Studies on the Programmed Cell Death in Rice During Starchy Endosperm Development

Morphological variations of the nucleus in starchy endosperm cell were observed by theelectron-transmisson microscope during endosperm development in rice. Along with thedevelopment of the starchy endosperm, the nuclei of the cells showed chromatin condensation,the typical feature of programmed cell death (PCD). The nuclei also showed nucleusdeformation, disruption of nuclear envelope, nucleoplasm leaking into the cytoplasm andnucleus disintegration resulting in nuclear residue formation. From the nucleus deformationto the nucleus disintegration, the morphological changes of the nucleus were orderlyprogressive. This indicated that the cell death of starchy endosperm in rice wasprogrammed cell death. Evans Blue staining observation showed that the cell death wasinitially detected in the central part of starchy endosperm in rice, then expandedoutward. The activities of superoxide dismutase (SOD) and catalase (CAT) in rice starchyendosperm both descended continuously as development progressed. The analysis of DNA ofrice starchy endosperm did not show the presence of DNA laddering. The above resultsshowed that the cell death of starchy endosperm in rice was a special form of PCD.

Recent advances in plant immunity with cell death:A review

Cell death is an important physiological phenomenon in life.It can be programmed or unprogrammed.Unprogrammed cell death is usually induced by abiotic or biotic stress.Recent studies have shown that many proteins regulate both cell death and immunity in plants.Here,we provide a review on the advances in plant immunity with cell death,especially the molecular regulation and underlying mechanisms of those proteins involved in both cell death and plant immunity.In addition,we discuss potential approaches toward improving plant immunity without compromising plant growth.

Programmed Cell Death in Relation to Petal Senescence in Ornamental Plants

Abstract: Cell death is a common event in all types of plant organisms. Understanding the phenomenon of programmed cell death (PCD) is an important area of research for plant scientists because of its role in senescence and the post-harvest quality of ornamentals, fruits, and vegetables. In the present paper, PCD in relation to petal senescence in ornamental plants is reviewed. Morphological, anatomical, physiological, and biochemical changes that are related to PCD in petals, such as water content, sink-source relationships, hormones, genes, and signal transduction pathways, are discussed. Several approaches to improving the quality of post-harvest ornamentals are reviewed and some prospects for future research are given.

Floret-specific differences in gene expression and support for the hypothesis that tapetal degeneration of Zea mays L. occurs via programmed cell death

The maize （Zea mays） spikelet consists of two florets, each of which contains three developmentally synchronized anthers. Morphologically, the anthers in the upper and lower florets proceed through apparently similar developmental programs. To test for global differences in gene expression and to identify genes that are coordinately regulated during maize anther development, RNA samples isolated from upper and lower floret anthers at six developmental stages were hybridized to cDNA microarrays. Approximately 9% of the tested genes exhibited statistically significant differences in expression between anthers in the upper and lower florets. This finding indicates that several basic biological processes are differentially regulated between upper and lower floret anthers, including metabolism, protein synthesis and signal transduction. Genes that are coordinately regulated across anther development were identified via cluster analysis. Analysis of these results identified stage-specific, early in development, late in development and bi-phasic expression profiles. Quantitative RT-PCR analysis revealed that four genes whose homologs in other plant species are involved in programmed cell death are up-regulated just prior to the time the tapetum begins to visibly degenerate （i.e., the mid-microspore stage）. This finding supports the hypothesis that developmentally normal tapetal degeneration occurs via programmed cell death.

Tomato Plants Overexpressing a Celery Mannitol Dehydrogenase (MTD) Have Decreased Susceptibility to <i>Botrytis cinerea</i>

The oxidative burst is a critical early event in plant-pathogen interactions that leads to a localized, programmed cell death (PCD) called the hypersensitive response (HR). The HR and associated PCD retard infection by biotrophic pathogens, but can, in fact, enhance infection by necrotrophic pathogens like Botrytis cinerea. In addition to signaling the induction of the HR, reactive oxygen species (ROS) produced during the oxidative burst are?antimicrobial. We hypothesize that pathogens such as B. cinerea survive the antimicrobial effects of ROS, at least partially by secreting the antioxidant mannitol during infection. This is supported by the previous observation that overexpression of the catabolic enzyme mannitol dehydrogenase (MTD) can decrease a plants susceptibility to mannitol-secreting pathogens like B. cinerea. To extend the above hypothesis, and test the general utility of this approach in an important horticultural crop, we overexpressed celery MTD in tomato (Solanum lycopersicum cv. “Moneymaker”). In these studies, we observed a significant increase (up to 90%) in resistance to B. cinerea in transgenic tomatoes expressing high amounts of MTD.

The Ca^(2+)-dependent DNases are Involved in Secondary Xylem Development in Eucommia ulmoides

Secondary xylem development has long been recognized as a typical case of programmed cell death （PCD） in plants. During PCD, the degradation of genomic DNA is catalyzed by endonucleases. However, to date, no endonuclease has been shown to participate in secondary xylem development. Two novel Ca^2＋-dependent DNase genes, EuCaN1 and EuCaN2, were identified from the differentiating secondary xylem of the tree Eucommia ulmoides Oliv., their functions were studied by DNase activity assay, in situ hybridization, protein immunolocalization and virus-induced gene silencing experiments. Full-length cDNAs of EuCaN1 and EuCaN2 contained an open reading frame of 987 bp, encoding two proteins of 328 amino acids with SNase-like functional domains. The genomic DNA sequence for EuCaN1 had no introns, while EuCaN2 had 8 introns. EuCaN1 and EuCaN2 digested ssDNA and dsDNA with Ca^2＋-dependence at neutral pH. Their expression was confined to differentiating secondary xylem cells and the proteins were localized in the nucleus. Their activity dynamics was closely correlated with secondary xylem development. Secondary xylem cell differentiation is influenced by RNAi of endonuclease genes. The results provide evidence that the Ca^2＋-dependent DNases are involved in secondary xylem development.

Programmed cell death in developing human fetal CNS

The spatial and temporal distributions of programmed cell death (PCD) in developing central nervous system (CNS) of human fetuses ranging from 12 to 39 weeks of gestation were investigated using techniques of flow cytometry and terminal transferase-mediated nick end labeling (TUNEL). The results showed that PCD did occur in every representative brain region of all fetuses examined in different stages. It was found that there were two peaks of PCD appearing at the 12th and 39th weeks respectively, which suggested that the first peak of apoptosis may be involved in the selective elimination of neurons overproduced during the early development and the second may play an important role in establishing the correct neuronal circuitry.

淹水胁迫下小麦根通气组织形成的PCD特征及活性氧作用初探

为了解淹水条件下小麦根通气组织形成的细胞学特点和活性氧（Reactive oxygen species，ROS）在通气组织形成中的作用，以高度耐湿的华麦8号幼苗为材料进行淹水处理，在显微水平上系统地观察了通气组织的形成过程，在分子水平上检测了细胞核DNA的断裂情况，并对ROS的动态变化进行了荧光观察。结果表明：（1）通气组织最先起源于根皮层中部，然后逐渐扩展，到淹水8d时基本形成，淹水60d时更为发达；（2）淹水1.5～48h根皮层出现大量细胞核DNA断裂，且细胞核DNA降解为180～200bp的片段，证明小麦根通气组织的形成过程是根皮层细胞发生细胞程序化死亡（Programmed cell death，PCD）的过程，而且淹水1．5～48h是根皮层细胞死亡高峰期；（3）ROS在细胞核DNA发生断裂前开始积累，在通气组织形成中呈现动态变化。上述结果表明，淹水胁迫下小麦根通气组织形成是一个皮层细胞PCD的过程，并且ROS可能参与介导了PCD的进程。另外，淹水胁迫在前期抑制了次生根的产生，随后又促进了次生根的产生。

植物细胞程序性死亡(PCD)的研究进展

细胞死亡是动、植物生长发育过程中常见的一种生命现象 ,而细胞程序性死亡 (PCD)是细胞遵循自身生命活动程序 ,并受多种因子调控的一种积极的死亡方式。近年来随着动物中PCD研究的深入 ,植物PCD亦得到相应的研究。植物细胞程序性死亡研究不仅可揭示植物衰老、死亡的内部变化规律 ,而且可为其生长发育的调控提供依据和技术。该文试对有关PCD的特点、研究意义及近年来的研究概况与方法进行简述与评价。

水稻PCD相关基因的定位研究

植物中的细胞程序化死亡 (PCD)在植物的发育、抗病及植物与环境互作等过程中发挥着极其重要的作用。本研究以我国学者发现的特殊的水稻细胞死亡控制突变体 30 37(M)为材料 ,采用微卫星DNA标记 (共计 15 9个微卫星引物 )技术对突变体性状进行基因定位研究。结果表明 ,该突变体PCD基因位于水稻的第 8染色体和第 12染色体 ,为下一步精细定位突变体基因及基因克隆奠定了基础。

植物细胞程序性死亡(PCD)分析测试方法的发展

对植物细胞程序性死亡(PCD)的分析测试方法进行了较全面的综述,包括细胞形态学观察法、反映细胞膜完整性的方法和反映DNA片段化的方法。并对植物细胞程序性死亡分析测试方法的发展趋势作了讨论。

PCD检测方法的建立及其在研究外来激素对大鼠睾丸细胞PCD影响的应用

本研究１．建立了检测ＰＣＤ的石蜡切片原位末端标记（ＩＳＥＬ）法，在石蜡切片原位用免疫组化法标记核ＤＮＡ，使ＰＣＤ细胞呈黄色或棕黄色的阳性着染，在普通光学显微镜下即可鉴别。本实验用加热和蛋白酶Ｋ同时处理背景，使非特异性染色几乎不存在；使用过氧化物酶—ＤＡＢ显色系统缩短时间２小时，提高了筛检速度。２．应用ＩＳＥＬ法研究外来激素对大鼠睾丸细胞的影响，结果发现ＧｎＲＨ－Ａ是一个促凋原，具有明显的生殖毒性。

替码板栗芽体PCD过程中Ca^(2+)的时空变化

【目的】探讨Ca^(2+)在替码板栗品种X12芽体细胞程序性死亡(PCD)过程中的时空变化及其与芽体PCD的关系。【方法】利用焦锑酸盐沉淀的电镜细胞化学方法,研究替码板栗X12芽体PCD过程中(S1～S5时期) Ca^(2+)的时空变化。【结果】S1时期,细胞结构正常,Ca^(2+)主要分布在细胞壁和细胞间隙处,细胞质和细胞核内有少量Ca^(2+),液泡内Ca^(2+)含量极少;S2时期,部分细胞器轻微降解,细胞间隙中Ca^(2+)减少,细胞质、液泡膜和细胞核膜附近Ca^(2+)开始增多;S3时期,细胞进一步解体,细胞壁、液泡、细胞核降解严重,细胞间隙和细胞壁上Ca^(2+)颗粒极少,细胞质、细胞核、破裂的液泡内及液泡周围Ca^(2+)明显增多;S4时期,细胞降解严重,Ca^(2+)在细胞内呈无规则分布,质膜和细胞壁上较少,集中于破碎的液泡膜和液泡碎片处;S5时期,细胞器均降解破碎,Ca^(2+)随降解的细胞器碎片成块状聚集。【结论】替码板栗芽体PCD过程中Ca^(2+)呈动态变化,Ca^(2+)可能参与了PCD过程;细胞质、液泡和细胞核的Ca^(2+)内流可能是引起替码板栗芽体PCD的部分重要原因。

黑松感染松材线虫后细胞结构变化及PCD

电镜观察到两年生黑松感染松材线虫后,茎中形成层细胞以及其他的薄壁细胞出现细胞程序性死亡PCD特征:细胞核变形、核染色质浓缩并边缘化;细胞质和液泡中出现大量环状片层及多泡体;细胞壁出现膨胀扭曲;线粒体峭数目减少直至双层膜破毁.在整个变化过程中,细胞质膜始终是完整的,内质网在细胞器降解过程中扮演了重要角色,细胞核在线粒体等细胞器降解之后才崩塌消失.这表明,黑松感染松材线虫后的系统反应过程中有PCD发生,其变化类似于动物细胞中的细胞死亡.黑松感染松材线虫后的系统反应过程中,PCD是持续发生的,最终引起植株全面崩溃,这可能是感病黑松死亡的内因.在感病10d后,形成层区才开始出现空洞化现象.因此,形成层的空洞化并非是植株死亡的主因,而是其感病症状.

大白菜核不育花药绒毡层的异常细胞程序性死亡(PCD)导致小孢子败育研究

【目的】观察大白菜花药发育中绒毡层与小孢子的细胞形态,为研究大白菜核不育花药败育机理提供依据。【方法】以大白菜核不育近等基因系10L03为试材,采用石蜡切片法和TUNEL法对可育和不育花药的细胞结构进行观察。【结果】大白菜核不育花药败育起始于减数分裂期绒毡层结构异常,小孢子在四分体时期开始败育;不育发生后,伴随着绒毡层细胞异常膨大,严重空泡化,提前降解,小孢子变形干瘪而死亡;不育与绒毡层提前发生细胞程序性死亡(programmed cell death,PCD)有关,绒毡层PCD过程失控,导致绒毡层爆发性提前降解,影响绒毡层对小孢子进一步发育的营养供应。【结论】不育四分体不能及时释放单核小孢子而影响小孢子的进一步发育,是导致小孢子败育的直接原因。

Dihydrosphingosine-lnduced Programmed Cell Death in Tobacco BY-2 Cells Is Independent of H2O2 Production

Sphinganine or dihydrosphingosine （d18：0, DHS）, one of the most abundant free sphingoid Long Chain Base （LCB） in plants, has been recently shown to induce both cytosolic and nuclear calcium transient increases and a correlated Programmed Cell Death （PCD） in tobacco BY-2 cells. In this study, in order to get deeper insight into the LCB signaling pathway leading to cell death, the putative role of Reactive Oxygen Species （ROS） has been investigated. We show that DHS triggers a rapid dose-dependent production of H2O2 that is blocked by diphenyleniodonium （DPI）, indicating the involvement of NADPH oxidase（s） in the process. In addition, while DPI does not block DHS-induced calcium increases, the ROS production is inhibited by the broad spectrum calcium channel blocker lanthanum （La^3＋）. Therefore, ROS production occurs downstream of DHS-induced Ca^2＋ transients. Interestingly, DHS activates expression of defense-related genes that is inhibited by both La^3＋ and DPI. Since DPI does not prevent DHS-induced cell death, these results strongly indicate that DHS-induced H2O2 production is not implicated in PCD mechanisms but rather would be associated to basal cell defense mechanisms.

向日葵柄锈菌效应子P2的定位及功能研究

由向日葵柄锈菌(Puccinia helianthi Schw.)引起的向日葵锈病严重威胁着向日葵的安全生产。效应子是一类病原菌侵染过程中分泌的蛋白,促进病原菌侵染或触发寄主免疫。为明确向日葵锈菌效应子P2在锈菌侵染过程中发挥的作用,对该基因序列进行了生物信息学分析;以向日葵锈菌夏孢子cDNA为模板,克隆了P2基因的编码序列,利用qRT-PCR技术分析了该基因在侵染过程中的表达特性;采用农杆菌瞬时表达系统在烟草上验证了P2的毒性功能,并在烟草上瞬时表达对其进行了亚细胞定位。研究结果表明,P2编码58个氨基酸,N端含24氨基酸的信号肽,无核定位信号及跨膜结构域,并在向日葵锈菌侵染早期上调表达。在本氏烟中瞬时表达P2可以抑制BAX诱导的细胞坏死,亚细胞定位结果表明P2定位在细胞膜及细胞核。

植物类病变形成机制与信号传导途径

植物类病变是指植物在无显著非生物胁迫、物理机械损伤或者外部致病因素的作用下,其叶片、叶鞘或整株上自发地出现坏死斑点的现象。这种局部细胞死亡的现象类似于某些致病菌感染的结果,其症状与植物超敏反应(Hypersensitive response, HR)的表征极为相似,是一种程序性细胞死亡(Programmed cell death, PCD)。许多类病变突变体组成性表达病程相关基因,并增强对某种或多种病原微生物的抗性,因而类病变突变体可作为研究植物防御反应和PCD的理想材料。本文对植物类病变突变体的来源、命名、类型、遗传方式、抗性特点、基因克隆、形成机制以及信号传导途径进行了总结,并展望了植物类病变突变体未来的研究方向,以期为进一步探索PCD调控机制和防御反应作用机理提供理论依据。

细胞程序性死亡与脊椎动物胚胎发育综述

脊椎动物胚胎发育是细胞通过分裂、增殖、分化、迁移及细胞程序性死亡等一系列行为进行自我组织的复杂过程。其中,细胞程序性死亡存在于胚胎发育的各个阶段,对胚胎的发育具有重要调控作用,是器官生成、形态建立和组织稳态维持等发育相关事件所必需的。本文对近年来细胞程序性死亡调控脊椎动物胚胎发育过程的相关研究进展进行了综述,包括早期胚胎发育过程中细胞程序性死亡的生物学功能、调节机制及死亡细胞的清除方式等,重点关注了细胞程序性死亡与脊椎动物胚胎发育过程之间的密切联系。本综述将为更全面地了解细胞程序性死亡在脊椎动物胚胎发育过程中的作用提供借鉴与帮助,并有望为将来通过人为调控细胞程序性死亡来提高胚胎发育质量提供一定的思路。