Uptake of endocytic markers by rice cells: variations related to the growth phase

Endocytosis is now considered a basic cellular process common to plant cells. Although both non-specific and receptor-mediated endocytosis appear to take place in plant cells, the physiological role of the latter remains unclear. We have investigated the endocytic process in rice cell suspensions using two biotinylated proteins, peroxidase and bovine serum albumin (bHRP and bBSA), as markers. First, we show that markers are internalized by rice cells and appear in intracellular membranes. The uptake of the two markers is temperature dependent, saturable with time and markers dose and it is competed by free biotin. Thus, it shows the properties of a receptor-mediated process. We also show that uptake of markers is strongly influenced by growth phase as optimal uptake occurs during the lag phase, but the initiation of the exponential growth phase decreases uptake drastically. Arrest of the cell cycle by starvation of either a nutrient (phosphate) or a growth regulator (2,4-dichlorophenoxyacetic acid), both components of the culture medium, does not modify the rate of bBSA uptake. Subsequent readdition of these components results in growth recovery and a dramatic decrease in bBSA uptake. On the other hand, nocodazole treatment, a method to arrest the cell cycle by microtubule depolymerization, inhibited bBSA uptake. The possible causes for this arrest of endocytosis are discussed.     

睾丸间质干细胞增殖分化及其调控

睾丸间质干细胞（stem Leydig cells, SLCs）是哺乳动物睾丸间质内的一种成体干细胞,可以分化成为成熟的睾丸间质细胞,参与精子发生。目前,仅在人、大鼠和小鼠中成功分离出SLCs,并证实其具有分化成为睾酮分泌细胞的潜能。最新研究发现：PDGFRα、Nestin、Thy-1、CD51和COUP-TFII等可作为SLCs的分子标记,但并不具有特异性。迄今,只在大鼠中建立了SLCs的基本分离培养体系。因此,本文拟从大鼠等SLCs的分子标记、分离培养条件、增殖分化调控以及哺乳动物LCs在精子发生过程中作用的研究进展等作一综述,以期为哺乳动物SLCs研究提供科学参考。     

一个先天性眼球震颤家系致病基因的初步定位

为确定一个X染色体显性遗传先天性眼球震颤家系的致病基因与X染色体的连锁关系, 选用X染色体上的DXS1214、DXS1068、DXS993、DXS8035、DXS1047、DXS8033、DXS1192和DXS1232共8个微卫星DNA标记对该家系进行基因扫描与基因分型,并利用LINKAGE等软件包对基因分型结果进行分析,探讨该家系致病基因与X染色体的连锁关系。 两点连锁分析时X染色体短臂4个基因座最大LOD值均小于-1,不支持与该家系致病基因连锁; X染色体长臂4个基因座中最大LOD值达到2,提示存在较大的连锁可能性。该家系的致病基因可初步定位于X染色体长臂,且提示Xq26-Xq28区间附近可能是先天性眼球震颤一个共同的致病基因座,但区间范围仍较大,仍须进一步选择合适的微卫星标记进行精确的定位以缩小候选基因的筛查范围。Abstract： To investigate the relationship between X chromosome and obligatory gene of a pedigree with congenital nystagmus,we used the following markers: DXS1214、DXS1068、DXS993、DXS8035、DXS1047、DXS8033、DXS1192 and DXS1232.Genome screening and genotyping were conducted in this pedigree of congenital nystagmus, and linkage analysis by LINKAGE package was used to determine the potential location. The linkage was not found on the Xp ( All LOD score <-1) but on Xq (the maximum LOD score=2). The related gene of this pedigree was located on the long arm of X chromosome. We demonstrate that Xq26-Xq28 is a common locus for CMN. It bring us closer to the identification of a gene responsible for X-linked CMN.     

Molecular mapping of a new gene Rrs4 CI 11549 for resistance to barley scald (Rhynchosporium secalis)

Doubled haploid (DH) progeny from a cross between the scald susceptible barley (Hordeum vulgare L.) cultivar Ingrid and the resistant accession CI 11549 (Nigrinudum) was evaluated for resistance in the pathogen Rhynchosporium secalis (Oudem) J.J. Davis. Two linked and incompletely dominant loci confer resistance CI 11549 against isolate 4004. One is an allele at the complex Rrs1 locus on chromosome 3H close to the centromere; the other is located 22 cM distally on the long arm. The latter locus is designated Rrs4. In BC₃-lines into Ingrid from CI 2222 (another Nigrinudum) resistance seems governed by one locus close to the telomeric region of chromosome 7H, probably allelic to Rrs2. In neither case did we find any trace of the recessive gene rh8 reported to be present in Nigrinudum. Various resistance donors of Ethiopian origin designated as Nigrinudum, Jet or Abyssinian were identical to a great extent with respect to markers, but differed in resistance to different isolates of scald or in barley yellow dwarf virus (BYDV) resistance. The implications for their use as differentials in scald tests and screening of germplasm collections are discussed.     

一种高等植物小片段RNA分子标记方法

分子生物学技术特别是分子标记方法越来越多应用于研究植物间相似关系及其进化规律。为试图寻找一种适合缺乏分子生物学数据的,以及能够在属以上高阶元间快速比较研究的小片段RNA分子标记方法,作者通过含HAc-NaAc缓冲体系的SDS总核酸提取方法,提取了53种高等植物的总核酸。将总核酸在7%的聚丙烯酰胺凝胶中电泳,结果发现:(1)在100-200 bases的位置有高丰度的RNA条带,条带稳定清晰,结果可重复再现,用DNaseI和RNaseA处理后认为这些片段属于小片段RNA。(2)比较了绿豆幼苗经0-8h不同光照处理,以及猕猴桃不同品种和器官之间的小片段RNA,表明不同光照时间、不同性别的花蕾、叶片和染色体倍性间的带型一致,说明这些片段部分具有一定的空间结构,其表达极其稳定,无明显差异。(3)同一科内的植物的带型存在多态性,主要是由地理隔绝造成的差异,并且分类阶元高的多态性百分比和多态性信息量高于分类阶元低的。(4)经过比较蕨类植物、裸子植物和被子植物53种植物的小片段RNA,发现在100-200bases中含3-6条清晰的条带,带型跟植物亲缘关系相关。因此,作者认为100-200bases位置的小片段RNA可作为鉴定植物科间和科内亲缘关系的一种分子辅助标记。     

Rap1-GTP-interacting adaptor molecule (RIAM) protein controls invasion and growth of melanoma cells

The Mig-10/RIAM/lamellipodin (MRL) family member Rap1-GTP-interacting adaptor molecule (RIAM) interacts with active Rap1, a small GTPase that is frequently activated in tumors such as melanoma and prostate cancer. We show here that RIAM is expressed in metastatic human melanoma cells and that both RIAM and Rap1 are required for BLM melanoma cell invasion. RIAM silencing in melanoma cells led to inhibition of tumor growth and to delayed metastasis in a severe combined immunodeficiency xenograft model. Defective invasion of RIAM-silenced melanoma cells arose from impairment in persistent cell migration directionality, which was associated with deficient activation of a Vav2-RhoA-ROCK-myosin light chain pathway. Expression of constitutively active Vav2 and RhoA in cells depleted for RIAM partially rescued their invasion, indicating that Vav2 and RhoA mediate RIAM function. These results suggest that inhibition of cell invasion in RIAM-silenced melanoma cells is likely based on altered cell contractility and cell polarization. Furthermore, we show that RIAM depletion reduces β1 integrin-dependent melanoma cell adhesion, which correlates with decreased activation of both Erk1/2 MAPK and phosphatidylinositol 3-kinase, two central molecules controlling cell growth and cell survival. In addition to causing inhibition of cell proliferation, RIAM silencing led to higher susceptibility to cell apoptosis. Together, these data suggest that defective activation of these kinases in RIAM-silenced cells could account for inhibition of melanoma cell growth and that RIAM might contribute to the dissemination of melanoma cells.     

基于分子生物学方法的外来入侵物种入侵历史重构

生物入侵是一个世界性的问题。全球每年因生物入侵造成的损失超过1万亿美元。探究入侵物种在入侵地的入侵历史对了解生物入侵的生物生态学机制、制定阻截及防除措施有重要意义。分子标记方法的兴起和大规模应用打开了入侵生物入侵历史研究的新天地。采用分子标记的方法可鉴定入侵物种的种类、追溯其来源地、回溯其扩散路径、分析扩散模式及探究物种入侵过程中对入侵种群本身的变化及其对生态系统所造成的各种影响。分子标记的应用使得多个入侵物种的入侵历史得以重现。由于分子标记方法重构的入侵历史受采样范围、采用的分子标记的种类及数量等因素的影响,该方法呈现入侵历史是否是真实发生的入侵过程还存在争议。     

Segregation of random amplified DNA markers in F1 progeny of conifers

Summary The recently developed approach to deriving genetic markers via amplification of random DNA segments with single primers of arbitrary nucleotide sequence was tested for its utility in genetic linkage mapping studies with conifers. Reaction conditions were optimized to reproducibly yield clean and specific amplification products. Template DNA from several genotypes of Douglas-fir (Pseudotsuga menziesii) and white spruce (Picea glauca) were tested against eight ten-base oligonucleotide primers. Most of the tested primer/parent tree combinations yielded polymorphic PCR products (RAPD markers). Selected primers were then used in PCR reactions with template DNA isolated from offspring in Douglas-fir and black spruce diallel crosses among the same parental lines. The diallel study confirmed the appropriate inheritance of RAPD markers in the F₁ generation. The value of these dominant RAPD markers for genetic linkage mapping in trees was established from both theoretical and applied perspectives.