植物胞吞和胞吐的耦合调控

真核细胞通过胞吞和胞吐作用将大分子和颗粒性物质运出或运送至质膜, 其中包括一些具有重要生物学功能的蛋白质。胞吞和胞吐途径之间的耦合对维持质膜的完整性以及调控质膜蛋白的丰度和活性至关重要。动物中, 突触小泡的胞吞和胞吐在时空上紧密耦合已被证明是持续神经传递的必要条件。近年来, 随着对植物囊泡运输的深入研究, 越来越多的证据表明, 植物细胞的胞吞和胞吐间同样存在耦合调控, 且在植物生长发育和对外界环境的响应中扮演重要角色。该文综述了植物协同调控胞吞和胞吐的生理学意义, 并结合网格蛋白介导囊泡运输的最新研究进展探讨了其可能的耦合机制。     

转录因子的胞间移动在植物生长发育中的作用

多细胞生物体的生长发育依赖于细胞和细胞之间物质的交流和信号的传递。细胞命运的特化受到来自旁临细胞信息的调控。作为细胞-细胞通讯方式之一的蛋白质胞间运输广泛的存在于植物各种发育过程中。本文总结了近年来有关植物重要发育调控转录因子在细胞间移动的研究进展,综述了这些因子移动的细胞学基础和分子调控模型,并对今后蛋白胞间移动研究面临的挑战和需引入的新技术手段进行了展望。     

tRNA核质动态分布与细胞命运

旺盛的细胞核、质间的物质运输(nuclear-cytoplasmic transport)是真核细胞代谢的基础．核质运输不仅将蛋白质运到目的地,还能通过在特定时间、地点结合靶分子,改变其在胞内的局部浓度,调控诸如有丝分裂等重要细胞活动．tRNA是细胞中最重要的大分子之一,合成于细胞核,在细胞质中参加蛋白质翻译．一直以来,学术界认为tRNA只是蛋白质合成的参与者,tRNA核质运输是tRNA跨越核膜进入细胞质是单向主动运输过程．然而,最近的研究成果在颠覆传统观念,tRNA不但能被转运出核,还能被逆向转运入核．2008年,新概念“tRNA核质动态分布”(tRNA nuclear-cytoplasmic dynamics)被提出,取代tRNA核质运输,描述tRNA在细胞核、质间的流动．在酿酒酵母中tRNA核质动态分布可以调控蛋白质翻译,锁定细胞周期．此领域内的最新研究正在改变着教科书中有关tRNA的传统论断．     

植物细胞自噬基因的功能与转录调控机制

自噬(autophagy)是真核生物长期进化形成的一种高度保守的细胞内物质降解和周转途径, 通过形成双层膜结构的自噬体将包裹其中的待降解大分子物质, 如受损伤的蛋白质、蛋白质复合物和细胞器, 运送至液泡或溶酶体进行降解并产生可循环利用的降解产物。细胞自噬在植物生长发育和环境应答等过程中发挥重要作用。在拟南芥(Arabidopsis thaliana)和水稻(Oryza sativa)等模式植物中已鉴定到40多个自噬基因, 并发现其中多个基因在植物叶片衰老、种子成熟等发育阶段以及营养饥饿、干旱和病原菌侵染等逆境胁迫响应过程中显著上调表达, 但具体的转录激活或抑制机制有待阐明。该文综述了自噬基因在植物生长发育和胁迫应答过程中的功能与转录调控网络。     

蛋白质可逆磷酸化调节植物细胞离子跨膜运动研究进展

蛋白激酶和蛋白磷酸酶催化的可逆磷酸化是植物细胞中多种信号转导途径中重要的组成因子.本文对蛋白质可逆磷酸化通过调节多种离子跨膜运动而参与植物细胞激发子信号途径、毒性物质诱导的钙离子内流、盐胁迫适应、气孔运动以及蛋白质可逆磷酸化参与胞外与胞内之间Ca2 状况信息传递,调节花粉管顶端Ca2 离子通道活性进行综述,以揭示蛋白质可逆磷酸化在植物细胞离子跨膜运动中的调控作用,为蛋白质可逆磷酸化调节植物生长发育、响应逆境胁迫等机理的研究提供参考.     

非细胞自主性转录因子对植物分生组织发育的调控

为了应对多变复杂的生长环境,植物进化出了独特的信号机制,几乎每一个器官和组织都能形成高效的信号转导系统。胞间转运是器官、组织或相邻细胞中形态建成的特定发生机制,参与这一运输方式的有转录因子、多肽、小RNA和植物激素。这四类移动分子介导不同的信号转导途径,但是这些移动分子能够产生互作并构成了完整的胞间信号网络。作为一类特殊的蛋白质,转录因子尤其是非细胞自主性转录因子在植物器官形成和发育过程中发挥重要作用。主要概述了植物中的非细胞自主性转录因子以及非细胞自主性转录因子与其他移动分子共同调控植物分生组织发育的机制。     

胞间连丝研究的进展

胞间连丝为多细胞植物有机体提供了一个直接的细胞间物质运输和信息传递的细胞质通道,把一个个独立的“细胞王国”转变成相互连接的共质体,它是当今细胞生物学中十分活跃的研究领域。日益增多的研究结果揭示,胞间连丝协调基因表达和许多的细胞生理生化过程,对细胞的分裂与分化、形态发生、植物体的生长与发育,以及植物对环境的反应与适应等诸方面都起着十分重要的作用。本文仅就胞间连丝结构的多样性;胞间通道的调节因子;大分子蛋白质和核酸的胞间运输;胞间连丝阻断和共质体分区的形成及其与形态发生、休眠和抗逆性的关系等几个方面的新进展做一个简要的综述,借此例证胞间连丝在植物生命活动中的重要意义。     

胞间连丝研究的进展

胞间连丝为多细胞植物有机体提供了一个直接的细胞间物质运输和信息传递的细胞质通道,把一个个独立的“细胞王国”转变成相互连接的共质体,它是当今细胞生物学中十分活跃的研究领域。日益增多的研究结果揭示,胞间连丝协调基因表达和许多的细胞生理生化过程,对细胞的分裂与分化、形态发生、植物体的生长与发育,以及植物对环境的反应与适应等诸方面都起着十分重要的作用。本文仅就胞间连丝结构的多样性;胞间通道的调节因子;大分子蛋白质和核酸的胞间运输;胞间连丝阻断和共质体分区的形成及其与形态发生、休眠和抗逆性的关系等几个方面的新进展做一个简要的综述,借此例证胞间连丝在植物生命活动中的重要意义。     

红细胞血影介导的大分子微量注入肝癌细胞

引言真核细胞的基因表达受多种因子或环境信号的调节,其中,外源蛋白质或核酸分子对细胞基因表达的影响日益受到重视。近年来,在细胞融合基础上建立的红细胞介导大分子进入哺乳类细胞的微量注射技术,为研究外源大分子物质在细胞内的功能及其对细胞基因表达的调控提供了有效的手段。它使一些已经在非细胞系统(如分离的染色质系统)得到证实的     

植物蛋白质翻译后修饰组学研究进展

蛋白质翻译后修饰(Protein post-translational modification,PTMs)是一种重要的细胞调控机制,通过在蛋白质的氨基酸侧链上共价结合一些化学小分子基团来调节蛋白质的活性、结构、定位和蛋白质间的互作关系,从而精细调控蛋白质生物学功能的动态变化。PTMs是植物对环境变化最快、最早的反应之一,是植物蛋白质组多样性的关键机制,在植物生长发育和对环境适应中起重要作用。主要介绍了近年来植物磷酸化、乙酰化、琥珀酰化、糖基化、泛素化、巴豆酰化、S-亚硝基化及2-羟基异丁酰化等PTMs研究进展,旨为认识植物PTMs的关键生物学功能和研究前景提供参考。     

The forever young gene encodes an oxidoreductase required for proper development of the Arabidopsis vegetative shoot apex

In plant development, leaf primordia are formed on the flanks of the shoot apical meristem in a highly predictable pattern. The cells that give rise to a primordium are sequestered from the apical meristem. Maintenance of the meristem requires that these cells be replaced by the addition of new cells. Despite the central role of these activities in development, the mechanism controlling and coordinating them is poorly understood. These processes have been characterized in the Arabidopsis mutant forever young (fey). The fey mutation results in a disruption of leaf positioning and meristem maintenance. The predicted FEY protein shares significant homology to a nodulin and limited homology to various reductases. It is proposed that FEY plays a role in communication in the shoot apex through the modification of a factor regulating meristem development.     

The auxin influx carrier is essential for correct leaf positioning

Auxin is of vital importance in virtually every aspect of plant growth and development, yet, even after almost a century of intense study, major gaps in our knowledge of its synthesis, distribution, perception, and signal transduction remain. One unique property of auxin is its polar transport, which in many well-documented cases is a critical part of its mode of action. Auxin is actively transported through the action of both influx and efflux carriers. Inhibition of polar transport by the efflux inhibitor N-1-naphthylphthalamic acid (NPA) causes a complete cessation of leaf initiation, a defect that can be reversed by local application of the auxin, indole-3-acetic acid (IAA), to the responsive zone of the shoot apical meristem. In this study, we address the role of the auxin influx carrier in the positioning and outgrowth of leaf primordia at the shoot apical meristem of tomato. By using a combination of transport inhibitors and synthetic auxins, we demonstrate that interference with auxin influx has little effect on organ formation as such, but prevents proper localization of leaf primordia. These results suggest the existence of functional auxin concentration gradients in the shoot apical meristem that are actively set up and maintained by the action of efflux and influx carriers. We propose a model in which efflux carriers control auxin delivery to the shoot apical meristem, whereas influx and efflux carriers regulate auxin distribution within the meristem.     

The pleiotropic mutation dar1 affects plant architecture in Arabidopsis thaliana

Shoot architecture is shaped upon the organogenic activity of the shoot apical meristem (SAM). Such an activity relies on the balance between the maintenance of a population of undifferentiated cells in the centre of the SAM and the recruitment of organ founder cells at the periphery. A novel mutation in Arabidopsis thaliana, distorted architecture1 (dar1), is characterised by disturbed phyllotaxy of the inflorescence and consumption of the apical meristem late in development. SEM and light microscopy analyses of the dar1 SAM reveal an abnormal partitioning of meristematic domains, and mutations known to affect the SAM structure and function were found to interact with dar1. Moreover, the mutant shows an alteration of the root apical meristem (RAM) structure. Those observations support the hypothesis that DAR1 has a role in meristem maintenance and it is required for the normal development of Arabidopsis inflorescence during plant life.     

Auxin: A major regulator of organogenesis

Plant development is characterized by the continuous initiation of tissues and organs. The meristems, which are small stem cell populations, are involved in this process. The shoot apical meristem produces lateral organs at its flanks and generates the growing stem. These lateral organs are arranged in a stereotyped pattern called phyllotaxis. Organ initiation in the peripheral zone of the meristem involves accumulation of the plant hormone auxin. Auxin is transported in a polar way by influx and efflux carriers located at cell membranes. Polar localization of the PIN1 efflux carrier in meristematic cells generates auxin concentration gradients and PIN1 localization depends, in turn, on auxin gradients: this feedback loop generates a dynamic auxin distribution which controls phyllotaxis. Furthermore, PIN-dependent local auxin gradients represent a common module for organ initiation, in the shoot and in the root.     

Directional cell-to-cell communication in theArabidopsis root apical meristem I. An ultrastructural and functional analysis

Summary As a foundation for studies on directional intercellular communication and its regulation in apical development, the network of plasmodesmata inArabidopsis root apical meristems was characterized by quantitative electron microscopy and dye-coupling analysis, using symplasmic probes, and real-time imaging in confocal laser scanning microscopy. A tissue-specific plasmodesmatal network, which interconnected the cells in the root apical meristem, was characterized by the following features, (a) Plasmodesmatal distribution and density were found to be tissue-specific, (b) Primary and secondary plasmodesmata were differentially grouped and regulated. Primary plasmodesmata were formed in large numbers in the transverse walls of each tissue, and were subject to deletion during cell differentiation. Secondary plasmodesmata were mostly distributed in longitudinal walls between cell files and common walls between neighboring tissues; they also provided a symplasmic path between different initial tiers in the meristem. Small fluorescent tracers moved through the plasmodesmatal network of the root apical meristem in two distinct phases. At low concentrations molecules trafficked in a non-tissue-specific manner, whereas at higher concentrations, their distribution reflected the presence of tissue-specific movement consistent with plasmodesmatal distribution. These findings are discussed in terms of the role of tissue-specific plasmodesmatal domains in the control of root development.     

Alterations of the glutathione redox state improve apical meristem structure and somatic embryo quality in white spruce (Picea glauca)

In white spruce, an improvement of somatic embryo number and quality can be achieved through experimental manipulations of the endogenous levels of reduced (GSH) and oxidized (GSSG) glutathione. An optimal protocol for embryo production included an initial application of GSH in the maturation medium, followed by replacement with GSSG during the remaining maturation period. Under these conditions, the overall embryo population more than doubled, and the percentage of fully developed embryos increased from 22% to almost 70%. These embryos showed improved post-embryonic growth and conversion frequency. Structural studies revealed remarkable differences between embryo types, especially in storage product deposition pattern and organization of the shoot apical meristem (SAM). Compared with their control counterparts, glutathione-treated embryos accumulated a larger amount of starch during the early stages of development, and more protein and lipid bodies during the second half of development. Differences were also noted in the organization of SAMs. Shoot meristems of control embryos were poorly organized and were characterized by the presence of intercellular spaces, which caused separation of the subapical cells. Glutathione-treated embryos had well-organized meristems composed of tightly packed cells which lack large vacuoles. The improved organization of the shoot apical meristems in treated embryos was ascribed to a lower production of ethylene. Differences in meristem structure between control and treated embryos were also related to the localization pattern of HBK1, a shoot apical meristem 'molecular marker' gene with preferential expression to the meristematic cells of the shoot pole. Expression of this gene, which was localized to the apical cells in control embryos, was extended to the subapical cells of treated embryos. Overall, it appears that meristem integrity and embryo quality are under the direct control of the glutathione redox state.     

Coordination of cell proliferation and cell fate decisions in the angiosperm shoot apical meristem.

A unique feature of flowering plants is their ability to produce organs continuously, for hundreds of years in some species, from actively growing tips called apical meristems. All plants possess at least one form of apical meristem, whose cells are functionally analogous to animal stem cells because they can generate specialized organs and tissues. The shoot apical meristem of angiosperm plants acts as a continuous source of pluripotent stem cells, whose descendents become incorporated into organ primordia and acquire different fates. Recent studies are unveiling some of the molecular pathways that specify stem cell fate in the center of the shoot apical meristem, that confer organ founder cell fate on the periphery, and that connect meristem patterning elements with events at the cellular level. The results are providing important insights into the mechanisms through which shoot apical meristems integrate cell fate decisions with cellular proliferation and global regulation of growth and development.