RETRACTED ARTICLE: An analysis of population structure and linkage disequilibrium using multilocus data in 187 maize inbred lines

This study analyzes population structure and linkage disequilibrium (LD) among 187 commonly used Chinese maize inbred lines, representing the genetic diversity among public, commercial and historically important lines for corn breeding. Seventy SSR loci, evenly distributed over 10 chromosomes, were assayed for polymorphism. The identified 290 alleles served to estimate population structure and analyze the genome-wide LD. The population of lines was highly structured, showing 6 subpopulations: BSSS (American BSSS including Reid), PA (group A germplasm derived from modern U.S. hybrids in China), PB (group B germplasm derived from modern U.S. hybrid in China), Lan (Lancaster Surecrop), LRC (derivative lines from Lvda Reb Cob, a Chinese landrace) and SPT (derivative lines from Si-ping-tou, a Chinese landrace). Forty lines, which formerly had an unknown and/or miscellaneous origin and pedigree record, were assigned to the appropriate group. Relationship estimates based on SSR marker data were quantified in a Q matrix, and this information will inform breeder’s decisions regarding crosses. Extensive inter- and intra-chromosomal LD was detected between 70 microsatellite loci for the investigated maize lines (2109 loci pairs in LD with D′ > 0.1 and 93 out of them at P < 0.01).This suggests that rapidly evolving microsatellites may track recent population structure. Interlocus LD decay among the diverse maize germplasm indicated that association studies in QTLs and/or candidate genes might avoid nonfunctional and spurious associations since most of the LD blocks were broken between diverse germplasm. The defined population structure and the LD analysis present the basis for future association mapping. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

粟酒裂殖酵母N-糖酰胺酶在大肠杆菌中的表达、纯化及活性分析

根据GenBank中公布的粟酒裂殖酵母(Schizosaccharomyces pombe)N-糖酰胺酶(Png1p)cDNA序列, 设计并合成一对特异性引物, 利用RT-PCR技术从粟酒裂殖酵母中克隆出糖酰胺酶cDNA。将得到的基因克隆到表达载体pET-15b中。重组质粒转入大肠杆菌BL21(DE3)中, 经诱导表达和纯化提取后, 进行酶活测定。实验结果表明, 该酶的分子量约为39 kD, 纯化后的重组N-糖酰胺酶可以对变性处理的糖蛋白进行糖链的切除, 且这种作用需要还原剂DTT的辅助作用; N-糖酰胺酶只对错误折叠的糖蛋白有作用, 对天然的糖蛋白没有作用。等量粟酒裂殖酵母Png1p在不同温度、pH、DTT浓度和底物变性温度下对等量核糖核酸酶B(RNase B)的脱糖基化检测发现, 重组酶的最适反应温度30°C, 最适反应pH为7.0, 需要的最适DTT浓度为10 mmol/L, 底物在100°C处理10 min时酶的脱糖基化率最高。     

番茄的耐盐性与耐盐转基因番茄

由于土壤盐渍化的日益加剧导致作物大量减产,通过基因工程的方法将耐盐基因转入作物,培育耐盐作物新品种是开发利用盐碱地的一种经济、有效的手段.番茄是一种栽培广泛,具有重要经济价值的蔬菜,又是基因工程的模式生物之一,开展番茄耐盐性研究具有重要意义.分析了番茄的耐盐性和转耐盐基因番茄的研究现状.     

长江口南北支浮游甲壳动物的比较及南水北调工程影响预测

南水北调东线、中线工程实施后将给长江口水生生物的生态环境带来影响.2005年秋季和2006年春季,对长江口南、北支浮游甲壳动物进行了2航次的调查.调查区域从长江口徐六径至河口 50号灯标,全长181.8 km,自西向东江面宽由约5.7 km扩展为约90km,平面形态呈扇形分布,设立3个断面14个调查采集点.采集到浮游甲壳动物共23科37属54种,其中枝角类6科8属15种,桡足类17科29属39种;秋季种类数多于春季,北支桡足类种类数多于南支;平均总密度为9.10 ind·L-1,平均总生物量为0.1179 mg·L-1,以桡足类为主;北支Ⅲ断面的现存量远远高于南、北支其他断面;长额象鼻溞、简弧象鼻溞为优势枝角类;中华华哲水蚤、汤匙华哲水蚤、球状许水蚤、广布中剑水蚤为优势桡足类.文中还对长江口南、北支浮游甲壳动物的总体水平及时空分布、南水北调对浮游甲壳动物的影响进行了分析.     

(2-Hydroxypropyl)-β-Cyclodextrin Is a New Angiogenic Molecule for Therapeutic Angiogenesis

BackgroundPeripheral artery disease (PAD), which is caused by atherosclerosis, results in progressive narrowing and occlusion of the peripheral arteries and inhibits blood flow to the lower extremities. Therapeutic angiogenesis is a promising strategy for treating ischemia caused by PAD. Nitric oxide (NO) has been shown to be a key mediator of angiogenesis. It has been demonstrated that β-cyclodextrincan stimulate vessel growth in rabbit corneas. In this study, we assessed the mechanism of action and therapeutic potential of a new angiogenic molecule, (2-hydroxypropyl)-β-cyclodextrin (2HP-β-CD).ConclusionsTherapeutic angiogenesis by 2HP-β-CD may be beneficial to patients with PAD.     

Mesenchymal Stromal Cell Secretome Up-Regulates 47 kDa CXCR4 Expression,and Induce Invasiveness in Neuroblastoma Cell Lines

Neuroblastoma accounts for 15% of childhood cancer deaths and presents with metastatic disease of the bone and the bone marrow at diagnosis in 70% of the cases. Previous studies have shown that the Mesenchymal Stromal Cell (MSC) secretome, triggers metastases in several cancer types such as breast and prostate cancer, but the specific role of the MSC factors in neuroblastoma metastasis is unclear. To better understand the effect of MSC secretome on chemokine receptors in neuroblastoma, and its role in metastasis, we studied a panel of 20 neuroblastoma cell lines, and compared their invasive potential towards MSC-conditioned-RPMI (mRPMI) and their cytokine receptor expression profiles. Western blot analysis revealed the expression of multiple CXCR4 isoforms in neuroblastoma cells. Among the five major isoforms, the expression of the 47 kDa isoform showed significant correlation with high invasiveness. Pretreatment with mRPMI up-regulated the expression of the 47 kDa CXCR4 isoform and also increased MMP-9 secretion, expression of integrin α3 and integrin β1, and the invasive potential of the cell; while blocking CXCR4 either with AMD 3100, a CXCR4 antagonist, or with an anti-47 kDa CXCR4 neutralizing antibody decreased the secretion of MMP-9, the expression of integrin α3 and integrin β1, and the invasive potential of the cell. Pretreatment with mRPMI also protected the 47 kDa CXCR4 isoform from ubiquitination and subsequent degradation. Our data suggest a modulatory role of the MSC secretome on the expression of the 47 kDa CXCR4 isoform and invasion potential of the neuroblastoma cells to the bone marrow.     

厚壳贻贝whirlin类贝壳基质蛋白的重组表达与功能分析

贝壳历来是生物工程和材料学研究的重要对象。贝壳中的贝壳基质蛋白质在贝壳的形成与发育过程中具有重要的调控作用。Whirlin类蛋白质(Whirlin-like protein,WLP)是一种从厚壳贻贝(Mytilus coruscus)中鉴定的新型贝壳基质蛋白质。序列分析结果显示,该蛋白质含有PDZ(postsynaptic density/Discs large/Zonula occludens)结构域,而该结构域对贝壳生物矿化的影响目前尚无报道。为深入了解WLP在贝壳形成中对碳酸钙晶体的影响,在序列分析基础上,采用密码子优化结合原核重组表达,获得其重组表达产物后,开展了重组WLP对碳酸钙晶体形貌及晶型的影响研究,结晶速度抑制以及碳酸钙晶体结合分析。分析结果表明,重组WLP能诱导文石型碳酸钙晶体的形貌和方解石型碳酸钙晶体的晶型发生改变;同时重组WLP对碳酸钙晶体具有结合作用,且能抑制碳酸钙晶体的结晶速度。上述结果表明,WLP对贝壳的形成及发育具有重要影响,并可能在贝壳肌棱柱层的形成中发挥了重要作用。     

Pre-zygotic embryological characters ofPlatycrater arguta, a rare and endangered species endemic to East Asia

Platycrater arguta Sieb. et Zucc. is a rare and endangered species endemic to East Asia. It produces two floral morphs viz. bisexual and male flowers. For bisexual flowers, simultaneous cytokinesis in the microsporocyte meiosis leads to a tetrahedral tetrad. The mature pollen grain is shed at 2-cell stage. The young anther wall is composed of epidermis, endothecium that develops fibrous thickenings at maturity, 1–2 middle layers and tapetum. The tapetum with uninucleate to binucleate cells, disintegrates in situ (glandular tapetum), yet in a small percentage of the anthers (about 37.6%), the tapetum does not disintegrate, causing complete male sterility. The ovules are anatropous, unitegmic, tenuinucellar and the formation of the embryo sac follows the monosporic, Polygonum type. Antipodal cells are lacking in the mature embryo sacs. Before fertilization, two polar nuclei fuse into a secondary nucleus. The formation of microsporangial wall, microsporogenesis and male gametogenesis in male flowers are analogous to those in the bisexual. Prezygotic embryological characters ofP. arguta were reported for the first time, revealing that its endangerment is correlated with the abortion of pollen of a part but not to the female development that is normal.     

Investigation of PVA/ws-chitosan hydrogels prepared by combined γ-irradiation and freeze-thawing

γ-Irradiation combined with freeze-thawing, i.e. irradiation followed by freeze-thawing and freeze-thawing followed by irradiation, was applied to prepare poly(vinyl alcohol) (PVA)/water soluble chitosan (ws-chitosan) hydrogels for wound dressing. The properties of these hydrogels were investigated and compared to those prepared by freeze-thawing and by irradiation, respectively. Hydrogels made by irradiation followed by freeze-thawing show larger swelling capacity and mechanical strength, higher thermal stability, lower water evaporation rate, and are less turbid than those made by pure freeze-thawing and freeze-thawing followed by irradiation. Hydrogels made by irradiation alone cannot be used as wound dressing due to their poor mechanical strength. SEM results show that the final structure of hydrogels made by combined irradiation and freeze-thawing is mainly determined by the first processing step. It is found that the appropriate amount of ws-chitosan can endow hydrogels with large swelling capacity and mechanical strength. The presence of ws-chitosan provides the hydrogels with good antibacterial activity against Escherichia coli (E. coli).     

3D Macroporous Nitrogen‐Enriched Graphitic Carbon Scaffold for Efficient Bioelectricity Generation in Microbial Fuel Cells

Microbial fuel cell (MFC) can generate electricity based on oxidation of organic compounds by exoelectogens, giving rise to a promising potential for recovering electrical energy from organic wastewater. The structure and property of anode materials have inherent impact to extracellular electron transfer (EET), an interfacial process that greatly limits bioelectricity production of MFC. Herein, a three dimensional (3D) macroporous nitrogen‐enriched graphitic carbon (NGC) scaffold is fabricated from commercially available melamine foam using facile pyrolysis method. The NGC electrode is demonstrated to promote EET ef?ciently, achieving a power density of 750 mW m^?2 based on pure cultured Shewanella oneidensis MR‐1 in acetate‐feeding MFC. The unique 3D open‐cell structure not only offers habitats for colonization of electroactive bio?lm up to a maximal density but also provides macroporous architecture for internal mass transfer without concern of bio‐blocking and bio‐fouling. Additionally, nitrogen incorporation also plays a signi?cant role in enhancing EET, where pyrrolic nitrogen is much more active than graphitic and pyridinic nitrogen as indicated by density functional theory calculation. This work provides a proof‐of‐concept demonstration of a high‐ef?ciency, cost‐effective, easily scaling‐up, and environmentally friendly anode material of bioelectrochemical systems for electricity generation, hydrogen production, and pollutant degradation.