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1.
The impact of high‐order epistasis in the within‐host fitness of a positive‐sense plant RNA virus 下载免费PDF全文
RNA viruses are the main source of emerging infectious diseases because of the evolutionary potential bestowed by their fast replication, large population sizes and high mutation and recombination rates. However, an equally important property, which is usually neglected, is the topography of the fitness landscape. How many fitness maxima exist and how well they are connected is especially interesting, as this determines the number of accessible evolutionary pathways. To address this question, we have reconstructed a region of the fitness landscape of tobacco etch potyvirus constituted by mutations observed during the experimental adaptation of the virus to the novel host Arabidopsis thaliana. Fitness was measured for many genotypes and showed the existence of multiple peaks and holes in the landscape. We found prevailing epistatic effects between mutations, with cases of reciprocal sign epistasis being common among pairs of mutations. We also found that high‐order epistasis was as important as pairwise epistasis in their contribution to fitness. Therefore, results suggest that the landscape was rugged due to the existence of holes caused by lethal genotypes, that a very limited number of potential neutral paths exist and that it contained a single adaptive peak. 相似文献
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Jing Guo Hongjuan He Qi Liu Fengwei Zhang Jie Lv Tiebo Zeng Ning Gu Qiong Wu 《Molecules and cells》2015,38(10):859-865
Most imprinted genes are concerned with embryonic development, especially placental development. Here, we identified a placenta-specific imprinted gene Qpct. Our results show that Qpct is widely expressed during early embryonic development and can be detected in the telecephalon, midbrain, and rhombencephalon at E9.5–E11.5. Moreover, Qpct is strikingly expressed in the brain, lung and liver in E15.5. Expression signals for Qpct achieved a peak at E15.5 during placental development and were only detected in the labyrinth layer in E15.5 placenta. ChIP assay results suggest that the modification of histone H3K4me3 can result in maternal activating of Qpct. 相似文献
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Nicole E. Pedersen Clinton B. Edwards Yoan Eynaud Arthur C. R. Gleason Jennifer E. Smith Stuart A. Sandin 《Ecography》2019,42(10):1703-1713
Population distributions are affected by a variety of spatial processes, including dispersal, intraspecific dynamics and habitat selection. Within reef‐building coral communities, these processes are especially important during the earliest life stages when reproduction provides mobility among sessile organisms and populations experience the greatest mortality bottlenecks both before and immediately after settlement. Here, we used large‐area imaging to create photomosaics that allowed us to identify and map the location of 4681 juvenile (1–5 cm diameter) and 25 902 adult (>5 cm diameter) coral colonies from eight 100‐m2 plots across the forereef of Palmyra Atoll. Using metrics of density, percent cover and the relative location of each colony within each plot, we examined abundance and spatial relationships between juvenile and adult coral taxa. Within coral taxa, juvenile density was generally positively related to the numerical density and percent cover of adults. Nearest neighbor analyses showed aggregation of juveniles near adults of the same taxon for two of the focal taxa (Pocillopora and Fungiids), while all other taxa showed random spatial patterning relative to adults. Three taxa had clustered distributions of juveniles overall. Additionally, we found that on a colony level, juveniles for five of nine focal taxa (accounting for >98% of all identified juveniles) associated with a specific habitat type, with four of those five taxa favoring unconsolidated (e.g. rubble) over consolidated substrata. The general lack of clustering in juvenile corals contrasts with consistent clustering patterns seen in adult corals, suggesting that adult spatial patterns are largely driven by processes occurring after maturity such as partial colony mortality, including fission and fragmentation. The association of many taxa with unconsolidated habitat also suggests that corals may play an important role in colonizing natural rubble patches that could contribute to reef stabilization over time. 相似文献
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Rheumatoid arthritis (RA) is a chronic autoimmune systemic inflammatory disease that is characterized by synovial inflammation and bone erosion. We have investigated the mechanism(s) by which essential trace metals may initiate and propagate inflammatory phenotypes in synovial fibroblasts. We used HIG-82, rabbit fibroblast-like synovial cells (FLS), as a model system for potentially initiating RA through oxidative stress. We used potassium peroxychromate (PPC, Cr+5), ferrous chloride (FeCl2, Fe+2), and cuprous chloride (CuCl, Cu+) trace metal agents as exogenous pro-oxidants. Intracellular ROS was quantified by fluorescence microscopy and confirmed by flow cytometry (FC). Protein expression levels were measured by western blot and FC, while ELISA was used to quantify the levels of cytokines. Trace metal agents in different valence states acted as exogenous pro-oxidants that generate reactive oxygen species (ROS), which signal through TLR4 stimulation. ROS/TLR4- coupled activation resulted in the release of HMGB1, TNF-α, IL-1β, and IL-10 in conjunction with upregulation of myeloid-related protein (MRP8/14) inflammatory markers that may contribute to the RA pathophysiology. Our results indicate that oxidant-induced TLR4 activation can release HMGB1 in combination with other inflammatory cytokines to mediate pro-inflammatory actions that contribute to RA pathogenesis. The pathway by which inflammatory and tissue erosive changes may occur in this model system possibly underlies the need for functioning anti-HMGB1-releasing agents and antioxidants that possess both dual trace metal chelating and oxidant scavenging properties in a directed combinatorial therapy for RA. 相似文献
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Patterns generated from ecological surveys are rarely tested in similar habitats to assess the accuracy of predictions. Testing empirically derived predictions provides a strong tool for establishing the consistency of general patterns in ecology. We test the consistency of beetle community associations with habitat complexity in open canopy forests and make both community and morphospecies-level comparisons with results from a previous study. We use Normalized Difference Vegetation Indices (NDVIs) from remote sensing as a surrogate for habitat complexity. The positive relationships between NDVIs and site-based beetle species richness and abundance were consistent in open canopy forests both south and north of Sydney, Australia. NDVIs were also useful for predicting differences in beetle composition in open canopy forests. Taxon-specific responses to NDVI differences in 'southern forests' were very similar to responses in 'northern forests', most likely reflecting beetle trophic roles. This study shows that NDVIs can be used as rapid biodiversity indicators, when integrated with identified faunal responses to vegetation structure, provided that the lower vegetation strata may be measured by remote sensing. 相似文献
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Vegetation,fire and soil feedbacks of dynamic boundaries between rainforest,savanna and grassland 下载免费PDF全文
Harry J. MacDermott Roderick J. Fensham Quan Hua David M. J. S. Bowman 《Austral ecology》2017,42(2):154-164
At fine spatial scales, savanna‐rainforest‐grassland boundary dynamics are thought to be mediated by the interplay between fire, vegetation and soil feedbacks. These processes were investigated by quantifying tree species composition, the light environment, quantities and flammability of fuels, bark thickness, and soil conditions across stable and dynamic rainforest boundaries that adjoin grassland and eucalypt savanna in the highlands of the Bunya Mountains, southeast Queensland, Australia. The size class distribution of savanna and rainforest stems was indicative of the encroachment of rainforest species into savanna and grassland. Increasing dominance of rainforest trees corresponds to an increase in woody canopy cover, the dominance of litter fuels (woody debris and leaf), and decline in grass occurrence. There is marked difference in litter and grass fuel flammability and this result is largely an influence of strongly dissimilar fuel bulk densities. Relative bark thickness, a measure of stem fire resistance, was found to be generally greater in savanna species when compared to that of rainforest species, with notable exceptions being the conifers Araucaria bidwillii and Araucaria cunninghamii. A transect study of soil nutrients across one dynamic rainforest – grassland boundary indicated the mass of carbon and nitrogen, but not phosphorus, increased across the successional gradient. Soil carbon turnover time is shortest in stable rainforest, intermediate in dynamic rainforest and longest in grassland highlighting nutrient cycling differentiation. We conclude that the general absence of fire in the Bunya Mountains, due to a divergence from traditional Aboriginal burning practices, has allowed for the encroachment of fire‐sensitive rainforest species into the flammable biomes of this landscape. Rainforest invasion is likely to have reduced fire risk via changes to fuel composition and microclimatic conditions, and this feedback will be reinforced by altered nutrient cycling. The mechanics of the feedbacks here identified are discussed in terms of landscape change theory. 相似文献
10.
城市森林景观格局与过程研究进展 总被引:14,自引:1,他引:13
大规模的城市化进程,改变了城市以及周边区域的景观格局,显著影响着城市森林生态系统的结构、过程与功能.景观尺度上的城市森林景观格局与生态过程研究已经成为当前城市森林学的研究热点.在阐明城市森林及其景观格局与过程概念的基础上,综述了国内外城市森林景观格局与过程的研究内容、研究方法的进展情况,指出了以下几个方面有望成为今后城市森林景观研究的发展方向:景观尺度上的城市森林系统能流、物质循环等生态学过程研究;城市森林景观格局演变的社会驱动力研究;基于生态服务功能的城市森林规划研究;半都市化地区的森林景观格局与过程研究;基于空间显式景观模型的城市森林景观格局与过程模块开发. 相似文献