Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Atypical epigenetic mark in an atypical location: cytosine methylation at asymmetric (CNN) sites within the body of a non-repetitive tomato gene | Gonzalez et al. BMC Plant Biology 2011 11 94 http 1471-2229 11 94 BMC Plant Biology RESEARCH ARTICLE Open Access Atypical epigenetic mark in an atypical location cytosine methylation at asymmetric CNN sites within the body of a non-repetitive tomato gene Rodrigo M Gonzalez Martiniano M Ricardi and Norberto D Iusem Abstract Background Eukaryotic DNA methylation is one of the most studied epigenetic processes as it results in a direct and heritable covalent modification triggered by external stimuli. In contrast to mammals plant DNA methylation which is stimulated by external cues exemplified by various abiotic types of stress is often found not only at CG sites but also at CNG N denoting A C or T and CNN asymmetric sites. A genome-wide analysis of DNA methylation in Arabidopsis has shown that CNN methylation is preferentially concentrated in transposon genes and non-coding repetitive elements. We are particularly interested in investigating the epigenetics of plant species with larger and more complex genomes than Arabidopsis particularly with regards to the associated alterations elicited by abiotic stress. Results We describe the existence of CNN-methylated epialleles that span Asr1 a non-transposon protein-coding gene from tomato plants that lacks an orthologous counterpart in Arabidopsis. In addition to test the hypothesis of a link between epigenetics modifications and the adaptation of crop plants to abiotic stress we exhaustively explored the cytosine methylation status in leaf Asr1 DNA a model gene in our system resulting from water-deficit stress conditions imposed on tomato plants. We found that drought conditions brought about removal of methyl marks at approximately 75 of the 110 asymmetric CNN sites analysed concomitantly with a decrease of the repressive H3K27me3 epigenetic mark and a large induction of expression at the RNA level. When pinpointing those sites we observed that demethylation occurred mostly in the intronic region.
