Squalene is a linear intermediate to nearly all classes of triterpenes and sterols and is itself highly valued for its use in wide range of industrial applications. Another unique linear triterpene is botryococcene and its methylated derivatives generated by the alga Botryococcus braunii race B, which are progenitors to fossil fuel deposits. Production of these linear triterpenes was previously engineered into transgenic tobacco by introducing the key steps of triterpene metabolism into the particular subcellular compartments. In this study, the agronomic characteristics (height, biomass accumulation, leaf area), the photosynthetic capacity (photosynthesis rate, conductance, internal CO2 levels) and triterpene content of select lines grown under field conditions were evaluated for three consecutive growing seasons. We observed that transgenic lines targeting enzymes to the chloroplasts accumulated 50–150 times more squalene than the lines targeting the enzymes to the cytoplasm, without compromising growth or photosynthesis. We also found that the transgenic lines directing botryococcene metabolism to the chloroplast accumulated 10- to 33-fold greater levels than the lines where the same enzymes were targeted to in the cytoplasm. However, growth of these high botryococcene accumulators was highly compromised, yet their photosynthesis rates remained unaffected. In addition, in the transgenic lines targeting a triterpene methyltransferase (TMT) to the chloroplasts of high squalene accumulators, 55%–65% of total squalene was methylated, whereas in the lines expressing a TMT in the cytoplasm, only 6%–13% of squalene was methylated. The growth of these methylated triterpene-accumulating lines was more compromised than that of nonmethylated squalene lines.
|Number of pages||15|
|Journal||Plant Biotechnology Journal|
|State||Published - Jun 2018|
Bibliographical noteFunding Information:
We are grateful for the advice and assistance provided by Dr. Bob Pearce and entire UK SpindleTop field operations personnel. This project was supported by a NIFA-USDA Grant (2010-04025).
© 2018 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.
- agronomic performance
- chemical performance
- field trials
- terpene engineering
ASJC Scopus subject areas
- Agronomy and Crop Science
- Plant Science