Contrasting effects of Krüppel‐like factor 4 on X‐ray‐induced double‐strand and single‐strand DNA breaks in mouse astrocytes

Astrocytes, the most common cell type in the brain, play a principal role in the repair of damaged brain tissues during external radiotherapy of brain tumours. As a downstream gene of p53, the effects of Krüppel‐like factor 4 (KLF4) in response to X‐ray‐induced DNA damage in astrocytes are unclear. In the present study, KLF4 expression was upregulated after the exposure of astrocytes isolated from the murine brain. Inhibition of KLF4 expression using lentiviral transduction produced less double‐strand DNA breaks (DSB) determined by a neutral comet assay and flow cytometric analysis of phosphorylated histone family 2A variant and more single‐strand DNA breaks (SSB) determined by a basic comet assay when the astrocytes were exposed to 4 Gy of X‐ray radiation. These data suggest that radiation exposure of the tissues around brain tumour during radiation therapy causes KLF4 overexpression in astrocytes, which induces more DSB and reduces SSB. This causes the adverse effects of radiation therapy in the treatment of brain tumours. Copyright © 2013 John Wiley & Sons, Ltd.     

Analysis of Xyloglucan Endotransglycosylase/Hydrolase (XTH) Genes and Diverse Roles of Isoenzymes during Persimmon Fruit Development and Postharvest Softening

Xyloglucan endotransglycosylase/hydrolase (XTH) enzymes have played a role in the remodeling of cell wall hemicelluloses. To investigate the function of XTHs in persimmon (Diospyros kaki L.) fruit development and postharvest softening, five cDNAs (DkXTH1 to DkXTH5), whose putative proteins contained the conserved DEIDFEFLG motif of XTH, were cloned. Real time quantitative PCR analysis revealed that DkXTH1, DkXTH4, and DkXTH5 peaked in immature expanding fruit, and their higher expression was observed along with higher fruit firmness in cold-treated fruit or firmer cultivar fruit during storage. The opposite gene expression patterns were observed in DkXTH2 and DkXTH3, which reached maxima concomitance with pronounced fruit softening. Meanwhile, the xyloglucan endotransglycosylase (XET) enzymes play important roles in both the rapid growth and ripening of persimmon fruit. Furthermore, the recombined DkXTH1 and DkXTH2 proteins showed significant XET activity without any detected XEH activity. However, the XET activity of recombined DkXTH2 protein had a higher affinity for small acceptor molecules than that of recombined DkXTH1 protein. The former might prefer to participate in cell wall restructuring, and the latter is more inclined to participate in cell wall assembly. Besides, DKXTH proteins could function by targeting to the cell wall under regulation of a signal peptide. The data suggested that individual DKXTHs could exhibit different patterns of expression, and the encoded products possessed specific enzymatic properties conferring on their respective functions in growth and postharvest softening of persimmon fruit.     

与木葡聚糖合成的糖基转移酶基因研究进展

半纤维素多糖木葡聚糖(XyG)存在于大多数植物的初生细胞壁中, 对细胞壁的结构组织和生长发育具有重要的调控作用。XyG在植物进化中存在结构的多样性。该文概述了参与XyG合成的糖基转移酶的最新研究进展, XyG合成需要多种糖基转移酶参与, 这些酶类很可能以蛋白酶复合体的形式存在并发挥作用, XyG的结构和组成的改变对植物的生长发育也产生影响。     

Contribution of potassium ion and split modes of G-quadruplex to the sensitivity and selectivity of label-free sensor toward DNA detection using fluorescence

In recent years, bioanalytical technology based on G-quadruplex has been paid significant attention due to its versatility and stimulus-responsive reconfiguration. Notwithstanding, several key issues for template-directed reassembly of G-quadruplex have not been resolved: what is the key factor for determining the sensitivity and selectivity of split G-quadruplex probes toward target DNA. Therefore, in this study, we designed three pairs of split G-quadruplex probes and investigated the sensitivity and selectivity of these systems in terms of potassium ion concentration and split modes of G-quadruplex. Due to its simplicity and sensitivity, N-methyl-mesoporphyrin (NMM) as fluorescence probes was used to monitor the target-directed reassembling process of G-quadruplex. A G-quadruplex sequence derived from the c-Myc promoter was split into "symmetric" probes, where each fragment contained two runs of guanine residues (2+2), or into "asymmetric" fragments each containing (3+1 or 1+3) runs of guanine residues. In all three cases, the sensitivity of target detection was highly dependent on the thermodynamic stability of the hybrid structure, which can be modulated by potassium ion concentrations. Using a combination of CD, fluorescence, and UV spectroscopy, we found that increasing potassium concentrations can increase the sensitivity of target detection, but can decrease the selectivity of discriminating cognate versus mismatched "target" DNA. The previous argument that asymmetrically split probes were always better than symmetrically split probes in terms of selectivity was not plausible anymore. These results demonstrate how the sensitivities and selectivity of split probes to mutations can be optimized by tuning the thermodynamic stability of the three-way junction complex.     

狂犬病病毒CVS株糖蛋白、核蛋白生物信息学分析

对狂犬病毒(rabies virus,RV)CVS株糖蛋白、核蛋白基因进行了克隆与测序,推导出相应的氨基酸序列。后采用Gamier-Robson方法和Chou-Fasman方法预测了蛋白的二级结构,用Kyte-Doolittle方法对蛋白的亲水性进行了分析,用Emi-ni方法预测了蛋白的表面可能性,以Jameson-Wolf方法预测了蛋白的抗原指数;综合分析预测蛋白的B细胞抗原表位。结果表明,糖蛋白在序列的121-126、133-137、161-165、191-193、201-204、214-216、221-225、264-267区域,核蛋白在序列的143-152、166-172、263-273、411-427区域或其附近最有可能是B细胞抗原表位的优势区域。     

飞来峡水库蓄水初期营养状态及浮游生物分布特征

于2000年丰水期和枯水期调查分析了新建河流型水库-飞来峡水库在蓄水初期的营养状态及浮游生物特征。结果表明:水库处于营养累积高峰期,已开始回落,但流域上游大量含磷废水使水库中磷含量继续上升,目前属于中营养型。共记录到浮游植物29种(属),以蓝藻门、绿藻门、硅藻门种类较多,其中丰水期以蓝藻和绿藻为主,枯水期是硅藻占优势,除大坝附近外,浮游植物两个季节密度变化不大,为0.39×10⁶cells·L^-1.浮游动物53种(属),其中包括僧帽溞和透明薄皮溞两种嗜寒性种类,丰度为52ind.·L^-1,枯水期高于丰水期,数量以轮虫和无节幼体为多。     

MapGene2Chrom基于Perl和SVG语言绘制基因物理图谱

遗传图谱表现形式简洁明了,为分析遗传规律、克隆基因提供了便利。Gbrowse、MapViewer等工具虽然能够协助研究人员绘制相似形式的物理图谱,但有很大的局限性:(1)数据需提前布置好;(2)输出结果无法灵活修改。鉴于此,文章基于Perl和SVG语言,开发了一款生物辅助作图软件MapGene2Chrom的本地版与网页版,该软件能够依据输入数据快速绘制相应的物理图谱。该软件输入数据格式简单,输出结果易于修改,图片格式为SVG矢量图,具有很好的移植性,以期为研究人员绘制物理图谱提供便利。     

Bacterial Cytolysin during Meningitis Disrupts the Regulation of Glutamate in the Brain,Leading to Synaptic Damage

Streptococcus pneumoniae (pneumococcal) meningitis is a common bacterial infection of the brain. The cholesterol-dependent cytolysin pneumolysin represents a key factor, determining the neuropathogenic potential of the pneumococci. Here, we demonstrate selective synaptic loss within the superficial layers of the frontal neocortex of post-mortem brain samples from individuals with pneumococcal meningitis. A similar effect was observed in mice with pneumococcal meningitis only when the bacteria expressed the pore-forming cholesterol-dependent cytolysin pneumolysin. Exposure of acute mouse brain slices to only pore-competent pneumolysin at disease-relevant, non-lytic concentrations caused permanent dendritic swelling, dendritic spine elimination and synaptic loss. The NMDA glutamate receptor antagonists MK801 and D-AP5 reduced this pathology. Pneumolysin increased glutamate levels within the mouse brain slices. In mouse astrocytes, pneumolysin initiated the release of glutamate in a calcium-dependent manner. We propose that pneumolysin plays a significant synapto- and dendritotoxic role in pneumococcal meningitis by initiating glutamate release from astrocytes, leading to subsequent glutamate-dependent synaptic damage. We outline for the first time the occurrence of synaptic pathology in pneumococcal meningitis and demonstrate that a bacterial cytolysin can dysregulate the control of glutamate in the brain, inducing excitotoxic damage.     

Nitrogen and α-Ketoglutaric Acid Application Modulate Grain Yield,Aroma, Nutrient Uptake and Physiological Attributes in Fragrant Rice

Journal of Plant Growth Regulation - The present study was conducted to assess the effects of nitrogen (N) and α-ketoglutaric acid application morpho-physiological attributes, aroma...