两系杂交小麦恢复系MR168抗条锈病基因遗传分析及分子标记定位

小麦条锈病是影响杂交小麦普及推广的重要因素。文章利用基因推导法和SSR分子标记技术,研究了温光型两系杂交小麦恢复系MR168的抗条锈性遗传规律及其控制基因染色体位置。结果表明,MR168对CY29、CY31、CY32、CY33等条锈菌生理小种表现高抗至免疫;对SY95-71/MR168杂交组合的正反交F1、BC1、F2和F3群体分单株接种鉴定显示,MR168对CY32号小种的抗性受1对显性核基因控制,该抗病基因来源于春小麦品种辽春10号。利用集群分离分析法(Bulked segregant analysis,BSA)和简单重复序列(Simple sequence repeat,SSR)分子标记分析抗病亲本MR168、感病亲本SY95-71及183个F2代单株,发现了与MR168抗条锈病基因连锁的5个微卫星标记Xgwm273、Xgwm18、Xbarc187、Xwmc269、Xwmc406,并将该基因初步定位在1BS着丝粒附近,暂命名为YrMR168;构建了包含YrMR168的SSR标记遗传图谱,距离YrMR168最近的两个微卫星位点是Xgwm18和Xbarc187,遗传距离分别为1.9 cM和2.4 cM,这两个微卫星标记可用于杂交小麦抗条锈病分子标记辅助育种。     

杂交水稻及其“三系”线粒体DNA的AP—PCR指纹图谱

为了研究水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）细胞质雄性不育（ＣＭＳ）与线粒体基因组的关系,应用ＡＰ－ＰＣＲ 分析,用７ 个任意单引物对６ 种水稻品系线粒体ＤＮＡ 进行了扩增。水稻线粒体ＤＮＡ 的ＡＰ－ＰＣＲ 产物可分为三种类型：（１）所有供试品系均能扩增的片段,它们代表了线粒体ＤＮＡ 在进化上的保守性序列。有４ 个引物检测到这类片段。（２）２ 个以上水稻品系共同出现而在全部供试材料间存在差异的扩增片段,这类片段是检测水稻线粒体ＤＮＡ多态性的主要来源。（３）一种细胞质类型所特有的扩增片段,从引物Ｒ２ 和Ｖ５ 的扩增产物中发现了这类片段,它们可能与ＣＭＳ有关联。另外,ＷＡ型不育系珍汕９７Ａ 与其杂种之间在６ 个引物的扩增图谱上均存在不同程度的差异,说明两者的线粒体ＤＮＡ序列结构可能存在某种差别     

猪眼角膜的生物力学特性

对猪眼角膜进行了有系统的单轴拉伸实验,通过实验来确定其极限强度,断裂能、显著非线性的应力-应变关系和滞后环.在不同的应变水平下进行了应为松弛实验并确定了连续松弛谱的各参数.从极限强度、断裂能和应力松弛来看,角膜的纵向和横向之间无重大的差异,据此,各向同性假定可用于初步的角膜力学模型.     

Organization and possible origin of the Bari-1 cluster in the heterochromatic h39 region of Drosophila melanogaster

The molecular organization of the heterochromatic h39 region of the Drosophila melanogaster second chromosome has been investigated by studying two BAC clones identified both by Southern blotting and by FISH experiments as containing tandem arrays of Bari1, a transposable element present only in this region. Such BAC clones appear to contain different portions of the h39 region since they differ in the DNA sequences flanking the Bari1 repeats on both sides. Thus, the 80 Bari1 copies estimated to be present in the h39 region are split into at least two separated subregions. On the basis of the analysis of the flanking sequences a possible mechanism depending on an aberrant activity of the Bari1 transposase is proposed for the genesis of the heterochromatic tandem arrays of the element.     

Inhibition of severe acute respiratory syndrome virus replication by small interfering RNAs in mammalian cells

Severe acute respiratory syndrome (SARS) is an acute respiratory infectious disease that spread worldwide in early 2003. The cause was determined as a novel coronavirus (CoV), SARS-associated CoV (SARS-CoV), with a single-stranded, plus-sense RNA. To date, no effective specific treatment has been identified. To exploit the possibility of using RNA interference as a therapeutic approach to fight the disease, plasmid-mediated small interfering RNAs (siRNAs) were generated to target the SARS-CoV genome. The expression of siRNAs from two plasmids, which specifically target the viral RNA polymerase, effectively blocked the cytopathic effects of SARS-CoV on Vero cells. These two plasmids also inhibited viral replication as shown by titer assays and by an examination of viral RNA and protein levels. Thus, our results demonstrated the feasibility of developing siRNAs as effective anti-SARS drugs.     

Solid Phase Synthesis of Phosphopeptides Incorporating 2,2-Dimethyloxazolidine Pseudoproline Analogs: Evidence for <Emphasis Type="Italic">trans</Emphasis> Leu-Pro Peptide Bonds in Stat3 Inhibitors

To answer the question of whether the conformation of the Leu-Pro bond is cis or trans in Ac-pTyr-Leu-Pro-Gln-Thr-Val-NH₂ when complexed with the SH2 domain of Stat3, we substituted 2,2-dimethyloxazolidines derived from serine (Ser(Ψ^Me,Mepro)) and threonine (Thr(Ψ^Me,Mepro)) for proline. The 2,2-dimethyloxazolidine and 2,2-dimethylthiazolidine pseudoproline (ΨPro) analogs induce predominantly cis Xxx-ΨPro peptide bonds. As these ΨPro analogs are acid-labile, the phosphopeptides were synthesized using Fmoc-based SPPS using unprotected phosphotyrosine and 4-hydroxybenzoate as the linker that allowed release from the support by alkaline ammonolysis, conditions that kept the oxazolidine rings intact. Incorporation of Ser(Ψ^Me,Mepro) resulted in 69% cis Leu-ΨPro bond content in aqueous solution whereas that for Thr(Ψ^Me,Mepro) analog was 63%. Affinities for Stat3 were 3–5 fold lower than the lead compound and were inversely correlated with cis content. Thus we conclude that the Leu-Pro peptide bond is trans when the peptide is bound to Stat3.     

Engineering mouse apolipoprotein A-I into a monomeric, active protein useful for structural determination

Apolipoprotein AI (apoAI), the major protein component of HDL, is one of the best predictors of coronary artery disease (CAD), with high apoAI and HDL levels being correlated with low occurrences of CAD. The primary function of apoAI is to recruit phospholipid and cholesterol for assembly of HDL particles. Like other exchangeable apolipoproteins, lipid-free apoAI forms a mixture of different oligomers even at 1.0 mg/mL. This self-association property of the exchangeable apolipoproteins is closely associated with the lipoprotein-binding activity of this protein family. It is unclear if the self-association property of apolipoprotein is required for its lipoprotein-binding activity. We developed a novel method for engineering an oligomeric protein to a monomeric, biologically active protein. Using this method, we generated a monomeric mouse apoAI mutant that is active. This mutant contains the first 216 residues of mouse apoAI and replaces six hydrophobic residues with either polar or smaller hydrophobic residues at the defined positions (V118A/A119S/L121Q/T191S/T195S/T199S). Cross-linking results show that this mutant is greater than 90% monomeric at 8 mg/mL. CD, DSC, and NMR results indicate that the mutant maintains an identical secondary, tertiary structure and stability as those of the wild-type mouse apoAI. Lipid-binding assays suggest that the mutant shares an equal lipoprotein-binding activity as that of the wild-type apoAI. In addition, both the monomeric mutant and the wild-type protein make nearly identical rHDL particles. With this monomeric mouse apoAI, high-quality NMR data has been collected, allowing for the NMR structural determination of lipid-free apoAI. On the basis of these results, we conclude that this apoAI mutant is a monomeric, active apoAI useful for structural determination.     

Nitrogen deposition enhances moss growth,but leads to an overall decline in habitat condition of mountain moss‐sedge heath

Ecosystems are subject to multiple, natural and anthropogenic environmental influences, including nitrogen (N) deposition, land use and climate. Assessment of the relative importance of these influences on biodiversity and ecosystem functioning is crucial for guiding policy and management decisions to mitigate global change; yet, few studies consider multiple drivers. In the UK, ongoing loss of the internationally important arctic/alpine moss‐sedge community, Racomitrium heath, has been linked to elevated N deposition, high grazing pressures and their combination; however, the relative importance of these drivers remains unclear. We used environmental gradients across the habitat's European distribution (UK, Faroes, Norway and Iceland) to investigate the relative impact of N deposition and grazing pressure, as well as climate, on the condition of the dominant moss species, Racomitrium lanuginosum. Key variables including tissue chemistry, growth and cover were measured at 36 sites, and multiple linear regressions were used to examine the relative importance of the drivers across sites. Our results clearly show that regional variation in the condition of R. lanuginosum across Europe is primarily associated with the impacts of N deposition, with climate (air temperature) and grazing pressure playing secondary roles. In contrast to previous experimental studies, we found moss growth to be stimulated by elevated N deposition; this apparent discrepancy may result from the use of artificially high N concentrations in many experiments. Despite increased growth rates, we found that moss mat depth and cover declined in response to N deposition. Our results suggest that this is due to increased decomposition of material in the moss mat, which ultimately leads to loss of moss cover and habitat degradation. This study clearly demonstrates both the key role of N deposition in degradation of Racomitrium heath and the importance of observational studies along natural gradients for testing predictions from experimental studies in the real world.