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861.
Newton Medeiros Vidal Adriana Ludwig Elgion Lucio Silva Loreto 《Molecular genetics and genomics : MGG》2009,282(4):351-362
LTR retrotransposons are the most abundant transposable elements in Drosophila and are believed to have contributed significantly to genome evolution. Different reports have shown that many LTR retrotransposon
families in Drosophila melanogaster emerged from recent evolutionary episodes of transpositional activity. To contribute to the knowledge of the evolutionary
history of Drosophila LTR retrotransposons and the mechanisms that control their abundance, distribution and diversity, we conducted analyses of
four related families of LTR retrotransposons, 297, 17.6, rover and Tom. Our results show that these elements seem to be restricted to species from the D. melanogaster group, except for 17.6, which is also present in D. virilis and D. mojavensis. Genetic divergences and phylogenetic analyses of a 1-kb fragment region of the pol gene illustrate that the evolutionary dynamics of Tom, 297, 17.6 and rover retrotransposons are similar in several aspects, such as low codon bias, the action of purifying selection and phylogenies
that are incongruent with those of the host species. We found an extremely complex association among the retrotransposon sequences,
indicating that different processes shaped the evolutionary history of these elements, and we detected a very high number
of possible horizontal transfer events, corroborating the importance of lateral transmission in the evolution and maintenance
of LTR retrotransposons. 相似文献
862.
863.
Díaz A Carro S Santiago L Estévez J Guevara C Blanco M Sánchez L Sánchez L López N Cruz D López R Cuetara EB Fuentes JL 《Genetics and molecular biology》2009,32(2):367-372
The analysis of DNA damage by mean of Comet or single cell gel electrophoresis (SCGE) assay has been commonly used to assess genotoxic impact in aquatic animals being able to detect exposure to low concentrations of contaminants in a wide range of species. The aims of this work were 1) to evaluate the usefulness of the Comet to detect DNA strand breakage in dolphin leukocytes, 2) to use the DNA diffusion assay to determine the amount of DNA strand breakage associated with apoptosis or necrosis, and 3) to determine the proportion of DNA strand breakage that was unrelated to apoptosis and necrosis. Significant intra-individual variation was observed in all of the estimates of DNA damage. DNA strand breakage was overestimated because a considerable amount (~29%) of the DNA damage was derived from apoptosis and necrosis. The remaining DNA damage in dolphin leukocytes was caused by factors unrelated to apoptosis and necrosis. These results indicate that the DNA diffusion assay is a complementary tool that can be used together with the Comet assay to assess DNA damage in bottlenose dolphins. 相似文献
864.
Angela Pennacchio Luciana Esposito Adriana Zagari Mosè Rossi Carlo A. Raia 《Extremophiles : life under extreme conditions》2009,13(5):751-761
A mutant of the thermostable NAD+-dependent (S)-stereospecific alcohol dehydrogenase from Sulfolobus solfataricus (SsADH) which has a single substitution, Trp95Leu, located at the substrate binding pocket, was fully characterized to ascertain the role of Trp95 in discriminating between chiral secondary alcohols suggested by the wild-type SsADH crystallographic structure. The Trp95Leu mutant displays no apparent activity with short-chain primary and secondary alcohols and poor activity with aromatic substrates and coenzyme. Moreover, the Trp → Leu substitution affects the structural stability of the archaeal ADH, decreasing its thermal stability without relevant changes in secondary structure. The double mutant Trp95Leu/Asn249Tyr was also purified to assist in crystallographic analysis. This mutant exhibits higher activity but decreased affinity toward aliphatic alcohols, aldehydes as well as NAD+ and NADH compared to the wild-type enzyme. The crystal structure of the Trp95Leu/Asn249Tyr mutant apo form, determined at 2.0 Å resolution, reveals a large local rearrangement of the substrate site with dramatic consequences. The Leu95 side-chain conformation points away from the catalytic metal center and the widening of the substrate site is partially counteracted by a concomitant change of Trp117 side chain conformation. Structural changes at the active site are consistent with the reduced activity on substrates and decreased coenzyme binding. 相似文献
865.
Adriana L Alejandro-Osorio Dana J Huebert Dominic T Porcaro Megan E Sonntag Songdet Nillasithanukroh Jessica L Will Audrey P Gasch 《Genome biology》2009,10(5):R57-13
Background
Yeast responding to stress activate a large gene expression program called the Environmental Stress Response that consists of approximately 600 repressed genes and approximately 300 induced genes. Numerous factors are implicated in regulating subsets of Environmental Stress Response genes; however, a complete picture of Environmental Stress Response regulation remains unclear. We investigated the role of the histone deacetylase Rpd3p, previously linked to the upstream regions of many Environmental Stress Response genes, in producing Environmental Stress Response gene expression changes in response to stress. 相似文献866.
867.
868.
Matthew W. Blair Alejandro Chaves Adriana Tofiño Juan Felipe Calderón Juan Diego Palacio 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,120(7):1381-1391
Common bean can be grown as a grain crop (dry beans) or as a fresh vegetable (snap beans/green beans), both items being important
in nutritional terms for providing essential minerals and vitamins to the diet. Snap beans are thought to be derived predominantly
from dry beans of the Andean genepool and to be of a recent European origin; however, the existence of Mesoamerican genepool
characteristics especially in traditional indeterminate growth habit snap beans indicates a wider origin. The objective of
this study was to evaluate genetic diversity within a set of 120 indeterminate (pole type) snap beans and 7 control genotypes
representing each genepool using amplified fragment length polymorphism (AFLP) and simple sequence repeat or microsatellite
(SSR) markers. The genotypes were predominantly from Asia, Europe and the United States but included some varieties from Latin
America and Africa. AFLP polymorphism ranged from 53.2 to 67.7% while SSR polymorphism averaged 95.3% for the 32 fluorescent
and 11 non-fluorescent markers evaluated and total expected heterozygosity was higher for SSR markers (0.521) than for AFLP
markers (0.209). Both marker systems grouped the genotypes into two genepools with Andean and Mesoamerican controls, respectively,
with the Mesoamerican group being predominant in terms of the number of genotypes assigned to this genepool. Phaseolin alleles
were not tightly associated with genepool assignment indicating that introgression of this locus had occurred between the
genepools, especially with phaseolin “S” in the Andean group (23.5%) and phaseolins “T” and “C” in the Mesoamerican group
(12.2 and 8.2%, respectively). The implications of these results on the origin of pole type snap beans and on breeding strategies
for this horticultural crop are discussed. 相似文献
869.
Alessandro Castorina Adriana Tiralongo Salvatore Giunta Maria Luisa Carnazza Giovanni Scapagnini Velia D’Agata 《Cell biology and toxicology》2010,26(4):367-377
Amyloid ß peptide (Aß), generated by proteolytic cleavage of the amyloid precursor protein (APP), plays a pivotal role in the pathogenesis of Alzheimer's disease (AD). The key step in the generation of Aß is cleavage of APP by ß-secretases (beta-site APP-cleaving enzyme 1 (BACE1) and BACE2). There has been suggestion of interaction between aluminum and several AD-associated pathways. However, the underlying mechanisms still remain unclear. Here, we report the effects of aluminum chloride (AlCl3) in Aß-induced toxicity using differentiated neuronal SH-SY5Y cells. The metal significantly enhances Aß-induced cell death at concentrations ranging from 50 to 300 µM after 24 and 48 h. After 72 and 96 h treatment, cell death is increased already at 10 µM. Early coexposure of cells to 10 µM AlCl3 and 2 µM Aß differentially affected ß-secretase mRNA levels as compared to single Aß treatment after 1 and 3 h. BACE1 levels were slightly reduced after 1 h and significantly increased after 3 h exposure, whereas BACE2 levels were increased at both times considered. Both genes’ mRNA levels were downregulated at longer times (6, 12, and 24 h). Although these results indicate that aluminum toxicity is correlated to changes in both BACE1 and BACE2 expression levels, the subsequent common downregulation observed suggests that aluminum involvement in the Aß cascade is subtle, and other underlying mechanisms might be involved. 相似文献
870.
Adriana Silva‐Iturriza Valerio Ketmaier Ralph Tiedemann 《Journal of Zoological Systematics and Evolutionary Research》2010,48(3):269-278
In this study, we have used fragments of three mitochondrial genes (Control Region, CR; transfer RNA for methionine, tRNA‐Met; NADH dehydrogenase subunit 2, ND2 for a total of 1066 bp) to reconstruct the phylogeographic history of the endemic Philippine bulbul (Hypsipetes philippinus) at the scale of the central area of the Philippine archipelago. The study includes two of the five recognized subspecies (guimarasensis and mindorensis), 7 populations and 58 individuals. Multiple phylogenetic and network analyses support the existence of two reciprocally monophyletic maternal lineages corresponding to the two named subspecies. Molecular clock estimates indicate that the split between the two subspecies is consistent with the Pleistocene geological history of the archipelago. Patterns of relationships within guimarasensis are biogeographically less clear. Here, a combination of vicariance and dispersal needs to be invoked to reconcile the molecular data with the geographical origin of samples. In particular, the two islands Boracay and Negros host mitochondrial lineages that do not form monophyletic clusters. Our genetic data suggest multiple independent colonization events for these locations. 相似文献