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Made available in DSpace on 2020-12-10T20:10:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-08-23 Conseil Regional des Pays de la Loire Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Directorate for Biological Sciences FP7 Food, Agriculture and Fisheries, Biotechnology Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) National Science Foundation European Regional Development Fund Angers Loire Metropole Region Pays de la Loire During the later stages of seed maturation, two key adaptive traits are acquired that contribute to seed lifespan and dispersal, longevity and dormancy. The seed-specific heat shock transcription factor A9 is an important hub gene in the transcriptional network of late seed maturation. Here, we demonstrate that HSFA9 plays a role in thermotolerance rather than in ex situ seed conservation. Storage ofhsfa9seeds ofMedicago truncatulaand Arabidopsis had comparable lifespan at moderate storage relative humidity (RH), whereas at high RH,hsfa9seeds lost their viability much faster than wild type seeds. Furthermore, we show that inM.truncatula, Mthsfa9seeds acquired more dormancy during late maturation than wild type. Transient expression of MtHSFA9in hairy roots and transcriptome analysis of Mthsfa9Tnt1 insertion mutants identified a deregulation of genes involved in ABA biosynthesis, catabolism and signalling. Consistent with these results,Mthsfa9seeds exhibited increased ABA levels and higher sensitivity to ABA. These data suggest that in legumes,HSFA9acts as a negative regulator of the depth of seed dormancy during seed development via the modulation of hormonal balance. Univ Angers, Inst Agro, SFR 4207 QuaSaV, IRHS,UMR1345,INRAE, F-49071 Beaucouze, France Univ Estadual Paulista, Fac Ciencias Agron, Dept Prod Vegetal, Botucatu, SP, Brazil Ctr Res Agr Genom CRAG, Barcelona, Spain Univ Estadual Paulista, Fac Ciencias Agron, Dept Prod Vegetal, Botucatu, SP, Brazil CAPES: 001 Directorate for Biological Sciences: 703285 FP7 Food, Agriculture and Fisheries, Biotechnology: FP7-609398 FAPESP: 17/50211-9 National Science Foundation: 703285

International audience; Mitogen-Activated Protein Kinase (MAPK) modules are often involved in stress responses and plant developmental processes. Among these MAPKs, MPK4 has a complex role in biotic stress signaling, cell division control and cytoskeletal organization. mpk4 knockout (KO) plants are dwarfed and very sick, making it difficult to distinguish between cause and effect of its phenotype. To overcome this difficulty, we developed mutations triggering constitutive MPK4 activity and created transgenic lines allowing phenotypic studies on a WT-like plant. By this approach, we confirmed that MPK4 functions as a negative regulator of pathogen defense, but our work also suggests that MPK4 interferes with stress signaling pathways at several distinct steps in pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) as well as in effector-triggered immunity (ETI). This study shows that CA mutations are valuable complementary tools to study MAPK signaling pathways in planta.