Variation and Patterns of DNA Methylation in Maize C-type CMS Lines and their Maintainers

DNA methylation plays an important role in gene expression regulation during biological development in plants. This study adopted methylation sensitive amplification polymorphism (MSAP) to compare the levels and patterns of cytosine methylation at CCGG sites in maize genome. The tissues assayed included seedlings and tassels of C-type cytoplasmic male sterility (C Huang Zao Si, C 48-2) and its maintainer lines. For each tissue, both C Huang Zao Si and C 48-2 were more methylated than their corresponding maintainers not only on MSAP ratios, but also on the full methylation levels. In different nuclear backgrounds, the two tissues were more methylated in Huang Zao Si than in 48-2, although the two lines shared the same cytoplasm. Full methylation of internal cytosine was the dominant type in the maize genome. In addition, four different classes of methylation patterns were identified in tassels between C-CMS lines and their maintainer lines; these were specific-methylation, demethylation, hypo-methylation, and hyper-methylation. The results obtained demonstrated the power of the MSAP technique for large-scale DNA methylation detection in the maize genome, and suggested the possible association between DNA methylation polymorphism and C-type cytoplasmic male sterility.