles; however, its usefulness in identifying robust methylation markers is limited and rely on the data analysis method. We have identified 16 non-CIMP-panel genes for which we provide rationale for inclusion in a more comprehensive characterization of CIMP+ CRCs. The identification of a definitive list for methylome specific genes in CRC will contribute to better clinical management of CRC patients.     

Genome sizes of mammalian and avian Ureaplasmas

The sizes of the genomes of 12 Ureaplasma strains isolated from six mammalian and one avian species, as determined by pulsed-field gel electrophoresis, varied from 760 to 1,170 kilobase pairs (470 to 723 megadaltons); and these values encompassed the values for the genomes of Ureaplasma urealyticum strains. Variation of at least 54% in the genome sizes restricts the usefulness of this taxonomic criterion for the genus Ureaplasma.     

Novel mammalian herpesviruses and lineages within the Gammaherpesvirinae: cospeciation and interspecies transfer

Novel members of the subfamily Gammaherpesvirinae, hosted by eight mammalian species from six orders (Primates, Artiodactyla, Perissodactyla, Carnivora, Scandentia, and Eulipotyphla), were discovered using PCR with pan-herpesvirus DNA polymerase (DPOL) gene primers and genus-specific glycoprotein B (gB) gene primers. The gB and DPOL sequences of each virus species were connected by long-distance PCR, and contiguous sequences of approximately 3.4 kbp were compiled. Six additional gammaherpesviruses from four mammalian host orders (Artiodactyla, Perissodactyla, Primates, and Proboscidea), for which only short DPOL sequences were known, were analyzed in the same manner. Together with available corresponding sequences for 31 other gammaherpesviruses, alignments of encoded amino acid sequences were made and used for phylogenetic analyses by maximum-likelihood and Bayesian Monte Carlo Markov chain methods to derive a tree which contained two major loci of unresolved branching details. The tree was rooted by parallel analyses that included alpha- and betaherpesvirus sequences. This gammaherpesvirus tree contains 11 major lineages and presents the widest view to date of phylogenetic relationships in any subfamily of the Herpesviridae, as well as the most complex in the number of deep lineages. The tree's branching pattern can be interpreted only in part in terms of the cospeciation of virus and host lineages, and a substantial incidence of the interspecies transfer of viruses must also be invoked.     

A comprehensive molecular phylogeny of the starlings (Aves: Sturnidae) and mockingbirds (Aves: Mimidae): congruent mtDNA and nuclear trees for a cosmopolitan avian radiation

We generated a comprehensive phylogeny for the avian families Sturnidae (starlings, mynas, Rhabdornis, oxpeckers, and allies) and Mimidae (mockingbirds, thrashers, and allies) to explore patterns of morphological and behavioral diversification. Reconstructions were based on mitochondrial DNA sequences from five coding genes (4108 bp), and nuclear intron sequences from four loci (2974 bp), for most taxa, supplemented with NDII gene sequences (1041 bp) derived from museum skin specimens from additional taxa; together the 117 sampled taxa comprise 78% of the 151 species in these families and include representatives of all currently or recently recognized genera. Phylogenetic analyses consistently identified nine major clades. The basal lineage is comprised of the two Buphagus oxpeckers, which are presently confined to Africa where they are obligately associated with large mammals. Some species in nearly all of the other major clades also feed on or around large vertebrates, and this association may be an ancestral trait that fostered the world-wide dispersal of this group. The remaining taxa divide into sister clades representing the New-World Mimidae and Old-World Sturnidae. The Mimidae are divided into two subclades, a group of Central American and West Indian catbirds and thrashers, and a pan-American clade of mockingbirds and thrashers. The Sturnidae are subdivided into six clades. The Phillipine endemic Rhabdornis are the sister lineage to a larger and substantially more recent radiation of South Asian and Pacific island starlings and mynas. A clade of largely migratory or nomadic Eurasian starlings (within which the basal lineage is the model taxon Sturnus vulgaris) is allied to three groups of largely African species. These reconstructions confirm that Buphagus should not be included in the Sturnidae, and identify many genera that are not monophyletic. They also highlight the substantial diversity among the major Sturnidae subclades in rates of species accumulation, morphological differentiation, and behavioral variation.