The leader sequence of tobacco mosaic virus RNA devoid of Watson-Crick secondary structure possesses a cooperatively melted, compact conformation

The 5'-untranslated region (5'-UTR) of RNA of tobacco mosaic virus (TMV), called omega sequence, is known as an mRNA leader promoting efficient initiation of translation. The central part of the sequence consists of many CAA repeats, which were reported to be mainly responsible for the enhancing activity of the omega leader. In this work we synthesized the polyribonucleotides containing either the natural omega sequence or the regular (CAA)(n) sequence, and studied them using UV spectrophotometry and analytical ultracentrifugation methods. It was demonstrated that the polyribonucleotides manifest significant hypochromicity, cooperative melting of their structures upon heating, high melting temperature, and the sedimentation coefficients typical of compactly folded RNAs of this size. Thus, the omega leader and its core (CAA)(n) repeat sequence devoid of secondary structure of the Watson-Crick type seem to be well structured elements of mRNA.     

Protection of transgenic tobacco plants expressing bovine pancreatic ribonuclease against tobacco mosaic virus

Transgenic tobacco plants (Nicotiana tabacum cv. SR1) expressing extracellular pancreatic ribonuclease from Bos taurus and characterized by an increased level of ribonuclease activity in leaf extracts were challenged with tobacco mosaic virus. The transgenic plants exhibited a significantly higher level of protection against the virus infection than the control non-transformed plants. The protection was evidenced by the absence (or significant delay) of the appearance of typical mosaic symptoms and the retarded accumulation of infectious virus and viral antigen. These results demonstrate that modulation of extracellular nuclease expression can be efficiently used in promoting protection against viral diseases.     

四种广普性植物病毒高效mPCR检测方法的建立

本研究建立了能同时检测出烟草花叶病毒(TMV)、黄瓜花叶病毒(CMV)、马铃薯X病毒(PVX)和马铃薯Y病毒(PVY)的多重RT-PCR体系。TMV、CMV、PVX、PVY是四种广普性植物病毒,寄主范围广泛,并且常常发生复合侵染。本研究以上述四种病毒的CP基因部分序列设计引物,以反转录的cDNA为模板,建立多重RT-PCR反应体系,分别扩增出211～417bp的不同长度的基因片断,并通过序列测定来确认扩增序列的特异性。将反转录合成的cDNA进行浓度稀释,来对多重RT-PCR与单重RT-PCR的灵敏度进行比较,结果证明,多重RT-PCR体系能够同时快速检测这四种病毒,并且有很高的灵敏度。     

苦瓜核糖体失活蛋白的分离纯化及其抑制烟草花叶病毒活性

目的:探讨分离纯化苦瓜种子核糖体失活蛋白(RIP)的方法,并研究利用纯化后的RIP抑制烟草花叶病毒(TMV)的活性。方法:用盐溶液抽提总蛋白后,经30%～90%的(NH4)2SO4分级沉淀,制成粗提液。用CMSepharoseFastFlow离子交换层析结合SephadexG-75凝胶柱分离纯化RIP。结果与结论:经SDS-PAGE检测及RNAN-糖苷酶活性鉴定,确定最终得到的蛋白为苦瓜RIP;所纯化的RIP对感染黄瓜和番茄的TMV有明显的抑制作用,但RIP的浓度并不与其抑制TMV的活性呈正相关。     

Linkage between Frl (Fusarium oxysporum f.sp. radicis-lycopersici resistance) and Tm-2 (tobacco mosaic virus resistance-2) loci in tomato (Lycopersicon esculentum)

A study was carried out on the linkage relationship between the Frl locus carrying resistance to Fusarium oxysporum f.sp. radicis-lycopersici and the Tm-2 locus carrying resistance to several races of tobacco mosaic virus in the tomato inbred line IRB-301-31. The inbred line Motelle (Frl⁺/Frl⁺, Tm-2⁺/Tm-2⁺) was crossed with the inbred line IRB-301-31 (Frl/Frl, Tm-2/Tm-l). The resulting 222 F₂ plants were selfed, and from each F₃ family groups of 15–60 seedlings were tested for resistance to either F. oxysporum f.sp. radicis-lycopersici or tobacco mosaic virus race 0. Segregation data indicated a very tight linkage between Frl and Tm-2, equal to 5.1 ± 1.07 map units.     

TMV对辣椒花药中游离脯氨酸含量和花粉萌发率的影响

对辣椒感染ＴＭＶ植株与健康植株花药中的游离琢磨一和花粉萌发力进行了比较研究,结果表明,染病毒植株花药中的游离脯氨酸含量和花粉萌发率均明显降低。     

烟草花叶病毒装配起始位点反义RNA表达型中间载体的构建

利用基因工程方法培育抗病毒植物新品种的途径之一,是在植株中建立一个产生病毒基因组功能片段的反义RNA的系统。本工作设计并合成了一段烟草花叶病毒(TMV)装配起始位点反义RNA的基因,再以pBR 325为基本质粒,构建了包含带有花椰菜花叶病毒(CaMV)35S启动子和PolyA信号的反义RNA表达单元,以及为筛选转基因植株所必须的NPT-Ⅱ表达单元的中间载体,为以后经土壤农杆菌而获得转基因烟草植株打下了基础。     

Purification of tobacco O-methyltransferases by affinity chromatography and estimation of the rate of synthesis of the enzymes during hypersensitive reaction to virus infection

The three tobacco (Nicotiana tabacum L.) S-adenosyl-L-methionine: o-diphenol-O-methyltransferases (OMTs; EC 2.1.1.6) were purified to homogeneity by affinity chromatography on adenosine-agarose. Amounts and catalytic actities of the enzymes were measured in tobacco leaves during the hypersensitive reaction to tobacco mosaic virus. The drastic increase in activity of each enzyme upon infection was shown to arise from the accumulation of enzymatic protein with constant specific enzymatic activity. Rates of OMT synthesis were determined from pulse-labeling experiments with L-[¹⁴C]leucine injected into the leaves. The specific radioactivities of the homogenous enzymes were compared in healthy and tobacco mosaic virus-infected tobacco. The results demonstrated that increase in OMT amounts is a consequence of de novo synthesis of the enzymes.Abbreviations DEAE diethylaminoethyl - OMT O-methyltransferase - SAM S-adenosyl-L-methionine - TMV tobacco mosaic virus     

Regulation of mRNA levels of rat liver carbamoylphosphate synthetase by glucocorticosteroids and cyclic AMP as estimated with a specific cDNA

The construction and cloning of a cDNA complementary to the mRNA of rat liver carbamoylphosphate synthetase (ammonia) is described. Using this cDNA, the size of the mature, cytosolic carbamoylphosphate synthetase (ammonia) mRNA is estimated to be 6.0 Kb. The levels of carbamoylphosphate synthetase (ammonia) mRNA in liver are shown to be regulated by glucocorticosteroids and cyclic AMP. By studying mRNA levels of carbamoylphosphate synthetase, albumin and phosphoenolpyruvate carboxykinase, using specific cDNA clones, we show that carbamoylphosphate synthetase gene expression, like that of albumin is liver-specific.