Poplar stems show opposite epigenetic patterns during winter dormancy and vegetative growth
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In this study the identification of epigenetic marks of closed and open chromatin states has been performed by immunofluorescence in vibratome-thick sections from poplar stems, followed by quantification of the signal in a representative population of individual nuclei on a confocal microscope. Unlike other methods often used for detection of global DNA methylation levels, the procedure hereby proposed can be applied to a wide range of specimens regardless of the purity and yield of genomic DNA extraction and in a tissue-dependent manner. Using antibodies to 5-methylcytidine and acetylated lysine 8 of histone H4, as reliable indicators of transcription incompatible and compatible chromatin states, respectively, the influence of epigenetic regulation on differential gene expression during the growth and arrest periods in xylem and phloem tissues was assessed. The fluorescence signal of 5-methylcytosine was significantly higher in winter as compared with summer. Conversely, the fluorescence signal for acetylated Lys 8 of histone H4 was significantly higher in summer than in winter in both tissues examined. Collectively, these results put forward an epigenetic control of winter dormancy in poplar stems.
KeywordsEpigenetics Immunofluorescence DNA methylation Acetylated histone H4 Poplar Winter dormancy
The authors thank Cipriano Aragoncillo (UPM, Madrid, Spain), María Berdasco (IDIBELL, L’Hospitalet de Llobregat, Spain) and Mario Fraga (IUOPA, Oviedo, Spain) for scientific advice and Rosa Casado (UPM, Madrid, Spain) for technical support. The JIM 7 antibody was kindly provided by Keith Roberts (John Innes Centre, Norwich, UK). We also thank the “Blue Brain Project”, and especially, Isabel Fernaud, José Rodrigo and Javier de Felipe from the Centro de Tecnología Biomédica (UPM, Pozuelo de Alarcón, Spain) for the use of the Zeiss 710 confocal microscope. This work was supported by the Spanish Ministry of Science and Innovation grants AGL2008-00168/FOR and AGL2011-22625/FOR and the Plant KBBE project PIM2010PKB-00702.
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