幽影病毒引起的几种主要植物病害

幽影病毒的基因组不编码外壳蛋白,不形成通常的病毒粒体结构。这类病毒往往和黄症病毒复合侵染引起植物病害,蚜虫传播是病害在田间传播流行的主要方式。对幽影病毒引起的胡萝卜杂色矮缩病、花生丛簇病以及烟草丛顶病等几种主要病害的症状、发生与危害、病原物特性以及病害的控制等进行了综述。     

Detection and Classification of Trypanosoma cruzi by DNA Hybridization with Nonradioactive Probes

ABSTRACT. Total or kinetoplast DNA (kDNA) from 72 isolates and clones of Trypanosoma cruzi as well as from nine related trypanosomatids were analyzed by dot hybridization using nonradioactive kDNA or cloned minicircle fragments as probes. Biotinylated-kDNA probes generated by nick-translation proved reliable for distinguishing Zymodeme 1 and Zymodeme 2bol of T. cruzi parasites. In contrast, digoxigenin-labeled kDNA obtained by random-priming did not distinguish among T. cruzi isolates but did distinguish among New World leishmanias. Cloned minicircle fragments labeled with digoxigenin gave the same results as digoxigenin-labeled kDNA, except for a 10-fold decrease in sensitivity. Digoxigenin-labeled DNA probes proved useful in unambiguously detecting T. cruzi from different geographic regions of America. However, T. rangeli and T. cruzi marinkellei were not distinguished by these probes.     

A New Screening Method for C-P Compound Producing Organisms by the Use of Phosphoenolpyruvate Phosphomutase

Phosphoenolpyruvate phosphomutase (PEPPM) catalyzes the C-P bond forming reaction by intramolecular rearrangement of phosphoenolpyruvate to phosphonopyruvate, and shows stronger activity in catalyzing the reverse reaction than the forward reaction. By exploiting the activity of PEPPM to catalyze the reverse reaction, 81 strains were screened as possible C-P compound producing microorganisms from 230 soil samples. Two of these strains, B-1 and L-b, were found to produce C-P compounds by ³¹P-NMR spectral analysis of their broth filtrates. The activity of PEPPM was detected in the cell extracts of these two strains. The strain B-1 was identified as Pseudomonas gladioli, and hydroxyethylphosphonic acid (HEP) was isolated from the broth filtrate of this strain as a C-P compound.     

高效聚磷菌的分离、筛选与构建的研究进展

高效聚磷菌的获得是深入把握生物除磷的复杂机制以及优化生物除磷工艺设计的基础。该文对比分析了近年来对高效聚磷菌的分离、筛选与构建等方面的研究进展。     

Base Composition of the DNA of Mycoplasma-Like Organisms Associated with Various Plant Diseases

DNA was isolated from periwinkle plants infected by various mycoplasma-like organisms (MLOs), and from apple trees affected by apple proliferation. The DNA of the causal agents was separated from the host plant DNA by repeated bisbenzimide-CsCl buoyant density gradient centrifugation which resulted in highly enriched MLO DNA bands characterized by a lower buoyant density than that of the host DNA. The MLO DNAs were hydrolyzed to free bases which were determined by HPLC. The analyses revealed a similar low G + C content as found in the DNAs of several culturable mycoplasmas and spiroplasmas. The values of the DNA of the agents of the diseases investigated were as follows: European aster yellows 23.0, periwinkle virescence 23.5, apple proliferation 23.7, rape virescence 24.2, and phyllody of Diplotaxis erucoidcs 26.2 mol % G + C, respectively. Methylated bases were detected in low amounts only.     

Evaluation of Two Direct Plating Methods Using Nonradioactive Probes for Enumeration of Vibrio parahaemolyticus in Oysters

Oysters (Crassostrea virginica) were collected monthly from May 1998 to April 1999 from Mobile Bay, Ala., and analyzed to determine Vibrio parahaemolyticus densities at zero time and after 5, 10, and 24 h of postharvest storage at 26°C. After 24 h of storage at 26°C, oysters were transferred to a refrigerator at 3°C and then analyzed 14 to 17 days later. The V. parahaemolyticus numbers were determined by the most-probable-number procedure using alkaline phosphatase-labeled DNA probe VPAP, which targets the species-specific thermolabile hemolysin gene (tlh), to identify suspect isolates (MPN-VPAP procedure). Two direct plating methods, one using a VPAP probe (Direct-VPAP) and one using a digoxigenin-labeled probe (Direct-VPDig) to identify suspect colonies, were compared to the MPN-VPAP procedure. The results of the Direct-VPAP and Direct-VPDig techniques were highly correlated (r = 0.91), as were the results of the Direct-VPAP and MPN-VPAP procedures (r = 0.91). The correlation between the Direct-VPDig and MPN-VPAP results was 0.85. The two direct plating methods in which nonradioactive DNA probes were used were equivalent to the MPN-VPAP procedure for identification of total V. parahaemolyticus, and they were more rapid and less labor-intensive.     

一种小量提取植物总RNA的有效方法

以水稻、玉米、辣椒为材料 ,摸索出了一套改良的异硫氰酸胍提取植物总RNA的方法 ,该方法简单、快速、纯度高、完整性强 ,方便有效 ,值得推广。     

Soilborne Plant Diseases Caused by Pythium spp.: Ecology,Epidemiology, and Prospects for Biological Control

Soilborne root diseases caused by plant pathogenic Pythium species cause serious losses in a number of agricultural production systems, which has led to a considerable effort devoted to the development of biological agents for disease control. In this article we review information on the ecology and biological control of these pathogens with the premise that a clear understanding of the ecology of the pathogen will assist in the development of efficacious biocontrol agents. The lifecycles of the pathogens and etiology of host infection also are reviewed, as are epidemiological concepts of inoculum-disease relationships and the influence of environmental factors on pathogen aggressiveness and host susceptibility. A number of fungal and bacterial biocontrol agents are discussed and parallels between their ecology and that of the target pathogens highlighted. The mechanisms by which these microbial agents suppress diseases caused by Pythium spp., such as interference with pathogen survival, disruption of the process of plant infection, and induced host resistance, are evaluated. The possibilities for enhancement of efficacy of specific biological control agents by genetic manipulation or deployment tactics are discussed, as are conceptual suggestions for consideration when developing screening programs for antagonists.     

Uptake and Compartmentation of Fluorescent Probes by Plant Cells

Several fluorescent compounds are now being used as probes forstudying plant transport processes. This review considers thepotential mechanisms of uptake of such probes with particularemphasis on their subsequent compartmentation within the cell.Physico-chemical parameters, such as the dissociation constant(pK_a) and polarity (log k^ow) of the dye molecule provide importantguides as to the likely permeability of the plasmalemma to differentfluorochromes and an ion-trap mechanism may explain the accumulationof many fluorescent probes by plant cells. However, physico-chemicalparameters alone do not always explain the subsequent compartmentationof fluorescent probes within the cell. Evidence is accumulatingthat many anionic fluorescent probes may cross the plasmalemmain the undissociated state, followed by carrier-mediated transportof the anion across the tonoplast. In the specialized case ofthe highly dissociated dye, Lucifer Yellow CH (LYCH), the physico-chemicalproperties of the molecule would predict that it should be unableto cross membranes. Despite this, there have been several reportsof the movement of LYCH from the apoplast to the vacuole ofplant cells. Fluid-phase endocytosis has been implicated inthe vacuolar accumulation of LYCH and also a range of high-molecularweight, purified fluorescent conjugates. This evidence is discussedin the light of some reports that membrane-impermeant dyes,including LYCH, may cross the tonoplast following their microinjectioninto the cytoplasm.     

一种简单、经济的植物RNA抽提方法

一种简单、经济的植物ＲＮＡ抽提方法孟玲谭德勇王焕效吕朝晖王晓燕周翔（云南大学生物系,昆明６５００９１）ＡＳｉｍｐｌｅＥｃｏｎｏｍｉｃａｌＭｅｔｈｏｄｆｏｒｔｈｅＩｓｏｌａｔｉｏｎｏｆＰｌａｎｔＲＮＡＭＥＮＧＬｉｎｇＴＡＮＤｅｙｏｎｇＷＡＮＧＨｕａｎｘ...     

朊病毒和朊病毒病研究进展

朊病毒病即海绵状脑病,是人和动物中的一类致死性中央神经系统疾病,近几年来在朊病毒病的致病机制及其诊断技术和防治策略方面取得了很大的研究进展.     

A Rapid and Efficient Method for In Vitro Screening of Taro for Leaf Blight Disease Caused by Phytophthora colocasiae

Taro leaf blight caused by Phytophthora colocasiae presents the single biggest constraint for taro cultivation globally. To accelerate breeding and selection for disease resistance to leaf blight, it is important to develop bioassays which could differentiate resistant and susceptible cultivars efficiently. In this study, thirty taro accessions and four released cultivars were evaluated for resistance to leaf blight using a modified floating leaf disc assay. A novel method for mass production of P. colocasiae zoospores was developed and used as inoculum for the assay. There were significant (P < 0.05) differences among accessions in their response to P. colocasiae infection in the detached leaf assay. The accessions could be efficiently classified into various resistance groups based on a 0–4 score. Also, the assay results were consistent with the field evaluation scores of taro accessions. Thus, this study reports the development of a rapid, simple and repeatable assay that can be used to screen large numbers of taro cultivars for resistance to P. colocasiae.     

双平板对照筛选跟踪分离细菌外排泵抑制剂

建立了细菌外排泵抑制剂的筛选与活性跟踪方法.准备2个平板,一个为普通营养琼脂平板,另一个为舍小蘖碱的普通营养琼脂平板,通过比较两个平板含药纸片周围抑菌圈的直径大小判断筛选结果,方法可靠稳定.筛选发现某霉菌提取物对细菌外排泵有抑制活性,经活性跟踪分离,得到单体化合物,经NMR鉴定为4′,5,7-三羟基异黄酮.方法简便易行,成本低,适宜于对大批样本进行快速筛选并在分离时进行活性跟踪.     

一种简捷提取植物总RNA的准备和操作方法

提取RNA是分子生物学实验中的常用技术。而RNA酶抑制程度成为提取RNA的主要决定因素。准备和操作不当造成的RNA酶污染是实验失败的重要原因。介绍一种简捷的“烧、烤”提取植物总RNA的准备和操作方法,可以有效地抑制外源RNA酶的污染,提取的RNA成功率很高。     

Identification of Polyphosphate-Accumulating Organisms and Design of 16S rRNA-Directed Probes for Their Detection and Quantitation

Laboratory-scale sequencing batch reactors (SBRs) as models for activated sludge processes were used to study enhanced biological phosphorus removal (EBPR) from wastewater. Enrichment for polyphosphate-accumulating organisms (PAOs) was achieved essentially by increasing the phosphorus concentration in the influent to the SBRs. Fluorescence in situ hybridization (FISH) using domain-, division-, and subdivision-level probes was used to assess the proportions of microorganisms in the sludges. The A sludge, a high-performance P-removing sludge containing 15.1% P in the biomass, was comprised of large clusters of polyphosphate-containing coccobacilli. By FISH, >80% of the A sludge bacteria were β-2 Proteobacteria arranged in clusters of coccobacilli, strongly suggesting that this group contains a PAO responsible for EBPR. The second dominant group in the A sludge was the Actinobacteria. Clone libraries of PCR-amplified bacterial 16S rRNA genes from three high-performance P-removing sludges were prepared, and clones belonging to the β-2 Proteobacteria were fully sequenced. A distinctive group of clones (sharing ≥98% sequence identity) related to Rhodocyclus spp. (94 to 97% identity) and Propionibacter pelophilus (95 to 96% identity) was identified as the most likely candidate PAOs. Three probes specific for the highly related candidate PAO group were designed from the sequence data. All three probes specifically bound to the morphologically distinctive clusters of PAOs in the A sludge, exactly coinciding with the β-2 Proteobacteria probe. Sequential FISH and polyphosphate staining of EBPR sludges clearly demonstrated that PAO probe-binding cells contained polyphosphate. Subsequent PAO probe analyses of a number of sludges with various P removal capacities indicated a strong positive correlation between P removal from the wastewater as determined by sludge P content and number of PAO probe-binding cells. We conclude therefore that an important group of PAOs in EBPR sludges are bacteria closely related to Rhodocyclus and Propionibacter.     

介绍一种简单高效的植物总RNA提取方法

在液氮中研磨小麦幼叶和不同发育时期的种子,经含0.1% SDS和0.1%十二烷基肌氨酸钠(LDS)的尿素缓冲液裂解后,醋酸钠和氯仿沉淀变性蛋白质,异丙醇沉淀核酸,溶解后经2.5mol/L LiCl沉淀总RNA,洗涤后就可得到高质量的总RNA,其OD260/OD280 为2.05~2.10,28S和18S RNA带清晰,叶片总RNA还可得到23S和16S RNA带,产率可达5mg RNA/10g材料。当使用含1% SDS和1% LDS的尿素缓冲液裂解材料时,则可用于DNA的分离提取,其分子大小可达50~100kb以上。 Abstract:Wheat leaf and seeds at different development stages had been squashed in liquid nitrogen,then lysised by urea buffer which contains 0.1% SDS and 0.1% LDS,denatured protein had been removed by NaAc and chloroform precipitation,total RNA was further purified by LiCl.The RNA we obtained had sharp bands of 28S and 18S after agarose gel electrophoresis,23S and 16S RNA bands can also be seen clearly in leaf RNA extract,the value of OD260/OD280 of RNA was 205~210.5mg RNA can been isolated from 10g leaf of wheat.This method can also been used in high molecular weight DNA isolation but the concentration of SDS and LDS must be increased to 1%.     

Recycling Isolation of Plant DNA,A Novel Method

DNA is one of the most basic and essential genetic materials in the field of molecular biology.To date,isolation of sufficient and good-quality DNA is still a challenge for many plant species,though various DNA extraction methods have been published.In the present paper,a recycling DNA extraction method was proposed.The key step of this method was that a single plant tissue sample was recycled for DNA extraction for up to four times,and correspondingly four DNA precipitations(termed as the 1st,2nd,3rd and 4th DNA sample, respectively) were conducted.This recycling step was integrated into the conventional CTAB DNA extraction method to establish a recycling CTAB method.This modified CTAB method was tested in eight plant species,wheat,sorghum,barley,corn,rice,Brachypodium distachyon,Miscanthus sinensis and tung tree.The results showed that high-yield and good-quality DNA samples could be obtained by using this new method in all the eight plant species.The DNA samples were good templates for PCR amplification of both ISSR and SSR markers.The recycling method can be used in multiple plant species and can be integrated with multiple conventional DNA isolation methods,and thus is an effective and universal DNA isolation method.     

Direct Access to Plant Epicuticular Wax Crystals by a New Mechanical Isolation Method

A new method for the isolation of wax crystals from plant surfaces is presented. The wax-covered plant surface, e.g., a piece of a leaf or fruit, is brought into contact with a preparation liquid, e.g., glycerol or triethylene glycol, and cooled to ca. -100 degrees C. When the plant specimen is removed, the epicuticular wax remains embedded in the frozen liquid. After it warms up, the wax layer can be captured on appropriate carriers for further studies. This isolation method causes very little stress on the wax crystals; thus the shape and crystal structure are well preserved. In many cases it is possible, by choosing a preparation liquid with appropriate wettability, to isolate either the entire epicuticular wax layer or only discrete wax crystals without the underlying wax film. These crystals are well suited for electron diffraction studies by transmission electron microscopy and high resolution imaging by atomic force microscopy. The absence of intracuticular components and other impurities and the feasibility of the selective isolation of wax crystals enable improved chemical analysis and a more detailed study of their properties.     

一种妥布拉霉素产生菌初筛方法的建立

从金黄色葡萄球菌１００１出发,选育到一株对妥布拉霉素和卡那霉素耐药而对阿泊拉霉素敏感的突变株１００１－１１。以金黄色葡萄球菌１００１－１１和对上述三种抗生素均敏感的枯草杆菌６３５０１为测定菌,建立了一种能同时检测妥布拉霉素产生菌菌落琼脂柱总效价和组分相对含量的初筛方法。