扁穗牛鞭草几个有性生殖特性的研究

以牛鞭草“广益”、“重高”两个品种为材料 ,对抽穗开花的形态学、花粉活力和结实率进行了研究。结果表明 :扁穗牛鞭草于 7月下旬至 8月上旬抽穗 ,每花序需 9d完成抽穗。开花集中在每天下午 5～ 7点 ,开花顺序为自上而下。每小花开花全过程 47～ 86min。“广益”和“重高”群体平均花粉粒活力分别为 2 4 0 %和 16 2 % ;同一花序顶端小花花粉粒活力较高 ,最高分别为 78 4%和 6 8 6 % ,自上而下分别于第 8小花和第 10小花以下的花粉粒全部无活力 ,一个花序花粉粒平均活力分别为 2 2 1%和 15 2 %。“广益”和“重高”牛鞭草的套袋结实率分别为 6 4%和4 2 % ,自然传粉结实率分别为 7 8%和 6 6 %     

水稻与拟南芥全基因组丝氨酸羧肽酶类蛋白家族比较分析(英文)

    基于水稻与拟南芥全基因组序列,在基因组与蛋白质组水平上对这2种模式植物的丝氨酸羧肽酶 (SCPs)基因家族进行比较分析.利用隐马可夫模型(hidden Markov models,HMM),发现水稻与拟南芥中分别存在71个与54个丝氨酸羧肽酶类(serine carboxypeptidases like,SCPL)蛋白编码基因,它们广泛分布于基因组中各条染色体上,并且存在多个基因簇聚区.基因结构分析显示,拟南芥的SCPL基因存在广泛的交替剪接方式,而这种现象在水稻SCPL基因中却不常见.蛋白结构分析表明,所有SCPL家族成员均具有α/β水解酶折叠亚族与S10家族典型的保守结构域与二级结构特征.系统进化分析表明,这125个SCPL蛋白可以分成3大类,与水稻不同,大多数拟南芥SCPL (88.9%)可归属于双链羧肽酶Ⅰ或Ⅱ.     

兔肺静脉心肌袖与心律紊乱相关的形态学研究

目的观察肺静脉心肌袖的组织学形态特性,以了解异位兴奋和局灶性房颤起源于肺静脉的形态学基础。方法取20只健康家兔的左心房和肺静脉,通过HE染色、Masson染色进行组织学研究,并用图像分析比较形态学差异。结果肺静脉心肌袖心肌纤维集合成束,走行不规则、方向各异;心肌袖组织中可观察到染色浅淡的苍白样细胞,与P细胞相似,成群或成对孤立存在;横切面肺静脉心肌袖心肌细胞的胞浆面积小、核面积小、核浆比值小、核圆形度大、核周长短,与左心房心肌细胞比较,差异有统计学意义(P<0.01)。结论肺静脉根部存在心房肌的延伸即心肌袖,其心肌纤维分布不均匀,走行方向各异,可能是电传导不均一、各向异性的原因;苍白样细胞的存在可能是引发异位兴奋和局灶自律性升高的形态学基础;肺静脉心肌袖心肌细胞体积较小,胞核较圆。     

Redesigning trypsin: alteration of substrate specificity

A general method for modifying eukaryotic genes by site-specific mutagenesis and subsequent expression in mammalian cells was developed to study the relation between structure and function of the proteolytic enzyme trypsin. Glycine residues at positions 216 and 226 in the binding cavity of trypsin were replaced by alanine residues, resulting in three trypsin mutants. Computer graphic analysis suggested that these substitutions would differentially affect arginine and lysine substrate binding of the enzyme. Although the mutant enzymes were reduced in catalytic rate, they showed enhanced substrate specificity relative to the native enzyme. This increased specificity was achieved by the unexpected differential effects on the catalytic activity toward arginine and lysine substrates. Mutants containing alanine at position 226 exhibited an altered conformation that may be converted to a trypsin-like structure upon binding of a substrate analog.     

Rice transformation with cell wall degrading enzyme genes from Trichoderma atroviride and its effect on plant growth and resistance to fungal pathogens

Three genes encoding for fungal cell wall degrading enzymes (CWDE), ech42, nag70 and gluc78 from the biocontrol fungus Trichoderma atroviride were inserted into the binary vector pCAMBIA1305.2 singly and in all possible combinations. The coding sequences were placed downstream of the rice actin promoter and all vectors were used to transform rice plants. A total of more than 1,800 independently regenerated plantlets in seven different populations (for each of the three genes and each…     

Chromosome localization of highly repetitive human DNA's and amplified ribosomal DNA with restriction enzymes

Restriction endonucleases cut and partially removed DNA throughout fixed air-dried human metaphase chromosomes. Some enzymes produced a G-banding pattern; some revealed the presence of multiple chromosome-specific classes of highly repetitive DNA in C-band heterochromatin. Enzymes that produced the informative C-band patterns had recognition sequences that were four or five, but not six, base pairs long and did not contain a cytosine-guanine doublet. In both rat and human chromosomes, regions containing amplified ribosomal RNA genes were specifically removed by the restriction endonuclease Msp I.     

蛋白质的 SUMO 化修饰及其在玉米中的研究进展

小泛素化修饰（Small ubiquitin-like modification,SUMOylation）是一种重要的蛋白质翻译后修饰,参与植物多种生命活动。在这个修饰过程中,SUMO 蛋白通过共价键与靶蛋白结合,影响其功能和活性。该修饰过程涉及多种酶类,包括 SUMO 特异性蛋白酶、SUMO 活化酶、SUMO 结合酶和 SUMO 连接酶。植物体内存在多种 SUMO 蛋白和酶类,且其结构和功能存在差异。然而,目前对于不同 SUMO 蛋白与修饰过程中涉及到的酶组合间的作用关系尚未完全明确。因此,厘清这些 SUMO 蛋白及其酶类的特点,对进一步的研究极为重要。此外,SUMOylation 底物鉴定也是研究中的一个挑战。虽然已有一些鉴定 SUMOylation 底物的方法,如质谱分析和酵母双杂交等,但仍存在局限性。特别是在作物中的研究力度更浅,包括玉米。因此,需要开发更多的鉴定方法来识别 SUMOylation 底物,并进一步揭示 SUMOylation 在玉米生长发育和逆境应答中的作用机制。由此,为推动 SUMOylation 研究,综述 SUMO 蛋白、SUMOylation 相关酶类、蛋白质的 SUMOylation 过程、SUMOylation 底物的鉴定方法和玉米蛋白质的 SUMOylation 研究进展。旨在通过了解 SUMOylation 的规律模式和当前的研究技术,为玉米育种和其他植物研究提供重要指导,并有助于相关人员深入理解 SUMOylation 在植物生长发育和逆境胁迫的响应规律。     

黄瓜果实维生素C合成关键基因克隆与分析

【目的】鉴定调控黄瓜果实中L-半乳糖途径维生素C(Vc)合成相关基因的位置、数量及表达特征,同时对关键基因进行克隆分析,旨在为黄瓜果实中Vc合成调控研究奠定基础。【方法】根据已报道的拟南芥中L-半乳糖途径合成Vc相关基因,利用蛋白编码的氨基酸序列在黄瓜9930＿V2参考基因组数据库中进行BLAST比对,确定黄瓜中的同源基因,借助TBtools软件绘制基因在染色体上的位置。通过q RT-PCR分析上述基因在果实Vc含量差异显著的两份黄瓜材料中的表达量。利用PCR扩增对限速酶GDP-L-半乳糖磷酸化酶（GGP）及GDP-甘露糖-3′5′-差向酶（GME）同源基因进行克隆,测序分析这些基因在高Vc含量与低Vc含量黄瓜果实中的序列差异。构建系统进化树,分析黄瓜果实GME、GGP与其他物种中同源基因的亲缘关系。【结果】在黄瓜基因组中比对到21个参与L-半乳糖途径合成Vc相关酶PMI、PMM、GMPase、GME、GGP、GPP、Gal DH、Gal LDH的同源基因,7条染色体均有分布,在5号染色体和1号染色体上分布最多。通过对21个基因在两份果实Vc含量高低差异显著的两份材料CG45（高Vc含...     

Mechanisms of oxygen metabolism

The enzymes which catalyze reactions of molecular oxygen occur in three principle classes: (i) oxygen transferases, (ii) mixed function oxidases, and (iii) electron transferases. The first class catalyzes the transfer of a molecule of molecular oxygen to substrate. The second class catalyzes the transfer of one atom of the oxygen to substrate; the other atom undergoes two-equivalent reduction. The third class catalyses the reduction of molecular oxygen to hydrogen peroxide or to water.     

Lactate dehydrogenase isozymes: kinetic properties at high enzyme concentrations

The kinetic properties of lactate dehydrogenase (LDH) isozymes have been determined at high enzyme concentrations. Spectrophotofluorometric assays revealed that the extent of substrate inhibition of LDH-1 and LDH-5 depends on enzyme concentration. At high enzyme concentrations, in the range of those that exist in most mammalian cells, no inhibition by pyruvate occurred. Pyruvate concentrations up to and including 20.0 millimoles per liter were used for each isozyme at 25 degrees and 40 degrees C at pH 7.0 and 7.4. These results suggest that substrate inhibition of LDH may not occur in vivo but only in vitro after appreciable dilution from physiologic enzyme concentrations. These experiments provide further evidence against the theory that substrate inhibition of LDH-1 in vivo accounts for the distribution of LDH isozymes within various tissues. They raise the possibility that, for other enzymes, kinetic properties determined at highly dilute concentrations in vitro may also be quite different from kinetic properties at the much higher concentrations that exist in vivo.     

植物油脂合成调控与遗传改良研究进展

植物种子油脂储存的主要形式是三酰甘油。在植物生长发育中,脂肪酸和三酰甘油具有重要功能。分析了植物种子油脂合成代谢过程调控研究进展,总结了改良植物种子油脂策略：①调节碳源分配,抑制碳源流入蛋白质合成路径的关键酶编码基因的表达、增强碳源流入脂肪酸合成路径的关键酶编码基因的表达;②干预油脂合成,促进脂肪酸生物合成,提高三酰甘油组装过程的关键酶编码基因的表达水平;③提高种子油脂的品质：改变植物脂肪酸组成,调节脂肪酸脱氢酶基因的表达,引入外源超长链多不饱和脂肪酸合成途径;④调控油脂合成代谢途径的转录因子表达,提高种子油脂含量。还讨论了植物油脂合成的三酰甘油前体转运机制及合成途径多基因共同调节合成途径等。     

Enzymatic modification of transfer RNA

The molecular events leading to the synthesis of mature tRNA are only now becoming amenable to experimental study. In bacterial and mammalian cells tRNA genes are transcribed into precursor tRNA. These molecules, when isolated, contain additional nucleotides at both ends (20) of the mature tRNA and lack most modified nucleosides. Presumably, specific nucleases ("trimming" enzymes) cut the precursor to proper tRNA size. The C-C-A nucleotide sequence of the amino acid acceptor end common to all tRNA's does not seem to be coded by tRNA genes (30), and may be added to the trimmed molecules by the tRNA-CMP-AMP-pyrophosphorylase (71). Modifications at the polynucleotide level of the heterocyclic bases or the sugar residues give rise to the modified nucleosides in tRNA. Although newly available substrates have allowed the detection of more of the enzymes involved in these reactions, there is still no knowledge about the sequence of modification or trimming events leading to the synthesis of active tRNA. Progress in these studies may not be easy because enzyme preparations free of nucleases or other tRNA modifying enzymes are required. The role of the modified nucleosides in the biological functions of tRNA is still unknown. Possibly pseudouridine is required for ribosome mediated protein synthesis; some other modified nucleosides in tRNA are not required for this reaction, but may enhance its rate. What might be the role of the large variety of modified nucleosides in tRNA? One is tempted to speculate that such nucleosides are important in other cellular processes in which tRNA is thought to participate such as virus infection, cell differentiation, and hormone action (2, 3). Mutants in a number of tRNA-modifying enzymes are needed in order to extend our knowledge of their purpose and of tRNA involvement in other biological processes. But unless tRNA-modifying enzymes specific for a particular tRNA species exist, no simple selection procedure can be devised. Possibly some of the regulatory mutants of amino acid biosynthesis may prove to affect tRNA-modifying enzymes (72). Transfer RNA's are macromolecules well suited for the study of nucleic acid-protein interactions. The tRNA molecules are structurally very similar, and they interact with a large number of enzymes or protein factors (2, 3). Each aminoacyl-tRNA synthetase, for instance, very precisely recognizes a set of cognate isoacceptor tRNA's (2, 73). The availability of the tRNA- modifying enzymes adds another dimension to the problem of the nature of specific recognition of tRNA by proteins. There are some tRNA-modifying enzymes, such as the uracil-tRNA methylase, which may recognize all tRNA species, while others, such as the isopentenyl-tRNA transferase, probably recognize only a selected set of tRNA molecules, even with different amino acid accepting capacities. With well-characterized RNA precursor and tRNA molecules we can hope to delineate those features of primary, secondary, and tertiary structure involved in the specific interactions of tRNA with these enzymes.     

Molecular evidence for the early evolution of photosynthesis

The origin and evolution of photosynthesis have long remained enigmatic due to a lack of sequence information of photosynthesis genes across the entire photosynthetic domain. To probe early evolutionary history of photosynthesis, we obtained new sequence information of a number of photosynthesis genes from the green sulfur bacterium Chlorobium tepidum and the green nonsulfur bacterium Chloroflexus aurantiacus. A total of 31 open reading frames that encode enzymes involved in bacteriochlorophyll/porphyrin biosynthesis, carotenoid biosynthesis, and photosynthetic electron transfer were identified in about 100 kilobase pairs of genomic sequence. Phylogenetic analyses of multiple magnesium-tetrapyrrole biosynthesis genes using a combination of distance, maximum parsimony, and maximum likelihood methods indicate that heliobacteria are closest to the last common ancestor of all oxygenic photosynthetic lineages and that green sulfur bacteria and green nonsulfur bacteria are each other's closest relatives. Parsimony and distance analyses further identify purple bacteria as the earliest emerging photosynthetic lineage. These results challenge previous conclusions based on 16S ribosomal RNA and Hsp60/Hsp70 analyses that green nonsulfur bacteria or heliobacteria are the earliest phototrophs. The overall consensus of our phylogenetic analysis, that bacteriochlorophyll biosynthesis evolved before chlorophyll biosynthesis, also argues against the long-held Granick hypothesis.     

果实软化的细胞壁降解酶及其调控研究进展

软化是果实成熟的一个重要标志,果实软化是由细胞壁降解酶促进细胞壁物质的降解,从而引起细胞壁超微结构发生变化所致.细胞壁降解酶活性的升高受基因的调控,采后生物技术为研究果实成熟软化提供了新的途径.反义基因技术证明,细胞壁降解酶基因的任何一种表达被抑制,果实都能够正常软化,表明果实的软化有其它因子的参与.文章就细胞壁降解酶在果实软化过程中的作用及其调控的研究进展进行了综述.     

查尔酮合酶蛋白表达技术、结构、活性和进化

查尔酮合酶(CHS)是类黄酮途径的首步关键酶,参与合成所有类黄酮和异黄酮物质,参与决定多种植物重要性状。NCBI已有2917条CHS序列登录和释放。单个物种基因组中的CHS普遍由基因家族编码,通过基因加倍而产生。CHS蛋白的表达技术目前均是基于大肠杆菌的原核表达,多采用Novagen公司的pET载体系统,最通行参数为37℃条件下1 mmol/L IPTG诱导3h,表达蛋白普遍采用His-Tag进行亲和纯化,采用质谱或免疫分析技术进行身份检测,通过对生化反应底物和产物的HPLC检测可以精确分析酶活。苜蓿等植物的CHS蛋白已完成X射线晶体衍射研究,获得了三维结构和活性位点构象的初步解析,并与植物Ⅲ型PKS超家族中的其它酶类进行了比较。CHS蛋白的催化活性中心含有一个Cys-His-Asn三联体,另外CoA结合通道和内部的起始/延伸/环化腔关系到CHS蛋白的底物特异性及聚酮化合物链延伸的长度。植物Ⅲ型PKS超家族中,其它酶的结构骨架和催化方式与CHS相似,但活性位点残基的变化可能会造成活性中心结构的改变,进而产生底物特异性、催化能力和产物种类的显著变化,是蛋白水平进化的根本动力。     

Redesigning metabolic routes: manipulation of TOL plasmid pathway for catabolism of alkylbenzoates

Increasing quantities of man-made organic chemicals are released each year into the biosphere. Some of these compounds are both toxic and relatively resistant to physical, chemical, or biological degradation, and they thus constitute an environmental burden of considerable magnitude. Genetic manipulation of microbial catabolic pathways offers a powerful means by which to accelerate evolution of biodegradative routes through which such compounds might be eliminated from the environment. In the experiments described here, a catabolic pathway for alkylbenzoates specified by the TOL plasmid of Pseudomonas was restructured to produce a pathway capable of processing a new substrate, 4-ethylbenzoate. Analysis of critical steps in the TOL pathway that prevent metabolism of 4-ethylbenzoate revealed that this compound fails to induce synthesis of the catabolic enzymes and that one of its metabolic intermediates inactivates catechol 2,3-dioxygenase (C23O), the enzyme that cleaves the aromatic ring. Consequently, the pathway was sequentially modified by recruitment of genes from mutant bacteria selected for their production of either an altered pathway operon regulator that is activated by 4-ethylbenzoate or an altered C23O that is less sensitive to metabolite inactivation. The redesigned pathway was stably expressed and enabled host bacteria to degrade 4-ethylbenzoate in addition to the normal substrates of the TOL pathway.     

SUMO1 haploinsufficiency leads to cleft lip and palate

The posttranslational modification sumoylation can have multiple effects on its substrate proteins. We studied a patient with isolated cleft lip and palate and a balanced chromosomal translocation that disrupts the SUMO1 (small ubiquitin-related modifier) gene, resulting in haploinsufficiency. In mouse, we found that Sumo1 is expressed in the developing lip and palate and that a Sumo1 hypomorphic allele manifests an incompletely penetrant orofacial clefting phenotype. Products of several genes implicated in clefting are sumoylated, and the Sumo1 hypomorphic allele interacts genetically with a loss-of-function allele for one of these loci. Thus, sumoylation defines a network of genes important for palatogenesis.     

Isolated chromaffin cells from adrenal medulla contain primarily monoamine oxidase B

Cultured chromaffin cells from bovine adrenal medulla were found to contain primarily the B form of monoamine oxidase. This monoamine oxidase B enzyme was somewhat distinct from B enzymes from other sources, in that noradrenaline was a much poorer substrate than serotonin. Nonetheless, studies with selective inhibitors of the A form (clorgyline) and the B form [(-)-deprenyl] confirmed that chromaffin cell monoamine oxidase was the B form. The observation that chromaffin cell monoamine oxidase has poor affinity for catecholamines is consistent with physiological needs that require the cell to synthesize and store large amounts of catecholamines.     

Regulatory Network of Transcription Factors in Response to Drought in Arabidopsis and Crops

Drought is one of the most important environmental constraints limiting plant growth, development and crop yield. Many drought-inducible genes have been identified by molecular and genomic analyses in ...