模式植物拟南芥开花时间分子调控研究进展

植物从营养生长到生殖生长的转变是开花发育的关键,在合适的时间开花对植物的生长和繁衍极为重要,植物开花时间的调控对农业生产发展意义重大。植物开花是由遗传因子和环境因子协同调节的一个复杂过程。近年来,对不同植物开花调控的研究,特别是对模式植物拟南芥（Arabidopsis thaliana（L.） Heynh.）的开花调控研究取得了显著进展,已探明开花时间分子调控的6条主要途径分别是光周期途径、春化途径、自主途径、温度途径、赤霉素途径和年龄途径。各遗传调控途径既相互独立又相互联系,构成一个复杂的开花调控网络。本文综述了模式植物拟南芥开花时间调控分子机制相关研究的最新进展,并对未来的研究进行了展望。     

高等植物开花诱导研究进展

高等植物由营养生长向生殖生长转换的过程称为开花诱导。开花诱导过程由遗传和外界环境两个因素决定, 受错综复杂的网络信号传导途径调控。近年来, 在双子叶模式植物拟南芥中, 开花诱导研究取得了很大进展, 探明了控制开花诱导的4条主要途径(光周期途径、春化途径、自主途径和GA途径)及调控机制。研究也表明, 开花基因在拟南芥、水稻以及其他高等植物之间具有很高的保守性。文章对相关研究的最新进展作一综述, 并指出了目前研究中存在的问题及相应的研究对策。     

植物开花时间调控的信号途径

开花是植物从营养生长到生殖生长的一个重要转折点。花启动的时机对生殖生长的成功至关重要。开花时间受内在因子和环境因子的共同调节。通过对拟南芥的分子遗传学研究,确定至少存在4条调控开花时间的信号途径,即光周期途径、春化途径、自主途径和赤霉素途径。本文以拟南芥 (Arabidopsis thaliana) 为主要研究对象简要综述了近年来在开花时间调控领域的研究进展。     

拟南芥开花时间调控的整合途径

拟南芥开花时间受光周期途径、春化途径、自主途径和赤霉素途径4条途径调控。开花途径整合因子LEAFY、SDC1和FT等可整合来自不同开花途径的信号,并将信号传递给花分生组织基因,从而实现对拟南芥开花时间的精确调控。文章就整合途径基因调控网络的最新研究进展作简要介绍。     

光和温度调控开花时间的研究进展

光和温度作为最重要的环境信号调控植物的生长与发育.植物在进化中具备了应对和适应各类环境改变的策略.它们通过整合外源信号与内源信号,继而调控各类生理过程,包括开花时间.在模式植物拟南芥中至少存在5种不同的开花调控途径:光周期途径、春化/温度响应途径、自主开花启始途径、赤霉素途径以及年龄途径.其中光周期途径与温度/春化途径主要感知外界环境信号调控开花时间,而自主途径与年龄途径则介导了植物内源信号调控开花启始.在许多植物物种中,开花时间受到光(光周期)和温度的精确调控,确保植物在特定环境下的最佳时机开花以确保产量.通过正向和反向遗传途径的研究,人们揭示了光和温度调控开花的部分分子机制,本文概述了最近的一些重要进展.     

拟南芥开花诱导途径分子机制研究进展

拟南芥是分子和遗传学研究的模式植物,对植物花发育及控制花形态建成的分子遗传机制的研究进展主要是建立在对拟南芥研究的基础之上,拟南芥开花主要受到4个途径(自主途径、赤霉素途径、春化作用和光周期途径)的内源和外界信号的同时诱导.该文对近年来国内外有关拟南芥开花诱导的4个途径的分子机制研究进展进行综述,并初步绘制出各开花诱导途径基因间的调控网络图,以进一步明确基因间的相互作用模式及其在整个开花过程中的作用地位.     

拟南芥SUA41基因的表达和功能分析

植物的开花受多条途径的控制, 其中包括光周期途径、春化途径、赤霉素途径、自主途径和温敏途径。SUA41(SUMO substrate in Arabidopsis 41)是本实验室筛选到的、SUMO(Small ubiquitin modifier)的潜在底物, 并且前人的研究发现它参与自主途径的开花调节, 但其对开花时间的调节机制没有详细报道。文章对SUA41基因的表达、sua41突变体对不同环境条件的反应以及SUA41对开花时间调节的可能机制进行初步分析。结果显示, 与野生型相比, sua41突变体在常温或低温、长日或者短日条件下均为早花, 并且在低温和常温下的开花时间没有太大差别。过表达SUA41能够恢复sua41突变体的早花表型。SUA41基因在拟南芥的幼苗、根、茎、叶和花以及各个植物发育阶段都有表达, 说明SUA41基因是一个组成型表达基因。SUA41基因的表达与GA处理无关, 长日低温条件能够诱导SUA41基因的表达, 且在温敏途径突变体fve和fca中SUA41基因的表达量减少。与野生型比较, sua41突变体中CO基因的mRNA表达量没有明显变化, FT和SOC1基因表达量增加且FT增加幅度更大, FLC的mRNA表达量减少。结果表明SUA41基因虽然在自主途径中起作用, 但主要在温敏途径中参与拟南芥开花时间调节。     

水稻开花期调控的分子机理研究进展

水稻准确地感知外部环境信号,通过内部复杂的基因网络做出反应,在一年中最适合的时候开花繁殖。与长日促进长日模式植物拟南芥开花相反,短日促进短日模式植物水稻开花。通过对水稻和拟南芥的开花期调控机理的对比分析,发现水稻和拟南芥有着一些相对保守的开花期控制基因,其调控机理也是相似的。另外,水稻也有一些独特的开花期控制基因和开花途径。本文着重从光周期对水稻开花期的调控途径和作用机理角度进行了阐述,并对水稻开花期的自然变异与其育种应用、生物钟关联基因、光中断现象和临界日长现象以及开花期与产量的关系进行了总结。     

拟南芥开花时间调控的分子基础

在合适的时间开花对大多数植物的生存和成功繁衍极为重要。开花时间受错综复杂的环境因素和植物自身的遗传因子影响,由开花调控因子所构成的光周期、春化、温度、赤霉素、自主以及年龄等至少6条既相互独立又相互联系的遗传途径调控。该文综述了有关拟南芥(Arabidopsis thaliana)开花时间调控的分子机制的最新研究进展,并对今后的研究进行了展望。     

国外大刊重要论文简介

通过比较双突变体和三突变体分析拟南芥中控制开花时间的模型ＲｅｅｖｅｓＰＨ ,ＣｏｕｐｌａｎｄＧＰｌａｎｔＰｈｙｓｉｏｌｏｇｙ 2 0 0 1 ,1 2 6:1 0 85～ 1 0 91在长日照光周期条件下 ,拟南芥中诱导开花的遗传途径至少有三条 ,即 :长日照途径、自主途径和赤霉素依赖途径 ,     

植物开花调控途径

开花是植物从营养生长转换为生殖生长的生理发育过程,受光周期、温度、激素、年龄等多个因素诱导,在植物生长和物种进化中处于核心地位。综合不断更新的开花分子遗传结果,将植物响应各种内源和外源信号启动开花的途径归纳为:经典的光周期途径、春化途径、自主途径、赤霉素途径和较新的年龄途径共5条。旨在描绘出这些不同途径间既独立又相互影响的复杂网络关系,为进一步探索和阐述更多植物的开花分子机理提供借鉴与参考。     

Analysis of Flowering Time Control in Arabidopsis by Comparison of Double and Triple Mutants

Three genetic pathways promote flowering of Arabidopsis under long photoperiods. These pathways are represented by the genes CO, FCA, and GA1, which act in the long-day, autonomous, and gibberellin pathways, respectively. To test whether these are the only pathways that promote flowering under long photoperiods, the co-2 fca-1 ga1-3 triple mutant was constructed. These plants never flowered under long- or short-day conditions, indicating that the three pathways impaired by these mutations are absolutely required for flowering under these conditions. The triple mutant background represents a "vegetative ground state" enabling the roles of single pathways to be described in the corresponding double mutants. The phenotypes of plants carrying all eight combinations of wild-type and mutant alleles at the three loci were compared under long- and short-day conditions. This analysis demonstrated that under long photoperiods the long-day pathway promoted flowering most effectively, whereas under short photoperiods the gibberellin pathway had the strongest effect. The autonomous pathway had a weak effect when acting alone under either photoperiod but appeared to play an important role in facilitating the promotion of flowering by the other two pathways. The vegetative phenotype of the triple mutant could be overcome by vernalization, suggesting that a fourth pathway promoted flowering under these conditions. These observations are discussed in light of current models describing the regulation of flowering time in Arabidopsis.     

Flowering responses to light and temperature

Light and temperature signals are the most important environmental cues regulating plant growth and development. Plants have evolved various strategies to prepare for, and adapt to environmental changes. Plants integrate environmental cues with endogenous signals to regulate various physiological processes, including flowering time. There are at least five distinct pathways controlling flowering in the model plant Arabidopsis thaliana: the photoperiod pathway, the vernalization/thermosensory pathway, the autonomous floral initiation, the gibberellins pathway, and the age pathway. The photoperiod and temperature/vernalization pathways mainly perceive external signals from the environment, while the autonomous and age pathways transmit endogenous cues within plants. In many plant species, floral transition is precisely controlled by light signals(photoperiod) and temperature to optimize seed production in specific environments. The molecular mechanisms by which light and temperature control flowering responses have been revealed using forward and reverse genetic approaches. Here we focus on the recent advances in research on flowering responses to light and temperature.     

New insights into gibberellin signaling in regulating flowering in Arabidopsis

In angiosperms,floral transition is a key developmental transition from the vegetative to reproductive growth,and requires precise regulation to maximize the reproductive success.A complex regulatory network governs this transition through integrating flowering pathways in response to multiple exogenous and endogenous cues.Phytohormones are essential for proper plant developmental regulation and have been extensively studied for their involvement in the floral transition.Among various phytohormones,gibberellin(GA)plays a major role in affecting flowering in the model plant Arabidopsis thaliana.The GA pathway interact with other flowering genetic pathways and phytohormone signaling pathways through either DELLA proteins or mediating GA homeostasis.In this review,we summarize the recent advances in understanding the mechanisms of DELLA-mediated GA pathway in flowering time control in Arabidopsis,and discuss its possible link with other phytohormone pathways during the floral transition.     

Does CK2 affect flowering time by modulating the autonomous pathway in Arabidopsis?

CK2 (Casein kinase II), a ubiquitous Ser/Thr kinase, affects multiple developmental and stress response pathways in Arabidopsis, including flowering time under both long- and short-day conditions through the photoperiod and autonomous pathways. CK2 phosphorylates central clock components, CCA1 and LHY, to modulate circadian clock that regulates flowering time through the photoperiod pathway. However, how CK2 regulates flowering time through the autonomous pathway is still unknown. Analyses of phosphorylation sites using several prediction softwares show that most of the autonomous pathway components have multiple CK2 phosphorylation sites. CK2 might phosphorylate any or all of these components to modulate their activity/stability resulting in altered expression of FLC that drives flowering time through the autonomous pathway.     

Understanding gibberellic acid signaling--are we there yet?

The phytohormone gibberellic acid (GA) controls important aspects of plant growth such as seed germination, elongation growth, and flowering. The key components of the GA signaling pathway have been identified over the past 10 years. The current view is that GA binds to a soluble GID1 receptor, which interacts with the DELLA repressor proteins in a GA-dependent manner and thereby induces DELLA protein degradation via the E3 ubiquitin ligase SCF(GID2/SLY1). GA-dependent growth responses can generally be correlated with and be explained by changes in DELLA repressor abundance, where the DELLA repressor exerts a growth restraint that is relieved upon its degradation. However, it is obvious that other mechanisms must exist that control the activity of this pathway. This review discusses recent advances in the understanding of GA signaling, of its homeostasis, and of its cross-talk with other signaling pathways.