Glycerolipid Biosynthesis

Cellular membranes act as structural components to define the boundaries of the cell and delineate subcellular compartments. Membranes also serve as scaffolds for diverse signaling events, and participate directly in essential metabolic processes. This chapter focuses on the predominant pathways of fatty acid biosynthesis, their modification, and on glycerolipid assembly in Chlamydomonas. It combines these in silico predictions with a thorough review of the experimentally verified pathways to present a comprehensive view of the identities and functions of genes involved in glycerolipid biosynthesis in Chlamydomonas. A distinguishing feature of lipid metabolism in Chlamydomonas is the lack of phosphatidylcholine (PtdCho), whose role appears to be partially assumed by the betaine lipid DGTS. The lack of PtdCho may also explain why chloroplast lipids in Chlamydomonas appear to be almost exclusively synthesized directly in the plastid. Several fatty acid desaturases have been isolated and characterized at the molecular level, and the biochemistry and genetics of fatty acid chain elongation and desaturation in Chlamydomonas are discussed here. Glycerophospholipids are the prevalent lipids in non-photosynthetic organisms. They are characterized by a phosphatidic acid (PtdOH) backbone. In plants, approximately one-third of the organic phosphorus is found in Phosphoglycerolipids and the biosynthesis of glycerolipid covers this.