Genome‐wide distribution and functions of the AAE complex in epigenetic regulation in Arabidopsis

Heterochromatin is widespread in eukaryotic genomes and has diverse impacts depending on its genomic context. Previous studies have shown that a protein complex, the ASI1‐AIPP1‐EDM2 (AAE) complex, participates in polyadenylation regulation of several intronic heterochromatin‐containing genes. However, the genome‐wide functions of AAE are still unknown. Here, we show that the ASI1 and EDM2 mostly target the common genomic regions on a genome‐wide level and preferentially interacts with genetic heterochromatin. Polyadenylation (poly(A) sequencing reveals that AAE complex has a substantial influence on poly(A) site usage of heterochromatin‐containing genes, including not only intronic heterochromatin‐containing genes but also the genes showing overlap with heterochromatin. Intriguingly, AAE is also involved in the alternative splicing regulation of a number of heterochromatin‐overlapping genes, such as the disease resistance gene RPP4. We provided evidence that genic heterochromatin is indispensable for the recruitment of AAE in polyadenylation and splicing regulation. In addition to conferring RNA processing regulation at genic heterochromatin‐containing genes, AAE also targets some transposable elements (TEs) outside of genes (including TEs sandwiched by genes and island TEs) for epigenetic silencing. Our results reveal new functions of AAE in RNA processing and epigenetic silencing, and thus represent important advances in epigenetic regulation.     

三江源国家公园执法体制改革经验及其可复制性

执法是实现依法行政的最终环节,是国家公园管理机构实现管理目标的重要工具,统一执法是我国国家公园管理体制改革中“统一”的重要方面.《建立国家公园体制总体方案》(以下简称《总体方案》)明确,国家公园体制建设需要坚持将“山水林田湖草作为一个生命共同体,统筹考虑保护与利用”.国家公园管理机构要实现对山水林田湖草这一生命共同体的...     

海南岛农业结构的生态经济系统分析

本文提出了一个综合考虑生态与经济的农业结构优化模型。以海南岛作一实例对农业结构系统分析中的模拟方法进行了具体研究。这个模型应用来为海南岛的农业计划和管理提供具体信息。用FELIXC-512计算机求出了20个海南岛农业结构的优化方案,并对其生态经济效果作了论证。     

植物蔗糖转运蛋白表达的调控因素与分子机制

植物光合作用的产物主要以蔗糖的形式在植物体内进行从源到库的运输.蔗糖转运蛋白是此过程的重要参与者,其表达和调控与植物中光合作用产物的分配紧密关联,从而调控着植物的生长发育、结果结实、抗逆抗病等性状.蔗糖转运蛋白的表达受到植物发育时期、外界环境条件及激素的影响.蔗糖转运蛋白的调控机制有转录因子的调节、基因内部序列调控、蛋...     

Electron acceptors for anaerobic oxidation of methane drive microbial community structure and diversity in mud volcanoes

Mud volcanoes (MVs) emit globally significant quantities of methane into the atmosphere, however, methane cycling in such environments is not yet fully understood, as the roles of microbes and their associated biogeochemical processes have been largely overlooked. Here, we used data from high‐throughput sequencing of microbial 16S rRNA gene amplicons from six MVs in the Junggar Basin in northwest China to quantify patterns of diversity and characterize the community structure of archaea and bacteria. We found anaerobic methanotrophs and diverse sulfate‐ and iron‐reducing microbes in all of the samples, and the diversity of both archaeal and bacterial communities was strongly linked to the concentrations of sulfate, iron and nitrate, which could act as electron acceptors in anaerobic oxidation of methane (AOM). The impacts of sulfate/iron/nitrate on AOM in the MVs were verified by microcosm experiments. Further, two representative MVs were selected to explore the microbial interactions based on phylogenetic molecular ecological networks. The sites showed distinct network structures, key species and microbial interactions, with more complex and numerous linkages between methane‐cycling microbes and their partners being observed in the iron/sulfate‐rich MV. These findings suggest that electron acceptors are important factors driving the structure of microbial communities in these methane‐rich environments.     

南京地区早产儿坏死性小肠结肠炎病原体特点和益生菌干预效果及预后影响因素分析

目的探究南京地区早产儿坏死性小肠结肠炎(NEC)的病原体特点,并观察益生菌辅助治疗对患儿血清炎症因子水平的影响,分析影响NEC早产儿预后的因素。方法将2014年5月至2018年12月于东南大学附属中大医院就诊的87例NEC早产儿选为研究对象,分析其病原体特点,观察不同治疗方法对患儿血清炎症因子的影响,并通过Logistic回归分析影响NEC患儿预后的危险因素。结果革兰阴性菌是NEC早产儿的主要致病菌,主要包括肺炎克雷伯菌(25株,27.78%)和大肠埃希菌(21株,23.33%)。肺炎克雷伯菌和大肠埃希菌对美罗培南、亚胺培南/西司他丁、哌拉西林/他唑巴坦、多粘菌素和阿米卡星敏感。益生菌干预后的NEC早产儿血清IL-1β、IL-10、TNF-α水平及TLR4的表达均显著低于常规治疗患儿(均P0.05)。发病前3 d内输血、新生儿窒息、益生菌干预、非营养性吮吸、腹膜炎、败血症、加奶速度、PDA均是影响NEC早产儿预后的相关因素(均P0.05),其中发病前3 d内输血、新生儿窒息、加奶速度、PDA是影响NEC早产儿预后的独立危险因素(均P0.05)。结论革兰阴性菌是NEC早产儿的主要致病菌,益生菌干预可有效降低NEC早产儿血清炎症因子水平。对于NEC早产儿的治疗可选用碳青霉烯类、氨基糖苷类等抗生素,同时需关注影响NEC早产儿预后的独立危险因素。     

Cloning,expression, and characterization of a novel diketoreductase from Acinetobacter baylyi

Reductions of carbonyl groups catalyzed by oxidoreductases are involved in all biological processes and are often a class of important biocatalyst. In this article, we report a novel enzyme designated as diketoreductase （DKR） that was able to reduce two carbonyl groups in a diketo ester to corresponding dihydroxy ester with excellent stereoselectivity. The DKR was cloned from Acinetobacter baylyi by reverse genetic method, heterogeneously expressed in Escherichia coli, and purified to homogeneity by two chromatographic steps. This novel enzyme exhibited dual cofactor specificity, with a preference of NADH over NADPH. The dihydroxy ester product catalyzed by the DKR was only 3R,5S-stereoisomer with both diastereomeric excess and enantiomeric excess values more than 99.5%. In addition, some biochemical properties of the enzyme, such as the optimal pH and temperature, were also characterized. Furthermore, sequence analysis indicated that this new enzyme was homologous to bacterial 3-hydroxyacyl coenzyme-A dehydrogenase. More importantly, based on the unique catalytic activity and excellent stereoselectivity, the DKR could be utilized in the synthesis of valuable chiral drug intermediates, such as Lipitor.     

越南篦齿苏铁传粉媒介的研究

利用排除法和引入昆虫的方法相结合,研究越南篦齿苏铁(Cycas elongata)的传粉媒介.结果表明,越南篦齿苏铁靠风媒传粉和虫媒传粉的雌株结实率分别55.3%和57.2%,自然传粉的结实率为63.5%,说明风和象鼻虫都是越南篦齿苏铁的有效传粉媒介.越南篦齿苏铁散粉高峰在白天,夜间散粉很少,在3.0 m以内风传花粉的密度较高,3.0 m之外的密度急剧下降.可见,风媒和虫媒都是越南篦齿苏铁的有效传粉途径,与泽米铁类植物为专一寄主性昆虫传粉的结论不一致.     

Noggin and bFGF cooperate to maintain the pluripotency of human embryonic stem cells in the absence of feeder layers

Human embryonic stem (hES) cells are typically maintained on mouse embryonic fibroblast (MEF) feeders or with MEF-conditioned medium. However, these xenosupport systems greatly limit the therapeutic applications of hES cells because of the risk of cross-transfer of animal pathogens. Here we showed that the bone morphogenetic protein antagonist noggin is critical in preventing differentiation of hES cells in culture. Furthermore, we found that the combination of noggin and basic fibroblast growth factor (bFGF) was sufficient to maintain the prolonged growth of hES cells while retaining all hES cell features. Since both noggin and bFGF are expressed in MEF, our findings suggest that they may be important factors secreted by MEF for maintaining undifferentiated pluripotent hES cells. Our data provide new insight into the mechanism how hES cell self-renewal is regulated. The newly developed feeder-free culture system will provide a more reliable alternative for future therapeutic applications of hES cells.