The Role of Ethylene in Interorgan Signaling during Flower Senescence

The roles of 1-aminocyclopropane-1-carboxylic acid (ACC) and ethylene in interorgan signaling during senescence in orchid (Cymbidium) flowers were investigated. Following application of radiolabeled ACC to the stigma or the rostellum (modified lobe of the stigma), radiolabeled ethylene is produced by all flower parts. In intact flowers as well as in excised central columns, stigma- or rostellum-applied ACC or [alpha]-aminoisobutyric acid were largely immobile. Local treatment of the central column of previously aminoethoxyvinylglycine-treated flowers with either ethylene or 2-chloroethylphosphonic acid (ethephon) rapidly induced emission of ethylene from the petals, showing that ethylene is readily translocated within the flower. Creation of alternative outlets (incisions) in the labellum or the central column significantly delayed the occurrence of senescence symptoms in ACC-treated flowers. The results do not confirm the presumed role of ACC as a signal in interorgan communication during flower senescence. In these flowers, ethylene produced in the stigmatic region following pollination or emasculation serves as a mobile factor responsible for senescence symptoms observed in other flower parts.     

Calcium Signaling Network in Plants: An Overview

Calcium ion (Ca²⁺) is one of the very important ubiquitous intracellular second messenger molecules involved in many signal transduction pathways in plants. The cytosolic free Ca²⁺ concentration ([Ca²⁺]_cyt) have been found to increased in response to many physiological stimuli such as light, touch, pathogenic elicitor, plant hormones and abiotic stresses including high salinity, cold and drought. This Ca²⁺ spikes normally result from two opposing reactions, Ca²⁺ influx through channels or Ca²⁺ efflux through pumps. The removal of Ca²⁺ from the cytosol against its electrochemical gradient to either the apoplast or to intracellular organelles requires energized ‘active’ transport. Ca²⁺-ATPases and H⁺/Ca²⁺ antiporters are the key proteins catalyzing this movement. The increased level of Ca²⁺ is recognised by some Ca²⁺-sensors or calcium-binding proteins, which can activate many calcium dependent protein kinases. These kinases regulate the function of many genes including stress responsive genes, resulted in the phenotypic response of stress tolerance. Calcium signaling is also involved in the regulation of cell cycle progression in response to abiotic stress. The regulation of gene expression by cellular calcium is also crucial for plant defense against various stresses. However, the number of genes known to respond to specific transient calcium signals is limited. This review article describes several aspects of calcium signaling such as Ca²⁺ requiremant and its role in plants, Ca²⁺ transporters, Ca²⁺-ATPases, H⁺/ Ca²⁺-antiporter, Ca²⁺-signature, Ca²⁺-memory and various Ca²⁺-binding proteins (with and without EF hand).Key Words: Calcium binding proteins, Ca²⁺ channel, Ca²⁺-dependent protein kinases, Ca²⁺/H⁺ antiport, calcium memory, calcium sensors, calcium signatures, Ca²⁺-transporters, EF hand motifs, plant signal transduction     

非折叠蛋白反应——一条综合的细胞内信号通路

内质网(endoplasmic reticulum,ER)作为细胞中蛋白成熟的场所,可以很敏感的感受细胞内外环境的变化.当ER内环境改变,细胞就会激活信号应对这些改变,并且重新恢复折叠蛋白的环境.内质网的这种改变就是内质网应激(endophsmic reticulum stress,ERS),而对这种应激作出的反应就是非折叠蛋白反应[1](Unfolded Protein Response,UPR ).UPR至少引起了3种不同的信号通路,这些通路不仅调控分泌途径中大部分基因的表达,而且还广泛影响细胞的各个方面包括蛋白质、氨基酸和脂类的代谢.同时,这3务通路可以综合的调控细胞分泌器官的重塑并根据ERS重新调节细胞的生理活性.就UPR相关的感受器及其信号通路作简要的介绍.     

乙烯受体在果实成熟及花衰老中的研究进展

乙烯受体是乙烯信号转导网络的第一个转导元件,通过调控受体基因的表达,可以调节植物对乙烯的敏感性,以调控果实的成熟及花衰老进程的响应.随着人们对乙烯受体研究的深入,乙烯受体突变体及受体抑制剂在采后果实和切花保鲜上的应用已受到广泛关注.就近年来关于乙烯受体的相关研究进展进行综述,重点介绍了乙烯受体的分子调控机制及乙烯受体在...     

An Integrated Global Analysis of Compartmentalized HRAS Signaling

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花衰老相关的乙烯信号转导基因研究进展

乙烯在许多切花衰老过程中起着重要的调节作用,不同的植物乙烯信号转导组分在花衰老过程中有不同的转录调节特性。根据乙烯信号转导标准模式,通过调节乙烯信号转导基因表达能够调控花对乙烯的敏感性,深入研究乙烯信号转导机制;可能有多条途径可延缓切花衰老。综述了香石竹和月季等几种观赏植物在花衰老过程中乙烯受体和乙烯信号转导基因表达及特性。     

Differential Oncogenic Ras Signaling and Senescence in Tumor Cells

Several studies have shown that forced expression of oncogenic H-ras can induce a senescence-like permanent growth arrest in normal cells. Here we report that expression of oncogenic H-ras in human osteosarcoma U2OS cells also resulted in a senescence-like flat and enlarged cell morphology and permanent growth arrest. In contrast to normal human fibroblasts, U2OS cells were arrested independently of the p16 and ARF tumor suppressors. Treatment with a MEK inhibitor or a p38MAPK inhibitor interrupted oncogenic H-ras-induced growth arrest in U2OS cells, suggesting that activation of MAPK pathways is important. To further determine whether this process is unique to oncogenic H-ras signaling, we examined the effect of oncogenic K-ras on normal cells and human osteosarcoma cells. Similar to oncogenic H-ras, oncogenic K-ras also induced senescence in normal fibroblasts, while transforming immortalized mouse fibroblasts. However, in contrast to oncogenic H-ras, oncogenic K-ras failed to induce a permanent growth arrest in osteosarcoma U2OS cells. Additionally, cells transduced with oncogenic K-ras exhibited distinguishable cellular changes compared to those transduced with oncogenic H-ras. In summary, we report for the first time that oncogenic H-ras signaling can trigger a senescence-like growth arrest in tumor cells, independent of the p16 and ARF tumor suppressors. This result suggests that tumor cells may harbor a senescence-like program that can be activated by ras signaling. Moreover, our study uncovered a cell type-dependent differential response to oncogenic K-ras, as compared to oncogenic H-ras.     

Relationship between Ethylene Evolution and Senescence in Morning-Glory Flower Tissue

An excised tissue system consisting of corolla rib segments was developed to study the relationship between senescence and ethylene production in morning-glory flowers (Ipomoea tricolor). Such segments, isolated 1 or 2 days (day −1 or day −2) before flower opening (day 0) passed through the same developmental phases as did the corresponding tissues of the intact organ. When excised on day −1 and incubated overnight, the rib segments turned from purple to blue and changed from a slightly curled to a flat configuration. On day 0, these segments rolled up during the afternoon and turned purple again, as did the ribs of an intact corolla; the rolling up coincided with an increased rate of ethylene production. Premature rolling up and associated ethylene evolution were induced by ethylene or propylene treatment. When segments were excised on day −2 and incubated overnight, there were no changes in color or shape; during day −1, no spontaneous rolling up and little ethylene evolution occurred. Application of ethylene or propylene to these immature segments elicited rolling up but did not stimulate endogenous ethylene production.     

Ectopic Expression of Two FOREVER YOUNG FLOWER Orthologues from Cattleya Orchid Suppresses Ethylene Signaling and DELLA Results in Delayed Flower Senescence/Abscission and Reduced Flower Organ Elongation in Arabidopsis

Plant Molecular Biology Reporter - Two orthologues of Arabidopsis FOREVER YOUNG FLOWER (FYF), CaFYF1 and CaFYF2, were identified from Cattleya intermedia. To investigate the function of these two...     

The Control of Flower Senescence in Petunia (Petunia hybrids)

Petunia corollas wilt and abscise between one and two weeksafter detachment when maintained in distilled water in vialsat 18 °C. The onset of wilting is brought forward substantiallyby the application of 1-aminocyclopropane-1-carboxylic acid(ACC) either to the vial solution or to the stigmatic surface.Both pollination and stigma removal also shorten the time tothe onset of wilting, colour change and to abscission. In thecase of stigma removal, the life span of the corolla is shortestwhen the treatment is made at the time of flower detachment(day 0), whereas pollination has the greatest effect if it occurson day 1. Stigma damage still has an effect on corolla senescenceeven when stigma and style are removed, as long as they havebeen left in place for a few hours after treatment. Evidencefrom several experiments shows that a 17 h period is sufficientfor the full effect to be shown, and that probably there aresome effects on the corolla even if the damaged stigma is onlyleft in position for 3–6 h. Treatments which advance corolladeath (to day 3) also advance the peak of ethylene productionby the pistil (to day 1) and the corolla (to day 2). The useof silver thiosulphate (STS) overcomes all manipulative andchemical treatments used, and greatly extends vase life. Theextension occurs even when STS application is delayed for 24h, i.e. after the peak of ethylene production by the pistiland after any senescence signal has arrived at the corolla.In this case, however, the time to first morphological changeis largely unaffected, but the STS greatly extends the timeperiod between first morphological change and corolla death.The evidence suggests that early symptoms of senescence e.g.colour change and slight loss of turgor, do not automaticallylead to corolla abscission. Petunia hybrida, abscission, ACC, STS, pollination, flower senescence, ethylene     

芍药花开放与衰老过程中生理指标的变化

以芍药品种‘红峰’为材料,对芍药花开放与衰老过程中不同发育时期的膜脂过氧化水平和内源激素(IAA、GA3、iPA、ZR、ABA、Eth)含量的动态变化进行了比较研究。结果显示,芍药花开放过程花瓣SOD活性先升高后下降,而丙二醛含量和细胞膜透性显著增加;随着花开放和衰老花瓣中IAA、iPA含量迅速下降而后小幅回升出现一峰值,开放后又下降;GA3、ZR含量迅速下降维持在较低水平,而衰老后ABA含量和Eth释放量显著增加。结果表明,芍药花开放与衰老过程受内源激素平衡的调节,ABA的积累促进了内源Eth的增加,ABA和Eth与IAA/ABA比率在芍药花的衰老过程中起着关键作用,细胞膜脂过氧化损伤可能是芍药花衰老的重要生理原因。     

Polyols Regulate the Flower Senescence by Delaying Programmed Cell Death in Gladiolus

Programmed cell death (PCD) is associated with petal senescence, but little is known about the triggering or execution of the process of cell death in petals. In the present study, membrane disruption and DNA fragmentation, events characteristic of PCD, were found to be present in the advanced stage of petal senescence studied with ethylene-insensitive flowers of gladiolus, indicating that plant and animal cell death phenomena share one of the molecular events in the execution phase. When the gladiolus florets were treated with inositol both wilting and DNA fragmentation of petals were suppressed/delayed. The present study has provided the initial evidence that inositol has an inhibitory/suppressive effect on apoptotic cell death.     

Flower Development and Senescence in Digitalis purpurea L., cv. Foxy

Flowers of Digitalis purpurea L. cv. Foxy, take just over aweek to develop from the smallest buds and open. Both the anthersand the stigma are closed when the flower opens, the anterioranthers dehisce 2 days after flower opening and the posterioranthers a day later. The stigma opens 2 days later still andthe corolla remains attached for a further 2 days. The maximum size of the corolla is reached soon after openingand then remains constant. The fresh weight increases throughoutthe attached life of the corolla, whereas the dry weight reachesa maximum at flower opening and decreases during the remainderof the corolla's attached life. The content of antho-cyaninvaries greatly from spike to spike. In some spikes the maximumcontent is at flower opening, in others it is much later, butin all cases the loss of anthocyanin with ageing is very smalland the corollas are abcissed without visible wilting or fading.Maximum protein, RNA and glucose contents occur at, or soonafter, flower opening and the levels decrease in the corollasas they age. Fructose reaches a maximum at the same time asglucose but does not decrease as rapidly, so that fructose becomesthe major reducing sugar in the older corollas. Sucrose cannotbe detected in any flowers. Ethylene production increases steadilywith flower age, but the maximum production is recorded fromflowers which have recently ab-scissed the corolla regardlessof whether this occurs before detachment from the spike or withinthe collection tube.     

Interrelationship between the Different Flower Parts during Emasculation-Induced Senescence in Cymbidium Flowers

In Cymbidium flowers emasculation by removal of the anther capand the pollinia, led to rapid colouration of the lip and advancedwilting of the petals and sepals. The ethylene production ofwhole flowers showed an emasculation-induced early peak in ethyleneevolution followed some days later by a second increase concomitantwith the wilting of the flower. In non-emasculated flowers theethylene production increased later and simultaneously withcolouration of the lip and wilting of the petals and sepals.At all stages of senescence, the contribution of the lip, petals,and sepals to the total amount of ethylene produced was negligible. Parallel to the increase in ethylene production of whole flowers,an increase in 1-aminocyclopropane-l-carboxylic acid (ACC) andmalonyl-ACC (MACC) in the central column and, to a lesser extent,in the ovary was observed. Also an increase in internal ethyleneconcentration was demonstrated and this, in contrast, was apparentin all the different flower parts. The activity of the ethylene-formingenzyme in lips, petals, and sepals showed an increase afteremasculation and such an effect could also be induced by treatmentof isolated lips with low concentrations of ethylene. The data indicate that senescence in Cymbidium flowers is regulatedby the central column and perhaps the ovary and that both ACCand ethylene may play a signalling role in inter-organ communication. Key words: 1-aminocyclopropane-l-carboxylic acid, ethylene, Cymbidium, senescence     

含矮壮素的保鲜剂对非洲菊切花衰老的影响

含矮壮素的保鲜剂能增加非洲菊切花瓶插衰老过程中SOD、CAT、POD的活性,削弱MDA含量的增加和的O-2生成速率,减少蛋白质的降解,降低脯氨酸含量和水分散失,维持膜结构的相对稳定性,延长切花瓶插寿命4 d左右.