Combinatorial signalling by Xwnt-11 and Xnr3 in the organizer ephithelium

The epithelium of the Spemann organizer plays an important role in embryonic axis formation and transplantation experiments have shown that epithelial organizer cells have potent axis-inducing potential. Known axis-inducing molecules like noggin and chordin are not expressed in the epithelium and cannot account for its inductive properties. Xwnt-11 is expressed in the epithelium but has only poor dorsalizing activity. In an expression screen for genes that are able to functionally cooperate with Xwnt-11 we have identified a cDNA encoding Xenopus nodal-related 3 (Xnr3), a member of the TGF-β family, coexpressed with Xwnt-11 in the organizer epithelium. Xwnt-11 and Xnr3 act highly cooperatively in inducing secondary embryonic axes and dorsalizing ventral mesoderm. Xwnt-11/Xnr3 interfere with BMP signalling without themselves inducing chordin or noggin. The results indicate that induction by the organizer epithelium may result from the combinatorial action of instructive Xnr3 and permissive Xwnt-11 signalling.     

基因CfATG6和CfATG14参与调控果生刺盘孢细胞自噬和致病力

【目的】炭疽病是油茶的主要病害,由刺盘孢属的多种真菌引起,其中果生刺盘孢分布范围最广、分离率最高,是油茶炭疽病的主要致病菌。研究自噬相关蛋白CfAtg6和CfAtg14的生物学功能,为进一步揭示果生刺盘孢通过细胞自噬调控致病的分子机制,并为油茶炭疽病的防治提供理论基础。【方法】根据同源重组原理,通过聚乙二醇(polyethylene glycol, PEG)介导的方法,在果生刺盘孢中敲除基因CfATG6和CfATG14,并进一步获得回补菌株ΔCfatg6-C和ΔCfatg14-C。【结果】酵母双杂交试验结果显示,果生刺盘孢蛋白CfAtg6和CfAtg14可能存在互作关系。生物学表型测定结果表明,相较于野生型和回补菌株,突变体ΔCfatg6和ΔCfatg14均表现出营养生长速率显著减慢,附着胞形成率分别只有野生型的5%和18%;突变体ΔCfatg6和ΔCfatg14致病力均极显著减弱,造成的油茶叶片病斑面积少于野生型和回补菌株的1/3;CfATG6和CfATG14基因缺失突变体均丧失转运和降解CfAtg8蛋白的能力,并对细胞壁胁迫更敏感。突变体ΔCfatg6的分生孢子产量显著降低,仅为野生型的20%左右;氧化胁迫试验结果表明,相较于野生型和回补菌株,过氧化氢对突变体的生长抑制率升高10%左右。内质网压力胁迫试验表明,ΔCfatg14对二硫苏糖醇抑制率升高5%以上。【结论】自噬相关基因CfATG6和CfATG14参与调控了果生刺盘孢生长发育、细胞自噬和致病力。     

Genome Analysis inNeurospora crassa;Cloning of Four Lociarginine-1(arg-1),methionine-6(met-6),unknown-7(un-7), andribosome production-1(rip-1) and Associated Chromosome Walking

We have cloned fourNeurospora crassagenes by complementation analysis. Cloned genes include thearginine-1(arg-1),methionine-6(met-6),unknown-7(un-7), andribosome production-1(rip-1) loci. Chromosome walks were initiated in ordered cosmid libraries from the cloned loci. A total of about 700 kb of theNeurosporagenome is covered in these walks.     

分别利用产甘油假丝酵母抗逆转录因子CgSTB5和CgSEF1对酿酒酵母菌株糠醛耐受改造

【背景】纤维素是生物转化解决能源问题的主要原料之一,其水解物中存在严重影响抑制菌株生长的糠醛,需脱毒才可应用于发酵,提高菌株耐受性是解决纤维素水解液实际生产应用的关键。【目的】酿酒酵母(Saccharomyces cerevisiae)是主要的纤维素水解液发酵工业菌株,但糠醛耐受性较低,通过分子改造获得具有高糠醛耐受性的菌株。【方法】利用新获得的产甘油假丝酵母(Candidaglycerinogenes)的相关抗逆转录因子CgSTB5、CgSEF1和CgCAS5,通过分子技术进行S.cerevisiae改造,考察其对酿酒酵母糠醛耐受性的影响,并尝试应用于未脱毒纤维素乙醇发酵。【结果】单个表达CgSTB5和CgSEF1的酿酒酵母,通过菌株点板实验表明菌株的糠醛耐受性提高25%以上,并且摇瓶发酵结果显示糠醛降解性能明显提高,生长延滞期明显缩短,S.cerevisiae W303/p414-CgSTB5的未脱毒纤维素乙醇发酵生产效率提高12.5%左右。【结论】转录因子CgSTB5和CgSEF1均能对提高酿酒酵母糠醛耐受性起到重要作用,并且有助于提高酿酒酵母菌株未脱毒纤维素乙醇发酵性能。     

Genomic organization of Tropomodulins 2 and 4 and unusual intergenic and intraexonic splicing of YL-1 and Tropomodulin 4

Background  

The tropomodulins (TMODs) are a family of proteins that cap the pointed ends of actin filaments. Four TMODs have been identified in humans, with orthologs in mice. Mutations in actin or actin-binding proteins have been found to cause several human diseases, ranging from hypertrophic cardiomyopathy to immunodefiencies such as Wiskott-Aldrich syndrome. We had previously mapped Tropomodulin 2 (TMOD2) to the genomic region containing the gene for amyotrophic lateral sclerosis 5 (ALS5). We determined the genomic structure of Tmod2 in order to better analyze patient DNA for mutations; we also determined the genomic structure of Tropomodulin 4 (TMOD4).     

Genomic distribution of retrotransposons 297, 1731, copia, mdg1 and roo in the Drosophila melanogaster species subgroup

The intragenomic distribution of five retrotransposon families (297, 1731, copia, mdg1 and roo) in the species of the melanogaster complex was studied by comparing results of the Southern blotting technique in males and females with those of in situ hybridization. The degree of structural polymorphism of each family in the different species was also investigated by restriction enzyme analysis. It was found that genomic distribution is a trait that depends on the family and species. The distribution of roo is mainly euchromatic in the four species and 1731 is heterochromatic, but the distribution of families 297, copia and mdg1 is markedly different in the melanogaster and simulans clades. These families were mainly euchromatic in D. melanogaster but heterochromatic in its sibling species. In the simulans clade most copia and mdg1 elements are located on chromosome Y. Differences in genomic distribution are unrelated with structural conservation. The relation of intragenomic distribution to phylogeny, transpositional activity and the role of the host genome are discussed.     

Behaviour of the transposons Tn5 and Tn7 in Xanthomonas campestris pv. campestris

Summary Xanthomonas campestris pv. campestris was tested for its ability to maintain various plasmids after they had been transferred by conjugation from Escherichia coli donors. Broad host-range plasmids belonging to incompatibility groups P and Q could be maintained but X. campestris was unable to support replication of narrow host-range ColE1, pACYC184 and pBR325 replicons. Delivery systems based on E. coli donors of suicide plasmids and on X. campestris Hfrs were used to introduce Tn7 and Tn5 into X. campestris. Tn7 insertions were recovered at high frequency while Tn5 transposed at low frequency. Three auxotrophic Tn5 insertions were isolated but transposition of Tn7 into the X. campestris genome did not generate any auxotrophs. DNA hybridization analysis showed that Tn7 had inserted into the same hot spot(s) in all cases tested.     

Characterization of CaGSP1, the Candida albicans RAN/GSP1 homologue

Gsp1p is a small nuclear-located GTP binding protein from the yeast Saccharomyces cerevisiae. It is highly conserved among eucaryotic cells and is involved in numerous cellular processes, including nucleocytoplasmic trafficking of macromolecules. To learn more about the GSP1 structure/function, we have characterized its Candida albicans homologue. CaGsp1p is 214 amino acids long and displays 91% identity to the ScGsp1p. There is functional complementation in S. cerevisiae, and its mRNA is constitutively expressed in the diploid C. albicans grown under various physiological conditions. Disruption of both alleles was not possible, suggesting that it could be an essential gene, but heterozygous mutants exhibited genomic instability.     

Isolation of the mini insertions IS6 and IS7 of E. coli

Summary The mini IS elements IS6 and IS7 have been detected in constitutive gal ⁺ revertants of galOP-308::IS2 (I), in which the expression of the gal operon is turned off by IS2 in orientation I. Both, IS6 and IS7, are integrated into IS2 proximal to the gal structural genes. IS6 is 115 base pairs long and causes 50% constitutive expression of the gal genes. IS7 is only 65 base pairs long and the gal operon is expressed 20% constitutively compared to the gal ⁺ wild type operon. Both IS6 and IS7 are excised frequently, in the absence of selective pressure. These findings are discussed with respect to the evolution of gene expression.     

Complementation studies with the repair-deficient uvrD3, uvrE156, and recL152 mutations in Escherichia coli

Summary Previous work showed that the mutations uvrD3, uvrE156, and recL152 were closely linked and increased UV-sensitivity. They were phenotypically distinguishable in that only the uvrD3 mutation significantly decreases host cell reactivation of UV-irradiated phage (Hcr^-) and repair of methylmethane sulfonate (MMS)-induced damage, and only the uvrE156 mutation increased mutation rates (Mut^-). MMS-resistant revertants of a uvrD3 mutant were still UV-sensitive and fell into two phenotypic classes, Hcr^- Mut⁺ (non-mutator) and Hcr⁺ Mut^-. In this work complementation tests were done by examining UV-and MMS-sensitivity and host cell reactivation in heterogenotes containing combinations of uvrD3, uvrE156, recL152, and the MMS-resistant mutations derived from uvrD3. The mutations could not complement each other in the repair of UV-damage, the one trait all had in common, indicating that they were in one gene. For the most part, the different mutations were able to complement each other in respect to traits in which one was deficient and the other had wild type activity.     

Evolution of Tom, 297, 17.6 and rover retrotransposons in Drosophilidae species

LTR retrotransposons are the most abundant transposable elements in Drosophila and are believed to have contributed significantly to genome evolution. Different reports have shown that many LTR retrotransposon families in Drosophila melanogaster emerged from recent evolutionary episodes of transpositional activity. To contribute to the knowledge of the evolutionary history of Drosophila LTR retrotransposons and the mechanisms that control their abundance, distribution and diversity, we conducted analyses of four related families of LTR retrotransposons, 297, 17.6, rover and Tom. Our results show that these elements seem to be restricted to species from the D. melanogaster group, except for 17.6, which is also present in D. virilis and D. mojavensis. Genetic divergences and phylogenetic analyses of a 1-kb fragment region of the pol gene illustrate that the evolutionary dynamics of Tom, 297, 17.6 and rover retrotransposons are similar in several aspects, such as low codon bias, the action of purifying selection and phylogenies that are incongruent with those of the host species. We found an extremely complex association among the retrotransposon sequences, indicating that different processes shaped the evolutionary history of these elements, and we detected a very high number of possible horizontal transfer events, corroborating the importance of lateral transmission in the evolution and maintenance of LTR retrotransposons.     

Oenothera mitochondrial orf454, a gene involved in cytochrome c biogenesis corresponds to orf169 and orf322 of Marchantia

We have characterized a mitochondrial gene in Oenothera, designated orf454, capable of encoding a component of the cytochrome c biogenesis system. This open reading frame is interrupted by an intron of 941 nucleotides showing high similarity to a group II intron residing in the rpl2 gene. RNA editing, which is observed at 18 cytidine positions within the orf454 reading frame, improves the similarity to protein-coding sequences in bacteria and higher plants and removes the last 16 amino acids. orf454 also shows high sequence similarity to two overlapping reading frames (orf169 and orf322) of Marchantia mitochondria. These ORFs belong to an operon-like cluster of genes in the liverwort that is not conserved in Oenothera mitochondria. However, in bacteria these reading frames are organized like the Marchantia gene cluster. It has been shown by genetical analysis in Rhodobacter capsulatus that these genes are essential for cytochrome c biogenesis. Genes of bacterial operons — ccl1 in Rhodobacter and yejR and nrfE in Escherichia coli — show high sequence similarity to the mitochondrial reading frames orf577 and orf454 of Oenothera. orf454, which we describe here, is homologous to the C-terminal region of these bacterial genes, while the previously described orf577 is homologous to the N-terminal region.     

乳酸乳球菌fabZ1和fabZ2基因功能的鉴定

大肠杆菌(Escherichia coli)是Ⅱ型脂肪酸合成系统的模式生物,3-羟基脂酰ACP脱水异构酶(FabA)是不饱和脂肪酸合成中的关键酶.生物信息学分析表明,乳酸乳球菌(Lactococcus lactis)的基因组中没有标注为3-羟基脂酰ACP脱水异构酶的基因,但有两个标注为3-羟基脂酰ACP脱水酶基因LlfabZ1和LlfabZ2,其编码的蛋白质与EcFabZ的相似性分别为41%和45.1%,且都具有3-羟基脂酰ACP脱水酶两个保守的α螺旋结构.用携带LlfabZ1和LlfabZ2的质粒载体遗传互补大肠杆菌fabA温度敏感突变株CY57,在42℃下不能恢复生长,但无细胞抽提物的结果显示LlFabZ1能够使反-2-癸烯酰ACP异构成顺-3-癸烯酰ACP,而LlFabZ2则不能.互补大肠杆菌fabZ突变株HW7显示,在诱导的条件下,含有LlfabZ2的转化子能够恢复生长,而LlfabZ1则不能.体外重建脂肪酸合成反应及蛋白质活性测定表明,LlFabZ1具有3-羟基脂酰ACP脱水异构酶功能,而LlFabZ2只具有3-羟基脂酰ACP脱水酶功能.另外,未得到LlfabZ1和LlfabZ2的突变株,表明LlFabZ1和LlFabZ2可能是乳酸乳球菌脂肪酸合成酶系中的必不可少的关键蛋白.上述结果证实了乳酸乳球菌fabZ1和fabZ2两个基因在脂肪酸合成中的功能.     

Activation of V(D)J recombination by RAG1 and RAG2

V(D)J recombination is normally limited to lymphoid cells, but expression of the RAG1 and RAG2 genes allows other cell types to carry out this reaction. The products of these recently discovered genes may form part of the recombination machinery, and are a focal point for lymphoid development.     

Genetic instability at the cut locus of Drosophila melanogaster induced by the MR-h12 chromosome

Summary Unstable mutations were generated at the cut locus by the MR-h12 factor which induces male recombination. The unstable allele ct ^MR2, containing the MR-transposon in the cut locus is a very powerful mutator producing a number of different viable and lethal mutations both in the cut locus and outside it.I describe several types of mutations: stable reversion to wild type, which were sometimes associated with the appearance of unstable mutations in other loci; of stable deficiencies at the cut locus (lethals); new unstable mutations at different loci with the ct ^MR2 allele conserved; new unstable cut alleles with a phenotype other than that of ct ^MR2. The possible mechanisms of these mutational events are discussed. The genetic system constructed in the present work affords an opportunity for molecular studies of the cut locus and the MR-transposon, as a sequence from the cut locus has recently been cloned (Tchurikov et al. 1981).