Location: Plant Genetics ResearchTitle: Phospholipase D¿ enhances diacylglycerol flux into triacylglycerol
|WANG, GEILANG - Danforth Plant Science Center|
|LI, JIA - Danforth Plant Science Center|
|BATES, PHILIP - University Of Southern Mississippi|
|WANG, XUEMIN - Danforth Plant Science Center|
|Allen, Douglas - Doug|
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2017
Publication Date: 5/1/2017
Citation: Yang, W., Wang, G., Li, J., Bates, P.D., Wang, X., Allen, D.K. 2017. Phospholipase D enhances diacylglycerol flux into triacylglycerol. Plant Physiology. 174(1):110-123. doi: 10.1104/pp.17.00026.
Interpretive Summary: Lipids (oils and fats) are an energy dense renewable resource, important for the diet, for biofuels, and for other industrial applications. Plant oilseeds are a concentrated source of lipids. Studying how carbon (in the form of sugar) derived from photosynthesis is partitioned between storage sugars, proteins, and lipids in oilseeds ultimately identifies the components in the processes that are involved in producing and storing lipids in the seed. These components can be quantified and better understood, potentially guiding future efforts to engineer enhanced oil production in plant tissues. In this study, seeds were genetically modified with an enzyme that alters the movement of carbon through lipid synthesis pathways. The changes hat were observed in the seed's metabolism led to 2-3% more oil as a percentage of total seed biomass. This change was further explored using marker (tracer) compounds called isotopes. The isotope labeling studies indicated that levels of intermediate lipid metabolites were altered along with the flow (flux) of carbon through lipid synthesis pathways. The results are important because increasing levels of lipids in seeds is a goal for agriculture in order to improve the quality of life, and as lipids are a part of a balanced diet, the enhanced production of specific healthy lipids can help provide better nutrition and meet future food needs.
Technical Abstract: Plant seeds are the primary source of triacylglycerols (TAG) for food, feed, fuel, and industrial applications. As TAG is produced from diacylglycerol (DAG) successful engineering strategies to enhance TAG levels have focused on the conversion of DAG to TAG. However, the production of TAG can be limited by flux through other enzymatic reactions that supply DAG. In this study, two Arabidopsis phospholipase D' genes (AtPLD'1 and AtPLD'2) were co-expressed in Camelina sativa to test whether the conversion of phosphatidylcholine (PC) to DAG impacts TAG levels in seeds. The resulting transgenic plants produced 2-3% more TAG as a component of total seed biomass and had increased 18:3 and 20:1 fatty acid levels relative to wild type. Increased DAG and decreased PC levels were examined through the kinetics of lipid assembly by [14C]acetate and [14C]glycerol incorporation into glycerolipids. [14C]acetate was rapidly incorporated into TAG in both WT and overexpression lines, indicating a significant flux of nascent and elongated acyl-CoAs into the sn-3 position of TAG. Although PC and DAG were labeled at similar rates, stereochemical analysis revealed that newly synthesized fatty acids were preferentially incorporated into the sn-2 position of PC, but the sn-1 position of de novo DAG, indicating similar rates of nascent acyl groups into the Kennedy pathway and acyl editing. [14C]glycerol studies demonstrated PC-derived DAG is the major source of DAG for TAG synthesis in both tissues. The results emphasize that the interconversions of DAG and PC pools can impact oil production and composition.