This may represent an upper limit to the flux of DAG through PC into TAG. However, as membranes do not have a large capacity for storage of neutral lipids and DAG can partition into the oil body (Kuerschner et?al., MK-2206 2008), the labeled DAG that accumulates at later time points is probably mixing with the PC-derived bulk DAG pool in the oil body. The labeled DAG that accumulates may be produced through route A as PC-derived DAG or route B by direct incorporation into the oil body. At 60?min of labeling DAG represents R428 chemical structure and by the similarity of bulk DAG and PC (Figure?4b). Therefore, the flux of DAG through PC is most likely closer to the upper limit of 93% through route A than the lower limit of 60%. The relative fluxes of TAG synthesis from de novo DAG or PC-derived DAG are especially important for the field of oilseed engineering. Many industrially useful FAs contain oxygenated functional groups and are efficiently removed from microsomal membranes in many plants (Bafor et?al., 1991; Banas et?al., 1992; Stahl et?al., 1995). This may present a problem for accumulating DAG containing two unusual FAs if the transgenic host plant uses PC-derived DAG for TAG synthesis. We analyzed the flux of TAG synthesis in CL37 plants which express RcFAH12 to determine how HFAs are incorporated into TAG in transgenic Arabidopsis seeds. Proposed pathways of HFA-containing TAG synthesis and corresponding bottlenecks in CL37 are summarized in Figure?9. [14C]glycerol labeling demonstrated a reduction of about 50% in total labeled glycerolipid accumulation, which was mostly due to a reduction of about 75% in accumulation of labeled PC, and was not compensated for by an increase in TAG synthesis from de novo DAG (Figure?5). The reduction in PC synthesis JQ1 purchase may be due to turnover of HFA-containing DAG (Figure?9, flux 6) or PC. The HFAs were rapidly incorporated into the sn-1/sn-2 positions of de novo synthesized mono-HFA-DAG representing around 50% of total DAG (Figure?6b). However, mono-HFA-DAG did not efficiently accumulate in PC (Figure?7) or TAG (Figure?8) and accumulated eight times more slowly than 0-HFA-DAG (Figure?6a). These results suggest that the flux of de novo DAG through PC is a bottleneck for the accumulation of di-HFA-DAG for tri-HFA-TAG synthesis (Figure?9, flux 5). The mechanisms that limit HFA-containing DAG or PC accumulation are unknown.