Epigenetics refers to chromatin marks that do not involve sequence changes, often reversible, heritable and triggered by environmental factors. In plants, there are cytosine methylation contexts other than the known CG dinucleotide, like CNG and CNN (asym

RODRIGO M GONZALEZ; MARTINIANO M. RICARDI; JOSE M. ESTEVEZ; NORBERTO D. IUSEM

San Luis

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2011

Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular

Epigenetics refers to chromatin marks that do not involve sequence changes, often reversible, heritable and triggered by environmental factors. In plants, there are cytosine methylation contexts other than the known CG dinucleotide, like CNG and CNN (asymmetric), the latter typically found in transposons and non-coding repetitive elements. Our goal was to test the hypothesis that stress-induced adaptive physiological responses in plants depend on epigenetic changes. We thus explored leaves and roots of tomato (bearing a genome 10 times larger than that of Arabidopsis) under basal and water-deficit conditions. We surveyed the epigenetic status (in the three methylation contexts) of our challenging model gene, Asr1, non-transposon, protein-coding, and a member of a stress-inducible family absent in Arabidopsis. We used bisulphite procedure to detect DNA methylation and, for histone modifications, we did ChIP using anti-H3K4me3 and H3K27me3 antibodies. We found high basal levels of atypical methylation at CNN sites in leaves, whereas stress caused their removal all over the gene, concomitantly with a moderate increase of CG methylation marks in exon 1, removal of the repressive mark H3K27me3 and a 36-fold increase in Asr1 transcript. These findings may represent a general mechanism for the acquisition of new epialleles, which are pivotal for regulating gene expression in plants.