Roles of EMS1 and TPD1 in gametogenesis and sporogenesis in the fern Ceratopteris richardii

Pollen development is particularly important for cereal crop plants such as maize and rice because the process of producing F₁ seeds to harness hybrid vigor often fails due to pollen malfunction. This prompted active research not only in cereal crop plants but also in other flowering plants such as Arabidopsis and led to the identification of multiple genes important for pollen development. In angiosperms, pollen development occurs by two major steps, sporogenesis and gametogenesis, they are sequential and occur in the same floral organ. We sought to investigate whether some of the pollen development genes identified in angiosperms are conserved in ferns, which are vascular plants like flowering plants, but have not evolved flowers. More importantly, sporogenesis and gametogenesis occur separately in of the two free-living phases of the fern life cycle. If these genes are conserved, I want to know whether they function in both the processes of gametogenesis and sporogenesis in ferns. In our laboratory, we applied a candidate gene approach to study the function and evolutionary implications of genes involved during reproduction using the model fern Ceratopteris richardii. In my thesis I identified the C. richardii homologs of EXCESS MICROSPOROCYTLESS 1 and TAPETUM DETERMINANT 1, both are required during pollen development in angiosperms, and investigated their functions throughout the life cycle of C. richardii, specifically during sporogenesis and gametogenesis. By determining the expression patterns and characterizing phenotypes of plants with the expression of these genes knocked down, I discovered that both genes are involved in sporogenesis and gametogenesis which occur in the two different phases in the fern.