Control of genic DNA methylation by a jmjC domain-containing protein in Arabidopsis thaliana

Differential cytosine methylation of repeats and genes is important for coordination of genome stability and proper gene expression. Through genetic screen of mutants showing ectopic cytosine methylation in a genic region, we identified a jmjC-domain gene, IBM1 (increase in bonsai methylation 1), in Arabidopsis thaliana. In addition to the ectopic cytosine methylation, the ibm1 mutations induced a variety of developmental phenotypes, which depend on methylation of histone H3 at lysine 9. Paradoxically, the developmental phenotypes of the ibm1 were enhanced by the mutation in the chromatin-remodeling gene DDM1 (decrease in DNA methylation 1), which is necessary for keeping methylation and silencing of repeated heterochromatin loci. Our results demonstrate the importance of chromatin remodeling and histone modifications in the differential epigenetic control of repeats and genes.     

Nutritional control of reproductive status in honeybees via DNA methylation

Fertile queens and sterile workers are alternative forms of the adult female honeybee that develop from genetically identical larvae following differential feeding with royal jelly. We show that silencing the expression of DNA methyltransferase Dnmt3, a key driver of epigenetic global reprogramming, in newly hatched larvae led to a royal jelly-like effect on the larval developmental trajectory; the majority of Dnmt3 small interfering RNA-treated individuals emerged as queens with fully developed ovaries. Our results suggest that DNA methylation in Apis is used for storing epigenetic information, that the use of that information can be differentially altered by nutritional input, and that the flexibility of epigenetic modifications underpins, profound shifts in developmental fates, with massive implications for reproductive and behavioral status.     

植物DNA甲基化的研究进展

DNA甲基化是重要的表观遗传修饰之一,在植物的生长发育过程中起着重要的调节作用。文章主要对DNA甲基化的作用机理及特征、表观遗传作用、检测方法和在植物育种中的应用进行了综述。     

反义抑制MnSOD转基因拟南芥构建及其抑制效果的分析

为阐明植物的线粒体MnSOD在逆境适应性反应中的作用,本研究利用分子生物学技术,以拟南芥Mn-SOD基因上游序列构建其反义序列表达载体,转化拟南芥获得转基因植株。经Northern b lot鉴定发现转基因拟南芥MnSOD mRNA水平降低,NBT法检测转基因拟南芥MnSOD活性下降,表明该反义DNA序列对MnSOD基因表达具有明显的抑制效果。     

Quality control by DNA repair

Faithful maintenance of the genome is crucial to the individual and to species. DNA damage arises from both endogenous sources such as water and oxygen and exogenous sources such as sunlight and tobacco smoke. In human cells, base alterations are generally removed by excision repair pathways that counteract the mutagenic effects of DNA lesions. This serves to maintain the integrity of the genetic information, although not all of the pathways are absolutely error-free. In some cases, DNA damage is not repaired but is instead bypassed by specialized DNA polymerases.     

荣昌猪基因组DNA甲基化水平分析

【目的】探讨荣昌猪基因组DNA甲基化水平随生长发育阶段和组织类型不同而变异的规律。【方法】采用HPLC法分别检测了荣昌猪阉公猪心脏、肝脏、半膜肌3种组织在10,20,35,50,80和100 kg体质量阶段基因组DNA的甲基化水平,分别以体质量和组织类型为影响因素进行单因素方差分析。【结果】与10 kg体质量阶段的基因组DNA甲基化水平相比,3种组织基因组DNA甲基化水平均随个体体质量的增加而呈下降趋势,但不同组织下降的幅度不同:心脏基因组DNA甲基化水平在35 kg时开始明显下降(P0.01),到100 kg时下降了44.00%;肝脏基因组DNA甲基化水平在80 kg时开始明显下降(P0.05),到100 kg时下降了26.06%;半膜肌基因组DNA甲基化水平在20 kg时开始明显下降(P0.01),到100 kg时下降了60.78%。半膜肌的基因组DNA甲基化水平在10 kg体质量阶段显著高于心脏(P0.05),极显著高于肝脏(P0.01),在20 kg体质量阶段极显著低于心脏和肝脏(P0.01);肝脏的基因组DNA甲基化水平在35 kg体质量阶段显著高于半膜肌(P0.05),在50和80 kg体质量阶段极显著高于心脏和半膜肌(P0.01),在100 kg体质量阶段显著高于心脏(P0.05),极显著高于半膜肌(P0.01)。【结论】体质量阶段是猪基因组DNA甲基化水平的重要影响因素之一。DNA甲基化水平在肝脏与半膜肌间具有组织特异性,而在心脏与肝脏间、心脏与半膜肌间是否具有组织特异性与体质量阶段明显相关。     

Cd胁迫诱导拟南芥幼苗DNA损伤分析

以拟南芥为供试植物,通过基于随机引物扩增多态性(RAPD)法的DNA损伤分析,酶联免疫吸附(ELISA)法的DNA甲基化分析以及Real-time PCR的DNA损伤修复与细胞周期相关基因的表达分析,研究了Cd(0、0.125、0.25、1.0、2.5 mg·L~(-1))胁迫5 d的拟南芥幼苗DNA损伤、DNA损伤修复系统以及细胞周期对胁迫的响应。结果显示,随Cd浓度的增加DNA损伤加剧,全基因组甲基化水平较对照组显著增加(P0.01或P0.05),细胞周期调控基因PCNA1、PCNA2,错配修复(MMR)基因MLH1、MSH_2、MSH6,非同源末端连接(NHEJ)标志基因KU70、MRE11、GR1,同源重组(HR)标志基因RAD51、BRCA1的表达均与Cd胁迫浓度呈明显的倒U型剂量效应关系,DNA修复系统对Cd胁迫的敏感性依次为MMRHRNHEJ。该结果表明:轻度Cd胁迫主要引起DNA错配损伤,并且该损伤易修复;随着Cd胁迫的增强,会引起DNA断裂与染色体损伤,损伤较难修复。另外,对Cd胁迫响应最敏感的MSH6、MLH1基因可作为表征Cd胁迫对于拟南芥遗传毒性效应的有效生物标记物。     

RAPD-PCR分析超重力处理对拟南芥基因组DNA的影响

超重力是诱变育种的一种有效途径,但基因水平研究超重力对动植物的影响还不够深入。为了深入研究超重力对DNA的直接影响,本论文设置不同的重力加速度条件,模拟超重力环境,对模式植物拟南芥种子进行诱变。然后,使用RAPD-PCR(Random Amplified Polymorphic DNA,随机扩增多态性DNA)的方法筛选后代植株基因组DNA的序列变化。结果显示,在M2代植株中,共筛选到了3处特异性变化。对其中一条464bp长的特异性条带进行测序及在线比对发现,该突变可能位于拟南芥琥珀酸脱氢酶复合体中铁硫蛋白亚基基因(AT3G27380.1)的第一个内含子处。根据本论文的结果,我们推测超重力引发突变的重要机理可能导致基因组DNA片段的断裂或丢失,即产生较为严重的损伤。从而激发机体启动易错修复(error-prone repair)机制,在损失保真性的前提下,最大限度的保证存活率。     

DNA methylation decreases in aging but not in immortal cells

When normal diploid fibroblasts from mice, hamsters, and humans were grown in culture, the 5-methylcytosine content of their DNA's markedly decreased. The greatest rate of loss of 5-methylcytosine residues was observed in mouse cells, which survived the least number of division. Immortal mouse cell lines had more stable rates of methylation.     

离子束介导外源全DNA转化拟南芥菜的诱变效应

用 30kev的Ar+ 离子 ,以 1.5× 10 17ions/cm2 的注入剂量分别介导外源拟南芥菜 (Lansberg生态型 )、甘蓝、红甜菜和芦荟的全DNA转化拟南芥菜种子 (Columbia生态型 )。转化当代营养期表型变异率与外源供体和转化受体的亲缘远近没有必然的联系 ,而低育性株率却随着外源供体亲缘关系的从近到远 ,呈现一种从低到高再变低的变化趋势。从低育性株后代中选育出 2个稳定的突变体 ,该突变体不但保持了其亲本的低育性 ,而且其他性状也有较显著的变异 ,如株型、叶型等。     

亚硫酸氢盐测序法检测小鼠胚胎Oct4启动子区甲基化

应用亚硫酸氢盐测序技术,以昆明小白鼠几种不同时期体内胚为研究对象,对其单拷贝基因Oct4启动子区进行甲基化检测.基因组经低熔点琼脂糖包埋、亚硫酸氢盐修饰后,运用巢式PCR对处理后的DNA进行两轮扩增,扩增产物通过琼脂糖凝胶电泳检测和单克隆测序进行分析.结果表明,亚硫酸氢盐测序法是一项敏感而有效的DNA甲基化检测手段.     

组织培养紫叶酢浆草DNA甲基化的研究

紫叶酢浆草是重要的观赏植物,是较早建立较为完善组织培养系统之一.本研究提取经组织培养获得的紫叶酢浆草基因组DNA,利用Southern杂交,分析了5S rDNA位点的DNA甲基化情况.结果表明,紫叶酢浆草的5S rDNA位点的CpG高度甲基化,而CNG的甲基化状况则较低.     

DNA methylation and epigenetic inheritance in plants and filamentous fungi

Plants and filamentous fungi share with mammals enzymes responsible for DNA methylation. In these organisms, DNA methylation is associated with gene silencing and transposon control. However, plants and fungi differ from mammals in the genomic distribution, sequence specificity, and heritability of methylation. We consider the role that transposons play in establishing methylation patterns and the epigenetic consequences of their perturbation.     

A histone acetyltransferase regulates active DNA demethylation in Arabidopsis

Active DNA demethylation is an important part of epigenetic regulation in plants and animals. How active DNA demethylation is regulated and its relationship with histone modification patterns are unclear. Here, we report the discovery of IDM1, a regulator of DNA demethylation in Arabidopsis. IDM1 is required for preventing DNA hypermethylation of highly homologous multicopy genes and other repetitive sequences that are normally targeted for active DNA demethylation by Repressor of Silencing 1 and related 5-methylcytosine DNA glycosylases. IDM1 binds methylated DNA at chromatin sites lacking histone H3K4 di- or trimethylation and acetylates H3 to create a chromatin environment permissible for 5-methylcytosine DNA glycosylases to function. Our study reveals how some genes are indicated by multiple epigenetic marks for active DNA demethylation and protection from silencing.     

干旱胁迫下复苏植物牛耳草基因组DNA甲基化分析

利用甲基化敏感扩增多态性(methylation sensitive amplified polymorphism,MSAP)技术,研究干旱复苏过程中,牛耳草叶片DNA甲基化水平及动态变化情况.5对引物对共扩增出376个CCGG位点,其中188个位点发生了甲基化或去甲基化变化.处理组总甲基化水平均高于对照组,且均以Ⅰ型CHG(半甲基化)位点为主,占约32.3%~40.2%.牛耳草干旱复苏过程DNA甲基化和去甲基化同时发生,但以去甲基化为主.此外,qRT-PCR技术检测Bh Dnmt2、Bh CMT2等DNA甲基化相关酶基因在干旱复苏过程中的表达,发现均有明显变化.综上,DNA甲基化参与了牛耳草的抗旱复苏过程,可能是通过甲基化/去甲基化调节基因表达,从而参与牛耳草的抗旱分子反应.