Production of C6–C14 Medium‐Chain Fatty Acids in Seeds and Leaves via Overexpression of Single Hotdog‐Fold Acyl‐Lipid Thioesterases. Issue 3 (6th February 2021)

• Record Type: Journal Article
• Authors: Kalinger, Rebecca S.; Williams, Danielle; Ahmadi Pirshahid, Ali; Pulsifer, Ian P.; Rowland, Owen
• Is Part Of: Lipids. Volume 56:Issue 3(2021)
• Page Start: 327
• Page End: 344
• Publication Date: 2021-02-06
• Subjects: Acyl‐lipid thioesterase -- Medium‐chain fatty acids -- Methylketones -- Plant lipids -- Triacylglycerol; Lipids -- Periodicals; Lipids -- Periodicals; Lipiden; Lipides -- Périodiques; 547.77
• DOI: 10.1002/lipd.12299
• Languages: English
• ISSNs: 0024-4201

Abstract

Abstract: ACYL‐LIPID THIOESTERASES (ALT) are a type of plant acyl–acyl carrier protein thioesterase that generate a wide range of medium‐chain fatty acids and methylketone (MK) precursors when expressed heterologously in Escherichia coli . While this makes ALT‐type thioesterases attractive as metabolic engineering targets to increase production of high‐value medium‐chain fatty acids and MKs in plant systems, the behavior of ALT enzymes in planta was not well understood before this study. To profile the substrate specificities of ALT‐type thioesterases in different plant tissue types, AtALT1‐4 from Arabidopsis thaliana, which have widely varied chain length and oxidation state preferences in E. coli, were overexpressed in Arabidopsis seeds, Camelina sativa seeds, and Nicotiana benthamiana leaves. Seed‐specific overexpression of ALT enzymes led to medium‐chain fatty acid accumulation in Arabidopsis and Camelina seed triacylglycerols, and transient overexpression in N. benthamiana demonstrated that the substrate preferences of ALT‐type thioesterases in planta generally agree with those previously determined in E. coli . AtALT1 and AtALT4 overexpression in leaves and seeds resulted in the accumulation of 12–14 carbon‐length fatty acids and 6–8 carbon‐length fatty acids, respectively. While it was difficult to completely profile the products of ALT‐type thioesterases that generate MK precursors ( i.e . β‐keto fatty acids), our results nonetheless demonstrate that ALT enzymes are catalytically diverse in planta . The knowledge gained from this study is a significant step towards being able to use ALT‐type thioesterases as metabolic engineering tools to modify the fatty acid profiles of oilseed crops, other plants, and microorganisms.