探讨水稻光周期开花调控途径.doc

探讨水稻光周期开花调控途径开花是许多高等植物生命周期循环的一个重要过程。植物开花包括开花决定、成花启动、花器官的发育1。植物能否成功地进行有性繁殖取决于精确的开花时间。开花决定受到环境信号和内源遗传信号的控制,是开花基因时空顺序表达的结果。在这些信号中,最重要的一个决定因素是植物对于光周期的反应。光周期指一日之内昼夜长度的相对变化,也即日长。植物对于这种相对变化做出的反应称为光周期现象。早在1852年,英国植物学家Arthur Henfrey就认识到日长对于开花的重要性。20世纪20年代,Garner 和Allard发现光照长度对植物的生长和发育,尤其是对决定植物开花时间起着重要作用。根据对光周期的反应,一般可将植物分为3种:对长日照敏感而成花的为长日照植物;对短日照敏感而成花的为短日照植物;对日照长度不敏感的为光期钝感植物。拟南芥和水稻分别作为开花时间调控研究的长日照植物和短日照植物的模型。目前,对控制拟南芥开花的光周期途径,已经有较为完整和深入的研究。现结合拟南芥有关光周期开花调控的研究进展,就有关决定模式生物水稻开花时间的光周期调控的主要研究进展作简要综述。Blossom is an important process in many higher plant life cycle. Plants blossom including development 1 blossom decided, floral evocation, floral organ. Plants can successfully reproduce sexually depends on the blossom time accurate. Blossom decided is controlled by environmental signals and endogenous genetic signal, is the result of expression of gene sequence blossom time. In these signals, a the most important determinant is plant for photoperiod response. A day night light cycle length variation, are now long. Plant for the relative change make this kind of reaction is called photoperiodism. As early as in 1852, the British botanist Arthur Henfrey recognized the importance of the length of day to blossom. Nineteen twenties, Garner and Allard found that the light length on plant growth and development, especially for the decision to blossom time plant plays an important role. Depending on the photoperiod response, the general can be divided into 3 kinds of plants: flowering of long-day sensitive to long-day plant; to short photoperiod sensitive and flowering of short-day plant; on the day length is not sensitive to photoperiod insensitive plants. Arabidopsis and rice were used as long-day plants blossom time control of short day plant model. At present, to control the photoperiod pathway of Arabidopsis thaliana blossom, there have been more complete and thorough research. Now with the research progress of Arabidopsis photoperiod regulation related to blossom, briefly summarized the major research advances in photoperiodic regulation time blossom relevant decision model organisms in rice.1光周期反应的控制模型The control model of the 1 photoperiodic response植物要对不同的光周期做出反应,那么应该存在某种机制对日长进行度量和记忆。关于植物度量日长存在2个模型:一是外部一致模型。Bnning首先提出,植物存在一个潜在的昼夜节律钟。24h单位的昼夜分为光敏期和暗敏期。当植物在光敏期,昼夜节律钟调节因子的表达达到一个阈值时,若处于光照条件下,则会促进长日照植物开花,而抑制短日照植物开花2,4,5。二是内部一致模型。光信号产生2个不同的周期性功能(促进或抑制),只有当2种节律是同步的时候才会诱导开花,反之则抑制开花。目前,外部一致模型已经被很多研究所证实,得到较多的认同3,5-7。Plants respond to different photoperiods, so there should be some mechanism to day length measurement and memory. On the day of the 2 plant metric model : one is the external consistency model. B nning first proposed plant, there is a potential circadian clock. The 24h unit is divided into light and dark night sensitive period. When the plants in the sensitive period, the expression of circadian clock regulation factor reaches a threshold, if in light conditions, it will promote the long-day plants blossom, and inhibition of short-day plants blossom 2,4,5. Two is the internal consistency model. 2 different periodic function of optical signal ( promote or inhibit), only when the 2 kinds of rhythm is the synchronization time will induce blossom, whereas inhibition of blossom. At present, the external consistency model has been confirmed by many studies, get more approval 3,5-7.2光信号感受和昼夜节律调节The 2 optical signal perception and regulation of circadian rhythms确定日长后,植物还需要区分白昼和黑夜,这主要是通过可以感受光信号的光受体来实现的。已知拟南芥中参与光周期开花时间决定的光受体包括光敏色素和隐花色素。在水稻中,光敏色素是光周期开花决定的主要光受体。水稻只存在3个光敏色素基因Phy A、Phy B和Phy C。Phy A在长日下抑制水稻开花,快速升柱器这同在拟南芥中的作用是相反的。Phy B的功能在拟南芥和水稻间是保守的,都抑制植物开花。Phy C的感光模式同拟南芥不同,在水稻中主要吸收远红光,而在拟南芥中主要吸收红光。此外,水稻中也存在隐花色素OsCRY1和OsCRY2,同拟南芥中的功能相似,均能促进水稻开花。To determine the length of day, plants also need to distinguish between day and night, it is mainly achieved through the light receptor can feel light signal. In the light receptor cycle blossom time decided to include the phytochrome and cryptochrome known arabidopsis. In rice, phytochrome is the main light receptor cycle blossom decision. There are only 3 rice phytochrome gene Phy A, Phy B and Phy C. Phy A inhibits rice blossom in long day, it with the Arabidopsis thaliana have opposite effects. The Phy B function is conserved in Arabidopsis and rice, and inhibition of plant blossom. Photographic mode of Phy C with different Arabidopsis, mainly absorb far-red light in rice, and the main absorption of light in Arabidopsis thaliana. In addition, there are also cryptochrome OsCRY1 and OsCRY2 in rice and Arabidopsis, the similarity in function, can promote the rice blossom.光受体接受光质信号后,将其传递给昼夜节律钟基因,节律基因收到光信号后启动表达。通过昼夜节律钟的输出系统将节律信号输出给下游响应节律的调节基因和开花时间基因。节律基因所表达的蛋白遵从一个自身反馈的环状调节的机制。目前比较清楚存在于拟南芥中响应昼夜节律的反馈调节机制是:TOC1和ELF4促进CCA1、LHY的表达,黎明,CCA1、LHY受到光的刺激开始表达,表达量逐渐增加,同TOC1和ELF4启动子调控元件结合,抑制TOC1和ELF4的表达。夜间,CCA1、LHY的表达降至最低,这时TOC1和ELF4的表达抑制被解除,随着表达的累积又重新起始对CCA1、LHY表达的激活,开始新一轮的循环10-12。Light receptors to receive light signal, pass it to the circadian clock genes, the light signals are received after the start of circadian gene expression. The rhythm signal output to the gene regulation and blossom time gene downstream response rhythm of the circadian clock output by the system. The mechanism of the circadian gene expression protein with a self feedback loop control. At present, more clearly exists in Arabidopsis in response to the circadian rhythm of feedback adjustment mechanism is: TOC1 and ELF4 CCA1, promote the expression of LHY, CCA1, LHY dawn, by the light stimulus onset expression, expression amount increased gradually, with the TOC1 and ELF4 promoter element binding, inhibition of expression of TOC1 and ELF4. At night, the expression of CCA1, LHY to the minimum, then the expression of TOC1 and ELF4 inhibition is relieved, as the expression of cumulative again initial activation of CCA1, LHY expression, began a new round of the cycle 10-12.水稻中只存在1个与拟南芥LHY和CCA1同源的基因OsLHY。该基因的表达也呈现昼夜节律性变化。此外,水稻中也发现存在PPRs基因家族OsPPR,受到昼夜节律的调控。Masaya Murakami等发现1条由OsPRR 73(OsPRR 37)OsPRR 95(OsPRR59)OsPRR1依次顺序表达的基因流。水稻OsPPR基因是否确实参与昼夜节律钟还需要进一步的研究验证。1 genes, OsLHY and Arabidopsis LHY and CCA1 homology existed only in rice. The expression of the gene also showed circadian variation. In addition, rice also revealed the presence of PPRs gene family, OsPPR, is regulated by the circadian rhythm. Masaya Murakami found that 1 by OsPRR 73 ( OsPRR 37 ), OsPRR 95 ( OsPRR59 ) OsPRR1 sequence expression gene flow. The rice OsPPR gene is involved in the circadian clock also need to study further tests.3光周期反应的分子机制The molecular mechanism of photoperiodic response 3昼夜节律信号的产生,使得下游开花基因得到激活或抑制,进而引起水稻开花或迟花。CO是拟南芥中第1个被发现受昼夜节律调控的开花基因。拟南芥通过对CO基因转录的丰度同CO蛋白的稳定性的调节将光信号同昼夜节律钟统一起来。水稻Hd1、CO的同源基因,作为昼夜节律钟的下游基因,通过同样的方式在整合光信号和节律信号上起着重要作用。Hd1 mRNA的表达不受日长的影响,受到光敏色素的介导。Takeshi Izawa13认为Hd1能与光敏色素形成转录复合物或者受到光敏色素的磷酸化;Hd1单独存在时,促进其下游基因FT-like的表达;同光敏色素相互作用时,Hd1作为FT-like的抑制子。在短日条件下,Hd1 mRNA表达的峰值在夜间,而在长日条件下,Hd1 mRNA出现表达的峰值时,正处于光敏期,此时光敏色素同Hd1的作用比短日强,故抑制水稻开花。因此,Hd1是一个双功能基因,短日促进开花,而长日抑制开花。Circadian rhythms are generated signal, makes the downstream blossom gene activation or inhibition, causing rice flowers blossom or later. CO first was found in Arabidopsis thaliana gene is regulated by circadian regulation of blossom. Arabidopsis thaliana by abundance on the transcription of CO gene and CO protein stability regulation of the optical signal with the circadian clock together. Rice Hd1, CO gene, as a downstream gene circadian clock, through the same way in integrated optical signal and the rhythm signal plays an important role. The expression of Hd1 mRNA was not affected by day length, phytochrome mediated. Takeshi Izawa13 think Hd1 and phytochrome transcription complex formation or by phosphorylation of phytochrome; Hd1 exist alone, promote the expression of its downstream gene FT-like; the same phytochrome interacting, Hd1 as an inhibitor of FT-like. In short day conditions, Hd1 mRNA expression peak at night, and in the long day conditions, the Hd1 mRNA expression in the peak, is in the light period, the role of phytochrome Hd1 shorter than the strong, the inhibition of rice blossom. Therefore, the Hd1 is a dual functional gene, short day Promoting Blossom, blossom and long day inhibition.拟南芥CO受到上游GI的调控,诱导1个编码移动开花信号的成花素基因FT的表达。FT蛋白移动至茎尖,同由FD基因编码的转录因子相互作用来激活决定花器官特性的基因AP1,诱导拟南芥开花。Arabidopsis CO is regulated by upstream of GI, expression of FT gene induced into flower 1 coding of moving blossom signal. FT protein is moved to the stem apex, with the interaction of AP1 gene transcription factor encoded by the FD gene to determine the activation of flower organ identity in Arabidopsis, blossom.OsGI是拟南芥GI基因的水稻同源基因。OsGI mRNA的表达受到昼夜钟的控制,在长日照和短日照条件下,表达模式与CO类似。OsGI过表达,不论在何种日长条件下均能引起水稻开花推迟,说明OsGI是水稻开花的抑制因子,而在拟南芥中,GI促进开花。Hd3a、FT的同源基因,由Hd1调控,同FT蛋白类似,Hd3a蛋白是水稻中的成花素,在叶片中表达,通过韧皮部运输至顶端分生组织,启动开花14。FT-like 1(RFT1),是水稻中13个FT-like家族基因中最接近Hd3a的同源基因,能在缺乏Hd3a的时候能促进开花,在短日下作用是冗余的。Reina Komiya等15,16进一步证明,在短日条件下,主要通过Hd3a激活水稻开花。在长日条件下,RFT1则是主要的开花促进因子。Hd3a/RFT1作用于OsMADS14和OsMADS15基因的上游。OsMADS14和OsMADS15基因均为拟南芥AP1基因的同源基因(OsMADS14/RAP1B、OsMADS 15/RAP1A)15,16。这些发现表明光周期开花诱导途径GI-CO-FT-AP1和OsGI-Hd1-Hd3a/RFT1-OsMADS14/OsMADS15,在拟南芥和水稻中是保守的,但是在这些长日照植物和短日照植物中,光周期的反应是有区别的。OsGI is the Arabidopsis GI gene homologous genes in rice. The expression of OsGI mRNA is controlled by the circadian clock, under long-day and short-day conditions, similar expression pattern with CO. Overexpression of OsGI, regardless of the day length conditions can cause delay rice blossom, indicating that OsGI is inhibitory factor of rice blossom, and in Arabidopsis, GI promotes the blossom. Hd3a, FT gene, regulated by Hd1, similar to FT protein, Hd3a protein in rice florigen, expressed in the leaves, through the phloem transport to the apical meristem, start blossom 14. FT-like 1 ( RFT1 ), 13 FT-like family genes in the closest to the Hd3a homologous gene in rice, can promote blossom in the absence of Hd3a, in short, is redundant. Reina Komiya 15,16 further proved, in short day conditions, mainly through the activation of Hd3a rice blossom. Under long day conditions, RFT1 is the key factor to promote blossom. Hd3a/RFT1 effect on upstream of OsMADS14 and OsMADS15 genes. OsMADS14 and OsMADS15 gene was AP1 gene in Arabidopsis thaliana homeobox genes ( OsMADS14/RAP1B, OsMADS, 15/RAP1A ) 15,16. These findings show that periodic blossom induction pathway GI-CO-FT-AP1 and OsGI-Hd1-Hd3a/RFT1-OsMADS14/OsMADS15, in Arabidopsis and rice is conservative, but in the long-day plant and short-day plants, photoperiod response is different.除去这些保守的开花时间基因的调控,水稻中还发现存在独特的调控因子。Ehd1编码一个B-型反应调节子,在拟南芥中不存在同源基因,能独立于Hd1促进水稻开花,作用于Hd3a、RFT1、部分MADS-box基因的上游17。Ghd7编码1个CCT结构域蛋白的基因,同拟南芥没有