Coexpressing Escherichia coli Cyclopropane Synthase with Sterculia foetida Lysophosphatidic Acid Acyltransferase Enhances Cyclopropane Fatty Acid Accumulation    

Abstract

(M.S., J.S.)Cyclopropane fatty acids (CPAs) are desirable as renewable chemical feedstocks for the production of paints, plastics, and lubricants. Toward our goal of creating a CPA-accumulating crop, we expressed nine higher plant cyclopropane synthase (CPS) enzymes in the seeds of fad2fae1 Arabidopsis (Arabidopsis thaliana) and observed accumulation of less than 1% CPA. Surprisingly, expression of the Escherichia coli CPS gene resulted in the accumulation of up to 9.1% CPA in the seed. Coexpression of a Sterculia foetida lysophosphatidic acid acyltransferase (SfLPAT) increases CPA accumulation up to 35% in individual T1 seeds. However, seeds with more than 9% CPA exhibit wrinkled seed morphology and reduced size and oil accumulation. Seeds with more than 11% CPA exhibit strongly decreased seed germination and establishment, and no seeds with CPA more than 15% germinated. That previous reports suggest that plant CPS prefers the stereospecific numbering (sn)-1 position whereas E. coli CPS acts on sn-2 of phospholipids prompted us to investigate the preferred positions of CPS on phosphatidylcholine (PC) and triacylglycerol. Unexpectedly, in planta, E. coli CPS acts primarily on the sn-1 position of PC; coexpression of SfLPAT results in the incorporation of CPA at the sn-2 position of lysophosphatidic acid. This enables a cycle that enriches CPA at both sn-1 and sn-2 positions of PC and results in increased accumulation of CPA. These data provide proof of principle that CPA can accumulate to high levels in transgenic seeds and sets the stage for the identification of factors that will facilitate the movement of CPA from PC into triacylglycerol to produce viable seeds with additional CPA accumulation.

Optimization of cyclopropane fatty acids production in Yarrowia lipolytica

“…Although JMY6064 have a higher TFA content, the ratio of CFA in JMY6068 is higher compared with JMY6064, and both strains reached 2071.4 and 2319.9 mg CFA/L, respectively. Overall, an increase in CFA content leads to a reduction of TFA as seen by others previously (Yu et al, ) and attributed to a possible feedback inhibition of the FAS. This might reflect some toxicity of the CFA in the cell and an attempt to reduce the quantity of such nonconventional FA by reducing the overall lipid content of the cell.…”

Understanding and manipulating plant lipid composition: Metabolic engineering leads the way

“…LPAT catalyzes the acylation of the sn -2 position of the glycerol backbone in the TAG biosynthetic pathway. Consistent with this activity, increased amounts of cyclopropane fatty acids in TAG in the engineered Arabidopsis seeds was due primarily to enhanced accumulation at the TAG sn -2 position [26]. Despite this, cyclopropane fatty acid levels were disproportionately high in PC, accounting for >40% of the PC fatty acids compared to ∼9% of the TAG fatty acids [26].…”

Increased Serum Level of Cyclopropaneoctanoic Acid 2‐Hexyl in Patients with Hypertriglyceridemia‐Related Disorders

“…These fatty acids (FA) have also been found in certain eukaryotes, including protozoa [2] and plants [3, 4]. However, few studies have documented the presence of CFA in animals [5–7].…”