Degree of DNA methylation in chicory (Cichorium intybus L.):: influence of plant age and vernalization

Chicory plants (Cichorium intybus L. var, foliosum cv. Flash) were harvested every 14 days from 43 to 168 days after sowing. The tissue was either immediately analyzed or after a 4 week post-harvest cold treatment at 5 degrees C. DNA methylation was measured, using high pressure liquid chromatography (HPLC), in the root tissue as well as in the shoot apices. During the growing season, the degree of methylation ranged between 10 and 16% for root tissue as well as for shoot apices. The reaction (methylation/ demethylation) to cold treatment depended on the tissue type and the plant age. For root tissue, demethylation was observed after cold treatment in the beginning of the growing season followed by methylation in the middle part and strong demethylation at the end of the season. Except for two harvest dates, a demethylation of DNA in the shoot apex tissue occurred during cold treatment. Demethylation was strongest for the two last harvest dales. This is the first report on changes in degree of DNA methylation during a whole growing season and differences in the effect of cold depending on the age of a biennial plant. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.