UNDERSTANDING EPIALLELES FORMATION IN RESPONSE TO ENVIRONMENTAL CUES AND THEIR HERITABILITY IN PLANTS

Epigenetics is defined as the study of heritable traits that do not depend on the primary DNA sequence. The discovery of epigenetic mechanisms acting on chromatin to regulate global gene expression has revealed how heritable variation need not be sequencebased. Particularly, environmental factors can induce novel variation through the activation of specific epigenetic mechanisms that determine mutations of spatial and temporal pattern of gene expression. The carriers of epigenetic information are identified in DNA methylation, histone tails post-translation modifications and histone variants. Specific combinations of these marks can influence chromatin structure that in turn affects transcription and genome stability. The environment can induce various types of epigenetic changes leading to alternative gene expression patterns, which can either be restricted to somatic and vegetative tissues or propagated through mitotic cell divisions. Of particular interest is the distinction between transient and stable changes in epigenetic marks and the formation and maintenance of epialles. Epigenetic alleles or epialleles show different distribution of epigenetic marks in their sequence and can exhibit distinct phenotypes. The search for natural occurring epialles and the understanding of the mechanisms leading to their formation and maintenance, particularly in response to environmental cues, is a great challenge for the future.