Molecular Relationship between DNA Methylation Pattern and Hybrid Vigor In Maize (Zea mays L.) By Using MSAP Technology


Results of molecular analysis of DNA methylation pattern with the use of specific restriction enzymes HpaII and MspI in MSAP (Methylation Sensitive Amplified Polymorphism) technique revealed that the five used primers were succeeded in diagnosing 51 specific restricted loci spread within parental lines and their half diallel genomes. The detected loci divided into 38 MSL (Methylation-Susceptible Loci) and 13 NML (No Methylated Loci). Thirty-two of MSL were found to be polymorphic, recording a polymorphism percentage of 84%. Whereas, 9 of NML were found to be polymorphic with a polymorphism percentage of 69%. Estimation of DMRs (Differentially Methylated Regions) pointed to a general decline in DNA methylation level in hybrids population compared with their parents population, as the percentages of unmethylated and hemi methylated regions reached 13.1 and 9.9% in hybrids compared with their percentages in parents with 9.5% and 6.6%, respectively. Offset by a rise in the percentage of internal cytosine methylation in the parents which was 20.7% compared with its percentage in the hybrids as 19.5%, also parents showed higher percentage of full methylation or absence of target by 63.2%, compared with their half diallel hybrids with 57.6%. Results of Principal Coordinates Analysis (PCoA) revealed that the magnitude of epigenetic diversity in both coordinates, the first (C1) and the second (C2) reached higher values in the parents population about 42.3 and 26.9%, respectively, compared with the same percentage in the hybrids population (26.1% and 11.4%, respectively) which indicating higher variance in the pattern of methyl group distribution in the parents genome against half diallel population. The parental lines divided into three main groups in the cluster analysis of MSL according to nearest neighbor method. The two lines 2 and 6 were the most divergent in the pattern of methyl group distribution as they belong to the most divergent groups on both sides of the hierarchical clustering, in addition to the opposite direction of epigenetic variation showed by line 6.