植物真菌致病基因的研究进展

通过标记突变技术，从真菌中找到79个致病基因。这些基因在侵染结构形成、细胞壁降解、克服和避免寄主的防卫反应、毒素产生、信号传递以及对寄主体内环境应答等方面发挥重要作用。随着技术的不断完善，陆续发现了一些具有其它功能的致病基因。本文介绍了近几年这方面的研究进展。     

松萎蔫病病原的研究

为了探讨松萎蔫病与松材线虫的关系,笔者研制了一种简单试验装置"冷闸",使接种的线虫被隔离在松树接种枝内而不能迁移.用该装置进行接种试验的结果表明:在松材线虫被局限于接种枝内而不能移动到寄主其他部位的情况下,接种无菌松材线虫与致病荧光假单胞菌Pseudomonas fluorescerns(GcM5-1A),以及该致病细菌体外培养的无细胞滤液,同样能诱发该病.该致病细菌又从接种无菌线虫和致病细菌后病死寄主中分离到并被鉴定,证明符合柯赫法则.致病荧光假单胞菌GcM5-1A体外培养的无细胞滤液接种试验结果说明,该致病菌株培养物中的内吸性毒素导致了寄主的萎蔫和死亡.由此,松萎蔫病经实验证实为首例由细菌和线虫互惠共生复合体引起的植物病害.     

松针褐斑病菌毒素的专化性研究

用松针褐斑病菌毒素粗提液处理湿地松、火炬松、黑松和马尾松的切根苗,发现湿地松和火炬松对毒素最为敏感,其次为马尾松,黑松最不敏感。毒素生测的结果与松树在田间自然感染的情况有一定的相似性,但不完全一致。不同湿地松抗病无性系对毒素的反应存在着差别,其中３３ 号所受伤害较轻,１０ 号及３６ 号较重。结合毒素薄层层析半定量试验,利用寄主愈伤组织对毒素的反应,发现毒素对寄主愈伤组织的最低作用浓度应在１００ μｇ／ｍ Ｌ 以下。试验了５ 种杂草对毒素的反应,其中空心莲子草和稞草对毒素敏感。进一步研究利用毒素作为除草剂不失为毒素利用的一个新思路。上述研究表明该毒素为非寄主专化性毒素。     

致病杆菌功能基因的分子生物学研究进展

致病杆菌是与斯氏线虫共生的肠杆菌科细菌,存在于昆虫病原线虫肠道内,可随线虫的侵染进入寄主昆虫血腔,迅速繁殖并产生多种代谢产物,抑制其他杂菌的污染,保护线虫繁殖的环境。多年研究发现,该菌的代谢产物具有广泛的杀虫、抑菌、抗癌等生物活性。本文介绍了致病杆菌外膜蛋白基因、菌毛蛋白基因、共生作用相关基因、溶血素相关基因、杀虫毒素蛋白基因、抗生素相关基因以及专利申请基因的研究进展。     

常见食物中毒菌毒素的研究进展

食物中毒是食品卫生中经常遇到的问题,而细菌(毒素)性食物中毒又是最常见的形式之一,其中O157:H7大肠杆菌的Vero毒素、金黄色葡萄球菌肠毒素和肉毒梭菌神经毒素是经常引起食物中毒的细菌毒素.对这3种食物中毒菌毒素的产生、中毒情况、毒素类型、基因特性、致病机理、检测方法、应用研究及发展趋势进行了综述.     

链格孢菌毒素的分离及活性测定

对链格孢菌（Alternaria alternata(Fr.)Keissler)产生的对紫茎泽兰（Eupatorium adenophorum Spreng.)有致病作用的毒素进行了分离纯化,并用生物法测定了该毒素的致病活性。     

球孢白僵菌毒素对昆虫体外培养细胞的超微结构和细？…

用吸附法从球孢白僵菌的代谢产物中提取毒素，并将毒素作用于草地夜蛾体外培养细胞Ｓｆ－２１细胞株，以研究球孢白僵菌毒素的昆虫致病机理，扫描和透射电镜观察结果表明，在毒素作用下，培养细胞的细胞膜，细胞核，线粒体和核糖体均有很大程度的损伤。     

杨树溃疡病菌致病力分化及杨树抗病性评价

用来源于不同地区、不同寄主上杨树溃疡病原Botryosphaeria dothidea的17个菌株在杨树上进行接种试验,结果表明,病原在杨树上存在致病力分化的现象,但不同来源地的菌株之间和不同寄主来源的菌株之间致病力没有明显的差异,说明病原致病力分化与地区分布和寄主来源无关。文章试用一种数值方法,对11种杨树感病性分别作了评价。     

竞争免疫荧光分析法高灵敏、高选择性检测赭曲霉毒素

基于半抗原与二抗竞争结合固相抗体的免疫模式,建立了一种高灵敏、高选择性检测赭曲霉毒素的新型免疫荧光分析法.赭曲霉毒素具有半抗原性,可与基底抗体作用.当赭曲霉毒素加入到该体系后,与异硫氰酸荧光素标记的羊抗兔(IgG-FITC)发生竞争反应,随着赭曲霉毒素浓度的增加,IgG-FITC与抗体结合的浓度减少,荧光强度降低.在最佳实验条件下,荧光强度的变化值(ΔF)与赭曲霉毒素浓度的对数在1nmol/L-100μmol/L范围内呈良好的线性关系,相关系数R=0.9932.方法的检出限为0.35nmol/L.将该方法用于不同种类的酒样中赭曲霉毒素的测定,结果令人满意.与传统方法相比,本方法是一种低成本、高灵敏度、高选择性的检测方法,在食品安全领域中具有潜在的应用价值.     

植物线虫寄生策略及致病机理

植物寄生线虫与其寄主在漫长的进化过程中，已形成复杂的寄生关系，包括其取食的寄主细胞的形态和功能的改变．现代分子生物学技术的不断发展为我们在分子水平上阐述线虫致病机理提供了基础，致病机理作为线虫生物学防治的理论依据成为线虫学研究的焦点．阐述了植物寄生线虫寄生策略和致病机理方面的研究进展．     

Inhibition of exocytosis in bovine adrenal medullary cells by botulinum toxin type D

Botulinum toxins are known to block transmitter release at peripheral cholinergic synapses, producing muscular weakness and paralysis. The toxins may also block adrenergic transmission, although this effect is less well understood. The mechanisms by which toxins act are unclear. They are proteins of relative molecular mass approximately 150,000 and are structurally similar to tetanus toxin. It is generally accepted that a rise in intracellular calcium concentration is sufficient to trigger secretion by exocytosis, but it is not known whether the toxins block secretion by preventing this Ca transient or whether they act downstream from Ca entry by interfering with the process of exocytosis itself. We have attempted to resolve these questions in the case of the adrenergic system by studying the effects of botulinum toxins (types A, B, D and E) on the secretory response of isolated bovine adrenal medullary cells maintained in culture. The cells were either challenged with various secretagogues or rendered leaky and challenged directly with Ca buffers. We report here that botulinum toxin type D inhibits secretion in a time- and dose-dependent manner, the results being entirely consistent with the idea that the toxin acts at or near the site of exocytosis rather than at the sites controlling the rise in free Ca.     

Symbiotic host-specificity of Rhizobium meliloti is determined by a sulphated and acylated glucosamine oligosaccharide signal

Rhizobia are symbiotic bacteria that elicit the formation on leguminous plants of specialized organs, root nodules, in which they fix nitrogen. In various Rhizobium species, such as R. leguminosarum and R. meliloti, common and host-specific nodulation (nod) genes have been identified which determine infection and nodulation of specific hosts. Common nodABC genes as well as host-specific nodH and nodQ genes were shown recently, using bioassays, to be involved in the production of extracellular Nod signals. Using R. meliloti strains overproducing symbiotic Nod factors, we have purified the major alfalfa-specific signal, NodRm-1, by gel permeation, ion exchange and C18 reverse-phase high performance liquid chromatography. From mass spectrometry, nuclear magnetic resonance, (35)S-labelling and chemical modification studies, NodRm-1 was shown to be a sulphated beta-1,4-tetrasaccharide of D-glucosamine (Mr 1,102) in which three amino groups were acetylated and one was acylated with a C16 bis-unsaturated fatty acid. This purified Nod signal specifically elicited root hair deformation on the homologous host when added in nanomolar concentration.     

海葵多肽类神经毒素的结构与药理学功能

海葵以其触手刺细胞中的毒液行使捕食和防御功能,其毒液中富含各种多肽类神经毒素,分子量为3￣7kDa之间,分子序列中含多对二硫键以稳定其结构。海葵神经毒素以钠离子通道毒素和钾离子通道毒素为其主要成分,此外还发现有作用于其他离子通道的成分,此外,还有部分海葵毒素目前尚不清楚其分子靶标。不同类型的海葵毒素具有不同的空间结构。海葵毒素多肽的分子多样性使其成为动物毒素研究的一个重要分支,同时海葵多肽毒素对不同离子通道的特异性和高亲和性,使得它们成为神经生理学和药理学研究的一种重要工具。     

地表水中藻毒素的监测与控制

随着大量含氮和磷的废水流入湖泊和江河,导致淡水污染现象日趋严重.污染的最主要危害是释放多种藻毒素,因此如何有效控制、去除藻毒素是摆在中外环境科学领域的一个难题,目前水体中藻毒素的监测方法主要有生物法、化学法、免疫法等;控制的方法主要有常规净水工艺、生物处理、光降解与光催化氧化以及臭氧氧化等.     

腹泻性贝毒在翡翠贻贝中的积累、排出及其对HSP70表达的影响

以利玛原甲藻(Prorocentrum lima)为饵料,通过室内滤食实验,考查了腹泻性贝毒(diarrheic shellfishpoisoning,DSP)在翡翠贻贝(Perna viridis)体内的累积与排出规律,分析了HSP70基因的表达与毒素累积与排出之间的关系.结果显示,翡翠贻贝暴露于产毒利玛原甲藻后,其滤食率显著下降,存在明显的剂量-效应关系.毒素积累阶段,翡翠贻贝鳃组织中DSP毒素显著增加,均明显高于对照组(P<0.05).停止染毒后,贻贝体内毒素含量显著下降.染毒后,随着毒素的累积,HSP70显著增加,并于第2天达到高峰.这些结果提示,翡翠贻贝对DSP毒素有一定的清除及耐受能力,HSP70基因的诱导表达可能是贻贝对DSP毒素胁迫的一种适应性反应,可能在贻贝抗DSP毒素中发挥重要作用.     

Cloning and sequencing of two depressant insect selective neurotoxin cDNAs from Buthus martensii Karsch

During evolution, scorpions have developed the ability to produce a series of toxins. Scorpion toxins, which are reserved in terminal segments of scorpion, serve as the arms for predation and self-defence. They have also been used as medicine for some human sickness. As far as the targets that they act on are concerned, these toxins can be divided     

基于风险分析方法的食品中天然毒素污染防控

对食品中毒素污染进行风险分析具有重要的公共卫生意义.天然毒素不仅可以污染食品引起食物中毒,而且还具有致癌、致畸、致突变作用.本文在分析食品中天然毒素及危害的基础上,运用风险分析方法对其进行评估,以期为食品中的天然毒素污染防控提出建议.     

河南省饮用水中藻毒素污染与控制对策

对河南省饮用水中藻毒素污染状况进行了调查研究 ,分析了水体中藻毒素的来源、毒理及迁移转化的影响因素 ,指出目前控制河南省饮用水中藻毒素污染必须将水源水控制治理与净水工艺处理结合起来 ,优化水处理工艺和强化水源水体保护是根本保障     

河南的鹅膏菌属毒菌及毒素与中毒类型

鹅膏菌属（Ａｍａｎｉｔａ）隶属于鹅膏菌科（Ａｍａｎｉｔａｃｅａｅ）,有毒菌多。本文就河南境内生长分布的鹅膏菌属毒菌种类及其毒素和中毒类型进行论述和分析,以供防治中毒与毒素的研究应用。     

Retrograde transport of endocytosed Shiga toxin to the endoplasmic reticulum.

Shiga toxin and some other protein toxins that act on targets in the cytosol have previously been shown to enter the trans-Golgi network. Transport by this route may be necessary for translocation of the toxin to the cytosol and for intoxication, but it is not known whether the enzymatically active part of the toxins actually enters the cytosol from the trans-Golgi network. It has been suggested that such toxins are transported in a retrograde manner to the endoplasmic reticulum and that translocation occurs in this organelle, but retrograde transport of endocytosed material beyond the trans-Golgi network has never been demonstrated. Here we show that in butyric acid-treated A431 cells endocytosed Shiga toxin is not only transported to the trans-Golgi network, but also to all Golgi stacks, to the endoplasmic reticulum and to the nuclear envelope. Furthermore, butyric acid sensitizes the cells to Shiga toxin, which is consistent with the possibility that retrograde transport is required for translocation of the toxin to the cytosol.