Because of plants immobility, quick and effective regulations of transcription are of crucial importance for adaptation to environmental changes. Recently, it has been demonstrated for the first time that general epigenetic silencing of heterochromatin, through mechanisms that differ from those previously known, is transiently released after heat stress treatment. To determine these stress-specific epigenetic mechanisms, an EMS mutagenesis has been performed on mom1-6 lines containing a silencing reporter. M2 lines were then subjected to long heat stress and mutant candidates were selected according to their altered activation of marker transcription. Here I performed the screening and characterization of some of the most interesting mutants resulting from this first screening. I obtained results on DNA methylation status and expression of LUC, SDC, and SQN in stressed and unstressed plants and an initiated mapping of the mutations.