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101.
p82H identifies sequences at every human centromere 总被引:4,自引:3,他引:4
Carmen Aleixandre Dorothy A. Miller Arthur R. Mitchell Dorothy A. Warburton Steven L. Gersen Christine Disteche Orlando J. Miller 《Human genetics》1987,77(1):46-50
Summary A cloned alphoid sequence, p82H, hybridizes in situ to the centromere of every human chromosome. After washing under stringent conditions, no more than 8% of the grains are located on any specific chromosome. p82H thus differs from other centromeric sequences which are reported to be chromosome specific, because it detects sequences that are conserved among the chromosomes. Two experimental approaches show that the p82H sequences are closely associated with the centromere. First, p82H remains with the relocated centromeres in an inv(19) and an inv(6) chromosome. Second, p82H hybridizes at the centromere but not to the centromeric heterochromatin of chromosomes 1, 9 and 16 that have elongated 1qh, 9qh and 16qh regions produced by short growth in 5-azacytidine. The only noncentromeric site of hybridization is at the distal end of the 9qh region. 相似文献
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Fabrícia F. Nascimento Ana Lazar Albert N. Menezes Andressa da Matta Durans Janio C. Moreira Jorge Salazar-Bravo Paulo S. D′Andrea Cibele R. Bonvicino 《PloS one》2013,8(4)
The Neotropics harbors a high diversity of species and several hypotheses have been proposed to account for this pattern. However, while species of forested domains are frequently studied, less is known of species from open vegetation formations occupying, altogether, a larger area than the Amazon Forest. Here we evaluate the role of historical barriers and the riverine hypothesis in the speciation patterns of small mammals by analyzing an ancient rodent lineage (Thrichomys, Hystricomorpha). Phylogenetic and biogeographic analyses were carried out with mitochondrial and nuclear DNA markers to analyze the evolutionary relationships between Thrichomys lineages occurring in dry domains along both banks of the Rio São Francisco. This river is one of the longest of South America whose course and water flow have been modified by inland tectonic activities and climate changes. Molecular data showed a higher number of lineages than previously described. The T. inermis species complex with 2n = 26, FN = 48 was observed in both banks of the river showing a paraphyletic arrangement, suggesting that river crossing had occurred, from east to west. A similar pattern was also observed for the T. apereoides complex. Thrichomys speciation occurred in Late Miocene when the river followed a different course. The current geographic distribution of Thrichomys species and their phylogenetic relationships suggested the existence of frequent past connections between both banks in the middle section of the Rio São Francisco. The extensive palaeodune region found in this area has been identified as a centre of endemism of several vertebrate species and is likely to be a center of Thrichomys diversification. 相似文献
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Gregory A. O'Neill Ian Dawson Carmen Sotelo-Montes Luigi Guarino Manuel Guariguata Dean Current John C. Weber 《Biodiversity and Conservation》2001,10(6):837-850
Forestry practices and high rates of land clearance for agriculture are causing genetic erosion of valuable tree species in the Peruvian Amazon, thereby endangering the economic sustainability of rural communities and limiting Peru's opportunities for the development of new timber and non-timber forest products. The potential utility and limitations of six low-input interventions to help forestall further genetic erosion in the region are discussed, with a focus on local community involvement. Improved agroforestry systems may help reduce deforestation by increasing farm productivity, although methods to increase the currently low adoption rate of these technologies need to be developed. Use of strategic tree domestication techniques can also improve farm productivity and prevent inadvertent genetic drift and inbreeding associated with traditional domestication practices, although to have a major impact, current programs need to be extended across the region. Woodlot forestry could supplant selective extraction of timber and offers an attractive opportunity for poverty alleviation if appropriate credit and land tenure policies can be developed. However, it may also result in increased deforestation if activities on public land cannot be controlled. The implementation of improved seed collection systems and simple seed transfer guidelines would help to reduce the collection of seed of poor quality and low genetic diversity, and avoid maladapted plantings, although such programs are difficult to monitor and seed costs may increase. Strategic identification and design of in situ conservation areas would help to ensure the viability of conserved populations, but requires the forfeiture of significant revenue from timber concessions. 相似文献
106.
Navascués J Pérez-Rontomé C Sánchez DH Staudinger C Wienkoop S Rellán-Álvarez R Becana M 《The New phytologist》2012,193(3):625-636
? Aluminum (Al) toxicity is a major limiting factor of crop production on acid soils, but the implication of oxidative stress in this process is controversial. A multidisciplinary approach was used here to address this question in the forage legume Lotus corniculatus. ? Plants were treated with low Al concentrations in hydroponic culture, and physiological and biochemical parameters, together with semiquantitative metabolic and proteomic profiles, were determined. ? The exposure of plants to 10 μM Al inhibited root and leaf growth, but had no effect on the production of reactive oxygen species or lipid peroxides. By contrast, exposure to 20 μM Al elicited the production of superoxide radicals, peroxide and malondialdehyde. In response to Al, there was a progressive replacement of the superoxide dismutase isoforms in the cytosol, a loss of ascorbate and consistent changes in amino acids, sugars and associated enzymes. ? We conclude that oxidative stress is not a causative factor of Al toxicity. The increased contents in roots of two powerful Al chelators, malic and 2-isopropylmalic acids, together with the induction of an Al-activated malate transporter gene, strongly suggest that both organic acids are implicated in Al detoxification. The effects of Al on key proteins involved in cytoskeleton dynamics, protein turnover, transport, methylation reactions, redox control and stress responses underscore a metabolic dysfunction, which affects multiple cellular compartments, particularly in plants exposed to 20 μM Al. 相似文献
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Yeast cells expressing the Glu418Lys human topoisomerase I mutant display a camptothecin resistance that slowly decreases as a function of time. Molecular characterization of the single steps of the catalytic cycle of the purified mutant indicates that it has a relaxation activity identical to the wild-type protein but a different DNA sequence specificity for the cleavage sites when compared to the wild-type enzyme, as assayed on several substrates. In particular the mutant has a low specificity for CPT sensitive cleavable sites. In fact, the mutant has, at variance of the wild-type enzyme, a reduced preference for cleavage sites having a thymine base in position −1 of the scissile strand. This preference, together with the strict requirement for a thymine base in position −1 for an efficient camptothecin binding, explains the temporary camptothecin resistance of the yeast cell expressing the mutant and points out the importance of the DNA sequence in the binding of the camptothecin drug. 相似文献
109.
The modulation of apoptosis has emerged as an important weapon in the pathogenic arsenal of multiple intracellular protozoan parasites. Cryptosporidium parvum, Leishmania spp., Trypanosoma cruzi, Theileria spp., Toxoplasma gondii and Plasmodium spp. have all been shown to inhibit the apoptotic response of their host cell. While the pathogen mediators responsible for this modulation are unknown, the parasites are interacting with multiple apoptotic regulatory systems to render their host cell refractory to apoptosis during critical phases of intracellular infection, including parasite invasion, establishment and replication. Additionally, emerging evidence suggests that the parasite life cycle stage impacts the modulation of apoptosis and possibly parasite differentiation. Dissection of the host-pathogen interactions involved in modulating apoptosis reveals a dynamic and complex interaction that recent studies are beginning to unravel. 相似文献
110.
S-nitrosoglutathione reductase affords protection against pathogens in Arabidopsis, both locally and systemically 下载免费PDF全文
Nitric oxide and S-nitrosothiols (SNOs) are widespread signaling molecules that regulate immunity in animals and plants. Levels of SNOs in vivo are controlled by nitric oxide synthesis (which in plants is achieved by different routes) and by S-nitrosoglutathione turnover, which is mainly performed by the S-nitrosoglutathione reductase (GSNOR). GSNOR is encoded by a single-copy gene in Arabidopsis (Arabidopsis thaliana; Martínez et al., 1996; Sakamoto et al., 2002). We report here that transgenic plants with decreased amounts of GSNOR (using antisense strategy) show enhanced basal resistance against Peronospora parasitica Noco2 (oomycete), which correlates with higher levels of intracellular SNOs and constitutive activation of the pathogenesis-related gene, PR-1. Moreover, systemic acquired resistance is impaired in plants overexpressing GSNOR and enhanced in the antisense plants, and this correlates with changes in the SNO content both in local and systemic leaves. We also show that GSNOR is localized in the phloem and, thus, could regulate systemic acquired resistance signal transport through the vascular system. Our data corroborate the data from other authors that GSNOR controls SNO in vivo levels, and shows that SNO content positively influences plant basal resistance and resistance-gene-mediated resistance as well. These data highlight GSNOR as an important and widely utilized component of resistance protein signaling networks conserved in animals and plants. 相似文献