杆状病毒p74基因具有种属特异性

选用苜蓿丫纹夜蛾核多角体病毒杆粒 (AcMNPVbacmid)为材料 ,通过在大肠杆菌中利用RecA基因介导的同源重组 ,将其p74基因剔除 ,并精确地用斜纹夜蛾核多角体病毒 (SpltMNPV)的p74基因进行了替换。所构建的重组AcMNPV杆粒在修饰后的p74基因位点中未留下任何有可能影响该基因表达及功能的选择标记 ,SpltMNPV的p74基因直接位于AcMNPVp74基因的启动子控制下。RT PCR显示替换后的p74基因得到了表达。生物测定结果显示 ,重组病毒AcMNPV杆粒 polhSL74无法通过口服方式感染银纹夜蛾幼虫 ,表明杆状病毒p74基因具有种属特异性。     

利用基因诱捕技术进行小鼠基因剔除的初步研究

对利用基因诱捕技术进行小鼠基因剔除做了初步的探索,为进一步应用该技术进行小鼠基因功能研究奠定了基础.利用基因诱捕载体转染小鼠ES细胞,获得了36株neo基因单拷贝整合的诱捕ES细胞,其中14株细胞表达有活性的β半乳糖苷酶.将3株诱捕ES细胞分别经显微注射引入到受体囊胚中,再植入假孕母鼠的子宫中使其发育成小鼠.两株细胞得到了程度不同的嵌合体小鼠,其中一株诱捕ES细胞整合至生殖系.利用质粒拯救实验获得了诱捕载体整合位点附近的基因组序列,通过序列比对发现被诱捕的基因可能是一个新基因.X-gal染色结果显示,该基因的表达局限于小鼠腹部及肢芽的部位.     

水稻矮化基因WLD1的图位克隆

水稻(Oryza sativa)矮化是与光合效率及产量等密切相关的重要农艺性状。发掘更多的水稻矮秆资源,不仅能够进一步加深对水稻株高分子遗传机制的认识,而且还能为水稻新品种培育提供新的种质资源。在水稻T-DNA插入突变体库中筛选到1个矮化、宽叶小粒突变体(wld1)。经图位克隆将WLD1基因定位在第5号染色体长臂,位于分子标记In Del37与InDel48之间,基因编号为LOC_Os05g32270,属于AP2转录因子家族。该基因第6外显子处胸腺嘧啶缺失,造成转录提前终止。石蜡切片观察结果显示,茎部第2节间横向细胞数目增加,而纵向细胞数目未变。RT-PCR检测结果表明,LOC_Os05g32270在突变体wld1中不表达,造成功能缺失。该基因与已报道的水稻OsSMOS1(SMALL ORGAN SIZE1)为等位基因。水稻突变体wld1的矮秆遗传效应可直接应用于育种中。该研究结果进一步明确了突变体wld1的表型特征与遗传基础,为解析其参与的信号途径提供参考。     

Identification of a Saxitoxin Biosynthesis Gene with a History of Frequent Horizontal Gene Transfers

The paralytic shellfish poisoning (PSP) toxins, saxitoxin, and its derivatives, are produced by a complex and unique biosynthetic pathway. It involves reactions that are rare in other metabolic pathways, however, distantly related organisms, such as dinoflagellates and cyanobacteria, produce these toxins by an identical pathway. Speculative explanations for the unusual phylogenetic distribution of this metabolic pathway have been proposed, including a polyphyletic origin, the involvement of symbiotic bacteria, and horizontal gene transfer. This study describes for the first time the identity of one gene, sxt1, that is involved in the biosynthesis of saxitoxin in cyanobacteria. It encoded an O-carbamoyltransferase (OCTASE) that was proposed to carbamoylate the hydroxymethyl side chain of saxitoxin precursor. Orthologues of sxt1 were exclusively present in PSP-toxic strains of cyanobacteria and had a high sequence similarity to each other. L. wollei had a naturally mutated sxt1 gene that encoded an inactive enzyme, and was incapable of producing carbamoylated PSP-toxin analogues, supporting the proposed function of Sxt1. Phylogenetic analysis revealed that OCATSE genes were present exclusively in prokaryotic organisms and were characterized by a high rate of horizontal gene transfer. OCTASE has most likely evolved from an ancestral O-sialoglycoprotein endopeptidase from proteobacteria, whereas the most likely phylogenetic origin of sxt1 was an ancestral alpha-proteobacterium. The phylogeny of sxt1 suggested that the entire set of genes required for saxitoxin biosynthesis may spread by horizontal gene transfer.     

Gene genealogies in a metapopulation

A simple genealogical process is found for samples from a metapopulation, which is a population that is subdivided into a large number of demes, each of which is subject to extinction and recolonization and receives migrants from other demes. As in the migration-only models studied previously, the genealogy of any sample includes two phases: a brief sample-size adjustment followed by a coalescent process that dominates the history. This result will hold for metapopulations that are composed of a large number of demes. It is robust to the details of population structure, as long as the number of possible source demes of migrants and colonists for each deme is large. Analytic predictions about levels of genetic variation are possible, and results for average numbers of pairwise differences within and between demes are given. Further analysis of the expected number of segregating sites in a sample from a single deme illustrates some previously known differences between migration and extinction/recolonization. The ancestral process is also amenable to computer simulation. Simulation results show that migration and extinction/recolonization have very different effects on the site-frequency distribution in a sample from a single deme. Migration can cause a U-shaped site-frequency distribution, which is qualitatively similar to the pattern reported recently for positive selection. Extinction and recolonization, in contrast, can produce a mode in the site-frequency distribution at intermediate frequencies, even in a sample from a single deme.     

人类生殖相关新基因的定位和组织表达

基因定位对研究基因之间以及基因与疾病之间的相互关系具有重要意义。应用辐射杂种细胞系技术（RH）对我们克隆的人类新基因HBRP（Human BSP-Related Protein）进行了染色体定位,结果将该基因定位于19q13.2～13.3,同时应用生物信息学方法在人类基因组重叠片段数据库进行该基因的定位,结果相吻合。研究证明,RH技术具有快速、精确、简便等优点,是基因定位研究中一强有力的技术。同时通过RT-PCR方法研究了HBRP基因在人体各组织中的表达分布,结果显示该基因在睾丸、肠、肾、肝、脾、胃、胰腺组织有较高的表达,而在检测的脑、肺、骨骼肌、心肌组织中表达较弱。 Abstract:Gene localization is significant in elucidating the interaction between genes,gene and diseases.Using radiation hybrid (RH) technique,we cloned and localized a novel gene,designated human BSP-related protein (HBRP) on 19q13.2～13.3,in line with its localization in data bank of overlapping fragment of human genome through bioinformatics method.It is suggested RH is rapid,precise,simple and powerful in gene localization.In addition,we detected the expression and distribution of HBRP in human tissues by RT-PCR.The results showed HBRP was highly expressed in intestine,kidney,liver,spleen,stomach and pancreas,whereas lowly in brain,lung,muscle and heart.     

Gene Transfer of a Part of a β-Lactamase Gene?

β-Lactamase is an enzyme which catalyzes the hydrolysis of the β-lactam ring of penicillins and cephalosporins. By similarity analysis of amino acid sequences in a database, the amino acid sequence deduced from the nucleotide sequence of the upstream region of cytochrome c oxidase subunit II from Paracoccus denitrificans was found to have an unusually high score of homology to that of a portion of β-lactamases from Gram-negative bacteria. Furthermore, the nucleotide sequences corresponding only to this region had a very high score of similarity among them. The phylogenetic tree constructed on the basis of the amino acid sequences was in accord with that constituted on the 5S rRNA's. Moreover, the molar G + C contents and the codon usage were similar to those in their respective bacteria. It is suggested, therefore, that the nucleotide sequence in P. denitrificans was positioned by a transfer of a part of a β-lactamase gene formed as a result of gene duplication or it was formed by a deletion of the essential region of the β-lactamase gene, although no β-lactamase gene has been yet detected in P. denitrificans.     

垂体瘤转化基因(PTTG1)可抵抗UV诱导的细胞凋亡作用

垂体瘤转化基因（PTTG1）在很多肿瘤中呈高水平表达.越来越多的研究表明,PTTG1与细胞增殖、细胞转化有关.但PTTG1在凋亡中的作用仍不清楚.通过在细胞中下调和过表达PTTG1,观察PTTG1在UV照射诱导凋亡中的作用.结果发现, RNAi-介导下调HeLa细胞PTTG1表达可增加对UV诱导凋亡的敏感性,而过表达PTTG1则降低对UV诱导凋亡的敏感性.此外,UV照射能降低PTTG1蛋白的表达水平,并且表现为明显的剂量和时间关系.这些研究结果显示,PTTG1在UV照射诱导的凋亡中发挥重要的抗凋亡作用.这为研究PTTG1在肿瘤发生、发展中的作用机制提供了新的实验证据.     

Molecular Mapping of a Gene Cluster Flanking the Drosophila Dopa Decarboxylase Gene

Nine lethal complementation groups flanking the Drosophila Dopa decarboxylase (Ddc) gene, have been localized within 100 kb of cloned chromosomal DNA. Six of these complementation groups are within 23 kb of DNA, and all ten complementation groups, including Ddc, lie within 78-82 kb of DNA. The potential significance of this unusually high gene density is discussed.     

Extensive Intra-Kingdom Horizontal Gene Transfer Converging on a Fungal Fructose Transporter Gene

Comparative genomics revealed in the last decade a scenario of rampant horizontal gene transfer (HGT) among prokaryotes, but for fungi a clearly dominant pattern of vertical inheritance still stands, punctuated however by an increasing number of exceptions. In the present work, we studied the phylogenetic distribution and pattern of inheritance of a fungal gene encoding a fructose transporter (FSY1) with unique substrate selectivity. 109 FSY1 homologues were identified in two sub-phyla of the Ascomycota, in a survey that included 241 available fungal genomes. At least 10 independent inter-species instances of horizontal gene transfer (HGT) involving FSY1 were identified, supported by strong phylogenetic evidence and synteny analyses. The acquisition of FSY1 through HGT was sometimes suggestive of xenolog gene displacement, but several cases of pseudoparalogy were also uncovered. Moreover, evidence was found for successive HGT events, possibly including those responsible for transmission of the gene among yeast lineages. These occurrences do not seem to be driven by functional diversification of the Fsy1 proteins because Fsy1 homologues from widely distant lineages, including at least one acquired by HGT, appear to have similar biochemical properties. In summary, retracing the evolutionary path of the FSY1 gene brought to light an unparalleled number of independent HGT events involving a single fungal gene. We propose that the turbulent evolutionary history of the gene may be linked to the unique biochemical properties of the encoded transporter, whose predictable effect on fitness may be highly variable. In general, our results support the most recent views suggesting that inter-species HGT may have contributed much more substantially to shape fungal genomes than heretofore assumed.     

Strict Regulation of Gene Expression Utilizing a Dual-control Gene Expression Vector System

可严格调控性是体现原核表达载体优越性的重要指标。构建了一种双控双调节原核表达载体系统,用双载体控制调节目的基因的表达,即SP6启动子（promoter）＋乳糖（lac）调节基因表达系统和araB启动子（promoter）＋ara C调节基因表达系统,分别由乳糖类似物IPTG和阿拉伯糖（L-arabinose）诱导目的基因的表达。该系统由2个表达载体共同完成目的基因的表达。pE SP-1为主表达载体,即目的基因克隆到此表达载体上,由SP6启动子（promoter）＋乳糖（lac）调节基因调控;pA RA-SP6为辅助表达载体,该载体通过SP6 RNA聚合酶的表达来控制调节主表达载体的启动子（SP6）,由araB启动子（promoter）＋ara C调节基因调控。实验结果显示该双控双调节表达载体系统控制严格,并且表达蛋白的量具有可调控性。     

Expression in Yeast of a Fusion Gene Composed of the Promoter of a Heat-Shock Gene from Arabidopsis and a Bacterial Gene for {beta}-Glucuronidase

Production of a functional ß-glucuronidase (GUS) proteinwas induced by exposure of exponentially growing yeast cellsto heat shock after transformation of the GUS gene under thecontrol of the promoter of the heat-shock gene, HSP18.2, fromArabidopsis. Yeast cyr and bcy mutations appeared to have essentiallyno effect. ¹Present Address: Laboratory of Plant Molecular Biology, TheRockefeller University, 1230 York Avenue, New York, NY 10021-6399,U.S.A.     

Decreased Expression of a Gene Caused by a T-DNA Insertion in an Adjacent Gene in Arabidopsis

ALADIN is a component of the nuclear pore complex in higher eukaryotes. An Arabidopsis knockout line that had a T-DNA insertion in the ALADIN gene was defective in plant growth and thylakoid development and had reduced photosynthetic activity resulting from lower chlorophyll accumulation. The mutation appeared to decrease the level of chloroplast RuBisCO subunits and PSBA and PGL35 proteins. Unexpectedly, the T-DNA insertion in the ALADIN gene decreased the expression of the neighboring gene PSRP5, which functions in translation in chloroplasts. The mutant phenotype was rescued by expressing PSRP5, but not by expressing ALADIN. The abnormal phenotypes were also detected in an artificial microRNA (amiRNA)-mediated PSRPS5 knockdown, but not in an amiRNA-mediated ALADIN knockdown line. Thus, users of T-DNA insertions should be aware that a T-DNA insertion in one gene can have effects on the expression of neighboring genes.     

一个新的性别决定基因DMY

虽然人们已经鉴定出了线虫、果蝇和哺乳动物的性别决定基因,但直到最近才首次在非哺乳类脊椎动物中发现了性别决定基因DMY.介绍了在青鳉中发现DMY基因的经过,发现DMY基因的意义和DMY基因在其他鱼类中的分布,最后对未来的研究进行了展望.