Combinatorial Effects of Fatty Acid Elongase Enzymes on Nervonic Acid Production in Camelina sativa

Abstract

Very long chain fatty acids (VLCFAs) with chain lengths of 20 carbons and longer provide feedstocks for various applications; therefore, improvement of VLCFA contents in seeds has become an important goal for oilseed enhancement. VLCFA biosynthesis is controlled by a multi-enzyme protein complex referred to as fatty acid elongase, which is composed of β-ketoacyl-CoA synthase (KCS), β-ketoacyl-CoA reductase (KCR), β-hydroxyacyl-CoA dehydratase (HCD) and enoyl reductase (ECR). KCS has been identified as the rate-limiting enzyme, but little is known about the involvement of other three enzymes in VLCFA production. Here, the combinatorial effects of fatty acid elongase enzymes on VLCFA production were assessed by evaluating the changes in nervonic acid content. A KCS gene from Lunaria annua (LaKCS) and the other three elongase genes from Arabidopsis thaliana were used for the assessment. Five seed-specific expressing constructs, including LaKCS alone, LaKCS with AtKCR, LaKCS with AtHCD, LaKCS with AtECR, and LaKCS with AtKCR and AtHCD, were transformed into Camelina sativa. The nervonic acid content in seed oil increased from null in wild type camelina to 6-12% in LaKCS-expressing lines. However, compared with that from the LaKCS-expressing lines, nervonic acid content in mature seeds from the co-expressing lines with one or two extra elongase genes did not show further increases. Nervonic acid content from LaKCS, AtKCR and AtHCD co-expressing line was significantly higher than that in LaKCS-expressing line during early seed development stage, while the ultimate nervonic acid content was not significantly altered. The results from this study thus provide useful information for future engineering of oilseed crops for higher VLCFA production.

Physicochemical Properties of Acer truncatum Seed Oil Extracted Using Supercritical Carbon Dioxide

“…Nervonic acid (cis-tetracos-15-enoic acid; 24:1 Δ15) is an important long-chain monounsaturated fatty acid beneficial for brain health through improving the biosynthesis and maintenance of nerve cell myelin [1] and enhancing neurodevelopment in premature infants [2]. The seed oils of a few plants such as Lunaria annua (Money Plant), Borago officinalis (Borage), Cannabis sativa (Hemp), Acer truncatum (Purpleblow maple), Tropaeolum speciosum (Flame flower), Cardamine graeca (Bittercress) and Malania oleifera have been reported to contain nervonic acid [3,4]. New natural plant resources rich in nervonic acid for large scale production are in high demand because most of these plants have limited availability and are not suitable for commercial production.…”

Two Acyltransferases Contribute Differently to Linolenic Acid Levels in Seed Oil

“…Moreover, the seed yield is adequate to facilitate the rapid production of oil in quantities large enough for small-scale testing and product development. In recent years, several different oil traits have been developed in C. sativa seeds, such as high 18:1n-9 (Kang et al, 2011;, high 16:0 , and high v-7 fatty acids (Nguyen et al, 2015), as well as the production of diverse extrinsic lipid compounds, such as wax esters (Iven et al, 2016), fish oils (Petrie et al, 2014;Ruiz-Lopez et al, 2014), nervonic acid (Huai et al, 2015), and acetyl glyceride oils (Liu et al, 2015).…”

Transcriptome analysis reveals crucial genes involved in the biosynthesis of nervonic acid in woody Malania oleifera oilseeds

“…At the fast oil accumulation stage (S2), the proportion of nervonic acid increased rapidly (from 0.88 to 29.39%), suggesting that FAs elongation began during oil accumulation at stage S2. There has been increasing evidence that KCS is the rate-limiting enzyme in fatty acid elongation and that its expression level is an importance determinant of the final VLCFAs content [ 27 , 28 , 44 , 45 ]. The heterologous expression of KCS cloned from Cardamine graeca or Lunaria annua can produce or increase nervonic acid content in transgenic cruciferous plants [ 15 , 18 ].…”