Patterning of the Female Gametophyte in Arabidopsis

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PI: Venkatesan SundaresanProposal Number: IOS-0745167Title: Patterning of the female gametophyte in ArabidopsisAbstractThe reproduction of flowering plants relies on the production of gametophytes, the haploid phase of the plant life cycle generated by the reproductive organs of the flower, containing half the chromosome set of the parent plant. Seed formation requires that female gametophytes called embryo sacs, be fertilized by male gametophytes which are pollen grains containing sperm cells. The mature female gametophyte or embryo sac consists of only four cell types, including two gametes ? the egg cell and central cell, resulting from the execution of a precise developmental program. This project will use the model plant Arabidopsis to study the molecular mechanisms that govern the formation of developmental pattern in the embyo sac. An unusual mutation, eostre, in which the embryo sac has an additional egg cell in place of another cell called a synergid cell, has been identified in Arabidopsis. Characterization of the eostre mutant shows that transcriptional regulators of the BELL and class II Knox homeodomain families, and interacting proteins of the OVATE family, regulate cell specification in the embryo sac. Identification of specific members of these gene families that function in female gametophyte development and their possible roles in specification of cell identities in the embryo sac will be undertaken. In addition, new experimental evidence indicates that signaling by the plant hormone auxin establishes cell identity in the embryo sac. The function of auxin in cell specification in the embryo sac will be further investigated through approaches employing genetic mutants and RNA silencing as well as cellular markers that track auxin concentrations and transport. The proposed studies will provide an understanding of the mechanisms underlying development and function of the female gametophyte. As the embryo sac plays a central role in seed formation, the knowledge gained from these studies has important potential applications towards the control of reproduction and increased seed production in crop plants. The project will also provide comprehensive training in genetics and molecular biology of plant reproduction for postdoctoral fellows, and research opportunities for undergraduate students, including students from underrepresented groups, by providing valuable research experience and training for the life sciences and biotechnology professions.