Lipidome analysis and characterization of Buglossoides arvensis acyltransferases that incorporate polyunsaturated fatty acids into triacylglycerols.

Buglossoides arvensis is a burgeoning oilseed crop that contains an unique combination of ω-3 and ω-6 poly�unsaturated fatty acids (PUFA), constituting ~80–85% of seed triacylglycerols (TAGs). To uncover the critical
TAG biosynthetic pathways contributing for high PUFA accumulation, we performed lipidome of developing
seeds and characterized acyltransferases involved in the final step of TAG biosynthesis. During seed develop�ment, distribution of lipid molecular species in individual lipid classes showed distinct patterns from an early�stage (6 days after flowering (DAF)) to the middle-stage (12 and 18 DAF) of oil biosynthesis. PUFA-containing
TAG species drastically increased from 6 to 12 DAF. The expression profiles of key triacylglycerol biosynthesis
genes and patterns of phosphatidylcholine, diacylglycerol and triacylglycerol molecular species during seed
development were used to predict the contribution of diacylglycerol acyltransferases (DGAT1 and DGAT2) and
phospholipid: diacylglycerol acyltransferases (PDAT1 and PDAT2) to PUFA-rich TAG biosynthesis. Our analysis
suggests that DGATs play a crucial role in enriching TAGs with PUFA compared to PDATs. This was further
confirmed by fatty acid feeding studies in yeast expressing acyltransferases. BaDGAT2 preferentially incorpo�rated high amounts of PUFAs into TAG, compared to BaDGAT1. Our results provide insight into the molecular
mechanisms of TAG accumulation in this plant and identify target genes for transgenic production of SDA in
traditional oilseed crops.