Epigenetic reprogramming and non-cell autonomous communication as mechanisms of seed formation

• Applicant: Dr. Duarte Figueiredo, Ph.D.
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 421178202

The ability to form seeds is a key factor that contributed to the ecological dominance of flowering plants. The development of a seed starts with the fertilization of the maternal gametes within the ovule, egg cell and central cell, by two paternal sperm cells. This leads to the formation of the embryo, which will originate a new plant, and of the endosperm, a nourishing tissue, analogous to the mammalian placenta. These two fertilization products are surrounded by a maternal tissue, called the seed coat, which is derived from the ovule integuments. During seed formation, these three structures, embryo, endosperm and seed coat, have to coordinate their development in order to ensure the successful transmission of the parental genomes to the next generation. Seeds, and seed endosperm in particular, comprise the majority of our food, as well as of animal feed. Nevertheless, we know surprisingly little about the molecular and genetic mechanisms that underlie the formation of a seed. This project aims to uncover those mechanisms that contribute to the formation of the endosperm and of the seed coat. The development of these two structures only starts after fertilization. This is because epigenetic mechanisms prevent the maternal ovule from forming a seed in the absence of fertilization. This also means that the paternal sperm cells carry signals that are responsible for initiating seed development. Previous work showed that the plant hormone auxin is produced after fertilization, in a paternal-dependent manner, and initiates endosperm and seed coat formation in the model plant species Arabidopsis thaliana. However, the mechanisms by which auxin bypasses the epigenetic repression of seed development remain unexplored. Furthermore, although auxin is sufficient to initiate seed development, it is not sufficient to sustain it, and additional factors seem to be required. This project aims at addressing these two questions. It will do so, first by searching for epigenetic "erasers" that may work with auxin in initiating seed coat development, and second by studying the role of another class of plant hormones, brassinosteroids, as potential signal molecules that are required for endosperm and seed coat communication. Finally, a genetic screen will be implemented to search for additional mechanisms that contribute to seed formation. This project thus aims at providing a better understanding of the molecular and genetic mechanisms that are necessary for seed formation. Consequently, this work is expected to be of interest for a wide audience, including plant developmental biologists, geneticists, and plant breeders.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partner: Dr. Wassim Chehab