CyMATE: a new tool for methylation analysis of plant genomic DNA after bisulphite sequencing

Cytosine methylation is a hallmark of epigenetic information in the DNA of many fungi, vertebrates and plants. The technique of bisulphite genomic sequencing reveals the methylation state of every individual cytosine in a sequence, and thereby provides high-resolution data on epigenetic diversity; however, the manual evaluation and documentation of large amounts of data is laborious and error-prone. While some software is available for facilitating the analysis of mammalian DNA methylation, which is found nearly exclusively at CG sites, there is no software optimally suited for data from DNA with significant non-CG methylation. We describe CyMATE (Cytosine Methylation Analysis Tool for Everyone) for in silico analysis of DNA sequences after bisulphite conversion of plant DNA, in which methylation is more divergent with respect to sequence context and biological relevance. From aligned sequences, CyMATE includes and distinguishes methylation at CG, CHG and CHH (where H = A, C or T), and can extract both quantitative and qualitative data regarding general and pattern-specific methylation per sequence and per position, i.e. data for individual sites in a sequence and the epigenetic divergence within a sample. In addition, it can provide graphical output from alignments in either an overview or a 'zoom-in' view as pdf files. Detailed information, including a quality control of the sequencing data, is provided in text format. We applied CyMATE to the analysis of DNA methylation at transcriptionally silenced promoters in diploid and polyploid Arabidopsis and found significant hypermethylation, high stability of the methylated state independent of chromosome number, and non-redundant patterns of mC distribution. CyMATE is freely available for non-commercial use at http://www.gmi.oeaw.ac.at/CyMATE.