红富士苹果芽变系DNA甲基化研究

以35份富士苹果(Malus×domestica Borkh.‘Fuji’)芽变材料为试材,利用甲基化敏感扩增多态性(Methylation Sensitive Amplified Polymorphism,MSAP)分析和UPGMA聚类方法,对其基因组甲基化修饰水平、变异模式以及表观遗传变异关系进行研究。结果表明:(1)不同富士系得到不同的MSAP扩增,总DNA甲基化水平27.90%～36.16%,平均32.87%,双链全甲基化为主要甲基化方式;(2)富士芽变材料绝大多数位点保持了原有甲基化模式;(3)绝大多数芽变(68.57%)检测到全部的甲基化变异模式(12种),去甲基化频率极显著高于甲基化频率(P <0.01),且CG去甲基化极显著高于CHG;(4)36份种质遗传相似系数平均值0.89(0.79～0.92),在聚类图上,富士原种分布在芽变系集中区外,新近发生的芽变系更倾向于聚在一起,着色系片红型和条红型芽变呈分散排布状态。总的来看,富士芽变的甲基化变异模式丰富,超甲基化和去甲基化相伴发生,但以去甲基化为主;‘富士’着色芽变与其最原始品种富士,以及芽变之间发生了较大表观遗传变异;片红和条红型芽变聚类未表现明显偏好性。本研究将为进一步开展富士着色系芽变机理研究提供指导,可以CG去甲基化为切入点展开深入研究。

DNA Methylation in Red Fuji Apple Bud Sports Lines

To understand the mechanism of bud mutation in Malus × domestica Borkh.‘Fuji’，DNA methylation patterns and epigenetic variations were identified using MSAP（Methylation Sensitive Amplified Polymorphism）molecular marker analysis and UPGMA cluster analysis in a population of 35 ‘Fuji’bud sports lines（Red Fuji）. Results indicated that：(1) MSAP amplication pattern varied among different bud sports lines. Total methylation was ranged from 27.90% to 36.16%，and 32.87% in average. Inner-methylation of double-stranded DNA was the main pattern in a primary‘Fuji’cultivar and its bud sports lines. (2) The CCGG sites remained primary methylation patterns during the occurrence of bud sports together with‘Fuji’. (3) In total，12 methylation variation patterns were detected from 68.57% Red Fuji lines. The frequence of hypomethylation was significantly higher than that of hypermethylation. Moreover，CG hypomethylation was significantly higher than that of CHG（P < 0.01）. (4) Average similarity coefficience among 36 bud sports lines was 0.89，ranging from 0.79–0.92. In the UPGMA dendrogram，the primary Fuji cultivar fell out of the group of bud sports lines. Most recently bud spot lines had tendency to cluster together；typeⅠ（flushed-skin color pattern）and typeⅡ（striped-skin color pattern）bud sports lines were mixed into differents. In summary，DNA methylation and demethylation happened at the same time，demethylation was the main methylation pattern. CG hypomethylation plays an important role in the occurrence of Red Fuji. Our results would be great help in future epigenetic study of‘Fuji’sports lines，and CG hypomethylation would be as an emphysis to explore the mechanism of sports line occurence.