Distinct evolutionary histories of the DNA-A and DNA-B components of bipartite begomoviruses

<p>Abstract</p> <p>Background</p> <p>Viruses of the genus <it>Begomovirus </it>(family <it>Geminiviridae</it>) have genomes consisting of either one or two genomic components. The component of bipartite begomoviruses known as DNA-A is homologous to the genomes of all geminiviruses and encodes proteins required for replication, control of gene expression, overcoming host defenses, encapsidation and insect transmission. The second component, referred to as DNA-B, encodes two proteins with functions in intra- and intercellular movement in host plants. The origin of the DNA-B component remains unclear. The study described here was initiated to investigate the relationship between the DNA-A and DNA-B components of bipartite begomoviruses with a view to unraveling their evolutionary histories and providing information on the possible origin of the DNA-B component.</p> <p>Results</p> <p>Comparative phylogenetic and exhaustive pairwise sequence comparison of all DNA-A and DNA-B components of begomoviruses demonstrates that the two molecules have very distinct molecular evolutionary histories and likely are under very different evolutionary pressures. The analysis highlights that component exchange has played a far greater role in diversification of begomoviruses than previously suspected, although there are distinct differences in the apparent ability of different groups of viruses to utilize this "sexual" mechanism of genetic exchange. Additionally we explore the hypothesis that DNA-B originated as a satellite that was captured by the monopartite progenitor of all extant bipartite begomoviruses and subsequently evolved to become the integral (essential) genome component that we recognize today. The situation with present-day satellites associated with begomoviruses provides some clues to the processes and selection pressures that may have led to the "domestication" of a wild progenitor of the DNA-B component.</p> <p>Conclusions</p> <p>The analysis has highlighted the greater genetic variation of DNA-B components, in comparison to the DNA-A components, and that component exchange is more widespread than previously demonstrated and confined to viruses from the Old World. Although the vast majority of New World and some Old World begomoviruses show near perfect co-evolution of the DNA-A and DNA-B components, this is not the case for the majority of Old World viruses. Genetic differences between Old and New World begomoviruses and the cultivation of exotic crops in the Old World are likely factors that have led to this dichotomy.</p

Pathobiology of saphenous vein grafts

The long saphenous vein graft is the commonest conduit used for coronary artery bypass surgery. The short and long term success of the procedure depends on the patency of these bypass grafts. Vein graft disease can be divided into early (in the fi rst 30 days), intermediate (1 month to 1 year) and late (over 1 year). Early graft failure is usually caused by graft thrombosis and may be related to the surgical procedure, intermediate graft disease results from intimal hyperplasia while late graft pathology is a consequence of atherosclerosis. The etiology and pathological processes leading to these damaging eff ects on saphenous vein grafts are tackled in this review. The loss of endothelial integrity, the phenotypic changes in vascular smooth muscle cells and involvement of adventitial cells with collaboration of blood borne factors lead to occlusive pathology of saphenous vein grafts. The accelerated intimal hyperplasia and atherosclerosis are characteristic pathobiological features of these vein grafts. Inflammatory and immunological changes and graft thrombosis are mediated through the secretion and up regulation of growth factors, pro coagulant substances and other proteins arising from the vein wall cells and the blood owing through them.peer-reviewe

Introduction of \u3cem\u3eMycobacterium ulcerans\u3c/em\u3e Mycolactone Genes into a Heterologous Host

Mycobacterium ulcerans is the causative agent of Buruli ulcer (BU), a necrotizing skin disease endemic to West Africa and Australia. The cytopathicity, cell cycle arrest and immunosuppression characteristic of BU are attributed to the production of a plasmid-encoded, macrolide toxin, mycolactone. The core of mycolactone is a product of two large polyketide synthases (PKS) and is conserved among all mycolactone congeners. Heterogeneity of the toxin is a result of differences in the polyketide side chain, the product of a third PKS. The mycolactone plasmid (MP) was initially thought to be restricted to M. ulcerans. However, other mycolactone producing mycobacteria (MPMs) have now been identified in association with diseased frogs and fish. Although plasmids are common in environmental mycobacteria, nothing is known about the ability of these plasmids to participate in horizontal transfer. This work investigates the expression of mycolactone in heterologous hosts, M. fortuitum and M. marinum, as well as the ability of MPMs to participate in conjugation. In this work a 152 kb fragment of the 154 kb MP plasmid from M. ulcerans 1615 was cloned into pBeloBAC11 and introduced into E. coli. This plasmid, pMYCO7017, contains the mycobacterial plasmid origin of replication as well as the mycolactone gene cluster. A Kanamycin resistance gene was introduced into pMYCO7017 by transposon mutagenesis. A construct, pMYCO7017::TnKm, containing an insertion outside the mycolactone gene cluster, was isolated for further work. Electroduction was used to transfer pMYCO7017:TnKm from its E. coli host into both M. marinum 1218 and a plasmid minus strain of M. fortuitum. One M. marinum and four M. fortuitum transformants were verified by PCR analysis. Lipids were extracted from the transformants, and then analyzed by TLC and cytotoxicity assay, but results were inconclusive. However, when lipid extracts were analyzed by mass spectrometry and HPLC, a novel molecule was discovered indicating that one transformant, M. fortuitum 10394.6 (pMYCO7017::TnKm) was able to produce the mycolactone core. This work is the first example of heterologous expression of an M. ulcerans mycolactone PKS genes. Importantly, the gene cluster contained on pMYCO7017::TnKm is expressed. These results further suggest that the requirements for synthesis of the mycolactone core differ from those for the side-chain

Arquitectura para Acceso Remoto

En la actualidad, la utilización de fuentes de datos compartidas facilita el trabajo en equipo. Por este motivo las organizaciones implementan en sus locaciones sistemas con controles de acceso para compartir los datos de acuerdo a los privilegios de los usuarios. Nuevas formas de trabajo son la distribución de los miembros de un equipo en distintos lugares físicos, el trabajo desde las casas de los empleados, el traslado temporal a otra locación. Por todas estas razones, acceder a los datos en forma remota es una necesidad en crecimiento. Una respuesta a esta necesidad es la propuesta de una arquitectura referente en capas ICSAD (Interfaz, Control y Sistemas de Archivos Distribuidos). La misma permite construir una implementación que facilita la descarga de los documentos y el control de versionado para el caso en el que varios usuarios estén accediendo en modo modificación. En el laboratorio de sistemas distribuidos comenzamos a trabajar en la implementación de la arquitectura propuesta.Eje: Procesamiento Distribuido y ParaleloRed de Universidades con Carreras en Informática (RedUNCI

Arquitectura para Acceso Remoto

En la actualidad, la utilización de fuentes de datos compartidas facilita el trabajo en equipo. Por este motivo las organizaciones implementan en sus locaciones sistemas con controles de acceso para compartir los datos de acuerdo a los privilegios de los usuarios. Nuevas formas de trabajo son la distribución de los miembros de un equipo en distintos lugares físicos, el trabajo desde las casas de los empleados, el traslado temporal a otra locación. Por todas estas razones, acceder a los datos en forma remota es una necesidad en crecimiento. Una respuesta a esta necesidad es la propuesta de una arquitectura referente en capas ICSAD (Interfaz, Control y Sistemas de Archivos Distribuidos). La misma permite construir una implementación que facilita la descarga de los documentos y el control de versionado para el caso en el que varios usuarios estén accediendo en modo modificación. En el laboratorio de sistemas distribuidos comenzamos a trabajar en la implementación de la arquitectura propuesta.Eje: Procesamiento Distribuido y ParaleloRed de Universidades con Carreras en Informática (RedUNCI