Research In Polyunsaturated Fatty Acid Synthesis Pathway And Desaturase In Nannochloropsis Oceanica

The heterokont Nannochloropsis oceanica is considered a potential feedstock for biofuel production owing to its higher growth rate, biomass accumulation, low cultivation cost and phenomenal accumulation of lipids. In recent years, oleaginous N. oceanica has been exploited in industries as well as large-scale photobioreactors and open pool system for various purposes. In addition to lipids, N. oceanica also synthesize bioactive components with significant health benefits and commercial value such as, lutein, astaxanthin, carotenoids and polyunsaturated fatty acids. Hence, N. oceanica have garnered a considerable industrial interest and this subsequently prompted a great deal of molecular work devoted to analyze the mechanisms of fatty acid biosynthesis. The recent advancement in the transcriptome sequencing technology has resulted in the availability of whole genome sequence of some algae. However, progress in understanding the molecular mechanism of fatty acid biosynthesis in N. oceanica was hampered by lack of complete genome sequences and also most of the genes are under annotation. In context of N. oceanica metabolic network analysis, this study employing transcriptome sequencing technology, aids in identification of key enzymes in polyunsaturated fatty acid biosynthesis. Here, we identified D6 and D5 b desaturases as the key-enzymes in fatty acid biosynthesis and endogenously expressed in N. oceanica. Physiological characterization of the transgenic lines showed that all these three transgenic cells exhibited normal growth rate and photosynthetic activity as of the WT cells. GC-MS analysis revealed that transgene expression significantly altered the fatty acid composition in transgenic lines. Moreover, TAG content of transgenic lines was significantly increased in transgenic lines when compared with WT lines. Intriguingly, fatty acid composition of the fractionated neutral lipid in transgenic lines revealed that saturated fatty acid was increased, whereas unsaturated fatty acid content was decreased. Transcriptome sequence analysis has led to the identification and elucidation of candidate genes that could account for lipid and fatty acid over-production. These findings provide further insights into synthesis of high commercial value compounds in N. oceanica.