"The lifestyle of plants requires them to constantly adapt their growth and development to environmental variation. While highly related plants coding transcriptome are conservated, the non-protein-coding RNA (npcRNA) trascriptome diverges during evolution and within species. It is known that npcRNA can modificate spatio-temporal gene expression patterns, and play a key role in developmental adaptation and plasticity. In the last years, small/miRNA (two npcRNA families) have emerged as a novel and important class of regulators, due to their capacity to mediate transcriptional and post-transcriptional regulation of specific targets, including members of the epigenetic machinery, in development and stress response. Epigenetic mechanisms cause some of the stress-induced stable modifications of transcriptional states. Epimutations occur at a higher frequency than DNA mutations because they are not associated to changes in DNA sequence, playing a major role in mechanisms of adaptation because they allow rapid changes in gene expression. In addition, they can be maintained through mitosis and/or meiosis.Improving drought and salt stress tolerance in crops have been major goals in agriculture research for several years using classical breeding or genetic engineering of specific traits. However, several drawbacks have often been observed, including retarded growth or instability of the agronomic trait, sometimes due to transgene silencing, calling for new methods. In this way, as epigenetic changes account for the plasticity of plant genome responses to developmental and environmental cues, studies need to be performed to elucidate the regulatory loop involving mi/siRNA and the epigenetic machinery.The aim of the proposed project is analyze the role of mi/siRNA in epigenetic regulation of salt stress response in Medicago truncatula, using bioinformatics and genetic approaches, in order to create new epigenetic germplasms and improve crop productivity."