脱落酸激素诱导拟南芥幼苗中花青素的合成

脱落酸(abscisic acid,ABA)激素是一类重要的生长调节物质,参与调控植物的多种生理过程。花青素(anthocyanins)是植物次生代谢产生的类黄酮化合物,对植物的生长发育和逆境胁迫响应有重要作用。该文以拟南芥(Arabidopsis thaliana)为研究对象,探讨ABA信号对花青素生物合成的调控功能和作用机制。结果表明:外源施加ABA显著提高野生型幼苗茎尖中花青素的积累。相一致的是,ABA能诱导某些与花青素合成相关的转录因子及合成酶基因的表达。遗传学分析发现,ABA诱导花青素合成部分依赖于MBW复合体中的核心转录因子,如TTG1、TT8及MYB75等。初步机制研究揭示,ABA信号途径中的bZIP类转录因子ABI5能与TTG1、TT8及MYB75等相互作用形成蛋白复合物。综上结果认为,ABA信号诱导拟南芥幼苗中花青素的积累,并可能通过ABI5与MBW复合体协同作用调控花青素的合成。     

MBW复合体在植物花青素合成途径中的研究进展

花青素是植物呈色的一种关键物质,它既能赋予植物丰富的色彩,又具有广泛的生物学功能,如抗氧化、抗紫外线、抗病虫害等。植物花青素生物合成途径由一系列结构基因和调节基因协同完成。结构基因表达受MYB、bHLH和WD40类转录因子以其组成的MBW复合体调控。综述了近年来MYB、bHLH和WD40类转录因子及MBW复合物在植物花青素合成中的功能研究进展,总结了花青素合成的各种生物过程和调控网络。     

拟南芥生物钟分子机制研究进展

本文主要概述了目前拟南芥生物钟分子机制的研究进展。生物钟通过调控导引节律的相位来调节植物的生理活动。拟南芥生物钟由CCA1、LHY和TOC1 3个主要基因构成了一个稳定的负反馈环,来调节昼夜节律中各个基因如APRR/TOC1 5重奏的作用, 从而调控昼夜节律的相位。在开花的光周期调控中, 提出了外协和模型, 其中的关键基因是CO , 它与拟南芥的开花时间直接相关。     

拟南芥生物钟分子机制研究进展

本文主要概述了目前拟南芥生物钟分子机制的研究进展.生物钟通过调控导引节律的相位来调节植物的生理活动.拟南芥生物钟由CCAJ、LHy和TOCJ 3个主要基因构成了一个稳定的负反馈环,来调节昼夜节律中各个基因如APRR/TOC15重奏的作用,从而调控昼夜节律的相位.在开花的光周期调控中,提出了外协和模型,其中的关键基因是CO,它与拟南芥的开花时间直接相关.     

硫化氢信号能够通过生物钟调控拟南芥对冷胁迫的响应

硫化氢(hydrogen sulfide, H_2S)是继一氧化氮(nitric oxide, NO)与一氧化碳(carbon oxide, CO)之后的第3种气体信号分子,在动植物中均发挥着重要的生理功能。生物钟是生物体的内在计时器,对动植物适应环境和生长发育至关重要。鉴于H_2S与生物钟调控的生理过程有较大的相关性,本文以拟南芥(Arabidopsis thaliana)为实验材料,对二者之间的关系进行了探索。结果发现,外源NaHS(H_2S供体)处理能够上调生物钟相关基因CCA1(circadian clock associated 1)和PRR9(pseudo-response regulator 9)的表达,而且在H_2S生成关键酶编码基因缺失的双突变体lcd/des1中,CCA1与PRR9的峰值表达时间明显滞后。CBFs(c-repeat binding factors)是受CCA1调控的冷胁迫响应基因,其表达也受H_2S的调控。lcd/des1中CBF1和CBF3的峰值表达时间延迟,同时在lcd/des1中CBF1、CBF2和CBF3都下调表达。lcd/des1幼苗对冷胁迫表现出更高的敏感性。本文也对拟南芥内源H_2S生成关键酶L-半胱氨酸脱硫基酶(L-cysteine desulfhydrase, LCD)与脱硫基酶1(desulfhydrase 1, DES1)编码基因的转录水平节律性进行了初步的探索。LCD的表达在1 d内未见明显的变化,而DES1的表达有明显的节律性,在早上8:00达到峰值。综上所述,H_2S能够通过调节CCA1与PRR9基因的表达调控生物钟,进而影响下游靶标CBFs基因的表达以增加拟南芥对冷胁迫的耐受性。     

CONSTANS-LIKE 7过量表达降低白光和蓝光下拟南芥幼苗花青素及叶绿素的含量

以拟南芥野生型(WT)、突变体col7、以及COL7过量表达转基因株系COL7-OX-10和COL7-OX-11为实验材料,观察比较了白光、红光以及蓝光下,生长在MS培养基上的幼苗表型,以及蓝光下生长在0、100 mmol/LNaCl MS培养基上的幼苗表型。结果发现,过量表达株系幼苗在白光和蓝光下出现黄化现象,并且NaCl处理导致蓝光下幼苗黄化现象更加严重。检测幼苗的花青素及叶绿素的含量,发现白光和蓝光下,过量表达株系幼苗中花青素和叶绿素的含量明显降低,其中蓝光下生长在含100 mmol/L NaCl的MS培养基上幼苗的花青素和叶绿素含量下降尤为明显,表明COL7可能参与调控花青素和叶绿素的合成,并依赖于蓝光。     

花青素合成中的WD40蛋白

本文着重概述了不同植物中花青素合成WD40类转录调控因子的研究进展。     

受光调节的拟南芥锌指蛋白DBB（DoubleB-Box）亚家族基因的转录表达

整合微阵列数据和采用实时荧光定量PCR分析拟南芥锌指蛋白DBB亚家族中8个基因在不同光周期和不同光质条件下转录表达的结果表明,在长日和短目照条件下该家族中6个基因的转录都具有光周期节律性,并且其中4个基因的表达受光诱导,有1个基因的表达受光抑制,1个基因的表达不受光调节。     

拟南芥转录因子Ethylene-insensitive3（EIN3）抑制花青素的合成

Ethylene-insensitive3（EIN3）和 EIN3-like1（EIL1）蛋白是乙烯信号转导途径中一类重要的核转录因子。花青素是植物体中的一类水溶性天然色素,在植物的许多生理过程中起重要作用。本研究以拟南芥双突变体ein3-1eil1-3为研究材料,通过RT-PCR技术确定了拟南芥双突变体ein3-1eil1-3中EIN3和EIL1基因均已被敲除,单突变体ein3-1中的EIN3基因被敲除。通过肉眼定性观察发现突变体ein3-1eil1-3的种子和叶片内均呈紫色。通过紫外分光光度计定量分析发现,花青素积累量也明显比突变体ein3-1和野生型多。通过GUS染色发现EIN3启动子主要在花、柱头、成熟花粉、种子胚和果荚等组织中有较强的表达。这与突变体ein3-1eil1-3的种子和叶片内均呈紫色并花青素含量增高一致。因此,拟南芥转录因子EIN3可能与EIL1共同参与抑制花青素的合成。     

拟南芥WD40蛋白

拟南芥植物中已经鉴定出十几个WD40蛋白.本文介绍这些蛋白在拟南芥生长发育过程中的功能及其分子机制的研究进展.     

A chromatin-dependent mechanism regulates gene expression at the core of the Arabidopsis circadian clock

The mechanisms of circadian clock function in Arabidopsis rely on the complex relationships among core clock components. The current model of the Arabidopsis oscillator comprises a myriad of repressors but the mechanisms responsible for activation remain largely unknown. In our recent studies, we have demonstrated that the rhythms in H3 acetylation (H3ac) and H3K4 trimethylation (H3K4me3) are a key mechanism at the positive arm of the oscillator. H3K4me3 rhythmic accumulation is delayed compared to that of H3ac, which opens the possibility for separate roles for each mark. Indeed, the use of inhibitors that block H3K4me3 accumulation was concomitant with increased clock repressor binding, suggesting that H3K4me3 might control the timing from activation to repression. Plants mis-expressing the histone methyltransferase SET DOMAIN GROUP 2 (SDG2/ATXR3) displayed altered H3K4me3 accumulation, oscillator gene expression and clock repressor binding, suggesting that SDG2/ATXR3 is a key component contributing to proper circadian expression.     

siRNA介导的ERA1表达下调对拟南芥抗旱性的影响

ERA1是控制植物气孔开闭的一个重要基因,根据其保守域构建RNA干扰(RNAi)载体并转化拟南芥,考察转基因植株的生长、气孔导度、离体叶片失水率以及ERA1和相关基因表达,探讨siRNA介导的ERA1表达下调对拟南芥抗旱性的影响。结果表明:转基因拟南芥株系中ERA1的表达受到明显抑制,其离体叶片失水率低于野生型,但并未出现ERA1缺失突变体的负面生长表型;转基因株系对ABA处理比野生型更敏感,其ABA处理株的根长显著变短,气孔孔径更小;转基因株ABI1、ABI2、ATHB6的表达量降低,而RAB18、RD29B、ADH1的表达量升高,siRNA介导的ERA1表达下调可能会激活RAB18、RD29B等逆境响应元件。研究发现,采用RNAi技术可以有效下调ERA1表达,在没有过多负面生长表型的前提下提高拟南芥的抗旱性,且ERA1表达下调可能通过ABA途径正面影响拟南芥的抗旱性。     

Sequence analysis of two null-mutant alleles of the single Arabidopsis Adh locus

Summary Data presented in this paper deal with a further molecular characterization of 2 out of 32 EMS-induced Arabidopsis ADH null mutants that we isolated previously. In order to localize and characterize each mutation at the molecular level, we have cloned and completely sequenced the R002 and R006 null mutant alleles. For mutant R002, which does not contain any detectable levels of ADH protein and mRNA, we have found that the mutation is due to a single C to T base pair substitution in the reading frame; this leads to the incorporation of a TAG stop codon (amber nonsense mutation). For mutant R006, which contains normal levels of inactive protein and mRNA levels, we found a G to A base pair transition. This gives rise to a Cys to Tyr amino acid substitution in the active site of the ADH enzyme.Abbreviations CRM cross-reacting material - 2,4-D 2,4-dichlorophenoxyacetic acid - EMS ethylmethanesulfonate     

Abscisic acid-insensitive mutations provide evidence for stage-specific signal pathways regulating expression of an Arabidopsis late embryo genesis-abundant (lea) gene

An Arabidopsis homolog of the abscisic acid (ABA)-inducible cotton D19 and wheat Em genes was cloned and its expression assayed at two developmental stages in wild-type, ABA-deficient (aba) and three ABA-insensitive (abi) lines of Arabidopsis thaliana. Expression of this gene was reduced slightly in seeds of aba mutants and approximately ten-fold in abi3 mutants, but seed expression was not decreased in either abi1 or abi2 monogenic mutants. In contrast, the abi1 and abi2 mutants showed a very slight reduction of ABA inducibility in 8-day-old plants, while the responses of aba and abi3 mutants were comparable to that of wild type. Although previous studies have shown that none of the abi mutations show completely stage-specific effects, the results reported here indicate that the importance of each of the ABI loci in regulating this single gene is stage-dependent. Furthermore, the fact that none of the abi mutations show more than minor effects on exogenous ABA inducibility of the Arabidopsis D19/Em homolog in young plants suggests that an additional ABA signalling pathway may be operating during vegetative growth.     

拟南芥基因密码子偏爱性分析

密码子偏爱性对外源基因的表达强度有一定影响,特别是编码蛋白质N端7～8个氨基酸残基的密码子.通过对拟南芥染色体中26 827个蛋白质对应的基因密码子进行分析,得到了编码氨基酸的61种密码子在拟南芥中的使用频率,并与大肠杆菌和哺乳动物进行了比较,结果表明三者间的密码子偏爱性有较大差异.这一分析结果对于动物基因在植物中的表达,及植物基因在微生物中的表达具有一定指导意义.同时提供了一种直接以XML文档为数据源解析巨型XML格式染色体数据的方法.     

Genetic and molecular characterization of embryonic mutants identified following seed transformation in Arabidopsis

Over 5000 transgenic families of Arabidopsis thaliana produced following seed transformation with Agrobacterium tumefaciens were screened for embryonic lethals, defectives, and pattern mutants. One hundred and seventy-eight mutants with a wide range of developmental abnormalities were identified. Forty-one mutants appear from genetic studies to be tagged (36% of the 115 mutants examined in detail). Mapping with visible markers demonstrated that mutant genes were randomly distributed throughout the genome. Seven mutant families appeared to contain chromosomal translocations because the mutant genes exhibited linkage to visible markers on two different chromosomes. Chromosomal rearrangements may therefore be widespread following seed transformation. DNA gel blot hybridizations with 34 tagged mutants and three T-DNA probes revealed a wide range of insertion patterns. Models of T-DNA structure at each mutant locus were constructed to facilitate gene isolation. The value of such models was demonstrated by using plasmid rescue to clone flanking plant DNA from four tagged mutants. Further analysis of genes isolated from these insertional mutants should help to elucidate the relationship between gene function and plant embryogenesis.     

拟南芥抵抗丁香假单胞杆菌过程中AZI1基因功能研究

AZI1属于脂转移蛋白家族,它在拟南芥抵抗病原菌侵染过程中可能起着传递信号物质的作用。该实验以过表达和T-DNA插入突变体及野生型拟南芥植株为材料,通过RNA印迹、蛋白质免疫印迹和原位免疫组织化学方法,研究了拟南芥壬二酸诱导基因AZI1对丁香假单胞杆菌的抗性功能。结果表明:(1)AZI1基因可以被丁香假单胞杆菌、H2O2和乙烯利诱导,它可能参与水杨酸和乙烯介导的抗菌途径。(2)蛋白质免疫印迹实验结果显示,丁香假单胞杆菌侵染叶片的叶柄渗出液中存在AZI1蛋白及其同源物EARLI1,并能够与其他蛋白质形成复合体,说明AZI1有可能通过维管组织移动到个体的其他部位,与信号分子的转移有关。(3)AZI1及其同源物EARLI1主要在花序茎的木质化部位表达,过表达AZI1基因能够促进木质素的合成,提高拟南芥对丁香假单胞杆菌的抗性。