小麦与叶锈菌互作过程中细胞程序性死亡的细胞学观察

小麦(Triticum aesetivum)品种洛夫林10和叶锈菌(Puccinia recondita f.sp tritici)小种162、165分别组成不亲和组合与亲和组合。透射电镜观察表明,在小麦与叶锈菌的不亲和组合中,接种后12h,侵染点周围叶肉细胞核变形;接种后24h,核内染色质开始凝聚,并趋于细胞核边缘,同时叶绿体膨胀;接种后48h,核内染色质凝聚加剧,叶绿体开始解体;最终在接种后72h,细胞核、叶绿体完全解体,线粒体开始退化。此外,内质网和液泡共同行使溶酶体功能,吞噬各种细胞器残体及原生质降解组分。以上结果表明:在小麦与叶锈菌不亲和组合的互作过程中,寄主细胞呈现细胞程序性死亡的典型特征。而在亲和组合中,叶肉细胞间隙中可见有大量菌丝蔓延,菌丝与寄主细胞壁接触后分化产生吸器母细胞。菌丝的存在对寄主细胞的超微结构产生一定影响。从接种后24h开始,与菌接触的细胞出现质膜下陷,叶绿体稍显膨胀;在接种后48h、72h,大部分叶绿体膨胀,而其它细胞器无明显变化。     

小麦与叶锈菌互作过程中细胞程序性死亡的生化证据（简报）

细胞程序性死亡(Programmed Cell Death,PCD)是一种受基因调控的、主动的、连续的程序化反应。一般发生程序性死亡的细胞具有较为典型的形态及生化特征：细胞收缩、核染色质浓缩、趋边化;DNA在一定位点被核酸内切酶降解成以180bp为基数的片段,在琼脂糖凝胶电泳中呈现“梯”状条带     

小麦与叶锈菌互作过程中细胞程序性死亡的生化证据(简报)

细胞程序性死亡(Programmed Cell Death,PCD)是一种受基冈调控的、主动的、连续的程序化反应一般发生程序性死亡的细胞具有较为典型的形态及生化特征:细胞收缩、核染色质浓缩、趋边化;DNA 在一定位点被核酸内切酶降解成以180bp 为     

小麦与叶锈菌互作过程中的H2O2与HR

以小麦品种洛夫林10为材料,与叶锈菌生理小种165和260分别组成亲和组合和不亲和组合.以荧光探针DCFHDA标记H2O2的变化,并借助荧光显微镜原位地直观显现了叶锈菌侵染过程中小麦叶片中H2O2的动态变化.结果表明,亲和组合中H2O2爆发表现为单峰曲线,峰值出现在接种后12h;不亲和组合中表现为双峰曲线.峰值分别出现在接种后12h和20h,第二个峰比第一个高约一倍,且不亲和组合中H2O2爆发的强度远远大于亲和组合.另外,通过药理学试验,采用活体注射法对小麦叶片在接种叶锈菌小种260之前分别预注射抗氧化药物AsA、DTT以及NADPH氧化酶抑制剂DPI和咪唑.观察这些药物对不亲和组合中寄主叶片产生的H2O2和HR的影响.结果表明,抗氧化药物和NADPH氧化酶抑制剂均使寄主叶片中H2O2爆发的强度降低,表现在两个H2O2峰均受到抑制,其中第二个峰受抑制的程度更明显,同时寄主细胞发生HR的面积减小.     

小麦与条锈菌互作中过氧化物酶的细胞化学研究

采用细胞化学方法对小麦与条锈菌互作过程中过氧化物酶的分布及其活性大小进行了研究,结果表明：过氧化物酶主要分布于细胞壁和细胞间隙中;在未行接种的小麦叶片中,抗病品种和感病品种的过氧化物酶活性均比较低;条锈菌侵染后,诱导抗、感病品种叶片中的过氧化物酶活性升高,且抗病品种升高的幅度明显大于感病品种;感病品种中过氧化物酶活性在侵染位点附近细胞壁上表现升高,而抗病品种中该酶的活性在侵染点细胞以及远离侵染点的叶肉细胞的细胞壁和细胞间隙中均显著升高。高活性的过氧化物酶是小麦抗条锈性的生化标记和重要机制之一。     

感染叶锈菌的小麦细胞间隙中激发子的定性及初步分离

感染叶锈菌后小麦叶片细胞间隙液（ＩＷＦ）中有激发子存在,它（们）能诱导寄主ＰＡＬ、ＰＯ活性的增强及细胞过敏性坏死的产生。这种有诱导活性的物质分别用ＮａＩＯ４和蛋白酶处理证明含有糖基和蛋白质成分,可能是糖蛋白。ＩＷＦ经凝胶过滤分离后,各部分诱导不同的防卫反应的活性强度不等。因此ＩＷＦ中可能含有几种不同成分的激发子,或是同种成分而聚合度不同的激发子。     

渗透胁迫诱导的小麦叶片细胞程序性死亡

用20％PEG6000（－0.63MPa）溶液对小麦（Triticum aestivum)根系进行渗透胁迫,在DNA琼脂糖凝胶电泳图谱上观察到明显的梯状DNA条带,表明PEG处理诱发了DNA核小体间的断裂,从而表现出典型的细胞程序性死亡的发生特征;末端脱氧核糖核酸转移酶介导的3′-OH末端标记法（terminal deoxynucleotidyl transferase(TdT)-mediated dUTP nick end labeling,TUNEL)检测出现阳性结果。这些结果表明在PEG诱导小麦叶片死亡过程中,有一个阶段存在明显的细胞程序性死亡过程。结果同时表明,在小麦叶片处于程序性死亡时期,蛋白质含量、叶绿素含量的下降和电解质泄漏率的增加都比处于坏死时期的慢。     

小麦叶锈菌侵染过程的显微和超微结构

采用光学显微技术和电子显微技术对小麦叶锈菌的侵染过程进行了研究。发现叶锈菌从气孔侵入后在气孔腔内形成气孔下泡囊,然后分化出圆形的膨大体,由膨大体产生1—2初生菌丝,初生菌丝在寄主细胞间隙延伸扩展,与叶肉细胞壁接触后分化形成吸器母细胞,吸器母细胞进入寄主细胞后形成吸器。初生菌丝在吸器母细胞处产生分枝,形成次生菌丝在叶肉细胞间蔓延。在病原菌侵染早期(接种后8—24h),寄主细胞的超微结构变化并不明显。侵染中、后期(接种48—72h),被侵染叶肉细胞发生严重质壁分离,叶绿体膨胀变形,基粒片层排列疏松。线粒体嵴突退化。     

细胞程序性死亡通路的研究进展

细胞程序性死亡(programmed cell death,PCD)一直被看做是细胞凋亡(apoptosis).随着细胞生物学研究的深入,新的细胞死亡途径逐渐被揭示出来,如胀亡、自噬、副凋亡等.这些通路有些是caspase依赖的,有些不依赖于caspase途径.在细胞程序性死亡过程中,各种通路不是单独起作用的,而是相互交联的,有彼此重叠的机制出现.目前,Clarke形态学分类法是得到大多数学者认可的细胞程序性死亡的分类方式.按照该分类法,可将PCD分为3大类,即:Ⅰ型细胞程序性死亡、Ⅱ型细胞程序性死亡和Ⅲ型细胞程序性死亡.     

多胺参与细胞程序性死亡调控的研究进展

多胺被认为是影响细胞存活的一个关键分子。有证据显示,多胺可直接或间接参与细胞程序性死亡的调控。多胺与细胞程序性死亡直接相关,是指其参与特定的生物学过程及与导致细胞程序性死亡的分子/结构发生相互作用;间接相关,是指多胺通过调控细胞程序性死亡的代谢衍生物,如异化和互变产物来调控这一过程。此外,多胺代谢过程中的细胞毒性产物也参与到细胞程序性死亡的级联反应中。因此,对动植物中依赖于多胺的细胞程序性死亡的最新研究进展进行综述,可为进一步研究提供一些参考。     

Erythrocyte programmed cell death

Eryptosis, the suicidal death of erythrocytes, is characterised by cell shrinkage, membrane blebbing and cell membrane phospholipid scrambling with phosphatidylserine exposure at the cell surface. Phosphatidylserine-exposing erythrocytes are recognised by macrophages, which engulf and degrade the affected cells. Reported triggers of eryptosis include osmotic shock, oxidative stress, energy depletion, ceramide, prostaglandin E(2), platelet activating factor, hemolysin, listeriolysin, paclitaxel, chlorpromazine, cyclosporine, methylglyoxal, amyloid peptides, anandamide, Bay-5884, curcumin, valinomycin, aluminium, mercury, lead and copper. Diseases associated with accelerated eryptosis include sepsis, malaria, sickle-cell anemia, beta-thalassemia, glucose-6-phosphate dehydrogenase (G6PD)-deficiency, phosphate depletion, iron deficiency, hemolytic uremic syndrome and Wilsons disease. Eryptosis may be inhibited by erythropoietin, adenosine, catecholamines, nitric oxide (NO) and activation of G-kinase. Most triggers of eryptosis except oxidative stress are effective without activation of caspases. Their signalling involves formation of prostaglandin E(2) with subsequent activation of cation channels and Ca2+ entry and/or release of platelet activating factor (PAF) with subsequent activation of sphingomyelinase and formation of ceramide. Ca2+ and ceramide stimulate scrambling of the cell membrane. Ca2+ further activates Ca2+-sensitive K+ channels leading to cellular KCl loss and cell shrinkage and stimulates the protease calpain resulting in degradation of the cytoskeleton. Eryptosis allows defective erythrocytes to escape hemolysis. On the other hand, excessive eryptosis favours the development of anemia. Thus, a delicate balance between proeryptotic and antieryptotic mechanisms is required to maintain an adequate number of circulating erythrocytes and yet avoid noneryptotic death of injured erythrocytes.     

Microgravity-induced programmed cell death in astrocytes

Cultured astrocytes were submitted to simulated microgravity using a Fokker clinostat under continuous rotation (60 rpm) for 15', 30', 1h, 20h and 32h. Samples processing included (i) nuclear stainings using Propidium Iodide and 4,6-diamidino-2-phenilindole, dihydro chloride, (ii) immunohistochemical identification of Caspase-7, (iii) identification of DNA fragmentation using the terminal dUTP nick end labelling and (iv) Scanning Electron Microscope analysis. After 30' at simulated microgravity the glial cells showed morphological evidence of apoptosis: cell shrinkage, chromatin condensation, nuclear blebs and fragmentation. The enzyme caspase-7 was present and DNA fragmentation was evident. After 32h the density of the cell population was much lower than that observed in controls.     

Developmentally programmed cell death in Drosophila

During the development of metazoans, programmed cell death (PCD) is essential for tissue patterning, removal of unwanted cells and maintaining homeostasis. In the past 20 years Drosophila melanogaster has been one of the systems of choice for studies involving developmental cell death, providing an ideal genetically tractable model of intermediary complexity between Caenorhabditis elegans and mammals. The lessons learned from studies using Drosophila indicate both the conserved nature of the many cell death pathways as well as novel and unexpected mechanisms. In this article we review the understanding of PCD during Drosophila development, highlighting the key mechanisms that are evolutionarily conserved as well as apparently unusual pathways, which indicate divergence, but provide evidence of complexity acquired during organismic evolution. This article is part of a Special Section entitled: Cell Death Pathways. Guest Editors: Frank Madeo and Slaven Stekovic.     

Developmental programmed cell death in plants

Mechanisms of plant developmental programmed cell death (PCD) have been intensively studied in recent years. Most plant developmental PCD is triggered by plant hormones, and the 'death signal' may be transduced by hormonal signaling pathways. Although there are some fundamental differences in the regulation of developmental PCD in various eukaryotes of different kingdoms, hormonal control and death signal transduction via pleiotropic signaling pathways constitute a common framework. However, plants possess a unique process of PCD execution that depends on vacuolar lytic function. Comparisons of the developmental PCD mechanisms of plants and other organisms are providing important insights into the detailed characteristics of developmental PCD in plants.     

Autophagy functions in programmed cell death

Autophagic cell death is a prominent morphological form of cell death that occurs in diverse animals. Autophagosomes are abundant during autophagic cell death, yet the functional role of autophagy in cell death has been enigmatic. We find that autophagy and the Atg genes are required for autophagic cell death of Drosophila salivary glands. Although caspases are present in dying salivary glands, autophagy is required for complete cell degradation. Further, induction of high levels of autophagy results in caspase-independent autophagic cell death. Our results provide the first in vivo evidence that autophagy and the Atg genes are required for autophagic cell death and confirm that autophagic cell death is a physiological death program that occurs during development.

Addendum to: Berry DL, Baehrecke EH. Growth arrest and autophagy are required for programmed salivary gland cell degradation in Drosophila. Cell 2007; 131:1137-48.