Re-routing of a secretory protein by fusion with human growth hormone sequences

Cells with electron-dense secretory vesicles use them to store only specialized secretory products such as peptide hormones; other types of secreted proteins are externalized by an alternative, constitutive route. One possible mechanism for such segregation is that proteins destined for dense secretory vesicles contain unique 'sorting domains' that allow for selective targeting. Here, we set out to determine whether a constitutively secreted protein could be diverted to the dense secretory vesicles by attachment to a peptide hormone sequence. We made use of the ability of the mouse pituitary tumour cell, AtT-20, to correctly sort exogenous secretory proteins introduced into them by DNA transfection. We constructed a plasmid encoding a hybrid protein in which a constitutively secreted viral protein was fused to the carboxy terminus of human growth hormone (hGH). Cells expressing the hybrid protein were found to target it to dense secretory vesicles with an efficiency close to that observed for the parental hGH. These results support the hypothesis that sorting domains on peptide hormones direct their packaging into dense secretory vesicles. The results also suggest that proteins secreted by the constitutive pathway either do not contain any sorting domain, or their sorting signals can be overridden by those which direct peptide hormones.     

植物组织结构与抗虫性的关系(综述)

植物对植食性昆虫的防御体系包括组成防御体系和诱导防御体系两个方面,笔者从叶片、树皮、树干等不同部分论述了植物组织结构与抗虫性的关系,说明植物的物理、化学防御体系在植物的抗虫机制中起着重要的作用.     

Nitric oxide in female reproductive system

Nitric oxide (NO), synthesized from L-arginine and oxygen by a family of enzymes known as nitric oxide synthase (NOS), is an effective and intercellular signal transduction molecule, and is ubiquitously present in vertebrates. To date, there are three distinct isoforms of NOS: neural NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS). Among them, eNOS and nNOS, also called constitutive isoforms (cNOS), require calcium for activity, and are expressed constitutively in the physiological condition. The third isoforms, iNOS, whose activity is not dependent on calcium, are produced only in response to some stimulus, including cytokines and immune stimulating factors, etc.[1].     

A saponin-detoxifying enzyme mediates suppression of plant defences

Plant disease resistance can be conferred by constitutive features such as structural barriers or preformed antimicrobial secondary metabolites. Additional defence mechanisms are activated in response to pathogen attack and include localized cell death (the hypersensitive response). Pathogens use different strategies to counter constitutive and induced plant defences, including degradation of preformed antimicrobial compounds and the production of molecules that suppress induced plant defences. Here we present evidence for a two-component process in which a fungal pathogen subverts the preformed antimicrobial compounds of its host and uses them to interfere with induced defence responses. Antimicrobial saponins are first hydrolysed by a fungal saponin-detoxifying enzyme. The degradation product of this hydrolysis then suppresses induced defence responses by interfering with fundamental signal transduction processes leading to disease resistance.     

GDO Ⅰ酶阻断对芳烃降解途径的影响

产碱假单胞菌NCIB 9867株(P25X)能够通过龙胆酸途径降解芳香烃.研究显示P25X在龙胆酸途径可能产生一组同工酶-其中一种酶是保守型,另一种则为严格诱导型表达.龙胆酸降解途径主要的酶是龙胆酸加双氧酶(GDO),它促进芳香环的裂解,产生顺丁烯丙酮酸,并通过一系列的反应最终进入TCA循环.目前,仅有保守型的龙胆酸加双氧酶及其下游片段被克隆.P25X的衍生株SNZ28,它的龙胆酸加双氧酶的基因(GDO I)被链霉素/奇霉素抗性基因所打断.本研究运用二维蛋白电泳法分析降解菌株SNZ28的蛋白提取物,并用考马斯亮兰染色鉴别.经软件比对分析,由龙胆酸诱导与元龙胆酸诱导菌株的蛋白表达提取物存在明显的蛋白质表达差异,其中有15个蛋白质点被识别.这一结果为诱导型龙胆酸酶的进一步研究打下了基础.     

GDO I酶阻断对芳烃降解途径的影响

产碱假单胞菌NCIB9867株（P25X）能够通过龙胆酸途径降解芳香烃．研究显示P25X在龙胆酸途径可能产生一组同工酶-其中一种酶是保守型，另一种则为严格诱导型表达．龙胆酸降解途径主要的酶是龙胆酸加双氧酶（GDO），它促进芳香环的裂解，产生顺丁烯丙酮酸，并通过一系列的反应最终进入TCA循环．目前，仅有保守型的龙胆酸加双氧酶及其下游片段被克隆．P25X的衍生株SNZ28，它的龙胆酸加双氧酶的基因（GDOI）被链霉素／奇霉素抗性基因所打断．本研究运用二维蛋白电泳法分析降解菌株SNZ28的蛋白提取物，并用考马斯亮兰染色鉴别．经软件比对分析，由龙胆酸诱导与无龙胆酸诱导菌株的蛋白表达提取物存在明显的蛋白质表达差异，其中有15个蛋白质点被识别．这一结果为诱导型龙胆酸酶的进一步研究打下了基础．     

Chloroquine diverts ACTH from a regulated to a constitutive secretory pathway in AtT-20 cells

AtT-20 cells, a mouse pituitary line, externalize a viral membrane glycoprotein and the precursor of ACTH constitutively, that is, rapidly without storage or regulation. They also have a regulated pathway in which they cleave the precursor to mature hormones, ACTH and beta-endorphin, store them in secretory granules and discharge them only in the presence of a secretagogue. An analogy exists for newly synthesized lysosomal enzymes which are either delivered to the lysosome or secreted from the cell. Targeting to the lysosomes may require a low pH step, since chloroquine causes the enzymes to be secreted from the cell. Here we show that chloroquine (200 microM) also appears to block the storage of newly synthesized ACTH in secretory granules and instead diverts it to the outside of the cell via the constitutive pathway. Chloroquine has no effect on the constitutive pathway and does not block the exocytosis of pre-packaged ACTH. Thus like lysosomal enzymes, peptide hormones are not sent to their correct destinations in the presence of chloroquine, but are diverted instead to a constitutive pathway that is chloroquine-insensitive.     

Induction of yeast mating pheromone a-factor by alpha cells

Saccharomyces cerevisiae cells of a and alpha mating types constitutively secrete cell-specific peptide mating pheromones. a-Factor is secreted by a cells and acts on alpha cells, while alpha-factor is secreted by alpha cells and acts on a cells. Confirming preliminary studies, we demonstrate here that cultures of a cells contain higher than constitutive levels of a-factor activity when grown with alpha cells or alpha-factor. This induction of a-factor may result from increased synthesis or increased secretion of a-factor, as opposed to modification or stabilization of preexisting a-factor, as part of the a cell response to alpha-factor, as an a ste2 mutant (which cannot respond to alpha-factor) is not induced by alpha-factor. In mixed cultures inoculated with equal numbers of a cells and alpha cells, a cells predominate by stationary phase. Thus, a series of sequential interactions between a and alpha cells may be involved in establishing optimal hormone concentrations and cell ratios for conjugation.     

豫北地区蜜粉源植物的考察研究

本调查研究河南北部,黄河北岸地区内蜜粉源植物,初步筛选出蜜粉源植物376种及变种,隶属于81科233属。中着重分析了本地区主要蜜源、主要粉源、重要辅助蜜粉源植物,为科研和持续开发利用植物资源提供了科学依据。     

混凝土随机损伤力学的初步研究

阐述了混凝土随机损伤力学研究的基本学术观点 ,系统介绍了确定性的混凝土弹塑性损伤本构关系、混凝土随机损伤本构关系、结构非线性反应分析的密度演化理论等内容 ,由此构成了混凝土随机损伤力学研究的基本框架     

厚荚相思石山地区造林试验初报

选用厚荚相思(Acacia crassicarpa)、台湾相思(Acacia confusa)和小叶榕(Ficus microcarpa)3个树种在崇左市石山地区进行造林试验,3年后调查分析造林绿化效果.结果表明,树高、地径和冠幅的净生长量,厚荚相思分别达到4.4m、7.1cm和2.8m,分别为台湾相思的2.0倍、2.4倍和1.6倍,为小叶榕的6.3倍、2.6倍和3.1倍.厚荚相思的石山造林绿化效果极显著地优于台湾相思和小叶榕.而且厚荚相思林下植被总盖度、枯落物等生态环境比后两种优良.厚荚相思是崇左市石山地区人工造林绿化的优良先锋树种.     

一种带有表型标记基因的诱导型抗旱植物表达载体的构建

为了克服组成型表达转录因子基因影响转基因植物性状的缺点,并构建一种具有级联放大作用并带有表型标记的诱导型植物双价表达载体。研究采用PCR方法从拟南芥克隆获得冷诱导转录因子CBF3基因,蜡质合成相关WIN1基因,干旱诱导RD29A基因启动子和冷诱导的LEA14基因启动子,并用CBF3转录因子所调控的下游RD29A基因启动子和LEA14基因启动子分别驱动CBF3基因和W1N1基因表达,构建了双价植物表达载体RD29AP-CBF3／LEA14P—WIN1／pcAMBIA2201。我们预测在转基因植物中,该表达系统可在干旱等逆境信号存在条件下,通过级联放大的方式诱导表达,在增加植物抗逆性的同时,增加叶片表层蜡质的积累,从而易于表型识别。本研究为利用花粉管通道法转化棉花,提高抗逆转基因棉花田间筛选的效率奠定了基础。     

徂徕山森林植物资源的调查研究

作者对徂徕山植物资源进行了野外调查、采集,制作标本3000余份,经研究整理结果表明：徂徕山是我省植物资源最丰富的地区之一,现人维管植物789种,隶属于128科,449属,其中木本植物224种,占总数的28.4%,草本植物565种,占总数的71.6%;植物区系分析结果显示,徂徕山区系植物属于华北植物区系与华北植物区系的交汇区,但与华北植物区系更为密切;徂徕山果树、中草药、野生观赏植物、野生蔬菜及蜜源植物资源极为丰富,可进一步扩大种植面积,进行合理的,保护的开发利用,以便更地发挥这些植物资源的生态、经济及社会效益,为林场的持续、健康发展奠定了经济基础。     

Herbivory-induced volatiles elicit defence genes in lima bean leaves

In response to herbivore damage, several plant species emit volatiles that attract natural predators of the attacking herbivores. Using spider mites (Tetranychus urticae) and predatory mites (Phytoseiulus persimilis), it has been shown that not only the attacked plant but also neighbouring plants are affected, becoming more attractive to predatory mites and less susceptible to spider mites. The mechanism involved in such interactions, however, remains elusive. Here we show that uninfested lima bean leaves activate five separate defence genes when exposed to volatiles from conspecific leaves infested with T. urticae, but not when exposed to volatiles from artificially wounded leaves. The expression pattern of these genes is similar to that produced by exposure to jasmonic acid. At least three terpenoids in the volatiles are responsible for this gene activation; they are released in response to herbivory but not artificial wounding. Expression of these genes requires calcium influx and protein phosphorylation/dephosphorylation.     

荆条泌蜜与蚱蝉始鸣的对应关系

荆条是华北名的山区蜜源植物。蚱蝉是习见的森林昆虫。通过对荆条花期泌蜜、蜂群活动、产蜜量、气候、蚱蝉始鸣等项目的观测。结果发现,荆条开始泌蜜与蚱蝉开始鸣叫出现日期一致,利用蚱蝉始鸣预报荆条泌蜜,方法简便、准确,对荆条蜜源的开发利用具有重要指导意义。     

硅对叶螨危害后棉花防御酶活性的调控作用及其与抗虫性的关系

以棉花品种新陆早33号感染土耳其斯坦叶螨（Tetranychus turkestani（Ugarov ＆ Nikolski））作个案研究,阐明硅提高棉花抗螨性的生理机理。网室条件下采用微区试验设计,硅肥采用喷施和基施处理,研究不同时间棉花的虫害指数、干物质积累量和硅含量,以及与植物抗性密切相关的过氧化物酶（POD）、多酚氧化酶（PP0）和苯丙氨酸解氨酶（PAL）活性变化。结果显示：不同施硅处理缓解了棉花叶片受叶螨危害的症状,在接种叶螨第6天硅处理降低了叶片受害指数;施硅处理提高了PPO和PAL的活性,而降低了参与清除植物体内活性氧功能的POD活性。硅能够调控棉花与抗虫有关的酚类物质代谢过程,参与植物防卫反应而增强棉花对土耳其斯坦叶螨的抗性。     

三色堇(Viola tricolor L.var.hortensis DC.)花蜜腺的亚显微结构

本文用透射和扫描电镜对三色堇花不同发育时期蜜腺进行了研究,了解到该植物花蜜中糖份主要来源于蜜腺分泌组织自身的光合产物;内质网参与了前蜜的加工和运输;质膜的啜入和反啜入作用是分泌组织细胞间前蜜传递的主要方式;蜜最后通过表皮细胞质膜的分子渗透作用而排放出体外;表皮细胞向外的指状突起是蜜汁分泌的主要部位.     

太子河河岸带植物群落特征及其物种多样性研究

 以野外样方调查数据为基础,调查了太子河干流河岸带植物物种的组成、种类和外貌,应用重要值计算了太子河河岸带植物丰富度指数、多样性指数、均匀度指数、优势度指数,分析了其物种的多样性差异,从而为太子河河岸带的生态修复提供理论和技术依据.结果表明:太子河干流河岸带23个植物样方中,共有36科124属201种,群落物种组成较为丰富,但仅限于草本植物;物种组成以菊科、禾本科、蓼科、莎草科、蔷薇科植物为主,植物种类以灯心草、菵草、狭叶水蓼、野稗、看麦娘、水蓼、酸模、丝叶蒿、薹草、中华结缕草、散穗早熟禾、东方藨草等为主;太子河干流河岸带植物物种结构简单,物种组成较少;植物物种多样性水平较低,从多样性指数的数量特征来看,Patrick丰富度指数的变化范围为3.00—28.00,Pielou均匀度指数的变化范围为0.66—0.89,Simpson多样性指数的变化范围为0.54—0.91,Shannon-Wiener多样性指数的变化范围为0.86—2.73,Simpson优势度指数的变化范围为0.09—0.46.太子河干流河岸带受到的人为活动干扰,如农业生产、挖沙等,降低了物种多样性水平.     

闽江源自然保护区植物区系成分及其特征

闽江源自然保护区具有维管束植物1078种（包括亚、变种），隶属于168科，635属。该区具有种类较为丰富，起源古老，孑遗植物较多，地理联系广泛等特点。在植物区系地理成分中，热带性质的成分占主导地位，主要为泛热带分布、热带亚洲分布、旧世界热带分布等。北温带分布及东亚分布等温带区成分亦较为丰富。还论述了闽江源与邻近地区植物区系的关系。     

Parasitoid secretions provoke ant warfare

Insect social parasites are extreme specialists that typically use mimicry or stealth to enter ant colonies to exploit the rich, but fiercely protected, resources within their nests. Here we show how a parasitic wasp (parasitoid) contrives to reach its host, itself an endangered species of social parasite that lives inside the brood chambers of ant nests, by releasing semiochemicals to induce in-fighting between worker ants, locking the colony in combat and leaving it underprotected. Four of these chemicals are new to biology and have the potential to control pest species by inducing different agonistic behaviours in ants.