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Dynamic changes in transcripts during regeneration of the secondary vascular system in Populus tomentosa Carr. revealed by cDNA microarrays
Minjie Wang, Xiaoli Qi, Shutang Zhao, Shougong Zhang, Meng-Zhu Lu
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-215
Abstract: In this study, cDNA microarrays were prepared from a subtracted cDNA library (cambium zone versus leaf) of Chinese white poplar (Populus tomentosa Carr.) and employed to analyze the transcriptional profiles during the regeneration of the secondary vascular system, a platform established in our previous study. Two hundred and seven genes showed transcript-level differences at the different regeneration stages. Dramatic transcriptional changes were observed at cambium initiation, cambium formation and differentiation, and xylem development, suggesting that these up- or downregulated genes play important roles in these stage transitions. Transcription factors such as AUX/IAA and PINHEAD, which were previously shown to be involved in meristem and vascular tissue differentiation, were strongly transcribed at the stages when cambial cells were initiated and underwent differentiation, whereas genes encoding MYB proteins and several small heat shock proteins were strongly transcribed at the stage when xylem development begins.Employing this method, we observed dynamic changes in gene transcript levels at the key stages, including cambium initiation, cambium formation and differentiation, and xylem development, suggesting that these up- or downregulated genes are strongly involved in these stage transitions. Further studies of these genes could help elucidate their roles in wood formation.Wood constitutes one of the most important natural resources on earth, and is a potential future alternative to fossil energy resources. Wood is the end product of secondary vascular system (SVS) development, and is mainly composed of fibers and tracheary elements with secondary cell walls [1]. Four major processes are involved in wood formation: cell expansion, secondary wall biosynthesis, lignification, and programmed cell death. Recent advances in the understanding of these processes have revealed that wood formation is under highly regulated genetic control [1]. In recent years, genomic
Study on Origin of Populus tomentosa Carr.

Li Kuan-yu,Huang Min-ren,Wang Ming-xiu,

中国科学院研究生院学报 , 1997,
Abstract: This study analyzed five varieties of P. tomentosa and their putative parents, P. alba, P. davidiana, P. adenopoda and P. tremula by RAPD and artificial cross. Of 78 bands revealed by 13 arbitrary primers selected, 58 (74.36%) bands were polymorphic among P. tomentosa and four putative parents. The RAPD statistical results showed the relationship between P. tomentosa and P. alba or P. adenopoda was closer than that between P. tomentosa and P. davidiana or P. tremula . There were higher similarity and lower genetic distance between P. tomentosa and P. alba or P. adenopoda than that between P. tomentosa and the other two putative parents. The results from UPGMA, Fitch margoliash phylogenetic dendrogram were similar. In addition, artificial hybrids including reciprocal cross between P. alba and P. adenopoda were used to compare with five varieties of P. tomentosa . And those hybrids between P. alba as female and P. adenopoda as male were closer to P. tomentosa than those from reciprocal cross. The results demonstrated that P. tomentosa was a natural hybrid between P. alba as female parent and P. adenopoda as male parent.
Correlations between megasporocytes and microsporocytes meiosis stages of Populus tomentosa Carr.

- , 2015,
Abstract: 【目的】对毛白杨大、小孢子母细胞减数分裂进程的相关性进行研究,为毛白杨多倍体诱导提供细胞学理论基础与技术支持。【方法】2014-01采集毛白杨雌、雄花枝于温室水培,自水培46 h开始每隔2~3 h取雌、雄花芽样品,采用石蜡切片和醋酸洋红压片技术对毛白杨大、小孢子母细胞减数分裂进程及其对应关系进行观察研究。【结果】毛白杨小孢子母细胞在水培52 h开始减数分裂,发育到双核花粉粒共历时约10 d;大孢子母细胞在水培118 h开始减数分裂,发育至二核胚囊期共历时约13 d。毛白杨大、小孢子母细胞减数分裂的进程以及与雌、雄花芽外部形态的变化之间均存在一定的相关性,在水培118 h毛白杨大孢子母细胞开始减数分裂进入细线期时,其小孢子母细胞减数分裂至四分体时期,此时雌花序微微露出芽鳞,雄花序1/4以上伸出芽鳞,花药呈块状微红色;在水培144 h大孢子母细胞减数分裂发育到粗线期时,其小孢子母细胞大多已发育至单核期,此时雌花序1/5伸出芽鳞,雄花序1/3以上伸出芽鳞,花药呈块状浅红色;在水培237 h大孢子母细胞减数分裂发育到中期Ⅰ时,其小孢子母细胞已发育至双核期,此时雌花序1/3伸出芽鳞,雄花序1/2以上伸出芽鳞,花药呈块状红色。【结论】根据大、小孢子母细胞减数分裂进程的时序相关性,通过观察相同培养条件下小孢子母细胞减数分裂的时期,可即时判别大孢子母细胞的减数分裂进程;还可从花芽长度、花药颜色等来估计大、小孢子母细胞减数分裂所处的时期。
【Objective】This study investigated the correlations in meiotic process of Populus tomentosa Carr.megasporocytes and microsporocytes to provide cytological basis and technical support for polyploid hybrid breeding.【Method】Flowering branches of P.tomentosa Carr.planted in water in greenhouse were collected and flower buds were picked every two to three hours after being cultured in water for 46 hours.The mother cell meiosis stages and their corresponding relations between megasporocytes and microsporocytes of P.tomentosa Carr.were studied using paraffin section method and acetic carmine squash technique.【Result】After being cultured in water for 52 hours,microspore mother cells of P.tomentosa Carr.started meiosis and it took 10 days for them to develop into binucleate pollen grains.Megaspore mother cells began meiosis after 118 hours and binucleate embryo sacs formed after 13 days.The meiosis stages and flower bud morphologies of megaspores and microspores closely related.After 118 hours in water,the meiosis of megaspore mother cells entered leptotene,while that of microspore mother cells developed into tetrads.Little female catkin and more than 1/4 of male catkin appeared and anthers appeared patches of slight redness.The meiosis of most megaspore mother cells developed into pachytene after 144 hours,and microspores developed into mononuclear.At the same time,1/5 of female catkin and more than 1/3 of male catkin extended and patches of pale redness appeared on anthers.When the meiosis of megasporocytes entered metaphase Ⅰ after 237 hours in water,the microsporocytes developed into binucleate.Meantime,1/3 of female catkin and more than 1/2 of male catkin extended and anthers had red patches.【Conclusion】According to the relationship of female and male gametes,the meiosis stages of megasporocytes could be discriminated timely through observing the meiosis of microsporocytes under the same culture circumstances.In addition,the meiosis stages
乡村社会内部的讨债博弈及策略特征――以西南农村的一起建筑业农民工讨薪案为例  [PDF]
南京农业大学学报(社会科学版) , 2017,
Abstract: 欠债与讨债是乡村社会中的常见现象,也是洞察熟人之间行为互动模式的重要切入点。文章以博弈论为视角,以讨债行为为基本单位,提出了乡村社会内部讨债行为中的序贯博弈模型,以及相关的概念与命题。文章探讨了乡村社会内部、熟悉人之间特定的信息结构与社会规范,以及如何影响和形塑债权人与债务人的互动博弈。此后,文章以西南农村中发生的一起建筑业农民工讨薪案的资料为基础,阐释了所提出的分析框架与理论思路。
Debt and debt collection are common phenomena in rural society, and it is also an important point to understand the patterns of interaction between acquaintances. This paper adopts the perspective of game theory to study the behavior of debt collection, and put forward the sequential game model, as well as related concepts and propositions, through the research on debt collection of rural society. This paper explores how specific information structures and social norms existing among acquaintances in rural society could influence and shape the interaction game between creditors and debtors. Besides, this paper illustrates the proposed analysis framework and theoretical ideas in a case study of construction migrantworkers’ debt collection in rural areas of southwest China
Violence and hope in Ariel, by Marina Carr
Zoraide Rodrigues Carrasco de Mesquita
Ilha do Desterro , 2010,
Abstract: This article deals with two forms of intertextuality: rewriting and allusion. On the one hand, by confronting Marina Carr's Ariel (2002) and the three Greek tragedies employed as the starting point for her play, we examine how our contemporary world is depicted by the Irish playwright through the shifts introduced in the texts used as sources. On the other hand, allusion, especially the one present on the title, is also analysed, since we understand that it offers new dimensions for the interpretation of the play.
Chili, un modèle au carré
Jorge Negrete Sepúlveda,Hervé Théry,Sébastien Velut
Mappemonde , 2002,
Abstract: Le Chili est pour certains un modèle économique, mais il peut aussi être un exemple instructif pour qui s'intéresse à l'aménagement du territoire, un modèle au carré en quelque sorte. Et c'est précisément en inscrivant dans un carré le modèle graphique qui dégage ses structures principales que l'on peut s'affranchir de sa forme, pour mieux y revenir ensuite.
Conservation and divergence of microRNAs in Populus
Abdelali Barakat, Phillip K Wall, Scott DiLoreto, Claude W dePamphilis, John E Carlson
BMC Genomics , 2007, DOI: 10.1186/1471-2164-8-481
Abstract: Analysis of almost eighty thousand small RNA reads allowed us to identify 123 new sequences belonging to previously identified miRNA families as well as 48 new miRNA families that could be Populus-specific. Comparison of the organization of miRNA families in Populus, Arabidopsis and rice showed that miRNA family sizes were generally expanded in Populus. The putative targets of non-conserved miRNA include both previously identified targets as well as several new putative target genes involved in development, resistance to stress, and other cellular processes. Moreover, almost half of the genes predicted to be targeted by non-conserved miRNAs appear to be Populus-specific. Comparative analyses showed that genes targeted by conserved and non-conserved miRNAs are biased mainly towards development, electron transport and signal transduction processes. Similar results were found for non-conserved miRNAs from Arabidopsis.Our results suggest that while there is a conserved set of miRNAs among plant species, a large fraction of miRNAs vary among species. The non-conserved miRNAs may regulate cellular, physiological or developmental processes specific to the taxa that produce them, as appears likely to be the case for those miRNAs that have only been observed in Populus. Non-conserved and conserved miRNAs seem to target genes with similar biological functions indicating that similar selection pressures are acting on both types of miRNAs. The expansion in the number of most conserved miRNAs in Populus relative to Arabidopsis, may be linked to the recent genome duplication in Populus, the slow evolution of the Populus genome, or to differences in the selection pressure on duplicated miRNAs in these species.The genus Populus encompasses approximately 30 species divided into 6 sections [1]. Cottonwood species are in the section Tacamahaca. The two North American cottonwood species P. balsamifera and P. trichocarpa are so closely related that the latter is often referred to as a s
A Proof of the Boyd-Carr Conjecture  [PDF]
Frans Schalekamp,David P. Williamson,Anke van Zuylen
Computer Science , 2011,
Abstract: Determining the precise integrality gap for the subtour LP relaxation of the traveling salesman problem is a significant open question, with little progress made in thirty years in the general case of symmetric costs that obey triangle inequality. Boyd and Carr [3] observe that we do not even know the worst-case upper bound on the ratio of the optimal 2-matching to the subtour LP; they conjecture the ratio is at most 10/9. In this paper, we prove the Boyd-Carr conjecture. In the case that a fractional 2-matching has no cut edge, we can further prove that an optimal 2-matching is at most 10/9 times the cost of the fractional 2-matching.
Higher Contou-Carrère symbol: local theory  [PDF]
Sergey Gorchinskiy,Denis Osipov
Mathematics , 2015, DOI: 10.1070/SM2015v206n09ABEH004494
Abstract: We construct a higher-dimensional Contou-Carr\`ere symbol and we study its various fundamental properties. The higher-dimensional Contou-Carr\`ere symbol is defined by means of the boundary map for $K$-groups. We prove its universal property. We provide an explicit formula for the higher-dimensional Contou-Carr\`ere symbol over $\mathbb Q$ and we prove integrality of this formula. A relation with the higher-dimensional Witt pairing is also studied.
The two-dimensional Contou-Carrère symbol and reciprocity laws  [PDF]
Denis Osipov,Xinwen Zhu
Mathematics , 2013,
Abstract: We define a two-dimensional Contou-Carr\`{e}re symbol, which is a deformation of the two-dimensional tame symbol and is a natural generalization of the (usual) one-dimensional Contou-Carr\`{e}re symbol. We give several constructions of this symbol and investigate its properties. Using higher categorical methods, we prove reciprocity laws on algebraic surfaces for this symbol. We relate also the two-dimensional Contou-Carr\`{e}re symbol with the two-dimensional class field theory.
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