伯克氏菌对水稻种子萌发及初生幼苗耐镉性的影响

在无菌条件下研究了伯克氏菌对镉胁迫下水稻种子萌发及初生幼苗耐镉性的影响。结果表明:伯克氏菌D54能在含500mg·L^-1Cd的培养基中正常生长,显示出极强的耐镉能力。在50 mg·L^-1的镉胁迫下,接种伯克氏菌能显著提高水稻种子的萌发率,但在其他镉处理下,接种伯克氏菌对种子萌发无显著影响。接种伯克氏菌对水稻种子的发芽指数没有影响,但在10 mg·L^-1Cd处理下,接种伯克氏菌能显著提高水稻种子的活力指数和初生幼苗的根长、根表面积、根尖总数和耐性系数。接种伯克氏菌对初生幼苗的芽鲜重无影响,但能显著提高根鲜重。在50 mg·L^-1和100 mg·Lz^-1的高浓度镉处理下,接种伯克氏菌对根系生长没有影响。     

植物延伸因子eEF1A研究进展

60年代初,首先从E．coli细胞中分离获得延伸因子,延伸因子eEF1A广泛存在于真核细胞内,是在核糖体上催化氨基酸链的延伸而推动、控制蛋白质的合成等方面起到重要作用的蛋白质因子。在植物蛋白质合成延伸过程中,eEF1A是一个主要的翻译因子;在快速增殖的细胞中,eEF1A基因的表达调控十分保守,其表达水平同细胞生长及增殖速度有关。eEF1A除了参与同翻译控制有关的信号传导外,还参与细胞生长、应激反应及与运动性有关的信号传导,并且与细胞凋亡等有关。eEF1A在体内和体外均能同肌动蛋白纤维及微管蛋白结合,是细胞骨架运动性的调节蛋白。目前许多植物的eEF1A基因已被分离,植物种间的eEF1A氨基酸序列高度保守;植物eEF1A由多基因编码,它的表达受激素、环境胁迫和生长发育过程等因素诱导。文章通过总结植物延伸因子eEF1A的生理作用以及eEF1A基因的克隆、鉴定、诱导表达等分子生物学研究,以期为今后进一步深入研究eEF1A奠定基础。     

The 1.2-megabase genome sequence of Mimivirus

We recently reported the discovery and preliminary characterization of Mimivirus, the largest known virus, with a 400-nanometer particle size comparable to mycoplasma. Mimivirus is a double-stranded DNA virus growing in amoebae. We now present its 1,181,404-base pair genome sequence, consisting of 1262 putative open reading frames, 10% of which exhibit a similarity to proteins of known functions. In addition to exceptional genome size, Mimivirus exhibits many features that distinguish it from other nucleocytoplasmic large DNA viruses. The most unexpected is the presence of numerous genes encoding central protein-translation components, including four amino-acyl transfer RNA synthetases, peptide release factor 1, translation elongation factor EF-TU, and translation initiation factor 1. The genome also exhibits six tRNAs. Other notable features include the presence of both type I and type II topoisomerases, components of all DNA repair pathways, many polysaccharide synthesis enzymes, and one intein-containing gene. The size and complexity of the Mimivirus genome challenge the established frontier between viruses and parasitic cellular organisms. This new sequence data might help shed a new light on the origin of DNA viruses and their role in the early evolution of eukaryotes.     

真核细胞翻译起始因子5A(eIF5A)研究进展

真核细胞翻译起始因子5A(eIF5A)是真菌、动植物体内普遍存在的蛋白质翻译起始因子。研究发现其不仅仅在部分蛋白质翻译起始中发挥作用,还在人体癌症发生、促进动植物细胞增殖、细胞衰老和死亡以及一些植物环境胁迫应答等方面都有一定的调控作用。进一步研究真核细胞翻译起始因子5A(eIF5A)的功能,对其生产实践中应用具有非常重要的意义。     

S6K1- and betaTRCP-mediated degradation of PDCD4 promotes protein translation and cell growth

The tumor suppressor programmed cell death protein 4 (PDCD4) inhibits the translation initiation factor eIF4A, an RNA helicase that catalyzes the unwinding of secondary structure at the 5' untranslated region (5'UTR) of messenger RNAs (mRNAs). In response to mitogens, PDCD4 was rapidly phosphorylated on Ser67 by the protein kinase S6K1 and subsequently degraded via the ubiquitin ligase SCF(betaTRCP). Expression in cultured cells of a stable PDCD4 mutant that is unable to bind betaTRCP inhibited translation of an mRNA with a structured 5'UTR, resulted in smaller cell size, and slowed down cell cycle progression. We propose that regulated degradation of PDCD4 in response to mitogens allows efficient protein synthesis and consequently cell growth.     

从传播学的角度看翻译原则

翻译作为一种跨文化的信息交流活动,其本质是传播。本文应用传播学理论重新审视翻译标准。从克服传统的翻译标准一味要求译者忠实于原文,对原作者负责,而忽视译者创造性和目标受众反映的局限,从一个更加开放和动态的视角探讨翻译标准问题。认为,译文应准确反映原文信息和译文易于目标受众所接受为原则。     

Multiphasic characterization of a plant growth promoting bacterial strain,Burkholderia sp.7016 and its effect on tomato growth in the field

Aiming at searching for plant growth promoting rhizobacteria(PGPR), a bacterium strain coded as 7016 was isolated from soybean rhizosphere and was characterized in the present study. It was identified as Burkholderia sp. based on 16 S r DNA sequence analysis, as well as phenotypic and biochemical characterizations. This bacterium presented nitrogenase activity, 1-aminocyclopropane-1-carboxylic acid(ACC) deaminase activity and phosphate solubilizing ability; inhibited the growth of Sclerotinia sclerotiorum, Gibberella zeae and Verticillium dahliae; and produced small quantities of indole acetic acid(IAA). In green house experiments, significant increases in shoot height and weight, root length and weight, and stem diameter were observed on tomato plants in 30 d after inoculation with strain 7016. Result of 16 S r DNA PCR-DGGE showed that 7016 survived in the rhizosphere of tomato seedlings. In the field experiments, Burkholderia sp. 7016 enhanced the tomato yield and significantly promoted activities of soil urease, phosphatase, sucrase, and catalase. All these results demonstrated Burkholderia sp. 7016 as a valuable PGPR and a candidate of biofertilizer.     

Dom34:Hbs1 promotes subunit dissociation and peptidyl-tRNA drop-off to initiate no-go decay

No-go decay (NGD) is one of several messenger RNA (mRNA) surveillance systems dedicated to the removal of defective mRNAs from the available pool. Two interacting factors, Dom34 and Hbs1, are genetically implicated in NGD in yeast. Using a reconstituted yeast translation system, we show that Dom34:Hbs1 interacts with the ribosome to promote subunit dissociation and peptidyl-tRNA drop-off. Our data further indicate that these recycling activities are shared by the homologous translation termination factor complex eRF1:eRF3, suggesting a common ancestral function. Because Dom34:Hbs1 activity exhibits no dependence on either peptide length or A-site codon identity, we propose that this quality-control system functions broadly to recycle ribosomes throughout the translation cycle whenever stalls occur.     

百脉根离子通道蛋白Pollux与翻译延伸因子EF1A的相互作用

利用酵母双杂交技术,以百脉根离子通道蛋白Pollux胞内结构域为诱饵,从百脉根AD-cDNA文库中筛选到与Pollux相互作用的多个阳性克隆,经DNA序列测定及NCBI数据库BLAST分析,其中有6个阳性克隆编码翻译延伸因子EF1A。进一步在大肠杆菌中表达与纯化Pollux和EF1A融合蛋白,通过Pull-down及Western杂交证实Pollux胞内结构域与EF1A的C-末端相互作用。     

翻译起始因子(eIF1A)基因的获得及抗旱性分析

从柽柳cDNA文库中测序得到一条长度为631bp,编码113个氨基酸的全长cDNA基因序列,利用生物信息学软件对该基因进行分析,确定其属于eIF1A家族。采用农杆菌介导法进行烟草的遗传转化,通过分子检测证明eIF1A基因已经整合到烟草基因组中,并且在mRNA水平上得到不同程度的表达。对各转基因烟草及非转基因对照烟草进行旱胁迫处理,测定抗逆生理指标、生长量大小。结果证明,柽柳的eIF1A基因具有提高烟草的抗干旱能力。     

Retrograde viral delivery of IGF-1 prolongs survival in a mouse ALS model

Amyotrophic lateral sclerosis (ALS) is a progressive, lethal neuromuscular disease that is associated with the degeneration of spinal and brainstem motor neurons, leading to atrophy of limb, axial, and respiratory muscles. The cause of ALS is unknown, and there is no effective therapy. Neurotrophic factors are candidates for therapeutic evaluation in ALS. Although chronic delivery of molecules to the central nervous system has proven difficult, we recently discovered that adeno-associated virus can be retrogradely transported efficiently from muscle to motor neurons of the spinal cord. We report that insulin-like growth factor 1 prolongs life and delays disease progression, even when delivered at the time of overt disease symptoms.     

Quercetin Increased Protein Utilization and Decreased Nitrogen Excretion in Broilers by Activating TOR Signaling Pathway

The study was conducted to investigate the effect and mechanism of dietary quercetin supplementation on protein utilization of Arbor Acres (AA) broilers.A total of 240 1-day-old AA broilers were randomly allocated to four treatments with six replicates,comprising 10 broilers each replicate (60 broilers per treatment).Birds were fed either a corn-soybean meal basal diet without quercetin (control) or a basal diet supplemented with 0.2,0.4 or 0.6 g of quercetin per kg feed,and the trial lasted 42 days.Dietary quercetin supplementation tended to increase the apparent metabolic rate of protein (p=0.076) and the content of serum albumin (p=0.062) in AA broilers.Compared with the control,dietary quercetin supplementation increased the contents of protein in breast muscle (p0.05) and in thigh muscle (p=0.053).In addition,quercetin up-regulated mRNA expression of insulin-like growth factor 1 (IGF-1),phosphatidylinositol 3-kinase (PI3K),target of rapamycin (TOR),ribosomal protein S6 kinase 1 (S6K1),eukaryotic translation initiation factor 4E (eIF4E),eukaryotic translation initiation factor 4G (eIF4G),eukaryotic elongation factor 2 (eEF2) and eukaryotic translation initiation factor 4B (eIF4B) genes and down-regulated mRNA expression of eukaryotic elongation factor 2 kinase (eEF2K) and eukaryotic initiation factor 4E binding protein1 (4E-BP1) genes in breast muscle,thigh muscle and liver of AA broilers (p0.05).The present results suggested that dietary quercetin supplementation enhanced protein utilization in broilers by activating TOR signaling pathway.     

A/J小鼠感染猪链球菌2型后脾脏消减cDNA文库的构建及相关差异基因表达分析

为了分离与猪链球菌2型感染密切相关的基因,利用抑制性消减杂交(SSH)技术构建了8周龄A/J小鼠感染猪链球菌2型后的脾脏消减cDNA文库,并对其中169个阳性克隆进行测序,去除冗余的cDNA序列载体并聚类拼接后共获得110条差异表达序列标签(EST)。利用GenBank的BLAST软件分析比较核酸和蛋白质同源性,发现共有36个基因与这些EST具有高度的同源性,它们分别参与细胞成分、免疫、信号转导、凋亡、转录等重要功能。这些差异表达基因主要有ATP/GTP结合蛋白1(Agtpbp1)、天冬氨酸-谷氨酸-丙氨酸-天冬氨酸盒多肽5、核蛋白p68、ATP-依赖RNA解旋酶、真核生物转录因子2亚基(Eif2s2)、Na+/K+-ATP酶转运β3多肽、溶菌酶1、溶菌酶2等基因。结论:这些差异表达基因在猪链球菌2型感染过程中可能发挥重要功能。