Transcriptome analysis of mangrove-isolated Chlorella vulgaris UMT-M1 reveals insights for vigorous growth and lipid accumulation through reduced salinity

Abstract

Salinity effectively triggers lipid accumulation in microalgae culture but adversely affects its growth parameters. In a previous study, mangrove-isolated Chlorella vulgaris UMT-M1 exhibited physiological evidence of high oil accumulation occurring together with uncompromised growth parameters at various salinity levels. At present, the genetic basis for successful mangrove-acclimated species is lesser studied. Hence, this study conducted transcriptome analysis on C. vulgaris UMT-M1 samples where unperturbed growth coincided with highest oil accumulation (15 ppt). De novo assembly furnished 77,727 transcripts while subsequent differential expression analysis identified a total of 9231 differentially expressed genes (DEGs). Functional enrichment under gene ontology (GO) and KEGG pathways analysis identified 51 terms and 14 significantly affected pathways respectively. Notably, transcripts involved in photosynthesis and carotenoid biosynthesis were crucial for salinity acclimation . Furthermore, enhancement of glycolysis , utilization of PDH bypass pathways, in addition to upregulation of intracellular energy routes and downregulation of β-oxidation represent an increased preference for fatty acid precursor accumulation in the cell. Key enzymes in fatty acid biosynthesis together with membrane-forming peroxygenase further supports the narrative that fatty acid precursors may be directed towards lipid droplet formation. The results thus highlight key genetic routes for successful growth and lipid accumulation in mangrove-isolated C. vulgaris UMT-M1. • Uncompromised growth and increased oil accumulation at 15 ppt salinity. • Transcripts of photosynthetic apparatus supported salinity acclimatization. • Lipid precursor pathways such as PDH bypass and glycolysis were upregulated. • Upregulation of membrane-forming peroxygenase in line with lipid droplet formation.