甘蓝型油菜珠孔与胚囊的超微结构研究

甘蓝型油菜的外珠孔基本上为开放结构,内珠孔为闭合结构。胚囊成熟时反足细胞已退化,仅由二个助细胞、一个卵细胞、与一个中央细胞组成。助细胞极性不明显,二个助细胞在花粉管到达前均显示同等退化迹象。卵细胞极性明显。中央细胞中含结构独特的质体。受精前,卵与中央细胞的质膜之间含有特殊的电子致密物质。     

Analysis of synonymous codon usage in H5N1 virus and other influenza A viruses

In this study, we calculated the codon usage bias in H5N1 virus and performed a comparative analysis of synonymous codon usage patterns in H5N1 virus, five other evolutionary related influenza A viruses and a influenza B virus. Codon usage bias in H5N1 genome is a little slight, which is mainly determined by the base compositions on the third codon position. By comparing synonymous codon usage patterns in different viruses, we observed that the codon usage pattern of H5N1 virus is similar with other influenza A viruses, but not influenza B virus, and the synonymous codon usage in influenza A virus genes is phylogenetically conservative, but not strain-specific. Synonymous codon usage in genes encoded by different influenza A viruses is genus conservative. Compositional constraints could explain most of the variation of synonymous codon usage among these virus genes, while gene function is also correlated to synonymous codon usages to a certain extent. However, translational selection and gene length have no effect on the variations of synonymous codon usage in these virus genes.     

Valuing urban green spaces in mitigating climate change: A city‐wide estimate of aboveground carbon stored in urban green spaces of China's Capital

Urban green spaces provide manifold environmental benefits and promote human well‐being. Unfortunately, these services are largely undervalued, and the potential of urban areas themselves to mitigate future climate change has received little attention. In this study, we quantified and mapped city‐wide aboveground carbon storage of urban green spaces in China's capital, Beijing, using field survey data of diameter at breast height (DBH) and tree height from 326 field survey plots, combined with satellite‐derived vegetation index at a fine resolution of 6 m. We estimated the total amount of carbon stored in the urban green spaces to be 956.3 Gg (1 Gg = 10⁹ g) in 2014. There existed great spatial heterogeneity in vegetation carbon density varying from 0 to 68.1 Mg C ha^‐1, with an average density of 7.8 Mg C ha^?1. As expected, carbon density tended to decrease with urban development intensity (UDI). Likely being affected by vegetation cover proportion and configuration of green space patches, large differences were presented between the 95th and 5th quantile carbon density for each UDI bin, showing great potential for carbon sequestration. However, the interquartile range of carbon density narrowed drastically when UDI reached 60%, signifying a threshold for greatly reduced carbon sequestration potentials for higher UDI. These findings suggested that urban green spaces have great potential to make contribution to mitigating against future climate change if we plan and design urban green spaces following the trajectory of high carbon density, but we should be aware that such potential will be very limited when the urban development reaches certain intensity threshold.     

重组马g-干扰素抗病毒活性测定及单克隆抗体抑制活性鉴定

为了测定大肠杆菌和杆状病毒表达的重组马g-干扰素是否具有抗病毒活性, 利用这两种干扰素处理马胎肾细胞(EFK-78), 然后接种表达绿色荧光蛋白(GFP)的重组水泡性口炎病毒(VSV*GFP), 观察干扰素对病毒表达GFP的抑制, 测出其抗病毒活性单位分别为1×103 AU/mL、1×105 AU/mL。评价了制备的九株抗重组马g-干扰素单克隆抗体是否可抑制重组马g-干扰素抗病毒活性, 证实其中一株可中和重组马g-干扰素的抗病毒活性。结果表明: 杆状病毒表达的马g-干扰素具有较高的抗病毒活性, 其活性可被一株制备的抗重组马g-干扰素单克隆抗体抑制; 首次获得原核表达的具有抗病毒活性的马g-干扰素。     

林可链霉菌黑色素生物合成基因的克隆与表达

以pIJ702的melCl－C2基因为探针杂交林可链霉菌（Streptomyceslincolnensis）78－11染色体DNA,呈现出3．2kb的BamHI片段和2．6kb的SphI片段等一系列阳性条带。构建了含3．0～3．5kbBamHI片段的林可链霉菌78-11基因文库,从中分离克隆了黑色素生物合成基因melCl和melC2,并测定了含有mel基因的重组子pRSB336插入片段的全部DNA顺序。3152bpBamHI片段含有5个开放阅读框架,其中melCl和melC2与链霉菌属三个种的相应基因具有较高的同源性。此外,林可链霉菌78－11的melC2基因产物与人和鼠的酪氨酸酶轻微同源,分别为17．3％和24．5％。种种迹象表明,melCl、melC2和orf3组成黑色素生物合成操纵子结构。为了进一步鉴定上述克隆的林可链霉菌78-11黑色素生物合成基因,构建了分别含有新霉素抗性基因启动子和正反方向mel基因的重组质粒pPZ518和pPZ519,并转化变铅青链霉菌TK23。随机挑选的12个pPZ518转化子在R2YE培养基上均能分泌淡褐色色素,而所有的pPZ519和pES1转化子则都呈白色。     

利用苏云金芽胞杆菌转座子Tn4430构建含cry1Ac10基因的解离载体

将cry1Ac10基因和苏云金芽胞杆菌的复制起始区连 接在一起,并在其两侧按相同方向各连接一个来自苏云金芽胞杆菌转座子Tn4430的解离位点,构成转移单位。再将革兰氏阳性细菌的抗性标记基因和大肠杆菌克隆载体pUC19与之连接,获得含cry1Ac10基因的解离载体pBMB801。将其转化苏云金芽胞杆菌无晶体突变体,再导入含解离酶基因的辅助质粒pBMB1200。在解离酶作用下,两个解离位点间发生重组,消除基在操作中的抗性标记基因等非必需基因片段,获得仅保留有完整cry1Ac10基因和来 自苏云金芽胞杆菌质粒复制起始区,在无抗生素选择压力下能稳定遗传的重组质粒pBMB801B 。     

水稻体细胞杂交研究进展

水稻是世界重要的粮食作物,全世界约有120个国家种植水稻。水稻的近缘或远缘种具有一些优良性状,如抗病、抗虫、抗逆等。将这些性状导入水稻,是科学家们所希望的,但因用普通杂交方法存在交配系统的不亲和性等难题而进展不大。随着组织培养技术的发展,特别是植物原生质体培养技术的日趋成熟,使得人类能够在细胞水平通过体细胞杂交方法实现遗传信息的重组。     

Homology modeling threedimensional structure of AnxB1 and reducing its immunogenicity by sequence-deleted mutagenesis

AnxB1,a novel annexin previously isolated from Cysticercus cellulose,shows high thrombi affinity and anticoagulant activity in vivo.In order to investigate the relationship between structure and biological function,a predicted three-dimensional(3D)model of AnxB1 was generated by homology modeling.This model contains four homologous internal-domains and the Cα trace of domain Ⅰ,Ⅱ and IV shows high similarity.Based on the structure characterization,four sequence-deleted mutants were constructed and expressed as GST fusion proteins in E.coli.Two of the mutants,GST-M3 and GST-M4 reserved high anticoagulant activity(p＜0.01 vs.GST).Furthermore,compared with the wild type GST-AnxB1,the immunogenicity of GST-M3 and GST-M4 was reduced significantly(p＜0.01)and the molecular weight was lowered to 27 kD and 34 kD,respectively.These observations laid a solid foundation for further study on developing new thrombolytic agents with higher efficiency and lower side effect.     

两株基因III型强毒新城疫的全基因组测序及其与I系苗的亲缘性分析

[目的]研究基因Ⅲ型新城疫(Newcastle disease,ND)强毒分离株Js/7/05/Ch和JS/9/05/Go与中等毒力疫苗株Mukteswar的亲缘性关系,分析三株新城疫病毒(Newcastle disease virus,NDV)的全基因差异.[方法]采用RT-PCR方法获得两株NDV分离株的全基因组核苷酸序列,与GenBank中公布的Mukteswar序列比对分析.[结果]强毒分离株与中等毒力疫苗株Mukteswar全基因组核苷酸同源性均为99.7%;病毒6个阅读框核苷酸序列与Mukteswar同源性为99.6%～99.9%;预测的8种病毒编码蛋白同源性在98.8%～99.8%.然而,测定MDT,ICPI和IVPI发现JS/7/05/Ch和JS/9/05/Go毒力明显强于Mukteswar,其中JS/7/05/Ch株的IVPI达到了2.18.[结论]综合3株NDV的遗传分析结果和已有的流行病学资料可以推断分离株JS/7/05/Ch和JS/9/05/Go是由疫苗株Mukteswar自然进化而来的返强毒株.因此,必须停止使用中等毒力疫苗以免造成更大的危害.     

外源钙对干旱胁迫下烤烟幼苗光系统Ⅱ功能的影响

以叶绿素快相荧光动力学曲线(OJIP)为探针,研究了外源钙对干旱胁迫下烤烟幼苗光系统Ⅱ(PSⅡ)功能的影响.结果表明:干旱胁迫降低了烤烟幼苗PSⅡ原初光能转换效率(Fv/Fm)和电子传递速率(ETR),抑制了光合作用的原初过程,烤烟幼苗叶片发生了明显的光抑制.叶面喷施10.0 mmol·L-1CaCl2溶液后烤烟叶片的光合电子传递能量比例(ФEo)在干旱胁迫下的降低幅度明显小于对照(喷施清水),电子转运效率(ET0/RC)在干旱胁迫下明显高于对照.叶面喷施CaC12溶液增加了PSⅡ捕获光能用于光合电子传递的比例、剩余有活性反应中心的效率和电子传递链中的能量传递,使烤烟叶片的光系统Ⅱ在干旱胁迫下保持相对较高的活性,从而提高了烤烟幼苗的抗旱能力.