玉米杂交种及其亲本基因组胞嘧啶甲基化水平研究

Genomic DNA Cystoine Methylations of Corn Hybrids and Their Parents

摘要：基因组DNA甲基化对基因表达起着重要的调控作用。本研究采用MSAP方法，对2个玉米杂交种及其相应亲本DNA 5'-CCG G位点胞嘧啶的甲基化水平进行分析，比较了2个玉米杂交种与其相应亲本的甲基化类型与差异。研究发现，2个玉米杂交种Mo17×Suwan 5和Suwan 1×太3221的F1代的甲基化敏感扩增多态性(MASP)比率分别为39．1％和40．1％，均略低于其相应的双亲(39．8％和39．7％、44．6％和43．2％)。2个杂交种的全甲基化(双链CmCGG)率分别为24．4％和23．3％，而其相应亲本Mo17、Suwan 5、Suwan 1和太3221分别为17．1％，24．4％、24．6％和21．6％。4个玉米亲本的MASP比率变化范围为39．7％-44．6％，平均为41．8％。全甲基化比率为17．1％-24．6％，平均为21．9％。杂交种与其相应亲本比较有4种类型的变化：A型，F1与其亲本甲基化横式相同；B型，去甲基化1C型，超甲基化；D型，次甲基化。杂交种F1代DNA的甲基化模式与其双亲比较，发生了较大的改变与调整。F1代基因组的杂合性与基因组DNA甲基化模式的重新调整有关。

Genomic DNA methylation in plays an important role in regulating gene expression. This study adopted methylation-sensitive AFLP to analyze cystoine methylations on 5＇-CCG G site of two corn hybrids and their parents,and comparatively examined their methylation types and the differences of the methylation types between the hybrids and their parents. It found that the MASP ratios in F1 plant of the two hybrids, Mo17 × Suwan and Suwan 1× Tai 3221, were 39.1 % and 40. 1 %, respectively, slightly lower than those of their corresponding parents （39.8%,39. 7%,44. 6% and 43. 2%）. The full methylation levels （double-chain 5＇-CmCGG） of the two hybrids were 24. 4% and 23. 3%,respectively,but their those of their corresponding parents,Mo17,Suwan 5,Suwan 1, and Tai 3221, were 17. 1 %, 24.4%, 24. 6% and 21.6% ,respectively. The MASP rations of the four parents ranged between 39.7% and 44.6% ,averaging at 41.8% ,and their full methylation levels stood between 17.1% and 24.6%4 ,averaging at 21.9%70. Comparatively,the hybrids and their parents showed four methylation types.A type in which the hybrids and their parents had same methylation patterns %B type in which demethylation occurred ;C type in which hyper-methyaltion occurred and D type in which hypo-methylation took place. Compared with their parents, The F1 plants got changed and adjusted in DNA methylation pattern to a higher extent. The heterogeneities of the F% genomes were associated with the readjustments in DNA methylation pattern.