A Specialized Diacylglycerol Acyltransferase Contributes to the Extreme Medium-Chain Fatty Acid Content of Cuphea Seed Oil

Abstract

Seed oils of many Cuphea sp. contain .90% of medium-chain fatty acids, such as decanoic acid (10:0). These seed oils, which are among the most compositionally variant in the plant kingdom, arise from specialized fatty acid biosynthetic enzymes and specialized acyltransferases. These include lysophosphatidic acid acyltransferases (LPAT) and diacylglycerol acyltransferases (DGAT) that are required for successive acylation of medium-chain fatty acids in the sn-2 and sn-3 positions of seed triacylglycerols (TAGs). Here we report the identification of a cDNA for a DGAT1-type enzyme, designated CpuDGAT1, from the transcriptome of C. avigera var pulcherrima developing seeds. Microsomes of camelina (Camelina sativa) seeds engineered for CpuDGAT1 expression displayed DGAT activity with 10:0-CoA and the diacylglycerol didecanoyl, that was approximately 4-fold higher than that in camelina seed microsomes lacking CpuDGAT1. In addition, coexpression in camelina seeds of CpuDGAT1 with a C. viscosissima FatB thioesterase (CvFatB1) that generates 10:0 resulted in TAGs with nearly 15 mol % of 10:0. More strikingly, expression of CpuDGAT1 and CvFatB1 with the previously described CvLPAT2, a 10:0-CoA-specific Cuphea LPAT, increased 10:0 amounts to 25 mol % in camelina seed TAG. These TAGs contained up to 40 mol % 10:0 in the sn-2 position, nearly double the amounts obtained from coexpression of CvFatB1 and CvLPAT2 alone. Although enriched in diacylglycerol, 10:0 was not detected in phosphatidylcholine in these seeds. These findings are consistent with channeling of 10:0 into TAG through the combined activities of specialized LPAT and DGAT activities and demonstrate the biotechnological use of these enzymes to generate 10:0-rich seed oils.

Towards the synthetic design of camelina oil enriched in tailored acetyl-triacylglycerols with medium-chain fatty acids

“…6 ). Similar reductions have been noted for other MCFA-producing camelina lines ( Iskandarov et al , 2017 ). The oil content of acetyl-TAG-producing lines derived from these two backgrounds was further reduced by 10–26%, depending on the specific line ( Fig.…”

“…Previous work has shown that acetyl-TAG-producing lines in a WT background also possess slightly lower oil content ( Liu et al , 2015 a ). Interestingly, expression of a MCFA-specific DGAT1 has been shown to rescue the reduced oil content of camelina lines producing MCFAs ( Iskandarov et al , 2017 ). Here, the development of EaDAcT variants with improved specificity for MCFAs containing DAG might be helpful in overcoming the reduced oil content of these lines.…”

Properties and Biotechnological Applications of Acyl‐CoA:diacylglycerol Acyltransferase and Phospholipid:diacylglycerol Acyltransferase from Terrestrial Plants and Microalgae

“…Moreover, overexpression of DGAT1 from microalgae, such as Chlorella ellipsoidea and Nannochloropsis oceanica, also led to increased oil content in Arabidopsis and B. napus (Guo et al, 2017;Zienkiewicz et al, 2017). Furthermore, DGAT1 has been used to increase the proportion of unusual fatty acids in seed oil, particularly epoxy fatty acid in G. max (coexpressed with an EPOXY-GENASE gene; Li et al, 2010a) and capric acid in C. sativa (in combination with fatty acyl-ACP thioesterase B1 and LPAAT from Cuphea viscosissima; Iskandarov et al, 2017). Similar to DGAT1, seed-specific overexpression of fungal DGAT2 resulted in enhanced seed oil content in G. max (Lardizabal et al, 2008) and Z. mays (Oakes et al, 2011).…”

PlantFAdb: a resource for exploring hundreds of plant fatty acid structures synthesized by thousands of plants and their phylogenetic relationships

“…acyl‐ACP thioesterases, phospholipid:diacylglycerol acyltransferases, diacylglycerol acyltransferases, lysophosphatidic acid acyltransferases) with high activity towards the unusual fatty acid. The low or modest amounts of unusual fatty acids produced in transgenic seeds expressing genes for production of the particular fatty acid have been significantly enhanced by co‐expressing genes encoding some of these auxiliary enzymes (Burgal et al ., ; Kim et al ., ; Iskandarov et al ., ). Thus, seeds with high amounts of unusual fatty acids have recruited, or developed, a number of highly specialized enzymes to ensure that the produced fatty acid is efficiently channeled into the oil and excluded from membranes.…”