6533b859fe1ef96bd12b734d

RESEARCH PRODUCT

Contribution de l'albumen au développement de la graine chez Medicago truncatula : caractérisation d'un facteur de transcription de type DOF exprimé dans l'albumen chalazal

subject

description

In the current context, which necessitates a reduction in inputs in crop systems and boosting of production of plant proteins to reduce France’s dependency on feed imports,, growing legumes represents an alternative. Grain legumes are major sources of proteins for animal and human nutrition. In the UMR1347 Agroécologie, the objectives of the study group "déterminismes Génétiques et Environnementaux de l’Adaptation des Plantes à des Systèmes de culture Innovants" (GEAPSI) are to promote legume cultivation and adaptation to environmental stresses, via multidisciplinary approaches (genetics, ecophysiology, molecular physiology). This thesis project was carried out in the "Étude des Mécanismes Moléculaires" team, particularly interested in seed quality traits such as protein content or seed size and identification of genes implicated in variations of these trait s. Experiments were performed using Medicago truncatula as a model species for legumes with a view to transferring the information to the target crop species Pisum sativum. Legume seed size is determined by the embryo’s capacity to divide during embryogenesis and to accumulate reserves during seed filling. At early developmental stages, nutrient assimilation occurs predominantly in embryo-surrounding tissues: the endosperm and seed coat. This thesis project aims to evaluate the endosperm contribution to seed development in Min M. truncatula. We have shown several DOF (DNA-binding One Zinc Finger) genes to be expressedbe expressed in this tissue. They belong to a large family of transcription factors implicated in numerous biological processes, but whose role remain to be elucidated. One of these genes, termed DASH for Dof Affecting Seed embryogenesis and Hormone metabolism, is expressed preferentially in the endosperm during embryogenesis. TILLING and TnT1 mutants isolated for this transcription factor are affected in seed development (abortion at 10 DAP). The cytology of development at early stages (6 to 10 DAP) revealed that the expression of this gene in the endosperm is required for the normal development of the embryo, demonstrating the role of the endosperm in the control of embryogenesis in legumes. A comparative transcriptomics study of dash vsdash vs wild-type pods allowed us to suggest hypothesis about the function of the DASH gene. Evidence for a deregulation of hormone metabolism, in particular for auxin, was obtained, and several potential target genes of this transcription factor were selected. . A comparison of the transcriptome of the three tissues of the seed at 12 DAP was carried out for the reference wild-type line (Jemalong A17). This allowed the tissue localization of the target genes, to reveal metabolic pathways preferentially expressed in the endosperm, and to propose hypotheses about the role of this tissue during seed development.