Abstract
This review covers the latest developments on the regulation of early seed development by phytohormones. The development of seeds in flowering plants starts with the fertilization of the maternal gametes by two paternal sperm cells. This leads to the formation of two products, embryo and endosperm, which are surrounded by a tissue of maternal sporophytic origin, called the seed coat. The development of each of these structures is under tight genetic control. Moreover, several phytohormones have been shown to modulate the development of all three seed compartments and have been implicated in the communication between them. This is particularly relevant, as embryo, endosperm, and seed coat have to coordinate their development for successful seed formation. Here, we review the latest advances on the hormonal regulation of early seed development in the model plant species Arabidopsis thaliana, with a focus on the endosperm and the seed coat. Moreover, we highlight how phytohormones serve as mechanisms of non-cell autonomous communication between these two compartments and how they are determinant in shaping seed formation.