TGDs are trigalactosyldiacylglycerol proteins required for chloroplast membrane lipid synthesis. The TGD1, -2, and -3 proteins form a putative ABC (ATP-binding cassette) transporter transporting ER-derived lipids through the inner envelope membrane of the chloroplast, while TGD4 binds phosphatidic acid and resides in the outer chloroplast envelope [].This entry represents TGD4, which is involved in endoplasmic reticulum-to-chloroplast lipid trafficking [].