Author ORCID Identifier

http://orcid.org/0000-0002-5250-1291

Year of Publication

2016

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Agriculture, Food and Environment

Department

Plant and Soil Sciences

First Advisor

Dr. Joe Chappell

Abstract

Isoprenoids are one of the most diverse classes of natural products and are all derived from universal five carbon, prenyl precursors. Squalene and botryococcene are linear, hydrocarbon triterpenes (thirty carbon compounds with six prenyl units) that have industrial and medicinal values. Squalene is produced by all eukaryotes as it is the first committed precursor to sterols, while botryococcene is uniquely produced by the green algae, Botryococcus braunii (race B). Natural sources for these compounds exist, but there is a desire for more renewable production platforms. The model plant Arabidopsis thaliana was engineered to accumulate botryococcene and squalene in its oil seeds using a combination of biosynthetic genes and subcellular targeting strategies. The model monocotyledonous grass, Brachypodium distachyon, was also engineered to accumulate botryococcene in its leaves, testing a variety of subcellular targeting methods. Both oilseeds and grasses have highly desirable characteristics as production platforms, and both can utilize photosynthesis to power the biosynthesis of these valued hydrocarbons. In each of these efforts, we were able to obtain high levels of triterpene accumulation and uncovered new aspects of isoprenoid metabolism and its regulation. Also investigated was a new gene from the green algae, Botryococcus braunii (race B), encoding for a novel methyltransferase, which in combination with a previously reported methyltransferase, was characterized as converting dimethylated squalene to tetramethylated. Tetramethylated derivatives of squalene (and botryococcene) are highly desirable for industrial applications, and the discovery of the genes encoding for this biosynthetic capacity portends opportunities to engineer other heterologous host organisms and create other amenable production platforms.

Digital Object Identifier (DOI)

https://doi.org/10.13023/ETD.2016.418

Available for download on Friday, November 09, 2018

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