Comparison of plant-based expression platforms for the heterologous production of geraniol

Abstract

We compared the ability of different plant-based expression platforms to produce geraniol, a key metabolite in the monoterpenoid branch of the terpenoid indole alkaloid biosynthesis pathway. A geraniol synthase gene isolated from Valeriana officinalis (VoGES) was stably expressed in different tobacco systems. Intact plants were grown in vitro and in the greenhouse and were used to generate cell suspension and hairy root cultures. VoGES was also transiently expressed in N. benthamiana. The highest geraniol content was produced by intact transgenic plants grown in vitro (48 g/g fresh weight, fw), followed by the transient expression system (27 g/g fw), transgenic plants under hydroponic conditions in the greenhouse and cell suspension cultures (16 g/g fw), and finally hairy root cultures (9 g/g fw). Differences in biomass production and the duration of cultivation resulted in a spectrum of geraniol productivities. Cell suspension cultures achieved a geraniol production rate of 1.8 g/g fresh biomass per day, whereas transient expression produced 5.9 g/g fresh biomass per day (if cultivation prior to agroinfiltration is ignored) or 0.5 g/g fresh biomass per day (if cultivation prior to agroinfiltration is included). The superior productivity, strict process control and simple handling procedures available for transgenic cell suspension cultures suggest that cells are the most promising system for further optimization and ultimately for the scaled-up production of geraniol

Silybum marianum cell cultures stably transformed with Vitis vinifera stilbene synthase accumulate t‐resveratrol in the extracellular medium after elicitation with methyl jasmonate or methylated β‐cyclodextrins

“…Taking into consideration the high cost of introducing genetically modified crops, and public resistance to the acceptance of transgenic food products, heterologous production of t ‐R by plant cell cultures, with a relatively high biomass yield and short cultivation time, could be a viable option for large scale production .…”

Bioconversion of stilbenes in genetically engineered root and cell cultures of tobacco

“…This trait may be harnessed for the heterologous expression of foreign genes harbored in engineered A. rhizogenes 26. The derived genetically transformed cultures exhibit a high growth capacity and genetic stability for long periods2728.…”

“…Nevertheless, the low levels of t -R remaining in the cell cultures, especially when MBCD was added, compared with the root cultures, suggests the transgenic cells have a high capacity to metabolize t -R. A greater capacity to bioconvert hyoscyamine to scopolamine in hairy roots compared with the corresponding derived cell lines was also found in tobacco transgenic cultures heterologously expressing the hyoscyamine-β-hydroxylase gene from Hyoscyamus muticus 21. In contrast, when comparing tobacco hairy roots and cell cultures expressing the geraniol synthase gene of Valeriana officinalis , Vasilev et al 26. obtained higher levels of geraniol in the cell cultures.…”

Synthetic biology for production of natural and new‐to‐nature terpenoids in photosynthetic organisms

“…For instance, hydroxylated and reduced derivatives of geraniol, as well as their corresponding aldehydes and acids, were observed, with the number and type of derivatives varying between different plant hosts (Figure , Table S1). While in some cases, geraniol and its derivatives occur in their free form, substantial amounts of the monoterpenoids accumulate as complex sugar conjugates or as acetylated or malonylated derivatives (Davidovich‐Rikanati et al ., ; Yang et al ., ; Dong et al ., ; Fischer et al ., ; Höfer et al ., ; Ritala et al ., ; Vasilev et al ., ). For instance, in tobacco plants stably transformed with geraniol synthase from Valeriana officinalis , a total of 19 compounds were produced, identified as mono‐, di‐ or tri‐glycosides and malonyl or acetyl conjugates of geraniol, hydroxy‐geraniol, geranic acid, hydroxy‐geranic acid and hydroxy‐dihydro‐geranic acid (Dong et al ., ).…”

“…These anti‐cancer drugs are produced by C. roseus at extremely low levels and consequently have a restricted availability and a resulting high market price (Miettinen et al ., ). Therefore, different geraniol synthases (Dong et al ., ), production hosts (Dong et al ., ; Fischer et al ., ) and plant organs and cultures (Vasilev et al ., ) have been analysed for their biosynthetic production capacities (see Table S1 for expression hosts and yields). By the combined expression of CYP76B6 for the oxidation of geraniol to 8‐oxogeraniol (Höfer et al ., ) and the remaining nine genes of the C. roseus seco‐iridoid pathway, strictosidine could be produced in N. benthamiana leaves (Miettinen et al ., ).…”