Project description:We have performed an N-glycoproteomic analysis of the green microalgae Botryococcus braunii, a promising candidate for the production of biofuels, accumulating considerable amounts of hydrocarbon oils. Thereby, three different strains have been compared: Showa (Race B), AC761 (Race B) and CCALA778 (Race A) which differ in the type of produced hydrocarbons. In total, 517 unique N-glycosylated peptides have been identified analyzing intact N-glycopeptides as well as deglycosylated, 18O-labeled peptides. Intact N-glycopeptides that harbored N-acetylhexosamine (HexNAc) at the non-reducing end were identified. Surprisingly, these GnTI-dependent N-glycans were also found to be modified with (di)methylated hexose. This type of methylated GnTI-dependent N-glycans has not been described so far.
Project description:The green algal Botryococcus braunii (Chlorophyte) is known for accumulating high levels of hydrocarbons that are a useful alternative to fossil fuels. B. braunii is categorized into three groups based on types of their accumulated hydrocarbons: alkadiene/triene in race A, botryococcenes in race B, and lycopadiene in race L. Transcriptomic studies in race A and race B have discovered tremendous information related to the genes encoding proteins involved in hydrocarbon biosynthesis. However, transcriptome of race L has not been reported. In this study, we report a transcriptome of race L B. braunii AC768 through the de novo assembly using Hiseq platform. Our analyses indicate that photosynthesis and protein biosynthesis are the most abundantly transcribed in actively growing race L B. braunii. We show that the transcriptome of race L shares similar amounts (~20%) of mutual best-hits with that of race A or race B. Sequence homologous analyses indicate that enzymes involved in squalene and phytoene biosynthesis are well separated into geranyl-diphosphate synthase, farnesyl-diphosphate synthase, geranylgeranyl-diphosphate synthase, phytoene synthase, and squalene synthase. Both B. braunii specific enzymes botryococcene synthase SSL3 and lycopaoctaene synthase LOS are found to form distinctive subgroups in the group of squalene synthase. One of the ESTs in AC768 transcriptome that falls into the subgroup with LOS and shares >88% identity with that of LOS. Together, our results show that SSL and LOS are unique to race B and race L B. braunii subspecies, respectively. We propose that phytoene synthase in race L shares higher homolog to squalene synthase than phytoene synthase in other algae.
