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101.
We sequenced a portion ( c . 475 bp) of the mitochondrial control region of three species of Antarctic phocid carnivores (Weddell seal, Leptonychotes weddellii , N = 181; crabeater seal, Lobodon carcinophaga , N = 143; and Ross seal, Ommatophoca rossii , N = 41) that live seasonally or permanently in the fast ice and seasonal pack ice of the western Amundsen and Ross seas of western Antarctica. We resolved 251 haplotypes with a haplotype diversity of 0.98 to 0.99. Bayesian estimates of Θ from the program LAMARC ranged from 0.075 for Weddell seals to 0.576 for crabeater seals. We used the values of theta to estimate female effective population sizes ( NEF ), which were 40 700 to 63 000 for Weddell seals, 44 400 to 97 800 for Ross seals, and 358 500 to 531 900 for crabeater seals. We used mismatch distributions to test for historical population size expansions. Weddell seals and crabeater seals had significant, unimodal mean pairwise difference distributions ( P = 0.56 and 0.36, respectively), suggesting that their populations expanded suddenly around 731 000 years ago (Weddell seals) and around 1.6 million years ago (crabeater seals). Both of these expansions occurred during times of intensified glaciations and may have been fostered by expanding pack ice habitat. 相似文献
102.
The evolutionary analysis of the Tnt1 retrotransposon in Nicotiana species reveals the high variability of its regulatory sequences 总被引:2,自引:0,他引:2
We studied the evolution of the tobacco Tnt1 retrotransposon by analyzing
Tnt1 partial sequences containing both coding domains and U3 regulatory
sequences obtained from a number of Nicotiana species. We detected three
different subfamilies of Tnt1 elements, Tnt1A, Tnt1B, and Tnt1C, that
differ completely in their U3 regions but share conserved flanking coding
and LTR regions. U3 divergence between the three subfamilies is found in
the region that contains the regulatory sequences that control the
expression of the well-characterized Tnt1-94 element. This suggests that
expression of the three Tnt1 subfamilies might be differently regulated.
The three Tnt1 subfamilies were present in the Nicotiana genome at the time
of species divergence, but have evolved independently since then in the
different genomes. Each Tnt1 subfamily seems to have conserved its ability
to transpose in a limited and different number of Nicotiana species. Our
results illustrate the high variability of Tnt1 regulatory sequences. We
propose that this high sequence variability could allow these elements to
evolve regulatory mechanisms in order to optimize their coexistence with
their host genome.
相似文献
103.
Hydrological and biogeochemical controls on the timing and magnitude of nitrous oxide flux across an agricultural landscape 总被引:4,自引:0,他引:4
MICHAEL J. CASTELLANO JOHN P. SCHMIDT JASON P. KAYE CHARLES WALKER CHRIS B. GRAHAM HENRY LIN CURTIS J. DELL 《Global Change Biology》2010,16(10):2711-2720
Anticipated increases in precipitation intensity due to climate change may affect hydrological controls on soil N2O fluxes, resulting in a feedback between climate change and soil greenhouse gas emissions. We evaluated soil hydrologic controls on N2O emissions during experimental water table fluctuations in large, intact soil columns amended with 100 kg ha?1 KNO3‐N. Soil columns were collected from three landscape positions that vary in hydrological and biogeochemical properties (N= 12 columns). We flooded columns from bottom to surface to simulate water table fluctuations that are typical for this site, and expected to increase given future climate change scenarios. After the soil was saturated to the surface, we allowed the columns to drain freely while monitoring volumetric soil water content, matric potential and N2O emissions over 96 h. Across all landscape positions and replicate soil columns, there was a positive linear relationship between total soil N and the log of cumulative N2O emissions (r2= 0.47; P= 0.013). Within individual soil columns, N2O flux was a Gaussian function of water‐filled pore space (WFPS) during drainage (mean r2= 0.90). However, instantaneous maximum N2O flux rates did not occur at a consistent WFPS, ranging from 63% to 98% WFPS across landscape positions and replicate soil columns. In contrast, instantaneous maximum N2O flux rates occurred within a narrow range (?1.88 to ?4.48 kPa) of soil matric potential that approximated field capacity. The relatively consistent relationship between maximum N2O flux rates and matric potential indicates that water filled pore size is an important factor affecting soil N2O fluxes. These data demonstrate that matric potential is the strongest predictor of the timing of N2O fluxes across soils that differ in texture, structure and bulk density. 相似文献
104.
BETH GARDNER J. ANDREW ROYLE MICHAEL T. WEGAN RAYMOND E. RAINBOLT PAUL D. CURTIS 《The Journal of wildlife management》2010,74(2):318-325
ABSTRACT DNA-based mark-recapture has become a methodological cornerstone of research focused on bear species. The objective of such studies is often to estimate population size; however, doing so is frequently complicated by movement of individual bears. Movement affects the probability of detection and the assumption of closure of the population required in most models. To mitigate the bias caused by movement of individuals, population size and density estimates are often adjusted using ad hoc methods, including buffering the minimum polygon of the trapping array. We used a hierarchical, spatial capture-recapture model that contains explicit components for the spatial-point process that governs the distribution of individuals and their exposure to (via movement), and detection by, traps. We modeled detection probability as a function of each individual's distance to the trap and an indicator variable for previous capture to account for possible behavioral responses. We applied our model to a 2006 hair-snare study of a black bear (Ursus americanus) population in northern New York, USA. Based on the microsatellite marker analysis of collected hair samples, 47 individuals were identified. We estimated mean density at 0.20 bears/km2. A positive estimate of the indicator variable suggests that bears are attracted to baited sites; therefore, including a trap-dependence covariate is important when using bait to attract individuals. Bayesian analysis of the model was implemented in WinBUGS, and we provide the model specification. The model can be applied to any spatially organized trapping array (hair snares, camera traps, mist nests, etc.) to estimate density and can also account for heterogeneity and covariate information at the trap or individual level. 相似文献
105.
Background
The leukocyte common antigen related receptor (LAR) protein has been shown to modulate the signal transduction of a number of different growth factors, including insulin and insulin-like growth factor 1. Splice variants exhibit differing roles and are expressed according to tissue type and developmental stage. 相似文献106.
SHAILAJA RABINDRAN † CECILE ROBERTSON DIANN ACHOR SYLVIE GERMAN-RETANA ‡ CURTIS A. HOLT § WILLIAM O. DAWSON 《Molecular Plant Pathology》2005,6(4):439-447
The experimental host range of Odontoglossum ringspot virus (ORSV), a member of the tobamoviruses, includes several species of Nicotiana , but not N. sylvestris . However, ORSV was able to replicate in protoplasts from N. sylvestris leaves. By using the green fluorescent protein (GFP) as a marker inserted into ORSV, it was found that a small number of single epidermal cells became infected in mechanically inoculated leaves, but the virus did not move cell to cell. The ORSV movement protein (MP) and coat protein (CP) were examined for their ability to effect movement by substitution into Tobacco mosaic virus (TMV) hybrids. Both proteins and the 3' non-translated region (NTR) of ORSV allowed movement of TMV hybrids in N. sylvestris . These results suggested that the inability of ORSV to move in N. sylvestris was due to the replicase gene or the 5'NTR. One possibility was that the replicase gene could indirectly affect movement by failing to produce subgenomic (sg) RNAs for expression of MP or CP, but this appeared not to be the case as ORSV replicated and produced MP and CP sgRNAs, both of which were translated in N. sylvestris protoplasts. Additionally, genomic RNA was encapsidated into virions in N. sylvestris protoplasts. Because the 5'NTR permitted efficient replication and production of replicase proteins, these findings suggest that the replicase of ORSV is responsible for the defect in cell-to-cell movement of ORSV in N. sylvestris . 相似文献
107.
Juan Hou Anita M Charters Sam C Lee Yongjun Zhao Mona K Wu Steven JM Jones Marco A Marra Pamela A Hoodless 《BMC developmental biology》2007,7(1):92
Background
The embryonic definitive endoderm (DE) gives rise to organs of the gastrointestinal and respiratory tract including the liver, pancreas and epithelia of the lung and colon. Understanding how DE progenitor cells generate these tissues is critical to understanding the cause of visceral organ disorders and cancers, and will ultimately lead to novel therapies including tissue and organ regeneration. However, investigation into the molecular mechanisms of DE differentiation has been hindered by the lack of early DE-specific markers. 相似文献108.
109.
Erik JM Toonen Pilar Barrera Jaap Fransen Arjan PM de Brouwer Agnes M Eijsbouts Pierre Miossec Hubert Marotte Hans Scheffer Piet LCM van Riel Barbara Franke Marieke JH Coenen 《Arthritis research & therapy》2012,14(6):R264
Introduction
The goal of this study is to investigate whether the -308G > A promoter polymorphism in the tumor necrosis factor alpha (TNFA) gene is associated with disease severity and radiologic joint damage in a large cohort of patients with rheumatoid arthritis (RA).Methods
A long-term observational early RA inception cohort (n = 208) with detailed information about disease activity and radiologic damage after 3, 6 and 9 years of disease was genotyped for the TNFA -308G > A promoter polymorphism (rs1800629). A longitudinal regression analysis was performed to assess the effect of genotype on RA disease severity and joint damage. Subsequently, a meta-analysis, including all publically available data, was performed to further test the association between joint erosions and the TNFA polymorphism. To learn more about the mechanism behind the effect of the polymorphism, RNA isolated from peripheral blood from RA patients (n = 66) was used for TNFA gene expression analysis by quantitative PCR.Results
Longitudinal regression analysis with correction for gender and disease activity showed a significant difference in total joint damage between GG and GA+AA genotype groups (P = 0.002), which was stable over time. The meta-analysis, which included 2,053 patients, confirmed an association of the genetic variant with the development of erosions (odds ratio 0.78, 95% CI 0.62, 0.98). No significant differences in TNFA gene expression were observed for the different genotypes, confirming earlier findings in healthy individuals.Conclusions
Our data confirm that the TNFA -308G > A promoter polymorphism is associated with joint damage in patients with RA. This is not mediated by differences in TNFA gene expression between genotypes. 相似文献110.
Rick Brouwer Wilma TM Vree Egberts Gerald JD Hengstman Reinout Raijmakers Baziel GM van Engelen Hans Peter Seelig Manfred Renz Rudolf Mierau Ekkehard Genth Ger JM Pruijn Walther J van Venrooij 《Arthritis research & therapy》2001,4(2):1-5
The autoantigenic polymyositis/scleroderma (PM/Scl) complex was recently shown to be the human homologue of the yeast exosome, which is an RNA-processing complex. Our aim was to assess whether, in addition to targeting the known autoantigens PM/Scl-100 and PM/Scl-75, autoantibodies also target recently identified components of the PM/Scl complex. The prevalence of autoantibodies directed to six novel human exosome components (hRrp4p, hRrp40p, hRrp41p, hRrp42p, hRrp46p, hCsl4p) was determined in sera from patients with idiopathic inflammatory myopathy (n = 48), scleroderma (n = 11), or the PM/Scl overlap syndrome (n = 10). The sera were analyzed by enzyme-linked immunosorbent assays and western blotting using the affinity-purified recombinant proteins. Our results show that each human exosome component is recognized by autoantibodies. The hRrp4p and hRrp42p components were most frequently targeted. The presence of autoantibodies directed to the novel components of the human exosome was correlated with the presence of the anti-PM/Scl-100 autoantibody in the sera of patients with idiopathic inflammatory myopathy (IIM), as was previously found for the anti-PM/Scl-75 autoantibody. Other clear associations between autoantibody activities were not found. These results further support the conception that the autoimmune response may initially be directed to PM/Scl-100, whereas intermolecular epitope spreading may have caused the autoantibody response directed to the associated components. 相似文献