Assimilation of sulfate-S is a central event in plant metabolism and the formation of organosulfur compounds such as amino acids, cofactors, and sulfolipid by the plant. The research planned is focused on sulfate activation that takes place on the inner mitochrondrial membrane of Euglena and the presumed, subsequent transfer of activated S in some form to the chloroplast. A critical assessment of sulfite's involvement in sulfolipid formation is another focus of this research. The flow of sulfur compounds from mitochondria to chloroplasts is an important part of understanding the origin of chloroplast components during plastid development. The metabolic intermediates involved in conversion of assimilated sulfate into the variety of S-containing compounds characteristic of plant biomass are, in significant details, unclear; the research planned is directed at understanding the extent to which sulfite is an actual intermediate in such conversions, and at enlarging the understanding of how a key enzyme involved in sulfate reduction functions in cysteine biosynthesis. This flow of sulfur is an important aspect of plastid development in plant growth.
