Genomic imprinting in an early-diverging angiosperm reveals ancient mechanisms for seed initiation in flowering plants

The evolution of the seed habit marks a pivotal innovation of the spermatophytes. Angiosperms further refined this trait by coupling the development of seed accessory structures to fertilization, optimizing resource allocation. Here, we demonstrate that post-fertilization auxin production is an evolutionarily conserved mechanism for seed initiation in angiosperms. We also provide evidence that this pathway likely emerged from a switch from maternal to paternal control after the divergence of angiosperms from their gymnosperm ancestors. Our study thus brings new insights into the evolutionary origins of the endosperm, which was a determining feature for the rapid rise to dominance of flowering plants.