Abstract
Oil-producing green alga Botryococcus braunii is a potential biological source of petroleum substitutes. However, the identities of genes associated with oil biosynthesis, and thus the detailed biosynthesis pathways, still remain largely unknown. In order to gain such fundamental insight, we used representative high-oil-producing strains of two major races of B. braunii, namely, Race A and Race B strains known to biosynthesize hydrocarbons derived from unsaturated very long-chain fatty acids (VLCFAs) and triterpenes, respectively. We first generated novel datasets of cDNA reads and retrieved candidate genes associated with oil biosynthesis. We then examined the race-dependant expression patterns of the oil biosynthesis-related genes by comparison of the EST counts and the real-time PCR quantification. Regarding the unsaturated VLCFA biosynthesis, our results suggested (i) acyl-acp elongation is the major pathway for fatty acid elongation and (ii) both acyl-acp desaturases and acyl-CoA desaturases participate in the fatty acid desaturation. Regarding the triterpene biosynthesis, it was inferred that two entry routes into the 2-C-methyl-D-erythritol-4-phosphate pathway are active.
