Metabolic Engineering for Medium Chain Fatty Acids in Plant Leaf Lipids

Kyle Reynolds

Research output: ThesisDoctoral Thesis

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Abstract

In this thesis the metabolic engineering of plant oils was revisited, with particular focus on the efficient incorporation of medium-chain fatty acids (MCFAs) into plant oils. The thesis begins by investigating the de novo assembled transcriptome of the developing endosperm from Cocos nucifera (coconut palm) to identify and characterise genes involved in lipid synthesis. Of
particular interest are those genes directly involved in either the determination of fatty acid composition or involved in achieving increased oil production. The high oil content and fatty acid composition of coconut endosperm advocates that many of the genes would elicit prospects for future engineering studies. Of particular interest are those genes, such as acyltransferases, that may exhibit explicit substrate preference for MCFAs, and hence may have an important role in the future development of plant oils with an enhanced MCFA content.
The following chapter utilises current knowledge of lipid synthesis to attempt the construction of novel metabolic pathways that achieve both increased triacylglycerol (TAG) production and also demonstrate a significant level of incorporation of MCFAs into TAG. This was investigated through testing different thioesterases in combination with a variety of lipid assembly genes.
In previous studies it was observed that a significant amount of MCFAs accumulate in membrane lipids, and thus suggests that the pathways did not mediate efficient TAG production. In this study, it was identified through the additional expression of the diacylglycerol acyltransferase (DGAT) from Elaeis guineensis (EgDGAT1) reduced the accumulation of MCFAs in membrane lipids, and also enabled the increased TAG production with an improved MCFA composition. The final chapter then attempts to replicate the transient model in the high biomass model crop of Nicotiana tabacum, through the transgenic expression of the metabolic pathways optimised for the production of TAG with tailored MCFA compositions. A total of seven constructs were used for the Agrobacterium-mediated transformation of N. tabacum, with the objective of producing oils that have enriched compositions of lauric, myristic or palmitic acids. Overall, this work presents a possible sustainable option for the production of MCFA-enriched oils that may assist in the satisfaction of increasing global demand of vegetable oil production, and hence may be utilised by the petroleum, industrial and food industries.
Original languageEnglish
QualificationDoctor of Philosophy
Supervisors/Advisors
  • Blanchard, Christopher, Principal Supervisor
  • Strappe, Padraig, Principal Supervisor
Thesis sponsors
Publisher
Publication statusPublished - 2017

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