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2.A.126 The Fatty Acid Exporter (FAX) Family

Fatty acid synthesis in plants occurs in plastids, and these compounds are exported for subsequent acyl editing and lipid assembly in the cytosol and endoplasmatic reticulum. Li et al. 2015 identified FAX1 (fatty acid export 1) in the chloroplast inner envelope. FAX1 mutants in Arabidopsis thaliana are deficient for biomass production, male fertility and synthesis of fatty acid-derived compounds such as lipids, ketone waxes, and pollen cell wall materials. Determination of lipid, fatty acid and wax contents revealed that endoplasmatic reticulum (ER)-derived lipids decreased when FAX1 was missing, but levels of several plastid-produced species increased. fax1 over-expression gave the opposite behavior, including a pronounced increase of triacyglycerol oils in flowers and leaves.The cuticular layer of stems from fax1 knockout lines was reduced in C29 ketone wax compounds. Since in yeast, FAX1 could complement fatty acid transport defects, Li et al. 2015 concluded that FAX1 mediates fatty acid export from plastids. In vertebrates, FAX1 homologues are related mitochondrial membrane proteins.

References associated with 2.A.126 family:

Li, N., I.L. G├╝gel, P. Giavalisco, V. Zeisler, L. Schreiber, J. Soll, and K. Philippar. (2015). FAX1, a novel membrane protein mediating plastid fatty acid export. PLoS Biol 13: e1002053. 25646734