摘要
DNA甲基化在真核生物的生长发育过程中起着重要的调控作用。本研究用改良AFLP方法（MSAP）分析了3个高粱杂交种及其相应亲本总DNA 5＇-CCCG位点胞嘧啶的甲基化水平和杂交种与相应亲本的甲基化差异模式。研究发现，以V4A、1383、Tx622A和晋粱5号为亲本，3个杂交组合V4A×1383、Tx622A×晋粱5号和V4A×晋粱5号，F1的甲基化敏感扩增多态性比率即扩增的总甲基化位点数占总扩增位点数的比率分别为48．7％、47．6％和41．8％，都低于双亲。全甲基化（双链CmCGG）率分别为27．7％、25．4％和28．0％，也均低于双亲值，表明杂交种比相应的亲本在形成杂合体时某些位点发生了去甲基化。高粱4个亲本的甲基化敏感扩增多态性比率为51．4％～63．0％，全甲基化率为28．3％～29．1％。杂交种与其相应亲本比较，有4种类型的变化。A型，F1与其亲本甲基化模式相同；B型，去甲基化，双亲或亲本之一甲基化，但在F1该位点无甲基化；C型，超甲基化，F1甲基化程度高于双亲；D型，次甲基化，F1甲基化程度低于双亲。杂交种F1代DNA甲基化模式经历了较大的改变与调整，以协调来源于双亲的异质基因的协同表达，使某些基因高效转录，而有些基因转录受到抑制。杂交种F1代的甲基化水平低于双亲，是由于F1代相对于其亲本甲基化模式经过重新调整，在其基因组中甲基化水平发生了总体变化。杂种优势的产生与杂交种F1代基因组DNA甲基化模式的改变和重新调整有关。
DNA methylation plays an important role in gene expression regulation during growth and development in eukaryotes. It also plays an important role in the expression of heterosis in F1 hybrids. A modified AFLP technique （methylation-sensitive AFLP, MSAP） was used in this study to detect the DNA methylation patterns in the 5＇-CCGG sites of three sorghum （ Sorghum bicolor Moench） hybrids and their parents for understanding the molecular basis of heterosis in F1 generation. The MSAP ratios, which were the ratios of MSAP sites to the totally amplified sites, in three sorghum hybrids （V4A × 1383, Tx622A × Jinliang 5, and V4A × Jinliang 5） were 48.7%, 47.6% and 41.8%, respectively. Full methylation levels （5＇-CmCGG in double strands） were 27.7% , 25.4% and 28.0% in 3 F1 s （Table 2）. Both MSAP and full methylation levels in 3 F1 s were lower than either of their parents, which suggested some demethylation occurred in certain amplified 5＇-CCGG sites. MSAP and full methylation levels in 4 sorghum parents, V4A, 1383, Tx622A and Jinliang 5, were 51.4% -61.3% and 28.3% - 29.1% （Table 3）. Four classes of MSAP patterns, A, B, C and D, among 3 sorghum hybrids and their parents were detected： Pattern A, methylation levels were not changed in both parents and F1 ; Pattern B, demethylation, both or one of the parent was methylated, but no methylation in the same site in F1 ; Pattern C, hypermethylation, the methylation level in F1 was higher than those in both parents; Pattern D, hypomethylation, methylation in F1 was lower than those in both parents. When two parents are hybridized, the methylation patterns in F1 are changed and tuned greatly to coordinate the expressions of genes from two heterogeneous parents. Some genes transcribe with greater efficiency, but the transcriptions of some other genes are restrained in F1 s. The lowered methylation level in F1 compared to its parents might be the balanced result from the methylations readjusted and changed. The heterosis in F1 s is associated with the change and readjustment of methylation in sorghum genome.
出处
《作物学报》
CAS
CSCD
北大核心
2005年第9期1138-1143,共6页
Acta Agronomica Sinica
基金
山西省科技攻关项目(021011)。
作者简介
仪治本，男，博士研究生；研究方向：作物分子育种。E-mail：zhibenyi@yahoo．com．cn
通讯作者：孙毅。E-mail：aunyi692003@yahoo．com．cn
