Seed size is a major agronomic trait: large seeds store more nutritious compounds and generate more vigorous seedlings. Like in many plant organs, seed growth in Arabidopsis relies on biochemical and mechanical interactions between two genetically and physically distinct seed compartments: the endosperm and the surrounding seed coat. Accordingly, the two layers of the seed coat outer integument play a key role in seed morphogenesis as distinct mechanical responses occurring in each of these layers are thought to determine both the size and the shape of the seed. The goal of my thesis was thus to test the mechanical contribution of these two outer integument layers to seed morphogenesis by studying the mechanical and growth defects of the mutant of outer integument identity apetala2 (ap2). The work of my thesis allowed me to show that AP2 activity initially promotes seed growth but then inhibits it by tuning the composition in pectin and hemicellulose, and thus the mechanical properties, of the walls of both layers of the outer integument. In parallel, my results also suggest that AP2 activity affects seed shape without influencing microtubule response to forces in the seed coat. Finally, I also proved that altering the properties of the seed coat can, in turn, affect endosperm development and mechanical properties. Taken together, the work of my thesis provides a better understanding on how mechanical interactions and responses control morphogenetic processes in plants.
Gratuit
Disciplines