苹果三倍体杂种后代基因组DNA甲基化水平和模式的MSAP分析

Analysis of DNA Methylation Level and Pattern in Apple Triploid Hybrid Progenies by MSAP

为了明确苹果三倍体杂种后代中基因组DNA甲基化水平及模式的变化特征，本文以‘金冠’ב四倍体嘎拉’苹果的6l份三倍体后代为试验材料，采用MSAP分子标记技术对其进行了分析。结果表明：（1）61份三倍体杂种后代的总甲基化率在10．74％～28．86％之间，全甲基化率在7．87％～24．22％之间，半甲基化率在2．10％～11．84％之间。与母本相比，总甲基化和全甲基化呈上升趋势，半甲基化呈下降趋势；与父本相比，均呈下降趋势。（2）在苹果三倍体杂种的基因组加倍和重组过程中，发生了大量过或超甲基化和去甲基化变异，少量发生了次甲基化现象，极少部分的甲基化状态介于双亲之间。（3）共获得4条DNA甲基化差异片段，有3条能够在苹果基因组中检测到，且同源性较高，分别位于第1条和第12条染色体的叠连群上，但是具体功能没有描述。研究结果表明，苹果三倍体杂种后代的DNA甲基化水平与倍性相关性不大，在其形成过程中发生了大量的过或超甲基化变异，为苹果三倍体育种中表观遗传变异的研究提供了依据。

The level and pattern ofDNA methylation in triploid apple hybrids which derived from the crossing of ＇ Golden Delicious＇ and ＇ 4xGala＇ were analyzed by methylation-sensitive amplification polymorphism （MSAP）. Results showed that： （1） The total methylation ratios of 61 triploid hybrid progenies of ＇Golden Delicious＇ were 10.74%-28.86%, full methylation ratios were 7.84%-24.22%, and hemi-methylation ratios were 2.10%-11.84%. Comparing with ＇Golden Delicious＇, the ratios of total methylation and full-methylation were mostly showed a rising trend, the ratios of hemi-methylation showed the downtrend. But all of that were downtrends compared with ＇4xGala＇. （2） In the processing of apple triploid hybrids genome polyploidization and recombination, a large number of hypermethylations and demethlation were proceeded, a small amout of hypomethylation were occured and a very small part of the methylation status were between parents. （3） In total 4 differential fragments were obtained by MSAP. 3 can be detected in the apple genome, and the high homology fragments were located in the contig of 1 and 12 chromosomes, but the specific function is not described. The results indicated that DNA methylation levels of triploid apple hybrids were less relevance to the ploidy level, and a great number of hypermethylations and demethylation were occurred, and that provided theoretical basis for epigenetic variation in apple triploid breeding.