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Engineering Triterpene and Methylated Triterpene Production in Plants Provides Biochemical and Physiological Insights into Terpene Metabolism.
- Source :
-
Plant physiology [Plant Physiol] 2016 Feb; Vol. 170 (2), pp. 702-16. Date of Electronic Publication: 2015 Nov 24. - Publication Year :
- 2016
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Abstract
- Linear, branch-chained triterpenes, including squalene (C30), botryococcene (C30), and their methylated derivatives (C31-C37), generated by the green alga Botryococcus braunii race B have received significant attention because of their utility as chemical and biofuel feedstocks. However, the slow growth habit of B. braunii makes it impractical as a production system. In this study, we evaluated the potential of generating high levels of botryococcene in tobacco (Nicotiana tabacum) plants by diverting carbon flux from the cytosolic mevalonate pathway or the plastidic methylerythritol phosphate pathway by the targeted overexpression of an avian farnesyl diphosphate synthase along with two versions of botryococcene synthases. Up to 544 µg g(-1) fresh weight of botryococcene was achieved when this metabolism was directed to the chloroplasts, which is approximately 90 times greater than that accumulating in plants engineered for cytosolic production. To test if methylated triterpenes could be produced in tobacco, we also engineered triterpene methyltransferases (TMTs) from B. braunii into wild-type plants and transgenic lines selected for high-level triterpene accumulation. Up to 91% of the total triterpene contents could be converted to methylated forms (C31 and C32) by cotargeting the TMTs and triterpene biosynthesis to the chloroplasts, whereas only 4% to 14% of total triterpenes were methylated when this metabolism was directed to the cytoplasm. When the TMTs were overexpressed in the cytoplasm of wild-type plants, up to 72% of the total squalene was methylated, and total triterpene (C30+C31+C32) content was elevated 7-fold. Altogether, these results point to innate mechanisms controlling metabolite fluxes, including a homeostatic role for squalene.<br /> (© 2016 American Society of Plant Biologists. All Rights Reserved.)
- Subjects :
- Biosynthetic Pathways
Carbon Cycle
Chlorophyta enzymology
Chlorophyta genetics
Farnesyl-Diphosphate Farnesyltransferase genetics
Farnesyl-Diphosphate Farnesyltransferase metabolism
Gene Expression
Geranyltranstransferase genetics
Geranyltranstransferase metabolism
Homeostasis
Methylation
Methyltransferases genetics
Methyltransferases metabolism
Mevalonic Acid metabolism
Organ Specificity
Phenotype
Plant Proteins genetics
Plants, Genetically Modified
Plastids metabolism
Squalene chemistry
Squalene metabolism
Nicotiana genetics
Nicotiana physiology
Triterpenes chemistry
Chlorophyta physiology
Plant Proteins metabolism
Triterpenes metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1532-2548
- Volume :
- 170
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Plant physiology
- Publication Type :
- Academic Journal
- Accession number :
- 26603654
- Full Text :
- https://doi.org/10.1104/pp.15.01548