• stress response;
  • dedifferentiation;
  • chromatin reorganization;
  • DNA methylation;
  • histone modifications;
  • Arabidopsis

Background: Previous data suggested that senescing cells or cells exposed to acute stress may acquire stem cell properties characterized by open chromatin conformation and by promiscuous expression of transcription factor genes. To further explore the link between stress response and dedifferentiation, we generated transgenic plants in which a reporter AtMBD6-GFP is controlled by a meristem-specific promoter derived from the ANAC2 gene together with the analysis of chromatin conformation. Results: We found that ANAC2 promoter is essentially active in the shoot and the root apical meristems including leaf primordia. ANAC2 was activated in mature leaves following exposure to various stress conditions including protoplasting and dark. This activity was associated with decondensation of pericentric but not of centromeric chromatin. Using epigenetic mutants, ddm1 and kyp/suvh4, we found that compaction at centromeric chromatin persists despite a significant reduction in DNA and histone methylation. Conclusions: Our results suggest that extreme environmental signals trigger plant somatic cells to acquire stem cell properties before assuming a new cell fate. Results also pointed to distinct mechanisms involved in controlling chromatin compaction at chromocenter and that compaction of centromeric chromatin may not be dependent on epigenetic means driven by DDM1 and KYP/SUVH4 chromatin modifier proteins. Developmental Dynamics, 242:1121–1133, 2013. © 2013 Wiley Periodicals, Inc.