DNA甲基化是一种重要的表观遗传机制，是影响植物进化的重要因素之一。以往对植物DNA甲基化的研究多集中于开花植物。裸子植物的转座因子（TE）和重复序列具有与被子植物相似的甲基化式样，但裸子植物基因DNA甲基化模式明显不同。迄今，基因DNA甲基化的功能仍然很不清楚。本项目拟对裸子植物不同支系的代表性物种进行基因组Bisulfite测序，比较CG和CHG甲基化水平分别较高的基因的进化模式，揭示直系同源基因间的DNA甲基化差异以及基因DNA甲基化与基因表达水平的关系，探讨基因DNA甲基化的进化模式和功能；与其它陆地植物比较，探讨植物基因不同类型DNA甲基化的水平与基因组大小间的关联；研究与甲基化及去甲基化相关的基因的进化，探讨裸子植物为什么具有独特的基因DNA甲基化模式。最后，对不同支系代表物种的多种组织的基因DNA甲基化分布进行研究，探讨裸子植物不同组织基因DNA甲基化的分布式样及其进化意义。

DNA methylation is a heritable epigenetic modification, and has emerged as a potentially important factor in plant evolution. Previous studies of plant DNA methylation focused mostly on angiosperms, especially on some model plants, such as Arabidopsis thaliana and Oryza sativa. Although similar patterns of DNA methylation have been found in TEs and repeats in seed plants, the pattern of gene-body methylation is largely different between angiosperms and gymnosperms. To date, the evolution and function of gene-body methylation remain largely unknown. In this project, we will do the bisulfite genomic sequencing for the main lineages of gymnosperms. The aims are to investigate the evolutionary patterns and functions of gene-body methylation in gymnosperms by analyzing the distribution modes of genes with enrichment of CG and enrichment of CHG methylation, respectively, and studying the difference of gene-body methylation between orthologous genes as well as the correlation between gene-body methylation and gene expression level. Based on the results from gymnosperms in combination with the available plant methylomes from public databases, we try to explore the relationships between different contexts of gene-body methylation and genome sizes. In addition, we will reconstruct evolutionary histories of genes related to DNA methylation/demethylation in order to unveil why angiosperms and gymnosperms have different gene-body methylation patterns. Finally, we will analyze the distribution patterns of gene-body methylation in different tissues of the representative species of the main lineages of gymnosperms.