Jasmonates regulate metabolic cascade towards Eicosapentaenoic acid and Docosahexaenoic acid biosynthesis in filamentous microalga Tribonema minus

Microalgae are considered a better alternative to fish and other aquatic resources to obtain essential omega-3 polyunsaturated fatty acids (PUFAs) of human metabolism. Tribonema minus is a fast-growing microalga; however, its natural PUFA content is low. The objective of present study was to increase the content of essential PUFAs in T. minus’ oil, to make its commercialization cost-effective. Exogenous methyl jasmonate (MeJA) was used as an elicitor to increase essential PUFAs. Treatment with 10 µM, 20 µM, and 30 µM MeJA was performed. Gas chromatography-mass spectrometry revealed that the concentration of essential omega-3 PUFAs: Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased by 52-fold and 3.54-fold, respectively, under 10 µM MeJA. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed a 87.5 % increase in PUFA biosynthesis under 20 µM MeJA. Quantitative real-time PCR analysis showed a significant increase in the expression of FA-regulating genes: malonyl-CoA ACP-transacylase, ß-ketoacyl synthase, and Δ12 fatty acid-desaturase under MeJA treatment, as predicted based on JA-binding motifs in their promoter sequences. An increase of 61 % in biomass productivity was obtained under 20 µM MeJA. Chlorophyll concentration and CO₂ fixation increased by 68 % and 59 % under 10 µM and 20 µM MeJA, respectively. A significant increase in the expression of Photosystem I P700 Chlorophyll-a Apoprotein A1 and RuBisCO large subunit was obtained under MeJA treatment. This study provided an efficient method to increase PUFAs’ concentration, and has the potential to produce inexpensive DHA-rich microalgal oil as a food supplement.