DNA甲基化介导的植物逆境应答和胁迫记忆

DNA甲基化是表观遗传修饰的重要形式,它不仅对植物生长发育具有重要的调控作用,而且参与了植物对各种逆境胁迫的应答过程。逆境通过改变植物DNA基化水平和模式对胁迫应答基因网络进行调控,从而增强当代或后代对逆境的适应性。本文主要对DNA甲基化介导的生物和非生物逆境应答及植物胁迫记忆的最新研究进展进行综述,同时对该领域研究中存在的问题和未来研究的方向进行讨论与展望。     

DNA甲基化模式及其在癌症中的作用

随着对癌症研究的不断深入,表观遗传调控在癌症发生发展中的作用也越来越受到人们的关注。DNA基化作为一种重要的表观遗传修饰机制,在基因表达调控中起着十分重要的作用。该文对DNA基化模式及其在癌症中的作用作了综述,并对DNA甲基化作为癌症早期诊断的生物标记以及癌症表观治疗的新策略作了总结和展望。     

植物大片段 DNA 的研究进展

植物大片段 DNA 的研究成为了基因组学研究的一个重要方面．对它的研究得益于容纳大片段 DNA 片段载体的发展．对构建植物大片段 DNA 的载体、植物大片段 DNA 的提取方法、植物大片段 DNA 的主要应用领域的最新进展进行了介绍．     

DNA甲基化与植物抗逆性研究进展

DNA甲基化是真核细胞基因组重要修饰方式之一.DNA甲基化通过与转录因子相互作用或通过改变染色质结构来影响基因的表达,从表观遗传水平对生物遗传信息进行调节,在生长发育过程中起着重要的作用,而且植物DNA甲基化还参与了环境胁迫下的基因表达调控过程.本文对植物DNA甲基化的产生机制、功能,以及DNA甲基化在植物应对逆境胁迫中的作用进行综述,以更好地理解植物DNA甲基化及其对环境胁迫的响应,为植物抗逆性研究及作物遗传改良提供理论参照.     

MSAP技术及其在植物遗传学研究中的应用

DNA甲基化是表观遗传学的重要组成部分,在调节植物基因表达、生长发育和抵御逆境等方面起着重要作用.随着对DNA甲基化研究的不断深入,基于PCR检测DNA甲基化状态的技术DNA甲基化敏感扩增多态性(MSAP)由于其检测多态性高,操作简单等优点被广泛应用于植物种质资源鉴定、植物改良、种群遗传结构分析及植物进化研究等遗传学各个领域.该文综述了MSAP技术的原理、实验方法以及其在植物遗传学研究中的应用,并对其今后应用前景进行了展望.     

湖泊沉积植物古DNA的现代过程

对植被历史变化过程的研究是理解现代植被组成、分布及其对全球变化响应的基础。近年来, 随着分子古生态学的发展, 分析沉积介质中的陆生植物古DNA信号, 以研究植被及植物多样性演变的历史过程正在成为研究热点, 湖泊沉积植物古DNA已成为古植被和古生态学研究的成熟代用指标。然而与第四纪孢粉分析相比较, 湖泊沉积植物古DNA的现代过程依然不明确, 成为其进一步发展和应用的限制因素。基于此, 该文综述了湖泊沉积植物古DNA技术研究进展, 尝试阐明湖泊沉积植物古DNA的现代过程, 包括植物DNA的来源、沉积和保存过程及其影响因素, 以及植物DNA与现代植被的关系等。已有研究表明, 湖泊沉积植物古DNA主要来自湖泊周边或流域范围, 其丰度和组成除受到源植物生物量的影响外, 同样受到沉积物的搬运和沉积过程中DNA降解作用、土壤以及沉积物中颗粒的吸附过程和稀释作用等因素的影响。湖泊沉积物中植物DNA的保存则主要受到微生物活动、湖水的化学性质(电导率和pH值)、湖泊深度、沉积物组成等一系列生物与非生物因素的共同影响。湖泊沉积植物古DNA可以揭示其沉积时代的植物群落类型以及气候环境信息, 但目前并不能够用来定量重建古植被变化过程。鉴于湖泊沉积植物古DNA现代过程的复杂性, 对研究结果的解释要格外小心。与孢粉分析相比, 湖泊沉积植物古DNA研究仍处于起步阶段, 但随着分子生物技术的进步、实验设计的优化、物种条形码的扩充及参考数据库的完善等, 以DNA宏条形码和宏基因组学为主要技术手段的植物古DNA技术, 必将推动我国植物古生态研究的进一步发展。     

植物DNA甲基化作用机制的研究进展

DNA甲基化是表观遗传学的一种重要修饰形式,也是一种重要的基因表达调控机制。DNA甲基化的异常模式可导致植物生长发育异常。文中从植物DNA甲基化模式入手,对DNA甲基化在调控基因表达和维持基因组稳定性的分子功能、DNA甲基化在植物发育、参与植物对生物和非生物胁迫的反应等方面的相关研究进行回顾和总结,为深入了解DNA甲基化的作用机制并将DNA甲基化应用于植物新品种的培育和遗传改良研究提供一定的参考。     

DNA 甲基化与植物生长发育的表观遗传调控研究进展

DNA 甲基化是表观遗传学的一种重要修饰形式, 已有大量研究证实其在植物的生长发育过程中起着重要作用。从植物 DNA 甲基化入手, 简要综述近年来 DNA 甲基化与生长发育、逆境胁迫表观遗传调节关系的研究结果,并对存在的问题进行讨论, 旨在进一步理解 DNA 甲基化在植物上的作用, 为植物育种提供指导。     

土壤环境中转基因植物重组DNA持留与水平转移研究进展

基因水平转移(horizontal gene transfer,HGT)是转基因植物环境风险评估的重要内容之一。转基因植物重组DNA通过根系分泌、花粉、残体等方式向土壤环境释放。已有研究表明,外源重组DNA很可能被土壤微生物通过同源重组的方式整合到基因组中,直接或间接地造成微生物群落结构和功能的改变,这将造成土壤生态环境系统的改变。本文论述了转基因植物重组DNA在土壤环境中的持留、水平转移及其影响因素和相关检测方法,讨论了转基因植物重组DNA在土壤环境中持留和水平转移的研究重点,并对其研究方法进行比较分析,提出今后的重点研究方向和方法,以期为转基因植物风险评估和安全管理提供技术支撑。     

植物中DNA甲基化模式及其相关机制

DNA甲基化是表观遗传修饰的重要形式之一,是植物中较早发现的DNA共价修饰方式。在植物的正常生长发育中,DNA甲基化与植物基因组维持、体细胞无性系变异、外来基因防御、内源基因的表达、转基因沉默以及基因印迹之间有着极大的关系,因此,植物DNA甲基化的研究对植物基因工程的发展有着举足轻重的作用。本文介绍了参与DNA甲基化的各种酶和蛋白质,阐述了DNA甲基化相关机制的最新研究进展。     

The downregulation of FLOWERING LOCUS C (FLC) expression in plants with low levels of DNA methylation and by vernalization occurs by distinct mechanisms

FLOWERING LOCUS C (FLC), a repressor of flowering, is a major determinant of flowering time in Arabidopsis. FLC expression is repressed by vernalization and in plants with low levels of DNA methylation, resulting in early flowering. This repression is not associated with changes of DNA methylation within the FLC locus in either vernalized plants or plants with low levels of DNA methylation. In both cases, there is a reduction of histone H3 trimethyl-lysine 4 (K4) and acetylation of both histones H3 and H4 around the promoter-translation start of FLC. The expression of the two genes flanking FLC is also repressed in both conditions and repression is associated with decreased histone H3 acetylation. The changes in histone modifications at the FLC gene cluster, which are similar in vernalized plants and in plants with reduced DNA methylation, must arise by different mechanisms. VERNALIZATION 1, VERNALIZATION 2 and VERNALIZATION INSENSITIVE 3 modulate FLC expression in vernalized plants; these proteins play no role in the downregulation of FLC in plants with low levels of DNA methylation. Chimeric FLC::GUS transgenes respond to vernalization but these same transgenes show a position-dependent response to low levels of DNA methylation. In plants with reduced DNA methylation, expression of the five MADS AFFECTING FLOWERING (MAF) genes is repressed, suggesting that DNA methylation alters the expression of a trans-acting regulator common to FLC and members of the related MAF gene family. Our observations suggest that DNA methylation is not part of the vernalization pathway.     

植物DNA甲基化及其研究策略

DNA甲基化是表观遗传学研究的热点问题之一,植物DNA甲基化的研究对植物研究领域的发展有着举足轻重的作用。本文阐述了植物DNA甲基化的相关机制,其中包括RdDM（RNA—dependent DNA methylation）、DNA甲基化与组蛋白修饰以及DNA去甲基化等近几年研究的热点问题：讨论了DNA甲基化在植物发育中的功能（包括基因组防御和调控基因表达）、DNA甲基化与转基因沉默的关系以及其在表观遗传学中的地位。最后就目前国内外研究植物DNA甲基化所采取的常用策略,即高效液相色谱法、亚硫酸盐测序法、甲基化敏感的限制性内切酶结合Southern杂交分析法和MSAP（methylation—sensitive amplified polymorphism）法进行了详尽的介绍和讨论。     

植物DNA甲基化及其研究策略

DNA甲基化是表观遗传学研究的热点问题之一, 植物DNA甲基化的研究对植物研究领域的发展有着举足轻重的作用。本文阐述了植物DNA甲基化的相关机制, 其中包括RdDM(RNA-dependent DNA methylation)、DNA 甲基化与组蛋白修饰 以及DNA 去甲基化等近几年研究的热点问题; 讨论了DNA甲基化在植物发育中的功能(包括基因组防御和调控基因表达)、DNA甲基化与转基因沉默的关系以及其在表观遗传学中的地位。最后就目前国内外研究植物DNA甲基化所采取的常用策略,即高效液相色谱法、亚硫酸盐测序法、甲基化敏感的限制性内切酶结合Southern杂交分析法和MSAP(methylation-sensitive amplified Polymorphism)法进行了详尽的介绍和讨论。     

植物DNA甲基化及胁迫诱导的变异

DNA中碱基的化学修饰近年来一直是生命科学领域研究的热点之一。DNA甲基化是一种常见的表观遗传现象,它能在不改变DNA序列的前提下改变遗传表型。各种胁迫因素能诱导植物DNA甲基化产生变异,但其应答胁迫机制仍然未知。本文对植物DNA甲基化研究进展进行了综述,结合本课题组的研究结果,对7Li离子束注入、~(60)CO-γ射线诱变诱导产生的DNA甲基化变异进行了报道,以期为DNA甲基化可能参与涉及植物的表型可塑性提供一定的依据。     

Gardening the genome: DNA methylation in Arabidopsis thaliana

DNA methylation has two essential roles in plants and animals - defending the genome against transposons and regulating gene expression. Recent experiments in Arabidopsis thaliana have begun to address crucial questions about how DNA methylation is established and maintained. One cardinal insight has been the discovery that DNA methylation can be guided by small RNAs produced through RNA-interference pathways. Plants and mammals use a similar suite of DNA methyltransferases to propagate DNA methylation, but plants have also developed a glycosylase-based mechanism for removing DNA methylation, and there are hints that similar processes function in other organisms.     

DNA methylation in plants: relationship to small RNAs and histone modifications, and functions in transposon inactivation

DNA methylation is a type of epigenetic marking that strongly influences chromatin structure and gene expression in plants and mammals. Over the past decade, DNA methylation has been intensively investigated in order to elucidate its control mechanisms. These studies have shown that small RNAs are involved in the induction of DNA methylation, that there is a relationship between DNA methylation and histone methylation, and that the base excision repair pathway has an important role in DNA demethylation. Some aspects of DNA methylation have also been shown to be shared with mammals, suggesting that the regulatory pathways are, in part at least, evolutionarily conserved. Considerable progress has been made in elucidating the mechanisms that control DNA methylation; however, many aspects of the mechanisms that read the information encoded by DNA methylation and mediate this into downstream regulation remain uncertain, although some candidate proteins have been identified. DNA methylation has a vital role in the inactivation of transposons, suggesting that DNA methylation is a key factor in the evolution and adaptation of plants.     

MicroRNA-mediated DNA methylation in plants

DNA methylation, a major event in epigenetics, plays an essential role in the control of gene expression. Increasing evidence suggests that long and short non-coding RNAs are involved extensively in plants to direct the establishment, spread, and removal of DNA cytosine methylation throughout their genomes. Yet, little has been known about the role of microRNAs (miRNAs) in DNA methylation although the role of small interfering RNAs (siRNAs) in DNA methylation has been well established. Several recent studies, however, provided the evidence for miRNA-directed DNA methylation in plants, and the working mechanisms still need to be fully explored. In this review, we highlight the key features of miRNA-directed DNA methylation in plants and provide insight into the complexities of such an event in plants. The interaction between miRNAs and the epigenetic machinery and the future potential research questions are briefly discussed.     

Divergent DNA methylation contributes to duplicated gene evolution and chilling response in tea plants

The tea plant (Camellia sinensis) is a thermophilic cash crop and contains a highly duplicated and repeat-rich genome. It is still unclear how DNA methylation regulates the evolution of duplicated genes and chilling stress in tea plants. We therefore generated a single-base-resolution DNA methylation map of tea plants under chilling stress. We found that, compared with other plants, the tea plant genome is highly methylated in all three sequence contexts, including CG, CHG and CHH (where H = A, T, or C), which is further proven to be correlated with its repeat content and genome size. We show that DNA methylation in the gene body negatively regulates the gene expression of tea plants, whereas non-CG methylation in the flanking region enables a positive regulation of gene expression. We demonstrate that transposable element-mediated methylation dynamics significantly drives the expression divergence of duplicated genes in tea plants. The DNA methylation and expression divergence of duplicated genes in the tea plant increases with evolutionary age and selective pressure. Moreover, we detect thousands of differentially methylated genes, some of which are functionally associated with chilling stress. We also experimentally reveal that DNA methyltransferase genes of tea plants are significantly downregulated, whereas demethylase genes are upregulated at the initial stage of chilling stress, which is in line with the significant loss of DNA methylation of three well-known cold-responsive genes at their promoter and gene body regions. Overall, our findings underscore the importance of DNA methylation regulation and offer new insights into duplicated gene evolution and chilling tolerance in tea plants.