Dystroglycan function requires xylosyl- and glucuronyltransferase activities of LARGE

Posttranslational modification of alpha-dystroglycan (α-DG) by the like-acetylglucosaminyltransferase (LARGE) is required for it to function as an extracellular matrix (ECM) receptor. Mutations in the LARGE gene have been identified in congenital muscular dystrophy patients with brain abnormalities. However, the precise function of LARGE remains unclear. Here we found that LARGE could act as a bifunctional glycosyltransferase, with both xylosyltransferase and glucuronyltransferase activities, which produced repeating units of [-3-xylose-α1,3-glucuronic acid-β1-]. This modification allowed α-DG to bind laminin-G domain-containing ECM ligands.     

Wnt gradient formation requires retromer function in Wnt-producing cells

Wnt proteins function as morphogens that can form long-range concentration gradients to pattern developing tissues. Here, we show that the retromer, a multiprotein complex involved in intracellular protein trafficking, is required for long-range signaling of the Caenorhabditis elegans Wnt ortholog EGL-20. The retromer functions in EGL-20-producing cells to allow the formation of an EGL-20 gradient along the anteroposterior axis. This function is evolutionarily conserved, because Wnt target gene expression is also impaired in the absence of the retromer complex in vertebrates. These results demonstrate that the ability of Wnt to regulate long-range patterning events is dependent on a critical and conserved function of the retromer complex within Wnt-producing cells.     

Golgi duplication in Trypanosoma brucei requires Centrin2

Centrins are highly conserved components of the centrosome, which in the parasitic protozoan T. brucei comprises the basal body and nucleates the flagellum used for locomotion. Here, we found TbCentrin2 in an additional bi-lobed structure near to the Golgi apparatus. One lobe was associated with the old Golgi, and the other became associated with the newly forming Golgi as the cell grew. Depletion of TbCentrin1 inhibited duplication of the basal body, whereas depletion of TbCentrin2 also inhibited duplication of the Golgi. Thus, a Centrin2-containing structure distinct from the basal body appears to mark the site for new Golgi assembly.     

Ectodermal Wnt function as a neural crest inducer

Neural crest cells, which generate peripheral nervous system and facial skeleton, arise at the neural plate/ectodermal border via an inductive interaction between these tissues. Wnts and bone morphogenetic proteins (BMPs) play roles in neural crest induction in amphibians and zebrafish. Here, we show that, in avians, Wnt6 is localized in ectoderm and in vivo inhibition of Wnt signaling perturbs neural crest formation. Furthermore, Wnts induce neural crest from naive neural plates in vitro in a defined medium without added factors, whereas BMPs require additives. Our data suggest that Wnt molecules are necessary and sufficient to induce neural crest cells in avian embryos.     

Hirschsprung disease is linked to defects in neural crest stem cell function

Genes associated with Hirschsprung disease, a failure to form enteric ganglia in the hindgut, were highly up-regulated in gut neural crest stem cells relative to whole-fetus RNA. One of these genes, the glial cell line-derived neurotrophic factor (GDNF) receptor Ret, was necessary for neural crest stem cell migration in the gut. GDNF promoted the migration of neural crest stem cells in culture but did not affect their survival or proliferation. Gene expression profiling, combined with reverse genetics and analyses of stem cell function, suggests that Hirschsprung disease is caused by defects in neural crest stem cell function.     

Intron removal requires proofreading of U2AF/3' splice site recognition by DEK

Discrimination between splice sites and similar, nonsplice sequences is essential for correct intron removal and messenger RNA formation in eukaryotes. The 65- and 35-kD subunits of the splicing factor U2AF, U2AF65 and U2AF35, recognize, respectively, the pyrimidine-rich tract and the conserved terminal AG present at metazoan 3' splice sites. We report that DEK, a chromatin- and RNA-associated protein mutated or overexpressed in certain cancers, enforces 3' splice site discrimination by U2AF. DEK phosphorylated at serines 19 and 32 associates with U2AF35, facilitates the U2AF35-AG interaction and prevents binding of U2AF65 to pyrimidine tracts not followed by AG. DEK and its phosphorylation are required for intron removal, but not for splicing complex assembly, which indicates that proofreading of early 3' splice site recognition influences catalytic activation of the spliceosome.     

大梨树移植技术

<正>近年来,大型果树已被列入城市绿化的重要树种,它以独特的气质和典雅的姿态供市民观赏,为城市绿化和空气净化起到了重要作用。大梨树传统的移植方法是:断根,重回缩修剪,生长1～2年再移植。此方法能确保移植后的成活率。但是,由于近年来市场需求紧迫,需要及时移植。针对萌芽不强的树种,根据多年的生产经验,总结得出大梨树移植新方     

对成人高等专科教育的思考

成人高等专科教育新生质量近几年逐渐下降,统考统招已渐无实质意义,学校管理机制有些滞后,教学改革深入不够,如何保证和提高学生质量已成当务之急.因此,建议改统考统招制度为开门办学,更新教育理念灵活办学,进一步改进教育方法和教学方式,加强学校与学生的互动作用,加强学生能力的培养,让学生适应社会需求和服务于社会.     

花斑皮蠹成虫行为观察

在适宜的温度范围内,随着温度的升高,花斑皮蠹成虫活动性越强,飞翔的虫口数越多;光照度为380 lx时,短时间内即可刺激成虫起飞,在黑暗的条件下,成虫比较安静;未交尾的雌、雄成虫起飞虫口数分别为31.1%和82.52%;交尾产卵后雌、雄成虫起飞虫口分别为6.67%和77.78%;配对成虫有61.2%的成虫飞翔,其中雌虫占14.3%,雌虫未产卵或开始产卵或羽化后7 d内起飞较多;成虫交尾呈"V"型,一生多次交尾;雌虫产卵前活动频繁,身体边爬行边后倾,后倾时露出产卵器上下左右摆动,寻找适当的产卵场所;卵有单产、串产、成排产、聚堆产,卵多产于缝隙等处.     

创新成人教育理念构建我国高校成人教育发展的新格局

面对新世纪的发展形势,成人教育必须树立新的发展理念,探索新的发展方向.新经济条件下,我国的成人教育有其自身的特点.从我国高校固有的职能、战略地位和历史使命来看,高校成人教育不应再处于整个教育系统的边缘,而应成为整个教育系统中越来越重要的组成部分,它应成为普通教育和成人教育两者之间紧密结合的典范.要注重办学的基地建设和管理职能的转变.优化配置成人教育资源,对高校进行合理的布局调整,实现成人教育与其他教育形式和社会资源的共享.     

关于林业成人教育与培训的思考

发展成人教育与培训是构建学习型社会的重要组成部分,新形势下林业成人教育与培训的发展途径在jr增强意识、改革办学模式、突出教育教学的针对性和实用性.当前林业成人教育与培训工作存在着经费缺乏、高层次培训少等问题,应积极采取相应对策.     

黄色潜蝇茧蜂成虫的生物学特性

为更好地利用天敌昆虫黄色潜蝇茧蜂(Opius flayus)防治美洲斑潜蝇(Liriomyza sativae),在实验室选用菜豆(Phaseolus vulgaris)上的美洲斑潜蝇为寄主,对黄色潜蝇茧蜂成虫的生物学特性进行初步研究。结果表明:黄色潜蝇茧蜂成虫羽化高峰期在8:00~10:00,且大多数在羽化当天就能进行交配;羽化成蜂的性比明显偏雌性(♀/♂=1.79/1);对雌成虫的寄主搜寻、取食及产卵过程进行了详细描述。     

法国梧桐大树移栽技术

介绍了法国梧桐大树移栽技术,主要包括移栽前准备、挖掘、栽植、栽植后管理、病虫害防治等内容,以供参考。