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31.
Ivan Laprevotte Sophie Brouillet Christophe Terzian Alain Hénaut 《Journal of molecular evolution》1997,44(2):214-225
A computer-assisted analysis was made of 24 complete nucleotide sequences selected from the vertebrate retroviruses to represent
the ten viral groups. The conclusions of this analysis extend and strengthen the previously made hypothesis on the Moloney
murine leukemia virus: The evolution of the nucleotide sequence appears to have occurred mainly through at least three overlapping
levels of duplication: (1) The distributions of overrepresented (3–6)-mers are consistent with the universal rule of a trend
toward TG/CT excess and with the persistence of a certain degree of symmetry between the two strands of DNA. This suggests
one or several original tandemly repeated sequences and some inverted duplications. (2) The existence of two general core
consensuses at the level of these (3–6)-mers supports the hypothesis of a common evolutionary origin of vertebrate retroviruses.
Consensuses more specific to certain sequences are compatible with phylogenetic trees established independently. The consensuses
could correspond to intermediary evolutionary stages. (3) Most of the (3–6)-mers with a significantly higher than average
frequency appear to be internally repeated (with monomeric or oligomeric internal iterations) and seem to be at least partly
the cause of the bias observed by other researchers at the level of retroviral nucleotide composition. They suggest a third
evolutionary stage by slippage-like stepwise local duplications.
Received: 3 January 1996 / Accepted: 27 March 1996 相似文献
32.
Erik Ziegler Ariane Foret Laura Mascetti Vincenzo Muto Anahita Le Bourdiec-Shaffii Johan Stender Evelyne Balteau Vinciane Dideberg Vincent Bours Pierre Maquet Christophe Phillips 《PloS one》2013,8(7)
Brain-derived neurotrophic factor (BDNF) modulates the pruning of synaptically silent axonal arbors. The Met allele of the BDNF gene is associated with a reduction in the neurotrophin''s activity-dependent release. We used diffusion-weighted imaging to construct structural brain networks for 36 healthy subjects with known BDNF genotypes. Through permutation testing we discovered clear differences in connection strength between subjects carrying the Met allele and those homozygotic for the Val allele. We trained a Gaussian process classifier capable of identifying the subjects'' allelic group with 86% accuracy and high predictive value. In Met carriers structural connectivity was greatly increased throughout the forebrain, particularly in connections corresponding to the anterior and superior corona radiata as well as corticothalamic and corticospinal projections from the sensorimotor, premotor, and prefrontal portions of the internal capsule. Interhemispheric connectivity was also increased via the corpus callosum and anterior commissure, and extremely high connectivity values were found between inferior medial frontal polar regions via the anterior forceps. We propose that the decreased availability of BDNF leads to deficits in axonal maintenance in carriers of the Met allele, and that this produces mesoscale changes in white matter architecture. 相似文献
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Moreau D Burstin J Aubert G Huguet T Ben C Prosperi JM Salon C Munier-Jolain N 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2012,124(4):755-768
Medicago truncatula is used as a model plant for exploring the genetic and molecular determinants of nitrogen (N) nutrition in legumes. In this
study, our aim was to detect quantitative trait loci (QTL) controlling plant N nutrition using a simple framework of carbon/N
plant functioning stemming from crop physiology. This framework was based on efficiency variables which delineated the plant’s
efficiency to take up and process carbon and N resources. A recombinant inbred line population (LR4) was grown in a glasshouse
experiment under two contrasting nitrate concentrations. At low nitrate, symbiotic N2 fixation was the main N source for plant growth and a QTL with a large effect located on linkage group (LG) 8 affected all
the traits. Significantly, efficiency variables were necessary both to precisely localize a second QTL on LG5 and to detect
a third QTL involved in epistatic interactions on LG2. At high nitrate, nitrate assimilation was the main N source and a larger
number of QTL with weaker effects were identified compared to low nitrate. Only two QTL were common to both nitrate treatments:
a QTL of belowground biomass located at the bottom of LG3 and another one on LG6 related to three different variables (leaf
area, specific N uptake and aboveground:belowground biomass ratio). Possible functions of several candidate genes underlying
QTL of efficiency variables could be proposed. Altogether, our results provided new insights into the genetic control of N
nutrition in M. truncatula. For instance, a novel result for M. truncatula was identification of two epistatic interactions in controlling plant N2 fixation. As such this study showed the value of a simple conceptual framework based on efficiency variables for studying
genetic determinants of complex traits and particularly epistatic interactions. 相似文献
38.
Funamoto S Anjard C Nellen W Ochiai H 《Differentiation; research in biological diversity》2003,71(1):51-61
In eukaryotic cells, the universal second messenger cAMP regulates various aspects of development and differentiation. The primary target for cAMP is the regulatory subunit of cAMP-dependent protein kinase A (PKA), which, upon cAMP binding, dissociates from the catalytic subunit and thus activates it. In the soil amoeba Dictyostelium discoideum, the function of PKA in growth, development and cell differentiation has been thoroughly investigated and substantial information is available. To obtain a more general view, we investigated the influence of PKA on development of the related species Polysphondylium pallidum. Cells were transformed to overexpress either a dominant negative mutant of the regulatory subunit (Rm) from Dictyostelium that cannot bind cAMP, or the catalytic subunit (PKA-C) from Dictyostelium. Cells overexpressing Rm rarely aggregated and the few multicellular structures developed slowly into very small fruiting bodies without branching of secondary sorogens, the prominent feature of Polysphondylium. Few round spores with reduced viability were formed. When mixed with wild-type cells and allowed to develop, the Rm cells were randomly distributed in aggregation streams, but were later found in the posterior region of the culminating slug or were left behind on the surface of the substratum. The PKA-C overexpressing cells exhibited precocious development and formed more aggregates of smaller size. Moreover, expression of PKA-C under the control of the prestalk-specific ecmB promoter of Dictyostelium leads to protrusions from aggregation streams. We conclude that Dictyostelium PKA subunits introduced into Polysphondylium cells are functional as signal components, indicating that a biochemically similar PKA mechanism works in Polysphondylium. 相似文献
39.
Lucie Guetzoyan Xiao-Min Yu Florence Ramiandrasoa Stéphanie Pethe Christophe Rogier Bruno Pradines Thierry Cresteil Martine Perrée-Fauvet Jean-Pierre Mahy 《Bioorganic & medicinal chemistry》2009,17(23):8032-8039
A series of acridine derivatives were synthesised and their in vitro antimalarial activity was evaluated against one chloroquine-susceptible strain (3D7) and three chloroquine-resistant strains (W2, Bre1 and FCR3) of Plasmodium falciparum. Structure–activity relationship showed that two positives charges as well as 6-chloro and 2-methoxy substituents on the acridine ring were required to exert a good antimalarial activity. The best compounds possessing these features inhibited the growth of the chloroquine-susceptible strain with an IC50 ? 0.07 μM, close to that of chloroquine itself, and that of the three chloroquine-resistant strains better than chloroquine with IC50 ? 0.3 μM. These acridine derivatives inhibited the formation of β-hematin, suggesting that, like CQ, they act on the haem crystallization process. Finally, in vitro cytotoxicity was also evaluated upon human KB cells, which showed that one of them 9-(6-ammonioethylamino)-6-chloro-2-methoxyacridinium dichloride 1 displayed a promising antimalarial activity in vitro with a quite good selectivity index versus mammalian cell on the CQ-susceptible strain and promising selectivity on other strains. 相似文献
40.