外源DNA导入技术培育抗旱耐盐小麦新品种

应用小麦自花授粉后外源DNA导入技术将长穗冰草 (Agropyronelongatum)DNA导入普通小麦 86(6) 0 0 2 ,在导入后代中出现株高、株型、穗型、抗病性、抗逆性等多种性状的变异 ,经筛选鉴定出抗旱耐盐小麦新品种济南 18号。室内耐盐实验表明 ,济南 18号盐害指数低、幼苗耐盐能力强。叶片SOD酶活性测定发现 ,济南 18号的倒二叶酶活性降低幅度较大 ,旗叶与倒二叶酶活性比值较高。在两年度三地区的盐碱旱地对比试验中 ,济南 18号表现出较强的抗旱、耐盐能力 ,产量比对照品种鲁麦 10号平均增产 8 57% ,在生产试验中增产 8 7%。     

Sequence-specific isotope effects on the cleavage of DNA by bleomycin

Bleomycin is a metal- and oxygen-dependent DNA cleaver. The chemistry of DNA damage has been proposed to involve rate-limiting abstraction of the 4'-hydrogen. A DNA fragment has been prepared that contains [4'-2H]thymidine residues of high isotopic content. Primary kinetic isotope effects have been directly observed at individual thymidine residues with DNA sequencing technology.     

Static and initiator protein-enhanced bending of DNA at a replication origin

DNA bending has been suggested to play a role in the regulation of gene expression, initiation of DNA replication, DNA packaging, and the recognition of specific DNA sequences by proteins. It has recently been demonstrated that DNA bending can be sequence-directed. Bent DNA has also been observed as a consequence of sequence-specific binding of proteins to DNA. In this report DNA of plasmid pT181 is shown to contain a bend at the replication origin. Furthermore, this bend is enhanced by the binding of the pT181 replication initiator protein, RepC, to the origin.     

DNA synthesis generates terminal duplications that seal end-to-end chromosome fusions

End-to-end chromosome fusions that occur in the context of telomerase deficiency can trigger genomic duplications. For more than 70 years, these duplications have been attributed solely to breakage-fusion-bridge cycles. To test this hypothesis, we examined end-to-end fusions isolated from Caenorhabditis elegans telomere replication mutants. Genome-level rearrangements revealed fused chromosome ends having interrupted terminal duplications accompanied by template-switching events. These features are very similar to disease-associated duplications of interstitial segments of the human genome. A model termed Fork Stalling and Template Switching has been proposed previously to explain such duplications, where promiscuous replication of large, noncontiguous segments of the genome occurs. Thus, a DNA synthesis-based process may create duplications that seal end-to-end fusions, in the absence of breakage-fusion-bridge cycles.     

序列分析在林蛙系统学研究中的进展

应用DNA序列研究生物的系统发育和进化规律成为当前分子系统学研究的热点,在现阶段的研究中,线粒体DNA序列分析已经被广泛的的用于林蛙的系统学研究,成为研究系统发育以及生物地理演化的重要手段,但核基因在系统发育研究中的作用不可忽视。近些年来研究者们发现核基因包含有更加丰富的生物学信息,运用核基因序列或将核基因序列与线粒体基因序列相结合研究两栖动物的系统发育正成为分子系统学领域的新的发展趋势。正因为对林蛙的研究多只局限于线粒体DNA,使得研究结果并不完善甚至存在一定的问题,因此需要借鉴研究者对其他两栖类的研究经验,利用核基因与线粒体基因结合对中国林蛙进行进行系统研究。     

Cloning and expression of a cocaine-sensitive rat dopamine transporter

The action of dopamine and other monoamine neurotransmitters at synapses is terminated predominantly by high-affinity reuptake into presynaptic terminals by specific sodium-dependent neurotransmitter transport proteins. A complementary DNA encoding a rat dopamine transporter has been isolated that exhibits high sequence similarity with the previously cloned norepinephrine and gamma-aminobutyric acid transporters. Transient expression of the complementary DNA in HeLa cells confirms the cocaine sensitivity of this transporter.     

Purification, cloning, and expression of ciliary neurotrophic factor (CNTF)

Ciliary neurotrophic factor (CNTF) is one of a small number of proteins with neurotrophic activities distinct from nerve growth factor (NGF). CNTF has now been purified and cloned and the primary structure of CNTF from rabbit sciatic nerve has been determined. Biologically active CNTF has been transiently expressed from a rabbit complementary DNA clone. CNTF is a neural effector without significant sequence homologies to any previously reported protein.     

苔藓植物DNA条形码的研究进展

[目的]概述DNA条形码在苔藓植物中的研究进展,为将该技术更广泛地用于苔藓植物研究提供参考。[方法]结合DNA条形码技术的发展及其在动、植物研究中的应用,概述了该技术在苔藓植物研究中的现状及研究进展,并呼吁建立专门的机构对苔藓植物进行系统的DNA条形码研究策略,加快苔藓植物的研究。[结果]DNA条形码技术已在动植物研究中得到了广泛的应用,在植物研究中尚未获得理想的被广泛认同的DNA条形码。但研究发现,各种候选片段为苔藓植物分子生物学的发展提供了便利的检测手段。随着该技术的逐步发展完善,其将会在苔藓植物的科学研究中发挥越来越大的作用。[结论]DNA条形码技术是近年来生物学研究的热点,该技术在生命科学、法医学、流行病学、医药及食品质量控制等领域均具有广泛的应用前景,其将极大地促进人类监测、了解以及利用生物多样性的能力。该研究为DNA条形码技术在苔藓植物研究中的应用提供了参考。     

URF6, last unidentified reading frame of human mtDNA, codes for an NADH dehydrogenase subunit

The polypeptide encoded in URF6, the last unassigned reading frame of human mitochondrial DNA, has been identified with antibodies to peptides predicted from the DNA sequence. Antibodies prepared against highly purified respiratory chain NADH dehydrogenase from beef heart or against the cytoplasmically synthesized 49-kilodalton iron-sulfur subunit isolated from this enzyme complex, when added to a deoxycholate or a Triton X-100 mitochondrial lysate of HeLa cells, specifically precipitated the URF6 product together with the six other URF products previously identified as subunits of NADH dehydrogenase. These results strongly point to the URF6 product as being another subunit of this enzyme complex. Thus, almost 60% of the protein coding capacity of mammalian mitochondrial DNA is utilized for the assembly of the first enzyme complex of the respiratory chain. The absence of such information in yeast mitochondrial DNA dramatizes the variability in gene content of different mitochondrial genomes.     

Cloning and expression of a rat brain GABA transporter

A complementary DNA clone (designated GAT-1) encoding a transporter for the neurotransmitter gamma-aminobutyric acid (GABA) has been isolated from rat brain, and its functional properties have been examined in Xenopus oocytes. Oocytes injected with GAT-1 synthetic messenger RNA accumulated [3H]GABA to levels above control values. The transporter encoded by GAT-1 has a high affinity for GABA, is sodium-and chloride-dependent, and is pharmacologically similar to neuronal GABA transporters. The GAT-1 protein shares antigenic determinants with a native rat brain GABA transporter. The nucleotide sequence of GAT-1 predicts a protein of 599 amino acids with a molecular weight of 67 kilodaltons. Hydropathy analysis of the deduced protein suggests multiple transmembrane regions, a feature shared by several cloned transporters; however, database searches indicate that GAT-1 is not homologous to any previously identified proteins. Therefore, GAT-1 appears to be a member of a previously uncharacterized family of transport molecules.     

PALEOCLIMATE: An Appealing Snowball Earth That's Still Hard to Swallow

The startling claim that Earth has frozen over from pole to pole for millions of years at a time, a hypothesis widely known as the "snowball Earth" scenario, has intrigued many earth scientists but as yet convinced few. But the theory, which would explain some previously inexplicable observations from the Neoproterozoic era 600 million to 700 million years ago, is gaining adherents. Last year, for example, most researchers agreed that one part of the sweeping hypothesis--the claim that glaciers once flowed into ice-covered tropical seas--is correct, even though this idea had been rebuffed for more than 30 years.     

Very heavy solar cosmic rays: energy spectrum and implications for lunar erosion

The energy spectrum of solar cosmic-ray particles of the iron group has been determined for the first time over the energy range from 1 to 100 million electron volts per nucleon by the use of glass removed from the Surveyor 3 spacecraft. The difference between the observed (energy)(-3) spectrum and the limiting spectrum derived previously from tracks in lunar rocks gives an erosion rate of 0 to 2 angstroms per year. High-energy fission of lead, induced by galactic cosmicray protons and alpha particles, has also been observed.     

DNA methylation and gene function

In most higher organisms, DNA is modified after synthesis by the enzymatic conversion of many cytosine residues to 5-methylcytosine. For several years, control of gene activity by DNA methylation has been recognized as a logically attractive possibility, but experimental support has proved elusive. However, there is now reason to believe, from recent studies, that DNA methylation is a key element in the hierarchy of control mechanisms that govern vertebrate gene function and differentiation.     

Genetics. Transposons help sculpt a dynamic genome

New research is showing that the mobile genetic elements called transposons cause more extensive restructuring of the genome than previously thought. Researchers have known for about 20 years that transposons can expand the genome, resulting in the repetitive DNA sequences sometimes called "junk," but the new work indicates that transposons can also contribute to substantial DNA losses. What's more, these changes can be rapid--at least on an evolutionary scale--and may help organisms adapt to their environments.     

Topologically linked protein rings in the bacteriophage HK97 capsid

The crystal structure of the double-stranded DNA bacteriophage HK97 mature empty capsid was determined at 3.6 angstrom resolution. The 660 angstrom diameter icosahedral particle contains 420 subunits with a new fold. The final capsid maturation step is an autocatalytic reaction that creates 420 isopeptide bonds between proteins. Each subunit is joined to two of its neighbors by ligation of the side-chain lysine 169 to asparagine 356. This generates 12 pentameric and 60 hexameric rings of covalently joined subunits that loop through each other, creating protein chainmail: topologically linked protein catenanes arranged with icosahedral symmetry. Catenanes have not been previously observed in proteins and provide a stabilization mechanism for the very thin HK97 capsid.     

DNA条形码在鱼类胃含物种类鉴定中的应用

DNA条形码技术是利用一段较短的DNA序列实现快速准确物种鉴定的工具,已成为近年来生物类群的研究热点,并逐步被引进到各个领域。在海洋生物群落生态学中,DNA条形码已被用于海洋生物系统分类、分子遗传多样性、种间亲缘关系、系统进化关系等研究;国外已有学者将其应用到海洋生物食性分析的研究中,国内相关文章较少。本文介绍了DNA条形码的由来、发展以及相关原理和基本实验步骤,并阐述了其优点以及局限性,分析了其在肉食性鱼类胃含物不可辨认种类鉴定中的应用价值,并展望其在未来分类学发展中的应用前景。     

Evolution of character displacement in Darwin's finches

Competitor species can have evolutionary effects on each other that result in ecological character displacement; that is, divergence in resource-exploiting traits such as jaws and beaks. Nevertheless, the process of character displacement occurring in nature, from the initial encounter of competitors to the evolutionary change in one or more of them, has not previously been investigated. Here we report that a Darwin's finch species (Geospiza fortis) on an undisturbed Galápagos island diverged in beak size from a competitor species (G. magnirostris) 22 years after the competitor's arrival, when they jointly and severely depleted the food supply. The observed evolutionary response to natural selection was the strongest recorded in 33 years of study, and close to the value predicted from the high heritability of beak size. These findings support the role of competition in models of community assembly, speciation, and adaptive radiations.     

Inhibition of L1210 tumor growth by thymus DNA

Growth of L1210 leukemia cells which had been previously incubated with thymus DNA was inhibited. Leukemia-cell DNA did not affect tumor growth under similar conditions. Pretreatment of the thymus DNA with deoxyribonuclease suppressed the DNA induced inhibition. Both ribonucleasetreated DNA and untreated DNA inhibited tumor growth.