FAX1 not to the max: Chloroplast export control on fatty acids during cold acclimation

Membranes of plant cells contain three main types of lipids, namely glycerolipids, sphingolipids, and sterols.Glycerolipids are the most abundant and are especially crucial for the structure and function of photosynthetic complexes in the thylakoid membrane.Their structure comprises a glycerol backbone to which two varied fatty acid chains and a varied head group are typically attached.Fatty acids synthesized in a plastid proceed to glycerolipid synthesis via either the prokaryotic pathway within the plastid or the eukaryotic pathway in the endoplasmic reticulum (see Fig.).Different plant species have varied relative contributions from the two pathways.In 16:3 plants such as Arabidopsis, spinach, and tomato, about half of the chloroplast glycerolipids are derived from each of the pathways (Browse and Somerville.1991).On the other hand, in 18:3 plants such as wheat, maize and pea, chloroplast glycerolipids are predominantly obtained from the eukaryotic pathway.