Vinculin activation by talin through helical bundle conversion

Vinculin is a conserved component and an essential regulator of both cell-cell (cadherin-mediated) and cell-matrix (integrin-talin-mediated focal adhesions) junctions, and it anchors these adhesion complexes to the actin cytoskeleton by binding to talin in integrin complexes or to alpha-actinin in cadherin junctions. In its resting state, vinculin is held in a closed conformation through interactions between its head (Vh) and tail (Vt) domains. The binding of vinculin to focal adhesions requires its association with talin. Here we report the crystal structures of human vinculin in its inactive and talin-activated states. Talin binding induces marked conformational changes in Vh, creating a novel helical bundle structure, and this alteration actively displaces Vt from Vh. These results, as well as the ability of alpha-actinin to also bind to Vh and displace Vt from pre-existing Vh-Vt complexes, support a model whereby Vh functions as a domain that undergoes marked structural changes that allow vinculin to direct cytoskeletal assembly in focal adhesions and adherens junctions. Notably, talin's effects on Vh structure establish helical bundle conversion as a signalling mechanism by which proteins direct cellular responses.     

Tagging major quantitative trait loci for sheath blight resistance in a rice variety, Jasmine 85

This study was conducted with a clonal F₂ population of rice from a cross between Jasmine 85, a resistant variety, and Lemont, a susceptible cultivar. The rice plants belonging to each F₂ clone were divided into two plots, which were put in two replicates, respectively. Clonal parents were tested as controls. The plants were inoculated by short toothpicks incubated with RH-9, a virulent isolate of the pathogenic fungus,Rhizoctonia solani, which causes rice sheath blight. The extreme resistant and susceptible clonal lines were selected for construction of resistant and susceptible DNA pools, respectively. A total of 94 polymorphic markers evenly distributed on 12 rice chromosomes were used for bulked segregant analysis, three positive ones were found polymorphic between the two DNA pools, and three major QTLs for sheath blight resistance, Rh-2, Rh-3 and Rh-7, were identified. The three major QTLs were located on chromosomes 2, 3 and 7, and could explain 14.4%, 26.1% and 22.2% of the phenotypic variation.     

面向所有人的科学素质

 美国科学促进协会（American Association for the Advancement of Science，AAAS）是一个全球性的非营利、会员制协会，也是一个出版机构，它的使命是通过在全球范围内促进科学和创新的发展以造福人类。AAAS在中国有着志同道合的伙伴--中国科协，它们有近40年的合作关系，这两个机构共同致力于实现相似的使命，并且共享会员团体和科学传播机构。     

On the glutamine and γ-aminobutyric acid contents of various regions of the cat brain

Résumé Les auteurs ont déterminé par la méthode de la chromatographie à deux dimensions, la teneur en glutamine et en acide -aminobutyrique des différentes parties du cerveau du chat. La concentration la plus élevée de l'acide -aminobutyrique a été trouvé dans l'hypothalamus, tandis que celle de la glutamine a été constatée dans le noyau caudé. Les concentrations les plus basses de ces deux protéines apparaissent dans la substance blanche du cerveau.     

"数字地球"时代的我国西部可持续发展

“数字地球”作为新世纪信息时代的新目标和制高点,必将在西部大开发战略的实施过程中起到至关重要的作用。从“数字地球”的基本概念出发,应用“数字地球”的理论和技术,阐述了“数字地球”技术对西部大开发的战略意义和应用方向,为我国西部地区的可持续发展提供了新的思路和技术方法。     

水稻品种Jasmine85抗纹枯病主效QTLs的分子标记定位

对水稻抗病品种Ｊａｓｍｉｎｅ８５与感病品种Ｌｅｍｏｎｔ的杂交组合构建Ｆ２世代的单株无性系群体,以牙签嵌入法对１２８个无性系群体进行纹枯病菌接种,选择极端抗感无性系构建抗感近等基因池。用９４个均匀分布于１２条染色体上的多态性探针,与抗感近等基因池进行Ｓｏｕｔｈｅｒｎ杂交,从池间筛选出３个阳性多态性分子标记,进而检测到３个主效抗病ＱＴＬｓ。     

Immunohistochemical localization of endogenous nerve growth factor

Nerve growth factor (NGF) has been proposed as a trophic molecule essential for the development of sympathetic and primary sensory neurones. In newborn mice and rats, administration of nerve growth factor results in an increase in the number of surviving neurones, whereas administration of antiserum to NGF decreases neuronal survival. Thus it has been proposed that the factor is produced and secreted by the relevant target tissues to provide trophic support for the ingrowing nerves. The site of synthesis of nerve growth factor is still unknown, and it has been emphasized that a precise physiological role for the molecule cannot be ascribed until the cell types that produce it are known. I report here the use of immunohistochemistry to localize endogenous NGF in the rat iris, a tissue in which there is sound biochemical evidence for the production of NGF activity. Surprisingly, the results reveal that NGF can be detected readily in Schwann cells, but not in smooth muscle cells of the iris when it is sympathetically denervated or cultured.