卵菌与真菌Argonaute家族基因的生物信息学分析

 Argonaute蛋白广泛存在于真核生物与原核生物中,可在非编码小RNA或DNA的引导下,对完全匹配或部分匹配的靶标进行切割、翻译抑制或染色体修饰。本研究利用生物信息学对127种卵菌与真菌的基因组进行分析,旨在了解各个物种中AGO家族基因的数量、蛋白结构域、进化关系及转录模式等。结果发现,大部分卵菌与真菌的基因组中(51%)含有2个AGO基因,而疫霉菌和壶菌等平均含有4个以上。卵菌与真菌的AGO基因在进化上相互独立,多拷贝AGO基因可能是通过基因复制形成;大部分AGO基因具有6个可预测的功能域(即:N端、Linker 1、PAZ、Linker 2、MID和PIWI),并且在PAZ和PIWI功能域上,与核酸5'和3'端结合及与催化活性相关的氨基酸位点整体相对保守,仅个别位点存在一定的差异。侵染大豆过程中,大豆疫霉和终极腐霉的两对同源AGO基因具有保守的表达模式,且基因表达水平相对较高,可能具有相似的生物学功能。上述结果将为深入解析AGO介导的RNA干扰机制及生物学功能奠定基础。     

Vertical distributions of two herbivorous cichlid fishes of the genus Tropheus in Lake Tanganyika, Africa

The vertical distributions of two herbivorous cichlid fishes, Tropheus moorii and Tropheus duboisi, were studied on the rocky slope at Luhanga and Bemba, 12 km apart, in Lake Tanganyika, Zaire, Africa. At Luhanga, where T duboisi were not present, T. moorii ranged from the shoreline to a site 30 m deep. At Bemba, T moorii occupied areas less than 18 m and T duboisi areas between 5 and 30 m. In the overlapping zone, 5–18 m depth, each fish held an intra- and interspecific feeding territory, involving size-dependent dominance relationship between neighbors irrespective of species. We indicate that the vertical distributions of these species are restricted by competitive interactions.     

Ingested RNA interference for managing the populations of the Colorado potato beetle, Leptinotarsa decemlineata

BACKGROUND: RNA interference (RNAi) is a breakthrough technology for conducting functional genomics studies and also as a potential tool for crop protection against insect pests. The major challenge for efficient pest control using RNAi in the field is the development of efficient and reliable methods for production and delivery of double‐stranded RNA (dsRNA). In this paper, the potential of feeding dsRNA expressed in bacteria or synthesized in vitro to manage populations of Colorado potato beetle, Leptinotarsa decemlineata (Say) (CPB), was investigated. RESULTS: Feeding RNAi successfully triggered the silencing of all five target genes tested and caused significant mortality and reduced body weight gain in the treated beetles. This study provides the first example of an effective RNAi response in insects after feeding dsRNA produced in bacteria. CONCLUSION: These results suggest that the efficient induction of RNAi using bacteria to deliver dsRNA is a possible method for management of CPB. This could be also a promising bioassay approach for genome‐wide screens to identify effective target genes for use as novel RNAi‐based insecticides. Copyright © 2010 Society of Chemical Industry     

RNA干扰技术及其在寄生线虫基因功能研究中的应用

介绍了RNA干扰（RNAi）的概念、线虫中RNAi的作用机理、RNAi的三个分子特性，即可遗传性、转移性RNAi的放大效应和RNAi信号的传播特性。从模板dsRNA的获取、dsRNA的导入和线虫中RNAi效应的检测方法三个方面概述了应用RNAi技术研究线虫基因功能的试验方法和最新进展。     

Construction and identification of eukaryotic expression vector of bcl-2 siRNA

AIM: To construct eukaryotic expression vector of small interfering RNA(siRNA) specific to bcl-2 and investigate the effect of recombinant plasmid on suppressing bladder cancer cell growth.METHODS: siRNA of bcl-2 gene was designed according to the principle of RNAi-based medicine, and was converted into cDNA coding expression of small hairpin RNAs(shRNA) of siRNA. The cDNA was synthesized and inserted into plasmid pGenesil-1. The recombinant eukaryotic expression vectors of pGenesil-1545 and pGenesil-1555 were controlled by the U6 promoter of RNA polymerase Ⅲ, identified by the restriction map and the sequence analysis, and transfected into T24 cells. After T24 cells were transfected for 72 h, expression of bcl-2 mRNA was assayed by RT-PCR; and MTT was used to observe the proliferation of T24 cells.RESULTS: The recombinant plasmids of pGenesil-1545 and pGenesil-1555 were identified by the restriction map and the sequence analysis. The sequences completely coincided with the designs. The expression of the bcl-2 mRNA in T24 cells transfected with recombinant plasmid decreased nearly 80%, and the growth of T24 cells was suppressed significantly.CONCLUSION: The siRNA eukaryotic expression vector against bcl-2 gene is successfully constructed. It effectively downregulates the expression of bcl-2 in T24 cells and suppresses the cell growth.     

Social effects on crowding preferences of urban forest visitors

An image-based stated choice approach was used to investigate the conditions determining why visitors to an urban forest in Vienna feel crowded or not. Respondents (N=213) evaluated several sets of images depicting trail use scenarios with different levels of social crowding conditions and several types of social interferences. Forest users were segmented into three groups based on their global evaluations of use levels during weekends and work days, resulting in a crowding-averse, a crowding-tolerant, and a crowding-indifferent segment. Crowding-averse respondents reacted much more negatively to scenarios with high-use levels, heterogeneous trail use conditions, and violations of personal minimum spatial requirements caused by the presence of others. This user group felt overcrowded because social conditions experienced in the area interfered with their main visiting goals, especially to walk with their dog unleashed and to recreate. By contrast, crowding-tolerant respondents disliked very low-use and high-use situations, and preferred a certain amount of social stimulation in the form of some encounters, and more heterogeneous trail use conditions.     

Critical periods for weed control in cotton in Turkey

Field studies were conducted over 4 years in south‐eastern Turkey in 1999–2002 to establish the critical period for weed control (CPWC). This is the period in the crop growth cycle during which weeds must be controlled to prevent unacceptable yield losses. A quantitative series of treatments of both increasing duration of weed interference and of the weed‐free period were applied. The beginning and end of CPWC were based on 5% acceptable yield loss levels which were determined by fitting logistic and Gompertz equations to relative yield data representing increasing duration of weed interference and weed‐free period, estimated as growing degree days (GDD). Total weed dry weight increased with increasing time prior to weed removal. Cotton heights were reduced by prolonged delays in weed removal in all treatments in all 4 years. The beginning of CPWC ranged from 100 to 159 GDD, and the end from 1006 to 1174 GDD, depending on the weed species present and their densities. Practical implications of this study are that herbicides (pre‐emergence residual or post‐emergence), or other weed control methods should be used in Turkey to eliminate weeds from 1–2 weeks post‐crop emergence up to 11–12 weeks. Such an approach would keep yield loss levels below 5%.     

区域农用GNSS基准站云端管理方法与系统研究

针对区域农用卫星导航定位基准站规模化应用中存在无效冗余、频率干扰和基准不统一问题,提出基于云端管理构架实现区域基准站管理与信息共享的初步解决方案。选择石河子市作为研究区,获得3个企业总计84个固定基准站的备案数据,计算任意2个基准站的站间距ΔD和频率差ΔF形成数据集E。在此基础上,利用GIS空间分析和数值统计方法,分析基准站无效冗余和同近频干扰,开展基准站坐标平差与精度验证,开发基准站管理服务系统原型。研究表明,由于缺乏技术和管理协调,区域农用GNSS基准站无效冗余、频率干扰和频率浪费难以避免,所统计的84个基准站占用了26.7 MHz频带,使用了47个频点,其中30个基准站使用单独频点,站间距40 km以内时多达18对基准站频率相同,29对基准站频率相近(ΔF≤25 k Hz)。石河子东北18个基准站,平均冗余率达263.2%,中心区冗余率更高。固定基准站通过坐标平差可以提高站址精度,有利于发挥基准站冗余的有效性和提高差分信号接入的可靠性,3个验证点的经度坐标差最大为0.011 m,纬度坐标差最大为0.023 m,精度分别达到毫米级和厘米级。管理服务系统原型和手机端APP原型的初步测试表明,系统可以实现基准站备案、建站辅助、基准站查询和频率推荐等功能,可以提高基准站管理效率和减少干扰现象。     

浑水膜孔灌多向交汇入渗及减渗特性

浑水灌溉是我国黄河流域引黄灌区灌溉的主要特点,其中浑水中的泥沙含量对土壤入渗特性有较大的影响,为揭示浑水膜孔灌交汇入渗的减渗特性,通过开展浑水及清水膜孔灌入渗试验,建立了浑水膜孔灌自由入渗相对于清水的减渗率及浑水膜孔灌多向交汇入渗相对于自由入渗的减渗率与入渗时间之间的量化关系,提出了由清水膜孔灌自由入渗量推求浑水膜孔灌多向交汇入渗量的模型。结果表明:浑水膜孔灌自由入渗较清水的减渗量随入渗时间的延长而增大,但增大幅度慢慢变小,入渗后期其减渗量基本呈线性增加,其减渗率随时间的增大先快速增大后缓慢减小,入渗后期减渗率基本稳定;当入渗产生交汇后,入渗能力明显减小,多向交汇入渗和单向交汇入渗相对自由入渗的减渗率均随入渗时间的增长而增大,多向交汇入渗相对单向交汇入渗也存在减渗作用,3条减渗率曲线的变化率随着时间的增长而逐渐减小。     

Breeding for provitamin A biofortification of maize (Zea mays L.)

Vitamin A deficiency is widely prevailing in children and women of developing countries. Deficiency of vitamin A causes night blindness, growth retardation, xerophthalmia and increases the susceptibility against epidemic diseases. Among different interventions of overcoming malnutrition, biofortification is the most acceptable and preferred intervention among researchers, growers and consumers. Maize is grown and consumed in those regions where vitamin A deficiency is most prevalent; thus, targeting this crop for provitamin A biofortification is the most appropriate solution. Different breeding strategies including diversity analysis, introduction and stability analysis of exotic germplasm, hybridization, heterosis breeding, mutagenesis and marker‐assisted selection are practised for exploring maize germplasm and development of provitamin A‐enriched cultivars. Genome‐wide association selection and development of transgenic maize genotypes are also being practised, whereas RNA interference and genome editing tools could also be used as potential strategies for provitamin A biofortification of maize genotypes. The use of these breeding strategies for provitamin A biofortification of maize is comprehensively reviewed to provide a working outline for maize breeders.