Light-dependent suppression of COP1 multimeric complex formation is determined by the blue-light receptor FKF1 in Arabidopsis

CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), a multifunctional E3 ligase protein with many target proteins, is involved in diverse developmental processes throughout the plant's lifecycle, including seed germination, the regulation of circadian rhythms, photomorphogenesis, and the control of flowering time. To function, COP1 must form multimeric complexes with SUPPRESSOR OF PHYA1 (SPA1), i.e., [(COP1)₂(SPA1)₂] tetramers. We recently reported that the blue-light receptor FKF1 (FLAVIN-BINDING, KELCH REPEAT, F-BOX1) represses COP1 activity by inhibiting its homodimerization, but it is not yet clear whether FKF1 affects the formation of COP1-containing multimeric complexes. To explore this issue, we performed size exclusion chromatography (SEC) of Arabidopsis thaliana proteins and found that the levels and composition of COP1-containing multimeric complexes varied throughout a 24-h period. The levels of 440–669?kDa complexes were dramatically reduced in the late afternoon compared to the morning and at night in wild-type plants. During the daytime, the levels of these complexes were reduced in FKF1-overexpressing plants but not in fkf1-t, a loss-of-function mutant of FKF1, suggesting that FKF1 is closely associated with the destabilization of COP1 multimeric protein complexes in a light-dependent manner. We also analyzed the SEC patterns of COP1 multimeric complexes in transgenic plants overexpressing mutant COP1 variants, including COP1^L105A (which forms homodimers) and COP1^L170A (which cannot form homodimers), and found that COP1 multimeric complexes were scarce in plants overexpressing COP1^L170A. These results indicate that COP1 homodimers serve as basic building blocks that assemble into COP1 multimeric complexes with diverse target proteins. We propose that light-activated FKF1 inhibits COP1 homodimerization, mainly by destabilizing 440–669?kDa COP1 complexes, resulting in the repression of CONSTANS-degrading COP1 activity in the late afternoon in long days, but not in short days, thereby regulating photoperiodic flowering in Arabidopsis.     

芥菜BjuWRKY75基因表达及其与开花整合子BjuFT互作

芥菜(Brassica juncea)是十字花科芸薹属一年或二年生蔬菜,其产品器官的产量和品质会受到开花时间的影响。WRKY家族成员具有响应生物和非生物胁迫、发育调控和信号转导等作用。WRKY75是WRKY家族中能够调节开花的重要成员,但在芥菜中的开花调控机制还未见报道。本研究克隆了芥菜BjuWRKY75基因,发现其编码蛋白具有高度保守的WRKY结构域,属于Ⅱ类WRKY蛋白,与黑芥BniWRKY75同源性最高。BjuWRKY75在花中表达丰度显著高于叶和茎,并且在叶中表达较为稳定。BjuWRKY75定位于细胞核,能够与含有W-box应答元件的开花整合子BjuFT的启动子相互作用,且能转录激活下游基因表达。BjuWRKY75转入拟南芥可显著提早开花。综上说明,BjuWRKY75能够直接靶向BjuFT从而促进开花。这为深入研究BjuWRKY75开花分子调控奠定了基础。     

ECT 6和ECT 7调控拟南芥开花时间的研究北大核心CSCD

m^(6)A修饰是mRNA上含量最丰富的一种修饰,调控mRNA的命运决定。YT521-B同源性(YTH)结构域蛋白是一类典型的m^(6)A“阅读器”,能识别并结合m^(6)A,完成基因的转录后调控。为了探究拟南芥YTH结构域蛋白ECT6和ECT7的功能及其分子机制,该研究对ect 6、ect 7和ect 6 ect 7双突变体进行基因型和半定量PCR鉴定及开花表型观察,通过细胞学观察分析ECT6和ECT7的亚细胞定位,并采用qRT-PCR检测开花关键基因的表达量。结果显示:(1)ECT 6基因组包含5个外显子和4个内含子,ect 6突变体分别插入在ECT 6基因的第3和第5外显子;ECT 7基因组包含6个外显子和5个内含子,ect 7突变体分别插入在ECT 7基因的第4和第6外显子。(2)突变体ect 6和ect 7均为完全敲除的功能缺失突变体,在长日照下二者均表现出开花提前和叶片数减少。(3)在长日照和短日照下ect6 ect7双突变体均表现出开花提前和叶片数减少。(4)开花抑制基因FLC和成花素基因FT是关键的开花调控因子,qRT-PCR分析结果显示,在ect 6 ect 7双突变体中,FLC的表达水平降低,FT的表达水平升高,且春化通路基因VIN 3、VRN 2、VRN 5和自主通路基因FVE的表达水平也显著升高。(5)ECT6和ECT7均定位于细胞核和细胞质中。     

世界上已知维管植物有多少种? 基于多个全球植物数据库的整合

维管植物是地球上生物多样性的重要组成部分, 拥有超过200年的研究历史。然而, 世界上有多少种维管植物, 其中有多少种已被发现和描述等问题迄今仍未很好回答。本文整合分析了全球4个主要植物数据库, 以期回答全球已发现和描述了多少物种的问题。结果表明, 全球已发现和描述的维管植物有376,366种(包括自然杂交种)。排除自然杂交种后, 全球共包含369,054种维管植物, 其中广义蕨类植物13,810种, 裸子植物1,172种, 被子植物354,072种。我们的结果比已有的4个数据库中的任何一个的物种数都至少要多17,700种。     

北京昌平区景观复杂度和局地管理对苹果园传粉蜂多样性的影响

传粉蜂为作物生产和粮食安全提供重要的生态系统服务。随着农业经济的不断发展,土地利用强度加剧,大量自然或半自然生境已经转变为农业用地。景观均质化和集约化管理导致野生蜂多样性下降,从而威胁到农业可持续生产。本研究以北京市昌平区苹果园为对象,探究景观复杂度(半自然生境比例)、局地管理强度(地表开花植物多样性和土壤全氮)及其交互作用对传粉蜂多样性的影响。结果表明: 共捕获传粉蜂8642头,其中人工蜂5125头,野生蜂分属5科14属49种3517头。传粉蜂多样性对景观复杂度和局地管理强度响应的最优尺度在500 m。样点半径500 m范围内,总传粉蜂和野生蜂多度随周围半自然生境增加均呈显著上升趋势。景观复杂度与开花植物多样性的交互作用对总传粉蜂和野生蜂物种丰富度有显著影响。当景观复杂度较低时(≤29.9%),总传粉蜂和野生蜂物种丰富度与开花植物多样性呈显著正相关;而当景观复杂度较高时(>29.9%),总传粉蜂和野生蜂物种丰富度与开花植物多样性呈显著负相关。此外,人工蜂多度随果园内局地开花植物多样性和土壤全氮增加呈显著升高趋势。土壤全氮与开花植物多样性的交互作用对人工蜂多度有显著影响。当土壤全氮含量较低时(≤1.9 g·kg^-1),人工蜂多度与开花植物多样性呈显著正相关;而当土壤全氮含量较高时(>1.9 g·kg^-1),人工蜂多度与开花植物多样性呈显著负相关。农业景观中半自然生境比例的增加有利于提高野生蜂多度,而地表开花植物多样性可以促进传粉蜂多样性,但是受到景观尺度(半自然生境比例)和局地尺度(氮肥施用)的影响。因此,农业景观中野生蜂多样性的维持需要综合考虑多尺度因素来制定保护策略。尽可能保留更高比例的耕地仍然是生产的长期需求,而保持中等景观复杂度,增加地表开花植物多样性,减少氮肥施用量将是促进苹果园传粉蜂多样性的有效方式。     

光周期影响植物花时的分子机制

日长感知是植物所具有的重要的生物学功能,光周期是决定植物开花时间的关键环境因子之一。光周期的暗期长度是决定植物成花的决定因素。通过形态学和遗传学研究,揭示了光周期敏感的一些遗传特性,并确定了光敏感指数的标准。构建了光周期性状相关的分子标记连锁图谱,是进行基因定位、克隆和分子标记辅助选择的重要基础工作,也是进行光周期机理研究的有效途径。通过模式植物拟南芥的研究,建立了一个长日促进开花的遗传途径。它的机理可以综合为:光和感光信息体系结合产生信号并传导,CO表达被激活。在每日日长循环、光体系及遗传背景的变化基础上,如果CO的表达和日长状况协调,那么CO激活FT表达,随后开花。水稻、小麦、玉米等作物在光周期机理研究方面也取得了一些进展。     

珠三角桃树摘叶期和气象因子对桃花应节盛花的影响

根据不同摘叶期、桃花盛花期观测资料和同期气象资料,研究了摘叶和气象因子对桃花应节盛花的影响.结果表明,摘叶期和盛花期的关系以分段线性方程拟合效果最佳,12月12日以前,线性方程的斜率为0.7594,12月12日以后,线性方程近似水平.11月中旬至盛花期平均气温、花前50 d总日照时数是桃花盛花期出现迟早的关键气象因子.它们与摘叶期至盛花期天数的相关系数分别为-0.62和-0.45,经检验,差异达到显著水平.在此基础上,利用多元线性回归分析,建立了桃花适宜摘叶期预测模型.样本回代检验79.2%的样本误差在2 d以内,2004年试报效果也较好.     

生殖物候与草甸草地多年生植物的消长

尽管草地管理研究较多,但从物候学进行的研究很少.目前尚未见到关于开花期和结实期如何影响科尔沁草原植物地位的报道.报道了科尔沁草甸草原34种多年生植物的始花期和果实始成熟期与其在割草和放牧利用下的消长关系.结果表明：（1）3种植物在4月、13种在5月、10种在6月、7种在7月、1种在8月开始开花.3种在5月、14种在6月、11种在7月、5种在8月、1种在9月开始出现成熟果实.（2）与割草草地相比,始花期晚的植物在自由放牧草地中频度和多度趋于减少,果实始成熟期晚的植物也表现同样的趋势.（3）当将具有营养繁殖能力的植物排除后,与割草草地相比,始花期和果实始成熟期晚的植物在自由放牧草地中频度和多度减少的趋势更强.（4）为了使植物完成生活史,割草应在秋季大多数植物结实期结束时实施.（5）为保证大多数禾本科植物顺利完成生活史,应在大多数植物开始分蘖时开始放牧,进入花蕾期停止放牧,至结实期晚期又开始放牧.     

The R1 gene for late blight resistance in early and late maturing potato cultivars

The method of polymerase chain reaction was used to amplify a fragment of the LZ-NBS-LRR receptor kinase gene R1; the gene was transferred into potato (Solanum tuberosum) from its wild-growing relative S. demissum and confers the race-specific recognition of the pathogen Phytophthora infestans. To verify this method as a test for the presence of the late blight resistance gene R1, the amplified genome fragment was cloned from the potato hybrid comprising the germplasm of S. demissum. The primary structure of this fragment, which corresponded to the receptor domain of kinase, did not practically differ from the matching sequence in S. demissum. In addition, the method was verified by scoring the set of plant differentials, wherein the presence of R1 was established with race-specific Phytophthora isolates. By screening 70 potato cultivars, we established a significant relationship between the presence of the gene R1 fragment and the phenotypic characters of late blight resistance and late maturity. This evidence supports the idea that R1 was introgressed from short-day S. demissum into potato plants together with some gene(s) conferring late transition to flowering.     

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.