Abstract
BackgroundWax esters (WE) are neutral lipids that consist of a fatty alcohol esterified to a fatty acid. WE are valuable feedstocks in industry for producing lubricants, coatings, and cosmetics. They can be produced chemically from fossil fuel or plant-derived triacylglycerol. As fossil fuel resources are finite, the synthesis of WE in transgenic plants may serve as an alternative source. As chain length and desaturation of the alcohol and acyl moieties determine the physicochemical properties of WE and their field of application, tightly controlled and tailor-made WE synthesis in plants would be a sustainable, beneficial, and valuable commodity. Here, we report the expression of ten combinations of WE producing transgenes in Arabidopsis thaliana. In order to study their suitability for WE production in planta, we analyzed WE amount and composition in the transgenic plants.ResultsThe transgenes consisted of different combinations of a FATTY ACYL-COA/ACP REDUCTASE (FAR) and two WAX SYNTHASES/ACYL-COA:DIACYLGLYCEROL O-ACYLTRANSFERASES (WSD), namely WSD2 and WSD5 from the bacterium Marinobacter aquaeoleoi. We generated constructs with and without plastidial transit peptides to access distinct alcohol and acyl substrate pools within A. thaliana cells. We observed WE formation with plastid and cytosol-localized FAR and WSD in seeds. A comparative WE analysis revealed the production of shorter and more saturated WE by plastid-localized WE biosynthesis compared to cytosolic WE synthesis.ConclusionsA shift of WE formation into seed plastids is a suitable approach for tailor-made WE production and can be used to synthesize WE that are mainly derived from mid- and long-chain saturated and monounsaturated substrates.
Highlights
Wax esters (WE) are neutral lipids that consist of a fatty alcohol esterified to a fatty acid
Previous studies showed that MaWSD2 is a bifunctional WAX SYNTHASES/ACYL-COA:DIACYLGLYCEROL O-ACYLTRANSFERASES (WSD) enzyme while M. aquaeolei WSD5 (MaWSD5) has only wax synthases (WS) activity
To compare plastidial and cytosolic WE production we designed constructs following our recently published analysis of transgenic A. thaliana Marinobacter aquaeolei FAR (MaFAR)/MaWSD5 plants [17] and generated nine additional constructs consisting of MaFAR combined with either MaWSD2 or MaWSD5 with and without plastidial transit peptides (Fig. 1; Table 1)
Summary
Wax esters (WE) are neutral lipids that consist of a fatty alcohol esterified to a fatty acid. Wax esters (WE) are in high demand for industrial applications They are neutral lipids, and are composed of a fatty alcohol esterified to a fatty acid. WE species synthesis in planta depends on the activities and substrate specificities of the expressed FAR and WS enzymes, and on the availability of acyl-CoA/ACP substrates. The combined expression of mouse FAR and mouse WS led to the formation of WE with mainly polyunsaturated 18 carbon acyl moieties in wild-type A. thaliana [9, 10]. Enzyme combinations of Marinobacter aquaeolei FAR (MaFAR) with jojoba WS (ScWS), Acinetobacter baylyi WSD1 (AbWSD1) or M. aquaeolei WSD5 (MaWSD5) produced WE with mainly monounsaturated 18 and 20 carbon acyl and alcohol moieties in wild-type A. thaliana [10, 13, 17]. Shorter WE were generated in C. sativa upon co-expression of a 14:0 ACP thioesterase [12]
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