高等植物开花诱导途径信号整合的分子机制

开花是高等植物从营养生长到生殖生长的重要转折点。花分生组织的形成是开花植物对内外环境信号的响应。近年来在开花诱导方面已获得许多研究成果,我们介绍了高等植物开花诱导的4条主要途径（光周期途径、春化途径、自主途径和赤霉素途径）和复杂的信号整合机制。     

高等植物开花时程的基因调控（Ⅰ）

高等植物从营养生长向生殖生长及发育转变的时程具有重要意义,但是了解得很少。近6年来利用分子遗传学方法详细地分析了拟南芥中的这一转变的时程变化,为高等植物开花时程的基因调控提供了一个很好的模式。有关早期或晚期开花表现型的大量突变体及遗传变异得到了阐述。这里谈到的表现型对影响开花转变的环境及内部因子的控制有重大作用。通过分子生物学、遗传学和生理学分析已经鉴定了参与此过程的不同组分,如光识别和昼夜节律（circadian rhythm）因子。另外,通过克隆某些花诱导基因及其相应的靶基因已经对参与开花信号转导途径（signal transduction pathway）的相关因子进行了系统的鉴定,这些开创性工作大大促进了高等植物开花时程的基因表达调控研究及其机理的阐明。本实验室在以黄瓜、新红宝西瓜、西葫芦为材料所获得的部分结果基础上,主要以近六年来在拟南芥方面获得的进展为依据,对高等植物开花时程的基因调控作一系统的总结,并对其开花时程基因调控的机理提出可能的作用理论模型。     

逆境诱导植物开花的研究进展

植物在长期的进化过程中形成了对环境改变的适应机制。在逆境条件下,例如干旱、高盐、低温、强光、弱光、紫外线等,植物会提前开花结实以尽早完成其生命周期,这种生物学现象被称为"逆境诱导的开花"。植物的这种避逆应激反应不但在进化上具有非常重要的生物学意义,而且对农业生产也具有重要的指导意义。逆境诱导植物开花与光周期、春化、环境温度、自主途径、赤霉素和年龄等开花途径的分子调控机制不同,有其自身的特点。文中对逆境诱导植物开花的研究历史、代谢调控以及分子机制等进行了阐述,并展望了未来的研究方向。     

高等植物开花时程的基因调控(Ⅱ)

主要探讨如下几个问题:转基因植物中的拟南芥开花时程基因;拟南芥中的甲基化与实验胚胎学研究;高等植物开花时程控制的可能机制.目前本领域已成为植物发育分子生物学的前沿热点研究领域之一.结合有关工作,对这一世界性热门领域进行了系统的评述,希望能为国内同行提供有关参考,赶超世界的植物分子生物学先进水平,对分子水平与生物技术角度改良黄土高原生态环境有指导意义.     

拟南芥开花时间调控的研究进展

调控开花时间是大多数植物由营养生长向生殖生长转化的一个重要生长发育过程.影响拟南芥开花时间的因素有很多,其中光照和温度是两个主要的外部因素,而赤霉素(GA)和一些自主性因子是主要的内部因素.目前,一般按照对以上因素的反应将晚花突变体归于四条开花调控途径:光周期途径、春化途径、自主途径和GA途径.在不断变化的外部环境条件和内部生理条件下,这些途径通过一些主要的整合基因如SOC1、FT、LFY等实现了对拟南芥开花时间的精确调控.     

高等植物开花时程的调控与光受体Ⅰ.开花时程的基因与光受体调控

系统评述了高等植物开花时程的调控与植物光受体的联系.重点说明了控制开花时程的遗传途径以及光周期途径的有关基因的研究进展.影响高等植物开花的最重要的因子之一便是光周期,光周期对高等植物开花的调控是通过相关基因间的相互作用来实现的,这些基因包括参与花启动发育控制基因,昼夜节律时间钟调控基因及光受体信号转导基因.近5年左右的时间通过对拟南芥及其一系列突变体的研究为我们展示了这一热门领域的广阔的前景.     

CO2诱导水稻开花技术的应用

1985年夏季,我们在用红外线气体分析仪测定稻穗的呼吸强度时观察到,水稻颖花在开花时呼吸强度显著升高。稻穗上每有一朵颖花开放,记录图上就出现一个CO_2释放峰,若几朵颖花同时开放,C_2释放峰就相应增大。根据颖花CO~2释放峰的面积推算,临开颖前水稻颖花内的CO_2浓度高达5％。由     

高等植物开花研究现状简述

本文阐述了高等植物开花（包括光周期和春化作用,花序分生组织形成和花发端,以及花器官发生和发育）研究的一些进展,着重介绍了花发育过程中的基因调控方面的研究成果     

拟南芥开花的光周期调节

拟南芥开花时间受先质、光周期影响。已鉴定出两类影响开花光周期反应的突变体：一类是通过影响内源生理节奏从而影响光周期测量,导致开花时间改变的突变体,包括elf3和lhy;另一类是影响长日光周期应答的突变作,如constans（co）和gigantea（gi）。CO基因已经克隆,通过转基因和原位杂交分析,表明CO转录水平是长日应答促进开花的主要决定因子。     

Understanding the genetic and epigenetic architecture in complex network of rice flowering pathways

Although the molecular basis of flowering time control is well dissected in the long day (LD) plant Arabidopsis, it is still largely unknown in the short day (SD) plant rice. Rice flowering time (heading date) is an important agronomic trait for season adaption and grain yield, which is affected by both genetic and environmental factors. During the last decade, as the nature of florigen was identified, notable progress has been made on exploration how florigen gene expression is genetically controlled. In Arabidopsis expression of certain key flowering integrators such as FLOWERING LOCUS C (FLC) and FLOWERING LOCUS T (FT) are also epigenetically regulated by various chromatin modifications, however, very little is known in rice on this aspect until very recently. This review summarized the advances of both genetic networks and chromatin modifications in rice flowering time control, attempting to give a complete view of the genetic and epigenetic architecture in complex network of rice flowering pathways.     

Cytokinin promotes flowering of Arabidopsis via transcriptional activation of the FT paralogue TSF

Cytokinins are involved in many aspects of plant growth and development, and physiological evidence also indicates that they have a role in floral transition. In order to integrate these phytohormones into the current knowledge of genetically defined molecular pathways to flowering, we performed exogenous treatments of adult wild type and mutant Arabidopsis plants, and analysed the expression of candidate genes. We used a hydroponic system that enables synchronous growth and flowering of Arabidopsis, and allows the precise application of chemicals to the roots for defined periods of time. We show that the application of N⁶‐benzylaminopurine (BAP) promotes flowering of plants grown in non‐inductive short days. The response to cytokinin treatment does not require FLOWERING LOCUS T (FT), but activates its paralogue TWIN SISTER OF FT (TSF), as well as FD, which encodes a partner protein of TSF, and the downstream gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). Treatment of selected mutants confirmed that TSF and SOC1 are necessary for the flowering response to BAP, whereas the activation cascade might partially act independently of FD. These experiments provide a mechanistic basis for the role of cytokinins in flowering, and demonstrate that the redundant genes FT and TSF are differently regulated by distinct floral‐inducing signals.     

水稻开花光周期调控相关基因研究进展

水稻开花调控是一个极其复杂的生命过程,由自身遗传因素和外界环境共同决定。光周期途径是调控水稻开花的关键途径,在这个途径中成花素基因Hd3a和RTF1处于核心地位,其上游调控途径主要包括Hd1依赖途径、Ehd1依赖途径及不依赖于Hd1和Ehd1的途径。这3条途径在汇集了光信号的各种信息后,将信号在Hd3a和RTF1处整合,并通过成花素形式将信息传递给下游开花基因,调控水稻开花。本文从成花素、光信号感受基因和昼夜节律基因、成花素上游调控基因、互作蛋白和下游调控基因等几方面阐述水稻开花光周期调控相关基因的研究现状,为水稻开花调控的深入研究提供参考。     

Florigen goes molecular: Seventy years of the hormonal theory of flowering regulation

As early as in 1936, the comprehensive studies of flowering led M.Kh. Chailakhyan to the concept of florigen, a hormonal floral stimulus, and let him establish several characteristics of this stimulus. These studies set up for many years the main avenues for research into the processes that control plant flowering, and the notion of florigen became universally accepted by scientists worldwide. The present-day evidence of genetic control of plant flowering supports the idea that florigen participates in floral signal transduction. The recent study of arabidopsis plants led the authors to conclusion that the immediate products of the gene FLOWERING LOCUS I, its mRNA and/or protein, move from an induced leaf into the shoot apex and evoke flowering therein.     

Florigen （Ⅱ）： It is a Mobile Protein

The true identity of florigen - the molecule（s） that migrates from leaves to apical meristem to initiate flowering - was notoriously elusive, having made it almost the ＂Bigfoot＂ of plant biology. There was never a lack of drama in the field of florigen study, and florigen researchers have once again experienced such a swing in the last two years. We wrote a minireview last year in this journal （Yu et al. 2006） to excitedly salute, among other discoveries, the notion that the flowering locus T （FT） mRNA might be the molecular form of a florigen. However, this hypothesis was challenged in a little less than two years after its initial proposition, and the original paper proposed that the FT mRNA hypothesis was retracted （Huang et al. 2005; Bohlenius et al. 2007）. Interestingly enough, the FT gene previously proposed to encode a florigen was never challenged. Rather, the FT protein, instead of the FT mRNA, is now believed to migrate from leaves to the apical meristem to promote floral initiation. In this update, we will share with our readers some entertaining stories concerning the recent studies of florigen in five different plant species. In addition to the published reports referenced inthis update, readers may also refer to our previous minireview and references therein for additional background information （Yu et al. 2006）.     

Molecular control of seasonal flowering in rice,arabidopsis and temperate cereals

Background

Rice (Oryza sativa) and Arabidopsis thaliana have been widely used as model systems to understand how plants control flowering time in response to photoperiod and cold exposure. Extensive research has resulted in the isolation of several regulatory genes involved in flowering and for them to be organized into a molecular network responsive to environmental cues. When plants are exposed to favourable conditions, the network activates expression of florigenic proteins that are transported to the shoot apical meristem where they drive developmental reprogramming of a population of meristematic cells. Several regulatory factors are evolutionarily conserved between rice and arabidopsis. However, other pathways have evolved independently and confer specific characteristics to flowering responses.

Scope

This review summarizes recent knowledge on the molecular mechanisms regulating daylength perception and flowering time control in arabidopsis and rice. Similarities and differences are discussed between the regulatory networks of the two species and they are compared with the regulatory networks of temperate cereals, which are evolutionarily more similar to rice but have evolved in regions where exposure to low temperatures is crucial to confer competence to flower. Finally, the role of flowering time genes in expansion of rice cultivation to Northern latitudes is discussed.

Conclusions

Understanding the mechanisms involved in photoperiodic flowering and comparing the regulatory networks of dicots and monocots has revealed how plants respond to environmental cues and adapt to seasonal changes. The molecular architecture of such regulation shows striking similarities across diverse species. However, integration of specific pathways on a basal scheme is essential for adaptation to different environments. Artificial manipulation of flowering time by means of natural genetic resources is essential for expanding the cultivation of cereals across different environments.