ARABIDOPSIS BSISTER AND SEEDSTICK MADS-BOX TRANSCRIPTION FACTORS MATERNALLY CONTROL THE OVULE AND SEED DEVELOPMENT IN ARABIDOPSIS THALIANA

Seeds derive from the fertilization of ovules and represent the next generation of the plant. Two key genes, ARABIDOPSIS Bsister (ABS) and SEEDSTICK (STK), encode MADS-domain transcription factors (TFs) that are expressed in the sporophytic tissues and are essential for proper ovule di􀆯erentiation and seed development. In the abs stk double mutant, ovule development and seed set are signi􀆱cantly impaired, leading to the production of very few viable seeds. Furthermore, the ovules in the double mutant exhibit defects in integument di􀆯erentiation and show an excessive accumulation of starch within the embryo sac. Although most abs stk ovules are successfully fertilized, the development of the embryo is arrested a few days after fertilization in most of the seeds. To better understand the roles of ABS and STK during ovule and early seed development, the phenotypes of the abs stk double mutant have been investigated using morphological, omics, and genetic approaches. This comprehensive analysis revealed that sugar metabolism is signi􀆱cantly impacted in the abs stk double mutant. 6 Additionally, two di􀆯erent strategies have been employed to modulate starch accumulation in the abs stk double mutant, which resulted in a partial rescue of the embryo and seed developmental defects. By examining callose deposition and nutrient 􀆲ow into developing seeds, a model has been proposed in which these two transcription factors modulate nutrient transfer during the transition from ovule to seed. In conclusion, these 􀆱ndings highlight the signi􀆱cance of maternal tissues in regulating genetic factors related to nutrient availability, as well as the delicate interaction between metabolic and developmental processes during seed development.