The Utilization of the Acyl‐CoA and the Involvement PDAT and DGAT in the Biosynthesis of Erucic Acid‐Rich Triacylglycerols in Crambe Seed Oil

Abstract

The triacylglycerol of Crambe abyssinica seeds consist of 95 % very long chain (>18 carbon) fatty acids (86 % erucic acid; 22:1∆13) in the sn-1 and sn-3 positions. This would suggest that C. abyssinica triacylglycerols are not formed by the action of the phospholipid:diacylglycerol acyltransferase (PDAT), but are rather the results of acyl-CoA:diacylglycerol acyltransferase (DGAT) activity. However, measurements of PDAT and DGAT activities in microsomal membranes showed that C. abyssinica has significant PDAT activity, corresponding to about 10 % of the DGAT activity during periods of rapid seed oil accumulation. The specific activity of DGAT for erucoyl-CoA had doubled at 19 days after flowering compared to earlier developmental stages, and was, at that stage, the preferred acyl donor, whereas the activities for 16:0-CoA and 18:1-CoA remained constant. This indicates that an expression of an isoform of DGAT with high specificity for erucoyl-CoA is induced at the onset of rapid erucic acid and oil accumulation in the C. abyssinica seeds. Analysis of the composition of the acyl-CoA pool during different stages of seed development showed that the percentage of erucoyl groups in acyl-CoA was much higher than in complex lipids at all stages of seed development except in the desiccation phase. These results are in accordance with published results showing that the rate limiting step in erucic acid accumulation in C. abyssinica oil is the utilization of erucoyl-CoA by the acyltransferases in the glycerol-3-phosphate pathway.Electronic supplementary materialThe online version of this article (doi:10.1007/s11745-014-3886-7) contains supplementary material, which is available to authorized users.

RNAi Targeting Putative Genes in Phosphatidylcholine Turnover Results in Significant Change in Fatty Acid Composition in Crambe abyssinica Seed Oil

“…Knockout in PDAT did not significantly affect the seed FA composition in Arabidopsis [33,34]. Reports have suggested that activity levels of both PDAT and PDCT are very low in Crambe [34,35], and are thus not expected to significantly influence the FA composition of the seed oil. However, both PDCT-RNAi and PDAT-RNAi lines showed a significant increase in 18:1 and decrease in 18:2, with no major change in 22:1 levels, although the changes were very subtle for the PDAT-RNAi lines.…”

“…Arabidopsis with knockout of both LPCAT1/2 and PDCT genes led to a further increase in 18:1 over the levels seen in the parents with PDCT or LPCAT1/2 knockout alone [14]. Knockout in PDAT did not significantly affect the seed FA composition in Arabidopsis [33,34]. Reports have suggested that activity levels of both PDAT and PDCT are very low in Crambe [34,35], and are thus not expected to significantly influence the FA composition of the seed oil.…”

Identification of multiple lipid genes with modifications in expression and sequence associated with the evolution of hydroxy fatty acid accumulation in Physaria fendleri

“…hydroxy, petroselinic, epoxy, conjugated, acetylenic and decanoic acids) in transgenic tissues through either single or multiple gene introductions (Jaworski and Cahoon, 2003;Snapp and Lu, 2013;Carlsson et al, 2014). Diverse research approaches have been utilized in attempts to understand potential difficulies in accumulating these unusual FAs, including: (i) characterizing the enzymes of native species by in vitro assays (Broadwater et al, 2002;Furmanek et al, 2014), (ii) using reverse genetics approaches to enhance or suppress select steps within the targeted pathway (Kumar et al, 2006;Burgal et al, 2008;Li et al, 2010b;Van Erp et al, 2015), (iii) using forward genetics approaches to identify important genes that alter a plant's ability to accumulate a transgenic product (Lu et al, 2006), and (iv) monitoring pathway fluxes through in vivo/in vitro radiolabeling of wild, model and transgenic species (Engeseth and Stymne, 1996;Reed et al, 1997;Bates and Browse, 2011;Bates et al, 2014). Here we have attempted to complement these approaches by transcriptional profiling of two genetically very closely related species [Physaria fendleri (Physaria) and Camelina sativa (Camelina)] to identify differences in lipid metabolism that may have evolved to enable the native Physaria species to accumulate high amounts of HFAs.…”

Heterogeneous Distribution of Erucic Acid in Brassica napus Seeds

“…In B. napus, there are six paralogs encoding FAE1 proteins (Qiu et al, 2006;Wu et al, 2008;Cao et al, 2010). BnaA8.FAE1 and BnaC3.FAE1 are the two major genes responsible for erucic acid synthesis in B. napus seeds and they elongate 18:1-CoA to 20:1-CoA, and then 20:1-CoA to 22:1-CoA (Furmanek et al, 2014;Kaur et al, 2019). These two genes are highly expressed in the seeds of high-erucic acid varieties and are minimally expressed in low-erucic acid varieties (Qiu et al, 2006;Cao et al, 2010).…”