Mobile DNA elements, referred to as Transposable Elements (TEs), are ubiquitous components of eukaryotic genomes. The earlier notion of TEs being junk DNA has been revolutionized by the discovery of their functional impacts, including their capacity to provide cis-regulatory elements (CREs) controlling the expression of nearby genes. While examples of such cases have been depicted, we still lack a complete understanding of the contribution of TEs to the evolution of biological functions, from conserved developmental functions to species-specific functions, including those underlying environmental response. In SATURN, we propose to determine the contribution of TEs to gene regulation across evolution using six plant species that diverged across a 20-200 My time scale and for which extensive genomic and functional data are available. Specifically, we aim to: (i) assess the contribution of TEs to CREs involved in developmental and stress-induced gene regulation, (ii) decipher how TEs contribute to conserved and species-specific expression regulation, and (iii) systematically test the role of TE-driven CREs in the regulation of gene expression. SATURN will decipher the contribution of recent and ancient TEs to functions that have shaped plant evolution and adaptation, using a highly interdisciplinary approach combining deep TE annotation, comparative genomics, innovative long-read-based epigenomics and transcriptomics developments, and in vivo functional validations. It will shed new light on the major TEs involved in species functional evolution, as well as on the type of functions that evolved due to TE insertions. Through the use of both model and crop species, it will bring fundamental knowledge on the molecular bases underlying the evolution of functional regulation, as well as valuable information for future breeding. The knowledge acquired by SATURN will be a cornerstone in the understanding of TEs’ functional contribution to species evolution.