摘要
随着植物微繁殖技术的广泛应用,组织培养导致的表观遗传变异问题引起了人们的重视。DNA甲基化是基因组DNA的一种重要的表观遗传修饰方式,在植物基因组中普遍存在,对植物生长发育及进化起着重要的调节作用。DNA甲基转移酶是DNA甲基化过程中的催化酶。本文首次分离了草莓中具有维持甲基化和重新甲基化功能的MET1类和DRM类DNA甲基转移酶基因全序列,利用实时定量PCR技术研究了两类DNA甲基转移酶基因在草莓微繁殖苗及其后代间的表达差异,同时探讨了病毒对DNA甲基转移酶基因表达的影响;此外,还利用半定量RT-PCR技术对两类基因在‘寒富'苹果二倍体与四倍体中的表达进行了分析。主要结果如下:
1.采用PCR简并引物扩增的方法分别从草莓和苹果中分离出了1条和2条MET1类DNA甲基转移酶基因片段。目的片段长度443bp,包含两个完整的基序(motif)(Ⅳ和Ⅵ)和两个不完整的基序(Ⅱ和Ⅶ)。从草莓和苹果中分别分离出了2条DRM类DNA甲基转移酶基因片段。目的片段长度323bp,包含两个完整的基序(Ⅰ和Ⅲ)和两个不完整的基序(Ⅹ和Ⅳ)。
2.采用染色体步移技术分离出草莓DNA甲基转移酶基因全序列。对于MET1基因,基因全序列的获得经过了1步3′下游步移和3步5′上游步移。得到较长特异片段依次为1634,1812,1308和2786 bp,重叠区域分别为57,76,87和195 bp。4步步移拼接后得到的片段长8171 bp。对于DRM基因,基因全序列的获得经过了1步3′下游步移和4步5′上游步移,得到较长特异片段依次为1405,1835,2354,2142和1847 bp,重叠区域分别为131,75,64,250和372 bp。5步步移拼接后得到的片段长9014 bp。
3.根据染色体步移得到的基因全序列设计分段引物进行分段扩增,并通过5′和3′RACE试验从草莓中分离得到2条MET1类DNA甲基转移酶基因cDNA全长序列,长度5032和5002 bp,分别编码1565和1557个氨基酸,分子量为173.946和173.064 kDa,命名为FaMET1a和FaMET1b。在FaMET1基因序列中预测到8个保守基序和2个BAH结构域。FaMET1a和FaMET1b基因核酸序列和氨基酸序列同源性分别为98.63%和98.72%。遗传进化分析将FaMET1与桃(PpMET1)和毛白杨(PtDMT901,PtDMT901)的MET1划分到同一组。通过5′和3′RACE试验从草莓中还分离获得了3条DRM类DNA甲基转移酶基因cDNA全长序列,长度分别为2273,2282和2288 bp,分子量依次为67.304,67.325和67.304 kDa。3条基因序列均编码596个氨基酸,分别命名为FaDRMa、FaDRMb、FaDRMc。在FaDRM基因序列中预测到7个保守基序和UBA结构域。FaDRM基因核酸序列同源性分别为94.78%(FaDRMa和FaDRMb),97.40%(FaDRMa和FaDRMc),97.17%(FaDRMb和FaDRMc);氨基酸序列同源性分别为100%(FaDRMa和FaDRMc),98.49%(FaDRMa和FaDRMb)。遗传进化分析将FaDRM与烟草(NtDRM1)和番茄(S1DRM5)的DRM划分到同一组。
4.通过基因全序列与cDNA全序列比对发现FaMET1基因有2个内含子,FaDRM基因有10个内含子,符合典型的GT-AG剪接模式。同时发现FaDRM基因中存在选择性剪接现象,包括:3′端选择性剪接和内含子保留两种形式。
5.建立了以总核酸为模板通过RT-PCR同时检测草莓RNA病毒和DNA病毒的简单快速技术体系,成功地检测出‘丰香'与‘全明星'微繁殖苗携带病毒种类。采用基于TaqMan探针的实时定量PCR技术,分析了‘丰香'和‘全明星'脱毒、带毒试管苗和脱毒、与带毒试管苗携带相同种类病毒的微繁殖一代苗中DNA甲基转移酶基因的表达,结果表明组培条件下,病毒会上调两类DNA甲基转移酶基因的表达。脱毒一代苗中两类DNA甲基转移酶基因的相对表达量都高于带毒一代苗中的相对表达量。
6.采用基于TaqMan探针的实时定量PCR技术,分析了‘丰香'微繁殖苗及其后代中两类DNA甲基转移酶基因表达情况。表明两类DNA甲基转移酶基因表达趋势相同,其中在组织培养和移栽阶段表现出低表达,在微繁殖苗后代中得到恢复。
7.利用半定量RT-PCR技术对‘寒富'苹果二倍体植株和秋水仙碱诱导的四倍体植株中两类DNA甲基转移酶基因表达进行分析。结果显示MET1基因在二倍体的幼嫩叶片中表达水平比四倍体植株略高(0.85/0.74),而成熟叶片中表达水平差别很小。无论二倍体植株还是四倍体植株,MET1基因在幼嫩叶片中的表达水平都显著高于成熟叶片中的表达水平。DRM基因表达水平在四倍体与二倍体植株之间没有差异,而且幼嫩叶片和成熟叶片中的表达水平也基本一致。
8.克隆得到FaMET1基因上游669 bp的调控区域和FaDRM基因上游901 bp的调控区域,用草莓DNA甲基转移酶基因启动子替换pCAMBIAl301上GUS基因的CaMV358启动子,分别构建了植物表达载体FMpro∷GUS和FDpro∷GUS。通过农杆菌注射法转化草莓果实细胞,GUS基因的瞬时表达结果表明克隆得到的草莓DNA甲基转移酶基因启动子片段具有启动子活性。
Along with the development of plant micro-propagation technique and the application of strawberry micropropagated plants in production,epigenetic variation in strawberry micropropagated plants attract researchers'attention.Methylation of cytosine residues,the most common epigenetic modification of DNA in higher eukaryotes,has been implicated in many biological processes as a regulator for plant growth,development and evolution. Cytosine methylation is catalyzed by DNA cytosine 5-methyltransferase(DMTs).Here,two families(MET1 and DRM) of DNA methyltransferase genes,most likely function as maintenance and de novo methyltransferase,respectively,were firstly isolated from strawberry.Expression profiles of strawberry DMTs were compared among micropropagated plants and their progeny by real-time quantitative PCR.Moreover,the effects of strawberry viruses on the transcript level of DMTs were analyzed.The expression profiles in diploid-and tetraploid apple plants were analyzed by semi-quantitative RT-PCR method.The main results were as follows.
1.One and two MET1 gene fragments were isolated from strawberry and apple, respectively,using degenerate PCR amplification.The fragment was 443 bp and contained two intact motifs(ⅣandⅥ) and two incomplete motifs(ⅡandⅦ).Two DRM gene fragments respectively,were isolated from strawberry and apple.The fragment was 323 bp and contained two intact motifs(ⅠandⅢ) and two incomplete motifs(ⅩandⅣ).
2.The full-length gene sequences were approached by chromosome walking.For MET1 gene,four steps including one step downstream and three successive steps upstream amplifications generated fragments of 1634,1812,1308 and 2786 bp,with overlapping sequences of 57,76,87 and 195 bp to establish a contig sequence of a maximum size of 8171 bp.For DRM gene,five steps including one step downstream and four successive steps upstream amplifications generated fragments of 1405,1835,2354,2142 and 1847 bp,with overlapping sequences of 131,75,64,250 and 372 bp to establish a contig sequence of a maximum size of 9014 bp.
3.Three primer pairs which were designed according to the full-length gene sequences obtained from chromosome walking were used to obtain full-length cDNA sequence of MET1 gene combined with 5'and 3' RACE methodologies.Two contig cDNA sequences of 5032 and 5002 bp were determined,which encoded the predicted protein of 1565 and 1557 amino acid residues with calculated mass of 173.946 and 173.064 kDa.The gene products were designated as Fragaria×ananassa MET1a(FaMET1a) and Fragaria×ananassa MET1b (FaMET1b),respectively.Two BAH(Bromo-adjacent homology) and eight conserved motifs were predicted in FaMET1 genes.The two fragments shared 98.63%nucleotide and 98.72% amino acid identity.FaMET1,PpMET1,PtDMT901 and PtDMT901 fell in the same clade of group 1 in phylogenetic analysis.For DRM gene,full-length cDNA sequences were obtained by 5' and 3' RACE methodologies.Three contig cDNA sequences of 2273,2282 and 2288 bp were determined,which encoded a predicted protein of 596 amino acid residues with calculated mass of 67.304,67.325 and 67.304 kDa.The gene products were designated as Fragaria×ananassa DRMa(FaDRMa),Fragaria×ananassa DRMb(FaDRMb) and Fragaria×ananassa DRMc(FaDRMc),respectively.The UBA(ubiquitin-associated) domains and seven conserved motifs were predicted in FaDRM genes.The nucleotide identity between FaDRMa and FaDRMb,FaDRMa and FaDRMc,FaDRMb and FaDRMc were 94.78%,97.40%and 97.17%,respectively and amino acid identity between FaDRMa and FaDRMc,FaDRMa and FaDRMb were 100%and 98.49%.FaDRM,NtDRM1 and SlDRM5 fell in the same clade of group 1 in phylogenetic analysis.
4.In order to identify introns,sequence alignment was performed on genomic DNA and cDNA.Two introns were scanned in FaMET1 genes and ten introns with different sizes were dispersed in FaDRM genes which harboured the GT-AG consensus.Sequence analysis revealed that there were alternately spliced transcripts in FaDRM genes,which might be classified into two types i.e.alternative 3' splicing and intron retention.
5.The simple and rapid technique system had been established with total nucleic acid as the template for simultaneous detection of strawberry RNA and DNA viruses by RT-PCR.The micropropagated plants from strawberry cultivars‘Toyonoka' and‘Allstar' were identified to confirm the types of virus.The micropropagated plants with/without vitus and the first runner generation of micropropagated plants with/without virus of‘Toyonoka' and‘Allstar' were used for studying expression profiles of DMTs by real-time quantitative PCR based on Taqman probe.The results indicated that virus could up-regulate DMTs expression,and the expression of DNA methyltransferase in the first runner generation of micropropagated plants without vitus was higher than that in plants with virus.
6.Expression of strawberry DMTs was compared among micropropagated plants and their progeny of‘Toyonoka' by real-time quantitative PCR based on Taqman probe.The results indicated that a consistent increase in transcript levels of FaMET1 and FaDRM was found.The transcriptional expression of both FaMET1 and FaDRM genes was down-regulated in three types of micropropagated plants,and the expression level of DMTs was recovered in the first and second runner generations of micropropagated plants.
7.Semi-quantitative RT-PCR method was used to investigate the expression of MET1 and DRM genes in diploid and colchicine- induced tetraploid plants of‘Hanfu' apple.The results indicated that MET1 gene expression level in the young leaves from diploid plants was slight higher than that from tetraploid plants(0.85/0.74),and very slight difference in the MET1 gene expression level was observed between the mature leaves both from diploid and tetraploid plants.But MET1 gene expression level in the young leaves was significantly higher than that in mature leaves both for diploid and tetraploid plants.The differences of DRM gene expression level between young and mature leaves and between diploid and tetraploid plants were very slight.
8.The regulatory regions of 669 bp and 901 bp upstream of FaMET1 and FaDRM genes respectively were cloned into the pCAMBIA1301 binary vector by replacing the CaMV 35S promoter giving rise to plasmids FMpro::GUS and FDpro::GUS.An Agrobacterium strain carrying the recombined plasmid was injected into strawberry fruits.The transient expression of GUS gene indicated that the cloned fragments of strawberry DNA methyltransferase genes had promoter activity.
引文
1.洪柳,邓秀新.2005.应用MSAP技术对脐橙品种进行DNA甲基化分析.中国农业科学,38(11):2301-2307.
2.李金耀,徐莉,马纪,周洁,张富春.2004.拟南芥AtNHX2启动子的克隆及表达模式分析.生物化学与生物物理进展,31(12):1114-1118.
3.李林光.2008.苹果多倍体种质创新及鉴定评价研究[博士论文].沈阳:沈阳农业大学.
4.刘立鸿,许璐,汪凯,张富春,马正海.2008.地高辛标记探针Southern印迹杂交技术要点及改进.生物技术通报,3:57-59.
5.刘敏,滕文静,董清华,晁慧娟,李凤岚,邱德有.2009.草莓果实外源基因瞬时表达系统的建立.果树学报,26(1):60-65.
6.米建梅,张志宏,李贺,高秀岩,杜国栋.2007.草莓微繁殖苗移栽后开花结果的研究.果树学报,24(4):472-476.
7.聂丽娟,王子成.2007.DNA甲基化抑制剂作用机理及其在植物发育生物学研究中的应用.核农学报,21(4):362-365.
8.欧春青,李林光,何平,张志宏.2008.寒富苹果叶片离体再生及四倍体诱导.果树学报,25(3):293-297.
9.沈关心,朱慧芬,张悦,王硕,朱志刚,周春.2000.菌落PCR和质粒PCR对转化菌的筛选.免疫学杂志,16(2):149-151.
10.生秀杰,周伟强,姜莉,王太一,张学.2002.应用以菌落为模板的聚合酶链反应技术筛选重组阳性克隆.中华检验医学杂志,25(4):139-140.
11.隋春,吴禄平,张志宏.2003.利用PCR技术检测草莓镶脉病毒.同艺学报,30(1):82-84.
12.肖敏,张志宏,代红艳,杨洪一,李贺.2005.PCR检测草莓镶脉病毒的稳定性研究.果树学报,22(5):483-487.
13.徐晓玲,杨平勋,白云秀,黄君健,黄翠芬.2006.地高辛标记法检测人源细胞系端粒长度生物技术通讯,17(4):580-582.
14.仪治本,孙毅,牛天堂,梁小红,刘龙龙,赵威军,李炳林.2005.高粱基因组DNA胞嘧啶甲基化在杂交种和亲本间差异研究.作物学报,31(9):1138-1143.
15.尹斌,陈雨亭,朱敏,罗一菁,朱宁,徐世才,吴冠芸,沈岩.1999.Dnmt3b cDNA及其在小鼠胚胎组织中选择剪接异构体的克隆.中国医学科学院学报,21(6):431-438.
16.张馨宇,张志宏,高秀岩,李贺,杜国栋.2006.草莓微繁殖苗及其后代性状表观遗传变异研究.果树学报,23(4):542-546.
17.Adams KL,Wendel JF.2005.Polyploidy and genome evolution in plants.Curr Opin Plant Biol,8(2):135-141.
18.Agius F,Kapoor A,Zhu JK.2006.Role of the Arabidopsis DNA glycosylase lyase ROS1 in active DNA demethylation.Proc Natl Acad Sci USA,103(31):11796-11801.
19.Anand A,Trick HN,Gill BS,Muthukrishman S.2003.Stable transgene expression and random gene silencing in wheat.Plant Biotechnol J,1:241-251.
20.Arnholdt-Schmitt B,Herterich S,Neumann KH.1995.Physiological aspects of genome variability in tissue culture.I.Growth phase-dependent differential DNA methylation of the carrot genome(Daucus carota L.)during primary culture.Theor Appl Genet,91(5):809—815.
21.Ashikawa I.2001.Surveying CpG methylation at 5'-CCGG in the genomes of rice cultivars.Plant Mol Biol,45:31-39.
22.Attwood JT,Yung RL,Richardson BC.2002.DNA methylation and the regulation of gene transcription.Cell Mol Life Sci,59:241-257.
23.Aufsatz W,Mette MF,Matzke AJ,Matzke M.2004.The role of MET1 in RNA-directed de novo and maintenance methylation of CG dinucleotides.Plant Mol Biol,54(6):793-804.
24.Barry C,Faugeron G,Rossignol JL.1993.Methylation induced premeiotically in Ascobolus:coextension with DNA repeat lengths and effect on transcript elongation.Proc Natl Acad Sci USA,90:4557-4561.
25.Bartee L,Malagnac F,Bender J.2001.Arabidopsis cmt3 chromomethylase mutations block non-CG methylation and silencing of an endogenous gene.Gene Dev,15:1753-1758.
26.Baumer A,Wiedemann U,Hergersberg M,Schinzel A.2001.A novel MSP/DHPLC method for the investigation of the methylation status of imprinted genes enables the molecular detection of low cell mosaicisms.Hum Mutat,17:423-430.
27.Bender J.2004.DNA methylation and epigenetics.Annu Rev Plant Biol,55(1):41-68.
28.Bennetzen JL,Schrick K,Springer PS,Brown WE,SanMiguel P.1994.Active maize genes are unmodified and flanked by diverse classes of modified,high repetitive DNA.Genome,37:565-576.
29.Berget SM.1995.Exon recognition in vertebrate splicing.J Biol Chem,270(6):2411-2414.
30.Bernacchia G,Para A,Pedrali-Noy G,Cella R.1998.Isolation of a cDNA coding for DNA(cytosine-5)-methyltransferase(Accession No.AJ002140)from Lycopersicon esculentum.Plant Physiol,116:446-446.
31.Bernacchia G,Primo A,Giorgetti L,Pitto L,Cella R.1998.Carrot DNA-methyltransferase is encoded by two classes of genes with differing patterns of expression.Plant J,13(3):317—329.
32.Brown PTH.1989.DNA methylation in plants and its role in tissue culture.Genome,31:717-729.
33.Burn JE,Bagnall DJ,Metzger JD,Dennis ES,Peacock WJ.1993.DNA methylation,vernalization,and the initiation of flowering.Proc Natl Acad Sci USA,90:287-291.
34.Cao X,Aufsatz W,Zilberman D,Mette MF,Huang MS,Matzke M,Jacobsen SE.2003.Role of the DRM and CMT3 methyltransferases in RNA-directed DNA methylation.Curr Biol,13(24):2212-2217.
35.Cao X,Jacobsen SE.2002.Role of the Arabidopsis DRM methyltransferases in de novo DNA methylation and gene silencing.CurrBiol,12(13):1138—1144.
36.Cao X,Springer NM,Muszynski MG,Phillips RL,Kaeppler S,Jacobsen SE.2000.Conserved plant genes with similarity to mammalian de novo DNA methyltransferases.Proc Natl Acad Sci USA,97(9):4979-4984.
37.Cervera MT,Ruiz-Garcia L,Martinez-Zapater JM.2002.Analysis of DNA methylation in Arabidopsis thaliana based on methylation-sensitive AFLP marker.Mol Genet Genomics,268:543-552.
38.Chan SW,Henderson IR,Jacobsen SE.2005.Gardening the genome:DNA methylation in Arabidopsis thaliana.Nat Rev Genet,6:351-360.
39.Chan SW,Zilberman D,Xie Z,Johansen LK,Carrington JC,Jacobsen SE.2004.RNA silencing genes control de novo DNA methylation.Science,303:1336.
40.Chang L,Zhang Z,Yang H,Li H,Dai H.2007.Detection of Strawberry RNA and DNA viruses by RT-PCR using total nucleic acid as a template.J Phytopathol,155:431-436.
41.Choquer M,Boccara M,Vidal-Cros A.2003.A semi-quantitative RT-PCR method to readily compare expression levels within Botrytis cinerea multigenic families in vitro and in planta.Curr Genet,43:303-309.
42.Christopher JL,Irizarry K.2003.Alternative Splicing in the Nervous System:An Emerging Source of Diversity and Regulation.Biol Psychiatry,54(8):771-776.
43.Comai L,Tyagi AP,Winter K,Holmes-Davis R,Reynolds SH,Stevens Y,Byers B.2000.Phenotypic instability and rapid gene silencing in newly formed arabidopsis allotetraploids.Plant Cell,12(9):1551-1568.
44.Cui H,Fedoroff NV.2002.Inducible DNA Demethylation Mediated by the Maize Suppressor-mutator Transposon-Encoded TnpA Protein.Plant Cell,14:2883-2899.
45.Curradi M,Lzzo A,Badaracco G,Landsberger N.2002.Molecular mechanisms of gene silencing mediated by DNA methylation.Mol Cell Biol,22(9):3157-3173.
46.Dahl C,Guldberg P.2003.DNA methylation analysis techniques.Biogerontology,4:233-250.
47.Dai H,Zhang Z,Guo X.2007.Adventitious bud regeneration from leaf and cotyledon explants of Chinese hawthorn(Crataegus pinnatifida Bge.var.major N.E.Br.).In Vitro Cell Dev Biol Plant,43:2-8.
48.Deng J,Szyf M.1998.Multiple isoforms of DNA methyltransferase are encoded by the vertebrate cytosine DNA methyltransferase gene.J Bio Chem,273:22869-22872.
49.Diaz-De-Leon F,Klotz KL,Lagrimini LM.1993.Nucleotide sequence of the tobacco(Nicotiana tabacum)anionic peroxidase gene.Plant Physiol,101(3):1117-1118.
50.Eads CA,Danenberg KD,Kawakami K,Saltz LB,Blake C,Shibata D,Danenberg PV,Laird PW.2000.MethyLight:a high-throughput assay to measure DNA methylation.Nucleic Acids Res,28:e32.
51.Engler-Blum G,Meier M,Frank J,Muller GA.1993.Reduction of background problems in nonradioactive northern and Southern blot analyses enables higher sensitivity than 32P-based hybridizations.Anal Biochem,210(2):235-244.
52.Finnegan EJ,Dennis ES.1993.Isolation and identification by sequence homology of a putative cytosine methyltransferase from Arabidopsis thaliana.Nucleic Acids Res,21:2383-2388.
53.Finnegan EJ,Genger RK,Kovac K,Peacock WJ,Dennis ES.1998.DNA methylation and the promotion of flowering by vernalization.Proc Natl Acad Sci USA,95:5824-5829.
54.Finnegan EJ,Genger RK,Peacock WJ,Dennis ES.1998.DNA methylation in plants.Annu Rev Plant Physiol Plant Mol Biol,49:223-247.
55.Finnegan EJ,Kovac KA,Jaligot E,Sheldon CC,Peacock WJ,Dennis ES.2005.The downregulation of FLOWERING LOCUS(FLC)expression in plants with low levels of DNA methylation and by vernalization occurs by distinct mechanisms.Plant J,44:420-432.
56.Finnegan EJ,Kovac KA.2000.Plant DNA methyltransferases.Plant Mol Biol,43:189-201.
57.Finnegan EJ,Peacock WJ,Dennis ES.1996.Reduced DNA methylation in Arabidopsis thaliana results in abnormal plant development.Proc Natl Acad Sci USA,93:8449-8454.
58.Flavell AJ,Dumbar E,Anderson R,Pearce SR,Hartley R,Kumar A.1992.Tyl-copia group retrotransposons are ubiquitous and heterogeneous in higher plants.Nucleic Acids Res,20:3639-3644.
59.Fraga MF,Rodriguez R,Canal MJ.2002.Genomic DNA methylation-demethylation during aging and reinvigoration of Pinus radiata.Tree Physiol,22(11):813-816.
60.Fujimoto R,Sasaki T,Nishio T.2006.Characterization of DNA methyltransferase genes in Brassica rapa.Genes Genet Syst,81(4):235-242.
61.Genger RK,Kovac KA,Dennis ES,Peachock WJ,Finnegan EJ.1999.Multiple DNA methyltransferase genes in Arabidopsis thaliana.Plant Mol Biol,41(2):269-278.
62.Genger RK,Peacock WJ,Dennis ES,Finnegan EJ.2003.Opposing effects of reduced DNA methylation on flowering time in Arabidopsis thaliana.Planta,216:461-466.
63.Giannino D,Mele G,Cozza R,Bruno L,Testone G,Ticconi C,Frugis G,Bitonti MB,Innocenti AM,Mariotti D.2003.Isolation and characterization of a maintenance DNA-methyltransferase gene from peach(Prunuspersica[L.]Batsch):transcript localization in vegetative and reproductive meristems of triple buds.J Exp Bot,54(393):2623-2633.
64.Gonzalgo ML,Jones PA.1997.Rapid quantitation of methylation differences at specific sites using methylation-sensitive single nucleotide primer extension(Ms-SNuPE).Nucleic Acids Res,25:2529-2531.
65.Goubely C,Arnaud P,Tatout C,Heslop-Harrison JS,Deragon JM.1999.SI SINE retroposons are methylated at symmetrical and non-symmetrical positions in Brassica napus:identification of a preferred target site for asymmetrical methylation.Plant Mol Biol,39(2):243-255.
66.Graveley BR.2001.Alternative splicing:increasing diversity in the proteomic world.Trends Genet,17(2):100-107.
67.Grigg G,Clark S.1994.Genes and genomes:Sequencing 5-methylcytosine residues in genomic DNA.Bioessays,16(6):431-436.
68.Gruenbaum Y,Naveh MT,Cedar H,Razin A.1981.Sequence specificity of methylation in higher plant DNA.Nature,292(5826):860-862.
69.Guggisberg A,Mansion G,Kelso S,Conti E.2006.Evolution of biogeographic patterns,ploidy levels,and breeding systems in a diploid-polyploid species complex of Primula.New Phytol,171(3):617-632.
70.Hao Y,Deng X.2003.Genetically stable regeneration of apple plants from slow growth.Plant Cell Tiss Org Cult,72:253-260.
71.Henikoff S,Comai L.1998.A DNA methyltransferase homolog with a chromodomain exists in multiple polymorphic forms in Arabidopsis.Genetics,149(1):307—318.
72.Herman JG,Graff JR,Myohanen S,Nelkin BD,Baylin SB.1996.Methylation-specific PCR:a novel PCR assay for methylation status of CpG islands.Proc Natl Acad Sci USA,93:9821-9821.
73.Higo K,Ugawa Y,Iwamoto M,Korenaga T.1999.Plant cis-acting regulatory DNA elements(PLACE)database.Nucleic Acids Res,27(1):297-300.
74.Hirochika H,Hirochika R.1993.Tyl-copia retrotransposons as ubiquitous components of plant genomes.Jpn J Genet,68:35-46.
75.Hirochika H,Okamoto H,Kakutani T.2000.Silencing of Retrotransposons in Arabidopsis and Reactivation by the ddm1 Mutation.Plant Cell,12:357-369.
76.Hirochika H.1997.Retrotransposons of rice:Their regulation and use for genome analysis.Plant Mol Biol,35:231-240.
77.Hoffmann T,Kalinowski G,Schwab W.2006.RNAi-induced silencing of gene expression in strawberry fruit(Fragaria x ananassd)by agroinfiltration:a rapid assay for gene function analysis.Plant J,48:818-826.
78.Holliday R.2001.Epigenetics comes of age in the twenty first century.Mutation Res,483(Suppl.1):S3.
79.Hou LP,Li ML.2001.DNA methylation and plant growth and development.Plant Physiol Commun,37(6):584-588.
80.Jaligot E,Rival A,Beule T,Dussert S,Vereil JL.2000.Somaclonal variation in oil palm(Elaeis guineesis Jacq.):the DNA methylation hypothesis.Plant Cell Rep,19:684-690.
81.Jeddeloh JA,Stokes TL,Richards EJ.1999.Maintenance of genomic methylation requires a SWI2/SNF2-like protein.Nat Genet,22:94-97.
82.Jefferson RA,Kavanagh TA,Bevan MW.1987.GUS fusions:beta-glucuronidase as a sensitive and versatile gene fusion marker in higher plants.EMBO J,6:3901-3907.
83.Johnson TB,Coghill RD.1925.Research on pyrimidines.CI 11.The discovery of 5-methyl-cytosine in tuberculinic acid,the nucleic acid of the tubercle bacillus.J Am Chem Soc,47:2838-2844.
84.Johnston JW,Harding K,Bremner DH,Souch G,Green J,Lynch PT,Grout B,Benson EE.2005.HPLC analysis of plant DNA methylation:a study of critical methodological factors.Plant Physiol Biochem,438:44-853.
85.Jost JP,Oakeley EJ,Zhu B,Benjamin D,Thiry S,Siegmann M,Jost YC.2001.5-Methylcytosine DNA glycosylase participates in the genome-wide loss of DNA methylation occurring during mouse myoblast differentiation.Nucleic Acids Res,29(21):4452-4461.
86.Joyce SM,Cassells AC.2002.Variation in potato microplant morphology in vitro and DNA methylation.Plant Cell Tiss Org Cult,70(2):125-137.
87.Jullien PE,Kinoshita T,Ohad N,Berger F.2006.Maintenance of DNA methylation during the Arabidopsis life cycle is essential for parental imprinting.Plant Cell,18:1360-1372.
88.Kaeppler SM,Phillips RL.1993.Tissue culture-induced DNA methylation variation in maize.Proc Natl Acad Sci USA,90:8773-8776.
89.Kakutani T,Jeddeloh J,Richards EJ.1995.Characterization of an Arabidopsis thaliana DNA hypomethylation mutant.Nucleic Acids Res,23:130-137.
90.Kakutani T,Munakata K,Richards EJ,Hirochika H.1999.Meiotically and mitotically stable inheritance of DNA hypomethylation induced by ddml mutation of Arabidopsis thaliana.Genetics,151:831-838.
91.Kankel MW,Ramsey DE,Stokes TL,Flowers SK,Haag JR,Jeddeloh JA,Riddle NC,Verbsky ML,Richards EJ.2003.Arabidopsis MET1 cytosine methyltransferase mutants.Genetics,163(3):1109-1122.
92.Kapoor A,Agarwal M,Andreucci A,Zheng X,Gong Z,Hasegawa PM,Bressan RA,Zhu JK.2005.Mutations in a conserved replication protein suppress transcriptional gene silencing in a DNA-methylation-independent manner in Arabidopsis.Curr Biol,15:1912-1918.
93.Kapoor A,Agius F,Zhu JK.2005.Preventing transcriptional gene silencing by active DNA demethylation.FEBS letters,579:5889-5898.
94.Karhu S.2001.Growth characteristics of micropropagated strawberries.Acta Hort,560:539-542.
95.Kato M,Miura A,Bender J,Jacobsen SE,Kakutani T.2003.Role of CG and Non-CG Methylation in Immobilization of Transposons in Arabidopsis.Curr Biol,13(5):421-426.
96.Kinet JM,Parmentier A.1989.The flowering behaviour of micropropagated strawberry plants cv.‘Gorella’:the influence of the number of sub-cultures on the multiplication medium.Acta Hort,265:327-334.
97.King GJ.1995.Morphological development in Brassica oleracea is modulated by in vivo treatment with 5-azacytidine.J Hort Sci,70(2):333-342.
98.Kovarik A,Matyasek R,Leitch A,Gazdova B,Fulnecek J,Bezdek M.1997.Variability in CpNpG methylation in highter plant genomes.Gene,204(1-2):25-33.
99.Kubis SE,Castilho AMMF,Vershinin AV,Heslop-Harrison JS.2003.Retroelements,transposons and methylation status in the genome of oil palm(Elaeis guineensis)and the relationship to somaclonal variation.Plant Mol Biol,52(1):69-79.
100.Kumar S,Cheng X,Klimasauskas S,Mi S,Posfai J,Roberts RJ,Wilson GG.1994.The DNA(cytosine-5)methyltransferases.Nucleic Acids Res,22(1):1-10.
101.Lander ES,Linton LM,Birren B,Nusbaum C.2001.Initial sequencing and analysis of the human genome.International Human Genome Sequencing Consortium.Nature,409(6822):860-921.
102.Law RD,Suttle JC.2002.Transient decreases in methylation at 5'-CCGG-3'sequences in potato(Solarium tuberosum L.)meristem DNA during progression of tubers through dormancy precede the resumption of sprout growth.Plant Mol Biol,51:437-447.
103.Lee JO,Kwun HJ,Jung JK,Choi KH,Min DS,Jang KL.2005.Hepatitis B virus X protein represses E-cadherin expression via activation of DNA methyltransferase 1.Oncogene,24:6617-6625.
104.Lescot M,Dehais P,Thijs G,Marchal K,Moreau Y,Peer YV,Rouze P,Rombauts S.2002.PlantCARE,a database of plant cis-acting regulatory elements and a portal to tools for in silico analysis of promoter sequences.Nucleic Acids Res,30(1):325—327.
105.Li X,Xu M,Korban SS.2002.DNA methylation profiles differ between field-and in vitro-grown leaves of apple.J Plant Physiol,159:1229-1234.
106.Libek A,Kikas A.2003.Influence of different planting material on production of strawberry runner plants.Agronomy Res,1:69-74.
107.Lindroth AM,Cao X,Jackson JP,Zilberman D,McCallum CM,Henikoff S,Jacobsen SE.2001.Requirement of CHROMOMETHYLASE 3 for maintenance of CpXpG methylation.Science,292(5524):2077-2080.
108.Lippman Z,Gendrel AV,Black M,Vaughn MW,Dedhia N,McCombie WR,Lavine K,Mittal V,May B,Kasschau KD,Carrington JC,Doerge RW,Colot V,Martienssen R.2004.Role of transposable elements in heterochromatin and epigenetic control.Nature,430:471-476.
109.Litwihczuk W.2004.Field performance of 'Senga Sengana' strawberry plants(Fragaria x ananassa Duch.)obtained by runners and in vitro through axillary and adventitious shoots.Electronic Journal of Polish Agricultural Universities,Horticulture 7(1):art-03.
110.Liu B,Brubaker CL,Mergeai G,Cronn RC,Wendel JF.2001.Polyploid formation in cotton is not accompanied by rapid genomic changes.Genome,44:321-330.
111.Long L,Lin X,Zhai J,Kou H,Yang W,Liu B.2006.Heritable alteration in DNA methylation pattern occurred specifically at mobile elements in rice plants following hydrostatic pressurization.Biochem Biophys Res Commun,340:369-376.
112.Luff B,Pawlowski L,Bender J.1999.An inverted repeat triggers cytosine methylation of identical sequences in Arabidopsis.Mol Cell,3(4):505—511.
113.Malagnac F,Bartee L,Bender J.2002.An Arabidopsis SET domain protein required for maintenance but not estab lishment of DNA methylation.EMBO J,21(16):6842-6852.
114.Manjunath S,Sachs M.1997.Molecular characterization and promoter analysis of the maize cytosolic glyceraldehyde 3-phosphate dehydrogenase gene family and its expression during anoxia.Plant Mol Biol,33:97-112.
115.Mathieu O,Bender J.2004.RNA-directed DNA methylation.J Cell Sci,117:4881-4888.
116.Mathieu O,Yukawa Y,Sugiura M,Picard G,Tourmente S.2002.5S rRNA genes expression is not inhibited by DNA methylation in Arabidopsis.Plant J,29:313-323.
117.Matthes M,Singh R,Cheah SC,Karp A.2001.Variation in oil palm(Elaeis guineensis Jacq.)tissue culture-derived regenerants revealed by AFLPs with methylation-sensitive enzymes.Theor Appl Genet,102(6-7):971-979.
118.Messeguer R,Ganal MW,Steffens JC,Tanksley SD.1991.Characterization of the level,target sites and inheritance of cytosine methylation in tomato nuclear DNA.Plant Mol Biol,16(5):753—770.
119.Meyer P,Niedenhof I,Lohuis M.1994.Evidence for cytosine methylation of non-symmetrical sequences in transgenic Petunia hybrida.EMBO J,13(9):2084-2088.
120.Michaels SD,Amasino RM.1999.FLOWERING LOCUS C encodes a novel MADS domain protein that acts as a repressor of flowering.Plant Cell,11:949-956.
121.Mikovits JA,Young HA,Vertino P,Issa JPJ,Pitha PM,Turcoski-Corrales S,Taub DD,Petrow CL,Baylin SB,Ruscetti FW.1998.Infection with Human Immunodeficiency Virus Type 1 Upregulates DNA Methyltransferase,Resulting in De Novo Methylation of the Gamma Interferon(IFN-g)Promoter and Subsequent Downregulation of IFN-g Production.Mol Cell Biol,18(9):5166-5177.
122.Modrek B,Resch A,Grasso C,Lee C.2001.Genome-wide analysis of alternative splicing using human expressed sequence data.Nucleic Acids Res,29(13):2850-2859.
123.Mraz I,Petrzik K,Franova-Honetslegrova J,Sip M.1997.Detection of Strawberry vein banding virus by polymerase chain reaction and dot blot hybridization.Acta Virol,41:241-242.
124.Muller E,Brown PTH,Hartke S,Lorz H.1990.DNA variation in tissue-culture derived rice plants.Theor Appl Genet,80:673-679.
125.Nakabayashi K,Okamoto M,Koshiba T,Kamiva Y,Nambara E.2005.Genome-wide profiling of stored mRNA in Arabidopsis thaliana seed germination:epigenetic and genetic regulation of transcription in seed.Plant J,41:697-709.
126.Nakano Y,Steward N,Sekine M,Kusano T,Sano H.2000.A tobacco NtMETl cDNA encoding a DNA methyltransferase:molecular characterization and abnormal phenotypes of transgenic tobacco plants.Plant Cell Physiol,41(4):448-457
127.Oakeley EJ,Jost JP.1996.Non-symmetrical cytosine methylation in tobacco pollen DNA.Plant Mol Biol,31:927-930.
128.Okuwaki M,Verreault A.2004.Maintenance DNA Methylation of Nucleosome Core Particles.J Biol Chem,279:2904-2912.
129.Papa CM,Springer NM,Muszynski MG,Meeley R,Kaeppler SM.2001.Maize chromomethylase Zea methyltransferase2 is required for CpNpG methylation.Plant Cell,13:1919-1928.
130.Pastuglia M,Roby D,Dumas C,Cock JM.1997.Rapid Induction by Wounding and Bacterial Infection of an S Gene Family Receptor-like Kinase Gene in Brassica oleracea.Plant Cell,9(1):49-60.
131.Pazin MJ,Kadonaga JT.1997.SWI2/SNF2 and related proteins:ATP-driven motors that disrupt protein-DNA interactions? Cell,88:737-740.
132.Pearce SR,Harrison GLD,Heslop-Harrison JS,Kumar A,Flavell AJ.1996.The Tyl-copia group retrotransposons in Vicia species:Copy number,sequence heterogeneity and chromosomal localization.Mol Gen Genet,250:305-315.
133.Peraza-Echeverria S,Herrera-Valencia VA,Kay A.2001.Detection of DNA methylation changes in micropropagated banana plants using methylation-sensitive amplification polymorphism(MSAP).Plant Sci,161:359-367.
134.Popescu CF,Falk A,Glimelius K.2002.Application of AFLPs to characterize somaclonal variation in anther-derived grapevines.Vitis,41:177-182.
135.Portis E,Acquadro A,Comino C,Lanteri S.2004.Analysis of DNA methylation during germination of pepper(Capsicum annuum L.)seeds using methylation-sensitive amplification polymorphism(MSAP).Plant Sci,166:169-178.
136.Posfai J,Bhagwat AS,Posfait G,Roberts RJ.1989.Predictive motifs derived from cytosine methyltransferases.Nucleic Acids Res,17(7):2421-2435.
137.Pradhan S,Cummings M,Roberts RJ,Adams RL.1998.Isolation,characterization and baculovirus-mediated expression of the cDNA encoding cytosine DNA methyltransferase from Pisum sativum.Nucleic Acids Res,26(5):1214—1222.
138.Rabinowicz PD,Palmer LE,May BP,Hemann MT,Lowe SW,McCombie WR,Martienssen RA.2003.Genes and transposons are differentially methylated in plants,but not in mammals.Genome Res,13:2658-2664.
139.Reyna-Lopez GE,Simpson J,Ruiz-Herrera J.1997.Differences in DNA methylation patterns are detectable during the dimorphic transition of fungi by amplification of restriction polymorphisms.Mol Gen Genet,253(6):703-710.
140.Rival A,Jaligot E,Beul(?)T,Finnegan EJ.2008.Isolation and expression analysis of genes encoding MET,CMT,and DRM methyltransferases in oil palm(Elaeis guineensis Jacq.)in relation to the ‘mantled’ somaclonal variation.J Exp Bot,59(12):3271—3281.
141.Rolland VG.2004.Semi-quantitative analysis of gene expression in cultured chondrocytes by RT-PCR.Methods Mol Med,100(1):69-78.
142.Ronemus MJ,Galbiati M,Ticknor C,Chen J,Dellaporta SL.1996.Demethylation-induced developmental pleiotropy in Arabidopsis.Science,273:654-657.
143.Ros F,Kunze R.2001.Regulation of Activator/Dissociation Transposition by Replication and DNA Methylation.Genetics,157:1723-1733.
144.Ruiz-Carcia L,Cervera MT,Martinez-Zapater JM.2005.DNA methylation increases throughout Arabidopsis development.Planta,222:301-306.
145.Rushton PJ,Torres JT,Parniske M,Wernert P,Hahibrock K,Somssich IE.1996.Interaction of elicitor-induced DNA-binding proteins with elicitor response elements in the promoters of parsley PR1 genes.EMBO J,15(20):5690-5700.
146.Salmon A,Ainouche ML,Wendel JF.2005.Genetic and epigenetic consequences of recent hybridization and polyploidy in Spartina(Poaceae).Mol Ecol,14(4):1163—1175.
147.SanMiguel P,Bennetzen JL.1998.Evidence that a recent increase in maize genome size was caused by the massive amplification of intergene retrotransposons.Ann Bot,81:37-44.
148.SanMiguel P,Tikhonov A,Jin YK,Motchoulskaia N,Zakharov D,Melake-Berhan A,Springer PS,Edwards KJ,Lee M,Avramova Z,Bennetzen JL.1996.Nested retrotransposons in the intergenic regions of the maize genome.Science,274:765-768.
149.Sano H,Kamada I,Youssefian S,Katsumi M,Wabiko H.1990.A single treatment of rice seedlings with 5-azacytidine induces heritable dwarfism and undermethylation of genomic DNA.Mol Gen Genet,220(3):441-447.
150.Sathe GM,Brien SO',McLaughlin MM,Watson F,Livi GP.Use of polymerase chain reaction for rapid detection of gene insertions in whole yeast cells.Nucleic Acids Res,1991,19(17):4775.
151.Schmid H,Cohen CD,Henger A,Irrgang S,Schlondorff D,Kretzler M.2003.Validation of endogenous controls for gene expression analysis in microdissected human renal biopsies.Kidney Int,64:356-360.
152.Sherman JD,Talbert LE.2002.Vernalization-induced changes of the DNA methylation pattern in winter wheat.Genome,45:253-260.
153.Simkova H.1998.Methylation of mitochondrial DNA in carrot(Daucus carota L.).Plant Cell Rep,17:220-224.
154.Simovic N,Wolyn D,Jelenkovic G.1992.Sequence analysis of 18S ribosomal RNA gene in Fragaria×ananassa Duch.cultivated octoploid strawberry.Plant Mol Biol,18(6):1217— 1220.
155.Singh A,Zubko E,Meyer P.2008.Cooperative activity of DNA methyltransferases for maintenance of symmetrical and non-symmetrical cytosine methylation in Arabidopsis thaliana.Plant J, 56(5):814-823.
156.Solanas M,Escrich E.1997.An improved protocol to increase sensitivity of Southern blot using dig-labelled DNA probes.J Biochem Biophys Methods,35(3):153-159.
157.Steward N,Ito M,Yamaguchi Y,Koizumi N,Sano H.2002.Periodic DNA methylation in maize nucleosomes and demethylation by environmental stress.J Biol Chem,277:37741-37746.
158.Steward N,Kusano T,Sano H.2000.Expression of ZmMETI,a gene encoding a DNA methyltransferase from maize,is associated not only with DNA replication in actively proliferating cells,but also with altered DNA methylation status in cold-stressed quiescent cells.Nucleic Acids Res,28(17):3250-3259.
159.Stokes TL,Kunkel BN,Richards EJ.2002.Epigenetic variation in Arabidopsis disease resistance.Genes Dev,16:171-182.
160.Szczygiel A,Pierzga K,Borkowska B.2002.Performance of micropropagated strawberry plantlets after planting in the field.Acta Hort,567:317-320.
161.Teerawanichpan P,Chandrasekharan MB,Jiang Y,Narangajavana J,Hall TC.2004.Characterization of two rice DNA methyltransferase genes and RNAi-mediated reactivation of a silenced transgene in rice callus.Planta,218(3):337-349.
162.Teyssier E,Bernacchia G,Maury S,How Kit A,Stammitti-Bert L,Rolin D,Gallusci P.2008.Tissue dependent variations of DNA methylation and endoreduplication levels during tomato fruit development and ripening.Planta,228(3):391-399.
163.Thompson JR,Jelkmann W.2004.Strain diversity and conserved genome elements in Strawberry mild yellow edge virus.Arch Virol,149:1897-1909.
164.Thompson JR,Leone G,Lindner JL,Jelkmann W,Schoen CD.2002.Characterization and complete nucleotide sequence of strawberry mottle virus:a tentative member of a new family of bipartite plant picorna-like viruses.J Gen Virol,83:229-239.
165.Thompson JR,Wetzel S,Klerks MM,Jelkmann W.2003.Multiplex RT-PCR detection of four aphid-borne strawberry viruses in Fragaria spp.in combination with a plant mRNA specific internal control.J Virol Methods,111:85-93.
166.Town CD,Cheung F,Maiti R,Crabtree J,Haas BJ,Wormian JR,Hine EE,Althoff R,Arbogast TS,Tallon LJ,Vigouroux M,Trick M,Bancroft L.2006.Comparative genomics of Brassica oleracea and Arabidopsis thaliana reveal gene loss,fragmentation,and dispersal after polyploidy.Plant Cell,18(6):1348-1359.
167.Tsaftaris AS,Kafka M.1998.Mechanisms of heterosis in crop plants.Crop Sci,1:95-111.
168.Tsaftaris AS.1995.Molecular aspects of heterosis in plants.Physiologia Plantarum,94:362-370.
169.Tsai CN,Tsai CL,Tse KP,Chang HY,Chang YS.2002.The Epstein-Barr virus oncogene product,latent membrane protein 1,induces the downregulation of E-cadherin gene expression via activation of DNA methyltransferases.Proc Natl Acad Sci USA,99(15):10084-10089.
170.Tuskan GA,DiFazio S,Jansson S,Bohlmann J,Grigoriev I,Hellsten U et al.2006.The Genome of Black Cottonwood,Populus trichocarpa(Torr.& Gray).Science,313(5793):1596-1604.
171.Vandesompele J,Preter KD,Pattyn F,Poppe B,Roy NV,Paepe AD,Speleman F.2002.Accurate normalization of real-time quantitative RT-PCR data by geometric averaging of multiple internal control genes.Genome Biol,3:research0034.1-0034.11.
172.Vanyushin BF.2006.DNA methylation in plants.Curr Top Microbiol Immunol,301:67-122.
173.Vaskova D,Spak J,Klerks MM,Schoen CD,Thompson JR,Jelkmann W.2004.Real-time NASBA for detection of Strawberry vein banding virus.Eur J Plant Pathol,110:213-221.
174.Vongs A,Kakutani T,Martienssen RA,Richards EJ.1993.Arabidopsis thaliana DNA methylation mutants.Science,26:1926-1928.
175.Voytas DF,Cummings MP,Konieczny A,Ausubel FM,ROdermel SR.1992.Copia-like retrotransposons are ubiquitous among plants.Proc Natl Acad Sci USA,89:7124-7128.
176.Wada Y,Miyamoto K,Kusano T,Sano H.2004.Association between up-regulation of stress-responsive genes and hypomethylation of genomic DNA in tobacco plants.Mol Genet Genomics,271:658-666.
177.Wada Y 2005.Physiological functions of plant DNA methyltransferases.Plant Biotechnol J,22:71-80.
178.Wada Y,Ohya H,Yamaguchi Y,Koizumi N,Sano H.2003.Preferential de Novo Methylation of cytosine residues in non-CpG sequences by a domains rearranged DNA methyltransferase from tobacco plants.J Biol Chem,278(43):42386-42393.
179.Wanger I,Capesius 1.1981.Determination of 5 methylcytosine from plant DNA by HPLC.Biochim Biophy Acta,654:52-56.
180.Wessler SR,Bureau TE,White SE.1995.LTR-retrotransposons and MITEs:Important players in the evolution of plant genomes.Curr Opin Genet Dev,5:814-821.
181.White AJ,Dunn MA,Brown K,Hughes MA.1994.Comparative analysis of genomic sequence and expression of a lipid transfer protein gene family in winter barley.J Exp Bot,45:1885-1892.
182.Wu C,Morris JR.2001.Genes,Genetics,and Epigenetics:A Correspondence.Science,293:1103-1105.
183.Xiao WY,Custard KD,Brown RC,Lemmon BE,Harada JJ,Goldbery RB,Fischer RL.2006.DNA methylation is critical for Arabidopsis embryogenesis and seed viability.Plant Cell,18:805-814.
184.Xie Z,Johansen L,Gustafson A,Kasschau KD,Lellis AD,Zilberman D,Jacobsen SE,Carrington JC.2004.Genetic and functional diversification of small RNA pathways in plants.PLoS Biol,2(5):642-652.
185.Xiong LZ,Xu CG,Saghai MA,Zhang Q.1999.Pattern of cytosine methylation in an elite rice hybrid and its parental lines detected by methylation sensitive amplification polymorphism technique.Mol Gen Genet,261:439-446.
186.Xiong Z,Laird PW.1997.COBRA:a sensitive and quantitative DNA methylation assay.Nucleic Acids Res,25:2532-2534.
187.Xu M,Li X,Korban SS.2000.AFLP-based detection of DNA methylation.Plant Mol Biol Rep,18:361-368.
188.Yamauchi T,Moritoh S,Johzuka-Hisatomi Y,Ono A,Terada R,Nakamura I,Iida S.2008.Alternative splicing of the rice OsMETl genes encoding maintenance DNA methyltransferase.J Plant Physiol 165(17):1774-1782.
189.Yan PS,Chen CM,Shi H,Rahmatpanah F,Wei SH,Caldwell CW,Huang THM.2001.Dissecting complex epigenetic alterations in breast cancer using CpG island microarrays.Cancer Res,61:8375-8380.
190.Yegnasubramanian S,Lin X,Haffner MC,DeMarzo AM,Nelson WG.2006.Combination of methylated-DNA precipitation and methylation-sensitive restriction enzymes(COMPARE-MS)for the rapid,sensitive and quantitative detection of DNA methylation.Nucleic Acids Res,34(3):e19.
191.Yoder JA,Walsh CP,Bestor TH.1997.Cytosine methylation and the ecology of intragenomic parasites.Trends Genet,13:335-340.
192.Zhu B,Benjamin D,Zheng Y,Angliker H,Thiry S,Siegmann M,Jost JP.2001.Overexpression of 5-methylcytosine DNA glycosylase in human embryonic kidney cells EcR293 demethylates the promoter of a hormone-regulated reporter gene.Proc Natl Acad Sci USA,98(9):5031—5036.
193.Zilberman D,Cao X,Johansen LK,Xie Z,Carrington JC,Jacobsen SE.2004.Role of Arabidopsis ARGONAUTE 4 in RNA-directed DNA methylation triggered by inverted repeats.Curr Biol,14(13):1214-1220.