Abstract
L-Tyrosine-derived specialized metabolites perform many important functions in plants, and have valuable applications in human health and nutrition. A necessary step in the overproduction of specialised tyrosine-derived metabolites in planta is the manipulation of primary metabolism to enhance the availability of tyrosine. Here, we utilise a naturally occurring de-regulated isoform of the key enzyme, arogenate dehydrogenase, to re-engineer the interface of primary and specialised metabolism, to boost the production of tyrosine-derived pigments in a heterologous plant host. Through manipulation of tyrosine availability, we report a 7-fold increase in the production of tyrosine-derived betalain pigments, with an upper range of 855 mg·kg−1·FW, which compare favourably to many in vitro and commercial sources of betalain pigments. Since the most common plant pathway for tyrosine synthesis occurs via arogenate, the de-regulated arogenate dehydrogenase isoform is a promising route for enhanced production of tyrosine-derived pharmaceuticals in diverse plant hosts.
Highlights
L-Tyrosine (Tyr) is an essential aromatic amino acid required for protein biosynthesis in all organisms, and is synthesised de novo in bacteria, fungi and plants, but not in animals
The production of Tyr-derived plant metabolites has already been achieved in microbial hosts, and considerable progress has been made in overriding the metabolic regulation of Tyr in these microbial platforms[10]
Betalain pigments have been previously employed as an enzyme-coupled bio-sensor to explore flux in the production of Tyr-derived metabolites[13], offering a powerful tool to visualise the impact of manipulating primary Tyr metabolism
Summary
Received: 28 February 2018 Accepted: 5 October 2018 Published: xx xx xxxx in Planta. Alfonso Timoneda[1], Hester Sheehan[1], Tao Feng[1], Samuel Lopez-Nieves[2], Hiroshi A. We utilise a naturally occurring de-regulated isoform of the key enzyme, arogenate dehydrogenase, to re-engineer the interface of primary and specialised metabolism, to boost the production of tyrosine-derived pigments in a heterologous plant host. Since the most common plant pathway for tyrosine synthesis occurs via arogenate, the de-regulated arogenate dehydrogenase isoform is a promising route for enhanced production of tyrosine-derived pharmaceuticals in diverse plant hosts. The expression of the de-regulated ADHα isoforms in heterologous plant platforms has the potential to enhance the production of Tyr-derived metabolites. Betalains are one such example of Tyr-derived metabolites, and are a class of pigments comprising yellow-orange betaxanthins and red-violet betacyanins, unique to Caryophyllales[11,12]. We demonstrate the capacity of de-regulated ADH to, in turn, boost the production of Tyr-derived metabolites in the heterologous plant platform, Nicotiana benthamiana
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