Seminars

Seed development is initiated with the double fertilization of the egg cell and central cell of the female gametophyte, resulting in the formation of the zygote and endosperm mother cell, respectively.  Subsequent development is divided conceptually into two phases.  During the morphogenesis phase, the zygote undergoes cell division, patterning, and differentiation events, ultimately resulting in the formation of an embryo that possesses the rudimentary tissue and organ systems of the vegetative plant.  The endosperm develops initially as a syncytium, with nuclear migration resulting in the formation of three distinct endosperm compartment that later cellularize.  During the maturation phase, morphogenesis of the embryo and endosperm becomes suppressed, storage macromolecules, such as proteins and lipids, accumulate in massive amounts, and the embryo acquires the ability to withstand desiccation that occurs at the latest stage of seed development.  The mature seed consists of a developmentally and metabolically quiescent embryo and endosperm surrounded by the protective seed coat.
I will focus primarily on development of the zygotic components of the seed, the embryo and endosperm.  Our profiles of mRNA populations in every cell type, tissue, and compartment of Arabidopsis seeds at all stages of development have provided the most comprehensive description of gene activity during seed development.  These datasets have enabled the identification of coexpressed gene sets which, in turn, have provided information about the processes that occur in zygotic seed compartments with high spatial and temporal resolution.  We also developed a simple approach to predict gene regulatory networks that operate during seed development.  I will discuss how a gene regulatory networks predicted to operate during the maturation phase corresponds to one centered on the LEC transcription factors that are critical regulators of the maturation phase.  Together, information derived from these studies reveal new insights into the relationship between embryo and endosperm development.  Seeds account directly for approximately 70% of the calories consumed by humans, and, therefore, they are a key to food security.  A mechanistic understanding of seed development is critical to the design of strategies to improve the nutritional quality of seeds for agriculture.