Structural and functional particularities of microsatellites in cattle and sheep genomes

A comparative analysis of polymorphism of DNA fragments flanked by microsatellite loci of cattle and sheep is performed. In all, 102 loci revealed in the polymerase chain reaction with the use of fragments of di- and trinucleotide microsatellite fragments as primers are analyzed. It is found that polymorphism of the spectra of amplification products depends substantially on the nucleotide sequence of the primer. The dependence of polymorphism of DNA fragments on the structural and functional organization of their flanks is discussed.     

In vivo footprinting of a muscle specific enhancer by ligation mediated PCR

In vivo protein-DNA interactions at the developmentally regulated enhancer of the mouse muscle creatine kinase (MCK) gene were examined by a newly developed polymerase chain reaction (PCR) footprinting procedure. This ligation mediated, single-sided PCR technique permits the exponential amplification of an entire sequence ladder. Several footprints were detected in terminally differentiated muscle cells where the MCK gene is actively transcribed. None were observed in myogenic cells prior to differentiation or in nonmuscle cells. Two footprints appear to correspond to sites that can bind the myogenic regulator MyoD1 in vitro, whereas two others represent muscle specific use of apparently general factors. Because MyoD1 is synthesized by undifferentiated myoblasts, these data imply that additional regulatory mechanisms must restrict the interaction between this protein and its target site prior to differentiation.     

Synteny and collinearity in plant genomes

Correlated gene arrangements among taxa provide a valuable framework for inference of shared ancestry of genes and for the utilization of findings from model organisms to study less-well-understood systems. In angiosperms, comparisons of gene arrangements are complicated by recurring polyploidy and extensive genome rearrangement. New genome sequences and improved analytical approaches are clarifying angiosperm evolution and revealing patterns of differential gene loss after genome duplication and differential gene retention associated with evolution of some morphological complexity. Because of variability in DNA substitution rates among taxa and genes, deviation from collinearity might be a more reliable phylogenetic character.     

Compensated deleterious mutations in insect genomes

Relatively little is known about the importance of amino acid interactions in protein and phenotypic evolution. Here we examine whether mutations that are pathogenic in Drosophila melanogaster become fixed via epistasis in other Dipteran genomes. Overall divergence at pathogenic amino acid sites is reduced. However, approximately 10% of the substitutions at these sites carry the exact same pathogenic amino acid found in D. melanogaster mutants. Hence compensatory mutation(s) must have evolved. Surprisingly, the fraction 10% is not affected by phylogenetic distance. These results support a selection-driven process that allows compensated amino acid substitutions to become rapidly fixed in taxa with large populations.     

Terraces in phylogenetic tree space

A key step in assembling the tree of life is the construction of species-rich phylogenies from multilocus--but often incomplete--sequence data sets. We describe previously unknown structure in the landscape of solutions to the tree reconstruction problem, comprising sometimes vast "terraces" of trees with identical quality, arranged on islands of phylogenetically similar trees. Phylogenetic ambiguity within a terrace can be characterized efficiently and then ameliorated by new algorithms for obtaining a terrace's maximum-agreement subtree or by identifying the smallest set of new targets for additional sequencing. Algorithms to find optimal trees or estimate Bayesian posterior tree distributions may need to navigate strategically in the neighborhood of large terraces in tree space.     

山地城市土地利用地形分异特征及功能分区研究

采集北碚区2014年的土地利用变更数据、土地利用现状图和DEM数据,运用GIS技术,从坡度和高程角度,引入分布指数、洛伦兹曲线以及基尼系数,研究北碚区土地利用的地形分异规律。结果发现,研究区土地利用类型分布特征与高程、坡度联系紧密。林地和未利用地的优势位主要分布在较高地形等级区间,建设用地、耕地、园地等受人为干扰较大的地类优势则随地形等级的减少逐渐显现。坡度对各地类空间分布影响显著,高程在300~400 m、坡度在6~15°之间的区域是城市扩展和耕地保护的主要空间。耕地和园地在地形上的分布相差不大,建设用地、林地以及其他农用地则表现出一定的区域差异。从优势度来看,土地利用类型分布呈现明显的层级性,地形优势等级由低到高依次为水域层、城镇层、耕地层、园地层、林地层。基于该地形分异规律,将研究区划分为核心水体区、城镇发展区、现代农业发展区、生态农业发展区和生态屏障区等5个功能区,并提出各区土地利用发展建议。     

延河流域植物功能性状变异来源分析

由于遗传背景对植物性状的影响,直接研究环境与植物性状的关系有一定的不确定性。因此,研究植物性状对环境变化的响应,必须明确遗传背景与环境对植物性状的相对影响,以排除遗传背景的作用。本研究以延河流域为研究区域,选取19个典型样点,调查了64种植物的6种功能性状,即比叶面积(SLA)、比根长(SRL)、叶片氮(LN)与磷含量(LP)、根的氮(RN)与磷含量(RP),并通过野外定位信息,从已有专题信息图中获取环境数据,采用方差分析和逐步回归的方法,分析了植物性状变异来源,研究了不同科属植物对环境变化的响应。结果表明：(1)不同气候条件下,植物的SLA、LN和RP性状存在显著差异,森林区植物SLA、RP较草原区植物偏低33.02%、19.94%,而LN则高于草原区植物19.33%;不同科属植物之间SLA、SRL、LN和RN存在显著差异,豆科植物具有较高的SLA、LN、RN,分别高出研究区平均值16.33%、65.23%、97.78%,而禾本科植物SRL具有最大值,高出平均值103.11%;(2)遗传背景差异是植物性状变异的首要决定因子,遗传背景对SRL、LN、RN变异的解释比例分别达到了27.86%、32.78%、42.70%,而LP、RP则受环境因子的影响更大,环境因子对LP、RP解释比例分别达到24%、15.58%;(3)豆科Leguminosae、禾本科Poaceae、菊科Asteraceae、蔷薇科Rosaceae植物性状的环境因子逐步线性回归模型,表明不同科属的植物对环境因子是否产生响应和响应的方式均不相同,豆科和禾本科植物对区域性气候条件较为敏感,而菊科和蔷薇科植物受地形因子和土壤含水量影响较大。     

Control of gene expression by artificial introns in Saccharomyces cerevisiae

Artificial yeast introns that show cold-sensitive splicing have been constructed. These conditional introns can be inserted into a target gene as an "intron cassette" without disrupting the coding information, allowing expression of the gene to be cold sensitive. Insertion of these intron cassettes rendered the yeast URA3 gene cold sensitive in its expression. The advantage of this intron-mediated control system is that any gene can be converted to a controllable gene by simple insertion of an intron.     

针对获奖成果分析科研工作中存在的问题及对策

文章以辽宁省蚕业科学研究所建所以来的获奖科技成果为研究对象,进行统计分析。认为柞蚕业整体科研水平进步缓慢、人才断层以及学科发展的失衡是导致现阶段获奖成果数量、水平下降的主要因素。建议农业科研单位以抓好人才队伍建设为出发点和落脚点,从解决生产中的突出矛盾入手,加强科研协作和产学研的紧密结合,使柞蚕科研能在科技快速发展的今天继续保持多出成果,出高质量的成果。     

Chromosome pairing within genomes in maize-Tripsacum hybrids

When the ten chromosomes of maize were inserted inlto a polyploid (2n = 72) Tripsacum dactyloides background they formed up to five pairs at meiosis. Two plants that each contained 36 Tripsacum and 14 maize chromosomes were deprived from the F(1) of maize x Tripsacum. Chromo. somes of these plants frequently formed 25 bivalents, 18 between Tripsacum chromosomes and seven between maize chromosomes. Maize chromosomes could be distinguished from Tripsacum chromosomes on the basis of size. The withint-genome pairing is probably induced by the genetic background.     

Merging genomes with geochemistry in hydrothermal ecosystems

Thermophilic microbial inhabitants of active seafloor and continental hot springs populate the deepest branches of the universal phylogenetic tree, making hydrothermal ecosystems the most ancient continuously inhabited ecosystems on Earth. Geochemical consequences of hot water-rock interactions render these environments habitable and supply a diverse array of energy sources. Clues to the strategies for how life thrives in these dynamic ecosystems are beginning to be elucidated through a confluence of biogeochemistry, microbiology, ecology, molecular biology, and genomics. These efforts have the potential to reveal how ecosystems originate, the extent of the subsurface biosphere, and the driving forces of evolution.     

不同生态类群藏獒亲缘关系的RAPD分析

采用RAPD技术对不同生态类群藏獒个体之间的亲缘关系进行了分析,从80个随机引物中筛选出27个引物,共扩增出369条带,其中339条带表现出多态性,多态性位点百分率为91.86%.根据20只藏獒个体之间的Nei氏标准遗传距离用UPGMA法构建了聚类分析图.结果表明:河曲藏獒和青海藏獒同类群个体之间亲缘关系较近,在聚类图上形成了河曲藏獒类群和青海藏獒类群各自独立的分支,这一结果有力地支持了按地域对藏獒进行生态类群划分的说法.     

Detection of two viral genomes in single cells by double-label hybridization in situ and color microradioautography

Double labeling and color microradioautography were used in a new method of hybridization in situ to identify different genes in individual cells. The method is based on the unequal penetration of 3H and 35S into two layers of nuclear track emulsion separated by a thin barrier film. Hybridization of a 35S-labeled probe specific for one kind of gene results in silver grains over cells in both layers of emulsion; a 3H-labeled probe for a second gene provides grains only in the first layer of emulsion. Silver grains are converted to magenta-colored grains in the first layer and to cyan-colored grains in the second to facilitate enumeration of grains in each layer. This technique should be widely applicable in analyses of differential gene expression in single cells or in discrete populations of cells.     

Accommodating phylogenetic uncertainty in evolutionary studies

Many evolutionary studies use comparisons across species to detect evidence of natural selection and to examine the rate of character evolution. Statistical analyses in these studies are usually performed by means of a species phylogeny to accommodate the effects of shared evolutionary history. The phylogeny is usually treated as known without error; this assumption is problematic because inferred phylogenies are subject to both stochastic and systematic errors. We describe methods for accommodating phylogenetic uncertainty in evolutionary studies by means of Bayesian inference. The methods are computationally intensive but general enough to be applied in most comparative evolutionary studies.     

通过多基因组比较的方法在5种绿球蓝细菌中识别基因组岛(英文)

为探索水平基因转移在绿球蓝细菌基因组多样性中的作用,5个高光适应性绿球蓝细菌基因组被比较.先用BLASTP两两最佳匹配搜索和基因位置保守性的方法预测直系同源基因,并进一步计算每个基因组中所有基因在其他4种绿球蓝细菌基因组中直系同源基因的数量,从而达到识别外源基因的目的;而基因组岛是指由1个或几个连续外源基因组成的区域.结果表明:在5个绿球蓝细菌基因组中共识别出了16至52个不等的基因组岛,它们中的许多基因在病毒基因组或富含病毒的环境样本中都有同源基因.以上这些结果显示,在绿球蓝细菌中,病毒可能介导了基因的水平转移,从而导致了基因组的多样性.     

糖化酵母糖化酶基因在酿酒酵母中的克隆与表达

[目的]使酿酒酵母高效表达糖化酵母糖化酶基因.[方法]利用PCR技术从糖化酵母中扩增出大小为2700 bp左右的带有启动子的糖化酶基因STA1.通过限制性内切酶BspDI与Acc65I双酶切,将目的基因STA1连接到穿梭质粒pRS416中构建重组质粒pRS416-sta1,转化酿酒酵母通过筛选.[结果]糖化酶活性最高为120 U/ml,酶的最适温度为60℃,最适pH为5.0,在酶催化反应2h后,酶剩余活力能达到约90％.[结论]通过基因工程手段得到高效表达糖化酶基因的酿酒酵母工程菌株.