Spatio-temporal expression and stress responses of DGAT1, DGAT2 and PDAT responsible for TAG biosynthesis in Camelina sativa

Camelina (Camelina sativa L.) is embraced as a dedicated Brassicaceae oilseed for its valued seed oil wildly used for food, feed and biofuel. The high resistance to environmental stresses of camelina enabled its cultivation expanding to increase largely across the world recently. To gain a better understanding of the molecular mechanism underlying camelina oil biosynthesis and great environmental adaptability, expression analysis was conducted for phospholipid diacylglycerol acyltransferase (PDAT), diacylglycerol acyltransferase 1(DGAT1) and diacylglycerol acyltransferase 2 (DGAT2), three genes responsible for the final acylation step during triacylglycerol (TAG) synthesis, in camelina seed and other tissues. Genome-wide identification revealed that each of those gene families had three members in camelina. The three families and their members showed various expression patterns in camelina seed development and other tissues. The positive correlation between the expression peaks of the CsDGATs and oil rapid accumulation in developing seeds indicates that both CsDGAT1-A and CsDGAT2-C contribute importantly in seed oil accumulation with CsDGAT1-A as the major player. CsPDAT3 and CsDGAT1-C highly expressed in leaf and flower, indicating that both enzymes, particular CsPDAT3 is the major contributor for oil accumulation in leaf and flower. CsDGAT2-A was active in root and stem. Under cold stress, with oil elevating, expressions of CsDGAT2-B and CsPDAT1 were induced to increase in the seedlings by 11-folds and 6-folds respectively compared to the control of 3-week-old plants, suggesting that CsDGAT2-B and CsPDAT1 mainly function for oil accumulation in plants beneficial for camelina against cold stress. Furthermore, salt stress induced CsDGAT1-B and CsPDAT2 to express up by 8-15 folds in the seedlings, demonstrating that CsDGAT1-B and CsPDAT2 play important roles in camelina salt resistance. The present data provide a new insight into the regulatory mechanism of oil accumulation, particularly functions of CsDGAT1, CsDGAT2 and CsPDAT family members in plant stress responses.