Yonghong Zhou, Katharina vom Dorp, Peter Dörmann and Georg Hölzl
from: Chloroplasts: Current Research and Future Trends (Edited by: Helmut Kirchhoff). Caister Academic Press, U.K. (2016) Pages: 1-24.
Chloroplasts are the major site of fatty acid de novo synthesis in the cells of plants and algae. Fatty acids are incorporated into glycerolipids in the chloroplast (prokaryotic pathway) or are exported to the endoplasmic reticulum for glycerolipid synthesis following the eukaryotic pathway. The four major glycerolipids of chloroplasts are monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG), which are the building blocks for thylakoids and play specific roles in photosynthesis. During phosphate deprivation DGDG and SQDG accumulate and replace phospholipids to save phosphate for other processes. In addition to glycerolipids, chloroplasts contain a large variety of isoprenoid lipids derived from the methyl-erythritol-phosphate pathway. Prenylquinones (tocopherol, plastoquinone, phylloquinone) are one class of chloroplast isoprenoid lipids and serve as antioxidants or electron carriers of photosystems II and I, respectively. β-Carotene (an isoprenoid-derived carotenoid), tocopherol, and phylloquinone (provitamin A, vitamin E and vitamin K1, respectively) are essential components of the human diet. Chlorophyll, the main photosynthetic pigment, carries an isoprenoid-derived phytyl chain which is released during chlorophyll breakdown. Phytol is employed for the synthesis of fatty acid phytyl esters and tocopherol. In contrast to plants, chloroplasts of eukaryotic algae contain further lipids and employ additional routes for lipid synthesis. Research on chloroplast lipids has seen major progress in the recent past due to the development of highly sensitive and accurate mass spectrometers for the analysis of extremely low abundant lipids or lipids only accumulating during stress conditions read more ...