植物叶发育的分子机理

叶是植物进行光合作用和蒸腾作用的主要场所, 对植物的生长发育具有重要的作用。叶的发育包括叶原基的形成和极性的建立, 大量研究表明, 叶发育建成受到众多转录因子、小分子RNA以及生长素等因子的调控。文章综述了近年来叶发育和形态建成的分子机制研究进展, 以期了解叶发育的调控网络。     

小分子RNA在植物叶发育中的调控作用

叶发育是叶原基细胞有序的分裂、生长和分化的过程,受到植物激素和多个转录因子的严格调控.近年的研究表明,在叶片发育的过程中,小分子RNA是基因调控网络的重要组分.小分子RNA通过对其中一些转录因子的抑制作用,影响其表达水平和空间分布,维持叶的正常发育.本综述介绍了小分子RNA及其靶基因调控模块在叶片发生、 叶片形状、叶子极性发育和叶子衰老等过程中的调控作用,并展望了未来研究中新方向.     

生长素对拟南芥叶片发育调控的研究进展

叶片（包括子叶）是茎端分生组织产生的第一类侧生器官,在植物发育中具有重要地位。早期叶片发育包括三个主要过程：叶原基的起始,叶片腹背性的建立和叶片的延展。大量证据表明叶片发育受到体内遗传机制和体外环境因子的双重调节。植物激素,尤其是生长素在协调体内外调节机制中起着不可或缺的作用。生长素的稳态调控、极性运输和信号转导影响叶片发育的全过程。本文着重介绍生长素在叶片生长发育和形态建成中的调控作用,试图了解复杂叶片发育调控网络。     

生长素对拟南芥叶片发育调控的研究进展

叶片(包括子叶)是茎端分生组织产生的第一类侧生器官, 在植物发育中具有重要地位。早期叶片发育包括三个主要过程: 叶原基的起始, 叶片腹背性的建立和叶片的延展。大量证据表明叶片发育受到体内遗传机制和体外环境因子的双重调节。植物激素, 尤其是生长素在协调体内外调节机制中起着不可或缺的作用。生长素的稳态调控、极性运输和信号转导影响叶片发育的全过程。本文着重介绍生长素在叶片生长发育和形态建成中的调控作用, 试图了解复杂叶片发育调控网络。     

植物叶缘和叶脉发育调控的研究进展

通常可通过植物叶片的形态来区分不同植物的种类。叶片由茎顶端分生组织侧翼发育而成,为多种多样大小和形状的扁平结构。叶片的结构看似简单,但调控叶片形态和结构发育的分子机理错综复杂,叶片的发育受植物激素、转录因子、一系列蛋白因子及环境的共同调控。本文回顾了叶片边缘形态和叶脉发育研究的最新进展。在叶边缘形态方面,Aux/IAA生长素响应抑制家族蛋白通过调节生长素浓度最大点的离散分布影响小叶的起始和生长以及叶边缘结构;NAM/CUC转录因子促进叶边缘锯齿的分离以及复叶中小叶的分离和分化,NAM/CUC和Aux/IAA通过不同通路实现对生长素的调控;拟南芥RAX1基因/番茄Potato-leaf基因和拟南芥JAG基因/番茄LYR基因促进叶边缘锯齿发育;RCO调控复叶小叶的发育不通过改变生长素的分布来实现;在番茄中反式小干扰RNA途径中的因子参与叶边缘形态发育;另外,在拟南芥中,mir164A、CUC2、PIN1、DPA4、SVR9-1及SVR9L-1构成复杂的调控网络影响叶边缘锯齿的发育。在叶脉发育方面,PIN1能否正确的定位会影响叶脉发育;AS1和AS2共同参与叶片远近轴极性的分化;另外AXR6、MP、BDL、CVP因子功能的缺失影响叶脉发育;生长素、PIN1、Aux/IAA、MP、ATHB8构成反馈循环调控子叶叶脉的形成。     

植物叶发育调控机理研究的进展

在植物的营养生长阶段,叶原基从植物地上部分顶端分生组织的周边区形成,在一系列细胞分裂和分化程序的指导下,最终发育成叶。近年来,通过遗传学和分子生物学研究已经鉴定和克隆了一批参与叶发育调控的关键基因,植物激素在叶原基的诱导和叶形态建成中也起十分重要的作用。目前这个领域的主要研究工作是鉴定调控叶发育的新基因并且解释叶调控基因之间的相互作用,同时了解基因调控和植物激素作用之间的关系。     

植物叶发育调控机理研究的进展

在植物的营养生长阶段,叶原基从植物地上部分顶端分生组织的周边区形成,在一系列细胞分裂和分化程序的指导下,最终发育成叶。近年来,通过遗传学和分子生物学研究已经鉴定和克隆了一批参与叶发育调控的关键基因,植物激素在叶原基的诱导和叶形态建成中也起十分重要的作用。目前这个领域的主要研究工作是鉴定调控叶发育的新基因并且解释叶调控基因之间的相互作用,同时了解基因调控和植物激素作用之间的关系。     

AS1/AS2基因在叶形态建成中的作用研究进展北大核心CSCD

植物叶片背-腹轴极性建立是叶片形态建成的重要过程之一。ASYMMETRIC LEAVES1/ASYMMETRIC LEAVES2(AS1/AS2)是植物叶片发育中背-腹面极性关键的转录因子,直接或间接与多个蛋白或miRNAs相互协作,共同调控植物叶片发育与形成过程。本文主要综述了拟南芥、大白菜等植物AS1/AS2保守结构特征及其参与叶片侧生器官形成的启动、叶片背腹极性建立的调控等功能,总结了AS2参与植物生长激素的运输及分布、植物育性及花器官发育、植物抗病反应等生物学功能,并对今后AS1/AS2调控植物发育机制中的具体研究方向进行了展望。本文对AS1/AS2在植物发育过程功能的总结与展望,将为深入揭示AS1/AS2生物学功能的分子机制提供思路,为叶类蔬菜的新种质资源创新提供重要的理论依据。     

水稻OsYABBY6基因参与叶片发育的初步研究

水稻YABBY基因家族在植物侧生器官发育过程中起着重要调控作用。在研究中,采用合成型转录因子的方法将转录抑制结构域EAR融合于OsYABBY6的C-端,获得转基因株系CE-OsYABBY6。表型分析发现,转基因株系CE-OsYABBY6-16和CE-OsYABBY6-19成熟期的剑叶均明显表现出朝近轴面卷曲,其卷曲指数相比于野生型均显著提高(P0.05),说明OsYABBY6参与了水稻叶的发育调控。进一步的细胞组织学分析发现,与野生型相比,CE-OsYABBY6-16叶片横切面中的泡状细胞束的总数、非正常泡状细胞束的数量和比率均显著增加,说明OsYABBY6蛋白与泡状细胞的发育相关。同时,转基因株系CE-OsYABBY6中细胞周期及细胞伸长相关基因的转录水平显著升高,说明OsYABBY6对细胞分裂及生长产生了影响,最终导致了叶片发育的异常。总之,水稻转录因子OsYABBY6参与了叶的近-远轴发育调控,尤其是叶片近轴面的发育调控,而且是泡状细胞发育和叶片伸展所必需的。     

植物叶缘形态的发育调控机理

生物多样性研究的关键问题之一是表型多样性的形成和演化机制, 因为表型多样性与物种多样性密切相关, 同时又承载着遗传和环境的变异信息。植物的叶具有丰富的形态多样性, 而叶形多样性很大程度上体现在叶边缘形态的变异。叶边缘的形态可从全缘、锯齿状到具有不同程度(深浅)和不同式样(羽状或掌状、回数等)的裂片(在发育研究中复叶的小叶也描述为裂片)。关于叶缘齿/裂的发育调控机制, 在拟南芥(Arabidopsis thaliana)、碎米荠(Cardamine hirsuta)、番茄(Solanum lycopersicum)等模式植物中已有较深入的探讨。研究发现, 很多转录因子、小分子RNA及植物激素对叶齿/裂或小叶的形成具有调控作用, 其中生长素输出途径中的转录因子NAM/CUC、miR164以及高浓度生长素的反馈调控可能起到核心作用, 而且该调控模块在真双子叶植物中较为保守; TCP类、SPL类转录因子和其他一些miRNA也在生长素输出途径中发挥作用; 关于KNOX家族转录因子的作用, 虽然多数研究是围绕复叶的形态建成, 但也有数据显示其在叶裂发育中发挥作用。此外, 对拟南芥和碎米荠等十字花科植物的研究还发现, 调控基因RCO通过抑制小叶/裂片之间的细胞增殖而对小叶/叶裂的发育发挥作用。本文综述上述多角度的研究进展, 并尝试概括叶边缘形态的发育调控网络, 为关于叶缘形态多样性形成机制的研究提供可参考的切入点。     

串果藤属(Sinofranchetia)叶的个体发育研究

对串果藤属(Sinofranchetia)叶的个体发育过程进行了观察,结果表明,其叶原基在发生时为不分裂的,其后叶原基两侧产生两个突起,形成两个侧生小叶原基,而中央部分形成中央小叶的原基。同时对串果藤属植物叶原基发生的类型等问题进行了讨论。     

CORKSCREW1 defines a novel mechanism of domain specification in the maize shoot

In higher plants, determinate leaf primordia arise in regular patterns on the flanks of the indeterminate shoot apical meristem (SAM). The acquisition of leaf form is then a gradual process, involving the specification and growth of distinct domains within the three leaf axes. The recessive corkscrew1 (cks1) mutation of maize (Zea mays) disrupts both leaf initiation patterns in the SAM and domain specification within the mediolateral and proximodistal leaf axes. Specifically, cks1 mutant leaves exhibit multiple midribs and leaf sheath tissue differentiates in the blade domain. Such perturbations are a common feature of maize mutants that ectopically accumulate KNOTTED1-like homeobox (KNOX) proteins in leaf tissue. Consistent with this observation, at least two knox genes are ectopically expressed in cks1 mutant leaves. However, ectopic KNOX proteins cannot be detected. We therefore propose that CKS1 primarily functions within the SAM to establish boundaries between meristematic and leaf zones. Loss of gene function disrupts boundary formation, impacts phyllotactic patterns, and leads to aspects of indeterminate growth within leaf primordia. Because these perturbations arise independently of ectopic KNOX activity, the cks1 mutation defines a novel component of the developmental machinery that facilitates leaf-versus-shoot development in maize.     

The Shoot Apex as a Marker of the Responsivity to Photoperiodic Treatment Inducing Flowering of Chenopodium rubrum L.

Two maxima in flowering response to one inductive dark period of 13 h were found in the short day plant Chenopodium rubrum within three weeks of cultivation under continuous illumination either in vitro or in vivo. These maxima correlated with the number of leaf primordia and their relation to the size of the apical meristem. The first maximum in flowering responsivity corresponded with the stage when primordia of the second leaf pair had not yet overtopped the apical meristem, the second one when the primordia of the fourth leaf overgrew the meristem. Maximum responsivity to flowering reached by a mother plant was reflected in explants derived from it. The above morphological markers of responsiveness to floral induction were not linked to plant age and/or to general growth habit. The explants flowered only when part of the stem was present.     

Gibberellin-induced reorganization of spatial relationships of emerging leaf primordia at the shoot apical meristem in Hedera helix L.

The transition from spiral to distichous leaf arrangement during gibberellic-acid (GA₃)-induced rejuvenation in Hedera was studied in detail by scanning electron microscopy of the shoot apical meristem. The transition, which involves the initiation of about 14 new leaf primordia, is accomplished by progressive increments in the divergence angle between the leaf primordia from an initial average value of 138.9 ° until it approaches 180 °. This process is preceded, as well as accompanied, by an increased radial displacement of young leaf primordia away from the apical meristem. Although the width of the leaf primordia also increases, this is unlikely to be a causal factor since it occurs only late in the transition. The size of the primordium-free area of the apical meristem is also unlikely to be involved. Quantitative analysis shows that the divergence angle of consecutive leaf primordia commonly fluctuates between relatively large and small values. Thus the transitional stages form a spirodistichous arrangement in which the divergence angle within each pair of leaves is large relative to that between leaf pairs. The stimulation of the radial displacement of the leaf primordia and the associated phyllotactic transition may involve GA₃-induced modification in the spatial organization of cortical microtubules in the apical meristem and related changes in directional cell expansion.Abbreviations DA divergence angle - GA₃ gibberellic acid We thank Mr. Gilbert Ahlstrand for his advice regarding scanning electron microscopy. This paper is contribution of the University of Minnesota Agricultural Experimental Station No. 18,726.     

Growth of Populus euramericana

Growth curves of successive leaves of Populus euramericana (Dode) Guinier 'Robusta' have been determined. With ample supply of water and nutrients the growth of a poplar shoot follows a fixed pattern: an initial logarithmic acceleration phase followed by a stationary phase in which leaves of equal size are produced at a constant rate. Analysis of growth curves of leaves enabled the growth curves of leaf primordia to be predicted. These primordial growth curves are compared to the indirectly determined growth curves of primordia by measuring the lengths of successive leaf primordia in the apex during the stationary phase of growth. The increase in length of successive leaves in the acceleration phase of growth continues for a longer period at high than at low irradiace. The relative growth rates of leaf primordia, leaves and internodes are discussed in terms of shoot growth and phyllotaxis.     

Leaf development in the absence of a shoot apical meristem in Zeylanidium subulatum (Podostemaceae)

* BACKGROUND AND AIMS: The Podostemaceae are a family of unusual aquatic angiosperms that live in rapids and waterfalls. To adapt to such extreme habitats, the family shows unusual morphologies. This study investigated the developmental anatomy of the shoot of Zeylanidium subulatum borne on the prostrate root attached to submerged rock surfaces. * METHODS: Shoots of Z. subulatum were observed under the microscope using resin-sections. * KEY RESULTS: The shoot has no shoot apical meristem (SAM) and, without it, forms leaves distichously dorsiventrally facing the immediately older leaf. A new leaf forms on the adaxial side of a pre-existing leaf and also on the abaxial side of a leaf on flowering shoots. In both cases, the young leaf is endogenous below the older leaf and maintains histological continuity with it. Shortly after internal initiation, the leaf primordia become separate from each other due to cleavage between adjacent leaves of opposite ranks. The cleavage is caused by intercellular separation as well as by degeneration of vacuolated cells. Loss of the SAM is probably linked with the speculated shift of the site of leaf formation to the root. * CONCLUSIONS: The 'shoot' of Z. subulatum is characterized by the absence of a SAM, endogenous leaf formation in the absence of a SAM, cleavage between leaf primordia, and adventitious leaf formations. These innovations occur in some Podostemaceae that have become increasingly adapted to extreme aquatic habitats.     

Leaf primordia initiation,leaf emergence and tillering in wheat (Triticum aestivum L.) grown under low-phosphorus conditions

In two simultaneous experiments we examined the effects of phosphorus (P) supply on leaf area development in wheat (Triticum aestivum L.) grown in sand with nutrient solutions. In Experiment 1 we studied leaf emergence, leaf elongation, tiller emergence, shoot growth, and P uptake under four levels of P supply (mM) 0.025 (P1), 0.05 (P2), 0.1 (P3), and 0.5 (P4), and. In Experiment 2 there were two levels of P supply, P1 and P4, and we examined the effects of P on leaf primordia differentiation and leaf emergence. The phyllochron was calculated as the inverse of the rate of leaf emergence calculated from the regression of number of leaf tips (PHY-Ltip), Haun index (PHY-Haun), and as the cumulated thermal time between the emergence of two consecutive leaves (PHYtt). The plastochron was calculated from the inverse of the rate of leaf primordia initiation in the apex. P deficiency delayed the emergence of leaves on the main stem and on the tiller 1. Phosphorus deficiency increased the time from emergence to double ridge and anthesis. The final number of leaves was not affected by P. The effects of P on the value of the phyllochron were attributed to both a reduced rate of leaf primordia initiation, and to a reduced leaf elongation rate. P deficiency delayed or even suppressed the emergence of certain tillers. In this work a phosphorus deficiency that reduced shoot growth by 25% at 44 days after emergence significantly modified the structure of the plants by increasing the value of the phyllochron and delaying tillering. These results suggest that any attempt to simulate leaf area development and growth of wheat plants for P-limited conditions should include the effects of the deficiency on leaf emergence.