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1.
Although oxidative stress has been previously described in plants exposed to uranium (U), some uncertainty remains about the role of glutathione and tocopherol availability in the different responsiveness of plants to photo-oxidative damage. Moreover, in most cases, little consideration is given to the role of water transport in shoot heavy metal accumulation. Here, we investigated the effect of uranyl nitrate exposure (50 μM) on PSII and parameters involved in water transport (leaf transpiration and aquaporin gene expression) of Arabidopsis wild type (WT) and mutant plants that are deficient in tocopherol (vte1: null α/γ-tocopherol and vte4: null α-tocopherol) and glutathione biosynthesis (high content: cad1.3 and low content: cad2.1). We show how U exposure induced photosynthetic inhibition that entailed an electron sink/source imbalance that caused PSII photoinhibition in the mutants. The WT was the only line where U did not damage PSII. The increase in energy thermal dissipation observed in all the plants exposed to U did not avoid photo-oxidative damage of mutants. The maintenance of control of glutathione and malondialdehyde contents probed to be target points for the overcoming of photoinhibition in the WT. The relationship between leaf U content and leaf transpiration confirmed the relevance of water transport in heavy metals partitioning and accumulation in leaves, with the consequent implication of susceptibility to oxidative stress.  相似文献   
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Cotyledonary somatic embryos (SEs) of maritime pine are routinely matured for 12 weeks before being germinated and converted to plantlets. Although regeneration success is highly dependent on SEs quality, the date of harvesting is currently determined mainly on the basis of morphological features. This empirical method does not provide any accurate information about embryo quality with respect to storage compounds (proteins, carbohydrates). We first analyzed SEs matured for 10, 12 and 14 weeks by carrying out biological (dry weight, water content) and biochemical measurements (total protein and carbohydrate contents). No difference could be found between collection dates, suggesting that harvesting SEs after 12 weeks is appropriate. Cotyledonary SEs were then compared to various stages, from fresh to fully desiccated, in the development of cotyledonary zygotic embryos (ZEs). We identified profiles that were similar using hierarchical ascendant cluster analysis (HCA). Fresh and dehydrated ZEs could be distinguished, and SEs clustered with fresh ZEs. Both types of embryo exhibited similar carbohydrate and protein contents and signatures. This high level of similarity (94.5 %) was further supported by proteome profiling. Highly expressed proteins included storage, stress-related, late embryogenesis abundant and energy metabolism proteins. By comparing overexpressed proteins in developing and cotyledonary SEs or ZEs, some (23 proteins) could be identified as candidate biomarkers for the late, cotyledonary stage. This is the first report of useful generic protein markers for monitoring embryo development in maritime pine. Our results also suggest that improvements of SEs quality may be achieved if the current maturation conditions are refined.  相似文献   
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During epithelial cell polarization, Yurt (Yrt) is initially confined to the lateral membrane and supports the stability of this membrane domain by repressing the Crumbs-containing apical machinery. At late stages of embryogenesis, the apical recruitment of Yrt restricts the size of the apical membrane. However, the molecular basis sustaining the spatiotemporal dynamics of Yrt remains undefined. In this paper, we report that atypical protein kinase C (aPKC) phosphorylates Yrt to prevent its premature apical localization. A nonphosphorylatable version of Yrt dominantly dismantles the apical domain, showing that its aPKC-mediated exclusion is crucial for epithelial cell polarity. In return, Yrt counteracts aPKC functions to prevent apicalization of the plasma membrane. The ability of Yrt to bind and restrain aPKC signaling is central for its role in polarity, as removal of the aPKC binding site neutralizes Yrt activity. Thus, Yrt and aPKC are involved in a reciprocal antagonistic regulatory loop that contributes to segregation of distinct and mutually exclusive membrane domains in epithelial cells.  相似文献   
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Insertions in the protease (PR) region of human immunodeficiency virus (HIV) represent an interesting mechanism of antiviral resistance against HIV PR inhibitors (PIs). Here, we demonstrate the improved ability of a phosphonate-containing experimental HIV PI, GS-8374, relative to that of other PIs, to effectively inhibit patient-derived recombinant HIV strains bearing PR insertions and numerous other mutations. We correlate enzyme inhibition with the catalytic activities of corresponding recombinant PRs in vitro and provide a biochemical and structural analysis of the PR-inhibitor complex.  相似文献   
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The Paraguayan territory and region, in the centre of South America, is a huge transition area with a succession of various vegetation types. However, this area has received little attention from researchers, with few works published on its flora and its delimitations. We aimed to identify the most important environmental driving forces and delimit floristic patterns in this region, since understanding the forces that drive floristic variations in this ecotonal region could help comprehend the distribution of vegetation not only in this region but throughout South America. We obtained 1234 tree species occurrence records, 205 geographic coordinates and 23 environmental variables and altitude from the ‘NeoTropTree’ database and verified the influence and contribution of environmental factors through variance partition. We tested the floristic consistency of the different vegetation types using dendrogram, indicator species and ordination analyses. We also constructed multiple linear models to check the correlation between species distribution and environmental variables. We found eight consistent vegetation types. The spatial variables coupled with environmental variables were more important than individual environmental or spatial variables. Among the environmental variables, the aridity index was the most important. Despite the importance of spatial factors, due to environmental heterogeneity, we found a gradient related to climate and edaphic variables related to tree flora. The results confirm that the Paraguayan territory and region can be considered to be a diversified and important ecotone area in South America with respect to tree flora.  相似文献   
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