Photosynthesis in green plants is the basis for all life on earth. The chlorophyll-protein complexes of photosynthesis are embedded into the thylakoid membranes of chloroplasts. Chloroplasts are capable of synthesizing a unique set of membrane lipids and isoprenoid lipids, some of which are essential for human nutrition, e.g., tocopherol (vitamin E), phylloquinone (vitamin K) and β-carotene (provitamin A). Galactolipids represent the most abundant membrane lipid class in chloroplasts. The analysis of Arabidopsis
mutants revealed that galactolipids are essential for growth and photosynthesis. Furthermore, galactolipids are critical during growth on phosphate-limiting soils, because they replace phospholipids in the membranes and make phosphate available for other important cellular processes. Tocopherol (vitamin E) is one of the most important antioxidants. Thus, vitamin E is used as a major dietary supplement for human nutrition. Interestingly, growth and photosynthesis of Arabidopsis
mutants carrying a defect in tocopherol biosynthesis are very similar to wild type, indicating that tocopherol can be substituted by other antioxidants in the plant cell. Employing biotechnological approaches, the natural form of vitamin E required to serve a growing population might be derived from transgenic crop plants in the near future.