| Throughout all phases of the plant life cycle, the development of an organelle termed the plastid is critical for normal cellular function. Plastids are structures that perform a variety of functions within a plant cell essential for survival. There are a variety of plastid types, and a specific type of plastid termed the chloroplast is found within the green tissues of the plant and is the site of the light-harvesting reactions of photosynthesis. My dissertation research focused on the proper development of chloroplasts in the flowering plant Arabidopsis thaliana.;Utilizing molecular and genetic techniques, I studied a class of mutations that affect chloroplast development in the embryo-derived cells of the seedling, resulting in a seedling-specific albinism phenotype. In these seedling plastid defective (spd) mutants, tissues derived from the shoot apical meristem typically develop normal chloroplasts. My research demonstrated that chloroplast development during embryogenesis and germination requires unique molecular components, such as SPD1 and SPD2, that are absent or found in a reduced capacity during plastid biogenesis in the adult leaf tissues.;A second stage of chloroplast development that I studied was in the tissues of the adult leaf. To that end, I isolated a novel variegated plant in Arabidopsis that contains a mutation in the gene encoding for geranylgeranyl diphosphate synthase 1. The GGPS1 protein is localized to the chloroplast and catalyzes the formation of the twenty-carbon isoprenoid geranylgeranyl diphosphate, which serves as a precursor to many plant secondary metabolites. My research demonstrated that GGPS1 functionality is essential for the proper development of chloroplasts in adult tissues.;In summary, the research conducted for my dissertation details critical, but previously poorly understood, aspects of chloroplast development that are an integral part of plant embryo maturation, seedling establishment, and whole plant development. |
