BUSCADOR RECOLECTA

Genome-wide cytosine methylation estimates of 200 plants of Helleborus foetidus obtained by HPLC and Methylation Scoring of MSAP data Genome-wide cytosine methylation estimates in young leaves of 200 plants of Helleborus foetidus obtained using HPLC and the percentage of cytosine methylation in CCGG sites obtained by Methylation Scoring of MSAP data. Methylation scoring (MS50) was calculated as the percentage of MSAP loci scored as methylated (condition II + III). HPLC_MS_data_doi_10.5061_dryad.04d0d.txt, Methylation of DNA cytosines affects whether transposons are silenced and genes are expressed, and is a major epigenetic mechanism whereby plants respond to environmental change. Analyses of methylation-sensitive amplification polymorphism (MS-AFLP or MSAP) have been often used to assess methyl-cytosine changes in response to stress treatments and, more recently, in ecological studies of wild plant populations. MSAP technique does not require a sequenced reference genome and provides many anonymous loci randomly distributed over the genome for which the methylation status can be ascertained. Scoring of MSAP data, however, is not straightforward, and efforts are still required to standardize this step to make use of the potential to distinguish between methylation at different nucleotide contexts. Furthermore, it is not known how accurately MSAP infers genome-wide cytosine methylation levels in plants. Here, we analyse the relationship between MSAP results and the percentage of global cytosine methylation in genomic DNA obtained by HPLC analysis. A screening of literature revealed that methylation of cytosines at cleavage sites assayed by MSAP was greater than genome-wide estimates obtained by HPLC, and percentages of methylation at different nucleotide contexts varied within and across species. Concurrent HPLC and MSAP analyses of DNA from 200 individuals of the perennial herb Helleborus foetidus confirmed that methyl-cytosine was more frequent in CCGG contexts than in the genome as a whole. In this species, global methylation was unrelated to methylation at the inner CG site. We suggest that global HPLC and context-specific MSAP methylation estimates provide complementary information whose combination can improve our current understanding of methylation-based epigenetic processes in nonmodel plants., Peer reviewed