Abstract
The green microalga Botryococcus braunii is considered a promising biofuel feedstock producer due to its prodigious accumulation of hydrocarbon oils that can be converted into fuels. B. braunii Race L produces the C 40 tetraterpenoid hydrocarbon lycopadiene via an uncharacterized biosynthetic pathway. Structural similarities suggest this pathway follows a biosynthetic mechanism analogous to that of C 30 squalene. Confirming this hypothesis, the current study identifies C 20 geranylgeranyl diphosphate (GGPP) as a precursor for lycopaoctaene biosynthesis, the first committed intermediate in the production of lycopadiene. Two squalene synthase (SS)-like complementary DNAs are identified in race L with one encoding a true SS and the other encoding an enzyme with lycopaoctaene synthase (LOS) activity. Interestingly, LOS uses alternative C 15 and C 20 prenyl diphosphate substrates to produce combinatorial hybrid hydrocarbons, but almost exclusively uses GGPP in vivo. This discovery highlights how SS enzyme diversification results in the production of specialized tetraterpenoid oils in race L of B. braunii.
| Original language | English |
|---|---|
| Article number | 11198 |
| Journal | Nature Communications |
| Volume | 7 |
| DOIs | |
| Publication status | Published - 6 Apr 2016 |
| MoE publication type | A1 Journal article-refereed |
Funding
This work was supported by grants NSF-EFRI-PSBR 1240478 and DOE-ARPA-EPETRO DE-AR0000203 to T.P.D.; by contract DE-EE0003046 awarded to the National Alliance for Advanced Biofuels and Bioproducts (NAABB) from the U.S. Department of Energy, of which T.P.D. and I.M. are members; and by a grant from the Japan Science and Technology (JST) agency, Core Research for Evolutionary Science and Technology (CREST) programme to S.O. We thank Joe Chappell, University of Kentucky, for yeast strain ZX 178-08 and XURA vector; Eric Bridenbaugh of Olympus Scientific Solutions Americas, for assistance with microscopy; and the following people at Texas A&M University: Craig Kaplan for yeast strain CKY457, Larry Dangott for HPLC use, Dan Browne for help with bioinformatics, and Indranil Malik and Ben Kaster for helpful comments.
