The Molecular Effect of Selfing in the DNA- Methylation Status and Its Relationship With Hybrid Vigor in Maize

Abstract

Analysis of molecular variance (AMOVA) indicated a significant difference in the differentially methylated regions (DMRs) spreading within all the studied genotypes genomes. The MSAP results revealed that the used HpaII and MspI methylation-sensitive enzymes with the aid of the four primers identified a total of 39 specific loci. The majority of the detected loci (30 loci) were found to be Methylation Sensitive Loci (MSL), whereas the rest 9 loci were described as Non-Methylated Loci (NML). More than a half of the MSL (16 loci) defined as polymorphic, accordingly scored a polymorphism percentage of 53%. As five out of the nine identified NML were polymorphic, the calculated polymorphism percentage was 56%. Two rounds of selfing did not affect the unmethylated state of the genomic DNA, as both the original and self-pollinated inbreds had the same number of unmethylated regions (22.7%). The hemimethylated regions were in higher rate in the original population (28.0%) compared with the self-pollinated counterpart (27.3%). The level of internal cytosine methylation was significantly magnified due to selfing and it was about 26.0%, meanwhile it was 22.7% in the original inbreds. Moreover, the fully methylated loci in the original inbreds (26%) were less than that existed in the self-pollinated match (24%). The Principle Coordinate Analysis (PCoA) of MSL data assured that the compared populations were more varied at the first coordinate (C1), while the second coordinate (C2) was in less variation (33.3% and 25%, respectively). The cluster analysis indicated that the inheritance of MSL has differed from one inbred to another. The 1 and 5 self-pollinated inbreds located far away from their original parents, consequently located in different clusters. Hybrid vigor was directly affected by the apparent variation of the epigenetic content. The statistical analysis pointed to significant differences in most of the studied traits in both populations, except the leaf area of the original population. The results of quantitative genetic analysis proved the biggest role of the non-additive gene action in the inheritance of most of the studied traits in the original population, and this role is magnified after two selfing generations. In general, the practice of self-pollination led to a marked increase in the level of DNA methylation, which was reflected in the phenotypic performance of the self-pollinated population. At the same time, the effect of hybridization was more pronounced in self-pollinated populations compared with their predecessors. The joint work of genetic and epigenetic variations can create a larger gap that may, in turn, improve the opportunities to get a hybrid vigor in the desired direction.