Dormancy is an adaptive trait that is established during seed maturation and prevents seed germination on the parent plant or out of proper season after seed dispersal. It is also an important agronomic trait as germination before harvest (vivipary) is a major cause of crop yield losses. Abscisic acid (ABA) is the key phytohormone promoting dormancy whereas nitrate (NO3-) stimulates germination by triggering ABA catabolism. Partners 1 & 2 have previously identified a new whole MAPK (Mitogen-activated protein kinase) module which is activated by both ABA and NO3- in Arabidopsis plantlets. They have also recently shown that mutants impaired in this module produce seeds which are more dormant. Strikingly and coherently, mutations in homologous MAPK genes in wheat and barley were reported to reduce vivipary. Taken together, these preliminary results suggest that this MAPK module is a new player controlling seed dormancy conserved throughout angiosperms. The fact that this module is activated by both ABA and NO3- also suggests that it may have a pivotal role as integrator of signaling pathways controlling dormancy. This project aims to better characterize this module in the frame of seed germination using Arabidopsis as a model plant and to exploit the results to develop new strategies to manipulate crop germination in the field. To achieve these goals, the first WP will aim to functionally validate the module by unveiling where and when it is required to modulate seed dormancy and which are the kinases involved in this function, a MAPK module being composed of at least 3 kinases. Importantly, we will test how the MAPK signaling module is modulated by and/or modulates ABA and NO3- signaling by using a combination of biochemical and genetic approaches to study mutants impaired in these signaling cascades. Furthermore, the MAPK module presents unique features when compared to other plant and animal MAPK modules described so far. The second WP will thus be devoted to the characterization of these specificities and will particularly study the translational and post-translational regulations of the module as well as decipher the unknown function of protein domains in the central MAP2K. The third WP will focus on the downstream events that are regulated by the module. Firstly, we will identify substrates which are phosphorylated by MAPKs and are important to control seed dormancy. Secondly, we will unveil the cellular processes which are regulated by the module by performing transcriptomic and metabolomic studies of mutants impaired in the module. Finally, a fourth WP will aim to identify molecules targeting this MAPK module and use them as chemical probes to investigate to which extent, across the plant kingdom, this module is important for seed physiology and to modulate seed dormancy in crops. This project relies on the collaboration of 4 groups recognized as leaders in their respective fields, who will bring their expertise and skills to challenge the novel hypothesis that the recently discovered MAPK module integrates distinct environmental signaling pathways to trigger the downstream processes that determine whether seeds germinate or not. Their joint work will lead to a better understanding of the factors that control seed physiological traits and new essential knowledge to enhance resilience through advanced breeding programs and to provide guidelines for optimal seed production, treatment and storage. It will also use an original strategy based on chemical genetics in yeast aiming at the identification of small molecules that modify the activity of the MAPK module and modulate dormancy in model species and crops. Thus, the MAPKSEED project brings together multidisciplinary expertises to tackle an important issue for optimizing sustainable agriculture in a changing environment by novel and original basic research.