Metabolic Engineering of Higher Plants and Algae for Isoprenoid Production

Abstract

Isoprenoids are a class of compounds derived from the five carbon precursors, dimethylallyl diphosphate, and isopentenyl diphosphate. These molecules present incredible natural chemical diversity, which can be valuable for humans in many aspects such as cosmetics, agriculture, and medicine. However, many terpenoids are only produced in small quantities by their natural hosts and can be difficult to generate synthetically. Therefore, much interest and effort has been directed toward capturing the genetic blueprint for their biochemistry and engineering it into alternative hosts such as plants and algae. These autotrophic organisms are attractive when compared to traditional microbial platforms because of their ability to utilize atmospheric CO2 as a carbon substrate instead of supplied carbon sources like glucose. This chapter will summarize important techniques and strategies for engineering the accumulation of isoprenoid metabolites into higher plants and algae by choosing the correct host, avoiding endogenous regulatory mechanisms, and optimizing potential flux into the target compound. Future endeavors will build on these efforts by fine-tuning product accumulation levels via the vast amount of available "-omic" data and devising metabolic engineering schemes that integrate this into a whole-organism approach. With the development of high-throughput transformation protocols and synthetic biology molecular tools, we have only begun to harness the power and utility of plant and algae metabolic engineering.

Engineering Triterpene and Methylated Triterpene Production in Plants Provides Biochemical and Physiological Insights into Terpene Metabolism

“…First, chloroplasts offer an abundance of carbon passing through the MEP pathway, and diverting an intermediate and carbon flux from this pathway does not adversely impact the biosynthetic needs in the chloroplasts for large amounts of carotenoids and chlorophylls. The second, equally important, observation is that the chloroplast provides an ideal environment for heterologous terpene production, perhaps due to the endogenous regulation of the MEP pathway in plastids, allowing for a new carbon sink in the form of the introduced triterpenes, as compared with the MVA pathway operating in the cytosol preventing the high IPP/DMAPP flux into these compounds (Kempinski et al, 2015).…”

“…hormones, aliphatic membrane anchors, and maintaining membrane structure) and ecological (i.e. defense compounds and insect/animal attractants) roles (Kempinski et al, 2015). Terpenes are also important for various industrial applications, ranging from flavors and fragrances (Schwab et al, 2008) to medicines (Dewick, 2009;Niehaus et al, 2011;Shelar, 2011).…”

“…Nonetheless, compared with microbial platforms, there are only a few examples of elevating terpene production in bioengineered plants. This is due partly to higher plants being complex multicellular organisms, in which terpene metabolism generally utilizes more complex innate machinery that can be compartmentalized intracellularly and to cell/tissue specificities (Lange and Ahkami, 2013;Kempinski et al, 2015). Significant efforts have been made to overcome these obstacles to improve the production of valuable terpenes in plants, including monoterpenes (Lücker et al, 2004;Ohara et al, 2010;Lange et al, 2011), sesquiterpenes (Aharoni et al, 2003;Kappers et al, 2005;Wu et al, 2006;Davidovich-Rikanati et al, 2008), diterpenes (Besumbes et al, 2004;Anterola et al, 2009), and triterpenes (Inagaki et al, 2011;Wu et al, 2012).…”

The Smell of Synthetic Biology: Engineering Strategies for Aroma Compound Production in Yeast

“…Aroma compounds have various applications in the food, feed, cosmetic and pharmaceutical industries [1]. Some compounds have applications beyond their sense-activating properties, including potential as a biofuel [2], the improvement of the shelf-life of certain fruit varieties [3] and antimicrobial activities [4]. They can either be desirable or unwanted in a given product and significant efforts can be made to either eliminate or increase levels depending on the application.…”

The Smell of Synthetic Biology: Engineering Strategies for Aroma Compound Production in Yeast

“…Aroma compounds have various applications in the food, feed, cosmetic and pharmaceutical industries [1]. Some compounds have applications beyond their sense-activating properties, including potential as a biofuel [2], the improvement of the shelflife of certain fruit varieties [3] and antimicrobial activities [4]. They can either be desirable or unwanted in a given product and significant efforts can be made to either eliminate or increase levels depending on the application.…”