An insight into the influence of random mutagenesis on growth and lipid accumulation in Chlorella vulgaris—a transcriptome study.

Microalgal-based biofuel replaces fossil fuel to meet the current global energy demand. The mutant strains, UV-2 and 5'FDU-1, generated using random mutagenesis through UV light exposure (60 s) and 5'fluorodeoxyuridine (5'FDU-0.25 mM) enhanced the lipid production in marine microalgae, Chlorella vulgaris, with suitable fatty acid profile for biodiesel production, under laboratory conditions. Augmentation in the lipid content in UV-2 (26%) and 5'FDU-1 (23%) mutants was observed in outdoor conditions. Decreased growth rate observed in the mutants under indoor conditions was reversed under outdoor environment compared to wild type. Transcriptome-based gene expression analysis of wild type and mutants explained the variation in growth rate and lipid production. Acetyl-CoA carboxylase and other important fatty acid biosynthesis were significantly upregulated in mutant strains under outdoor conditions, correlating with the increased lipid production in outdoor mutants. Significant upregulation observed in genes related to photosystems in the mutant samples under both indoor and outdoor conditions corroborated with the increased biomass observed in mutant samples. Transcriptome study also provided pointers to the expression levels of key genes involved in carotenoid biosynthesis. Impact of physiological parameters like temperature played vital role in regulating genes related to growth, carotenoid biosynthesis, etc. Variation of gene expression levels of carotenoid biosynthesis genes and transcription factors with respect to indoor and outdoor conditions provided crucial pointers for further downstream studies. The current study evaluating the role of mutation substantiated with transcriptome data could be a precursor towards exploring specific targets for augmenting biomass, lipid leading to enhanced biodiesel production. [ABSTRACT FROM AUTHOR]