Fig. 8.

A hypothesized working model illustrating the localization and possible roles of CzDGAT1A and CzDGTT5 in TAG biosynthesis in C. zofingiensis. The de novo synthesized fatty acids, together with those released from membrane polar lipids, constitute the acyl-CoA pool. In response to ND, CzDGAT1A and CzDGTT5 are up-regulated considerably and localize at ER. DGAT1A utilizes more C16:0- and C18:1-CoAs than CzDGTT5 and prefers eukaryotic DAGs as the acyl acceptor for TAG assembly, while CzDGTT5 prefers prokaryotic DAGs for TAG assembly. The prokaryotic DAGs may be translocated from chloroplast to the ER by diffusion along the delimiting monolayer of lipid droplet, which has contact sites with both chloroplast and ER. Not all intermediates or reactions were displayed. ER endoplasmic reticulum, Cp chloroplast, FA fatty acids