Variations of Cytosine Methylation Patterns between Staminate and Perfect Flowers within Andromonoecious Taihangia rupestris (Rosaceae) Revealed by Methylation-Sensitive Amplification Polymorphism

DNA methylation is an epigenetic modification that plays important roles in flower development through regulation of gene expression. Taihangia rupestris is an andromonoecious plant species, which can produce staminate and perfect flowers within the same individual. In this study, we employed methylation-sensitive amplified polymorphism (MSAP) to investigate cytosine methylation patterns in staminate and perfect flowers within the andromonoecious T. rupestris. Our data showed the cytosine methylation patterns varied in staminate and perfect flowers at early and late developmental stages. The level of cytosine methylation was slightly higher in perfect flowers than in staminate flowers, and an increase of cytosine methylation levels was found alongside developmental stages in both staminate and perfect flowers. Based on MSAP profiles, a total of 116 differentially methylated fragments (DMFs) were obtained and sequenced. Of these obtained DMFs, 42 fragments showed sequence similarity to functional genes involved in a wide range of biological processes such as flower development, signal transduction, and cell proliferation, and transcription regulation. By integrative analysis of MSAP and transcriptome data, we found transcript levels correlated with cytosine methylation patterns for majority of DMF-associated genes. This study revealed that DNA methylation could play important roles in regulation of gene expression during establishment and development of staminate and perfect flower within andromonoecious T. rupestris and would be helpful to shed light on the underlying molecular mechanisms responsible for flower formation at epigenetic scale in andromonoecious sexual system.