De novo transcriptomic analysis of Graesiella emersonii NC-M1 reveals differential genes expression in cell proliferation and lipid production under glucose and salt supplemented condition

Abstract In the present study, under single-stage cultivation (mixotrophic mode), the effect of glucose and salt addition on biomass growth, lipid productivity, and FAME profiles in Graesiella emersonii NC-M1 were performed and analyzed. Under this condition (1.75 g/L glucose and 0.3M NaCl addition), a 3.3-, 4.65- and 4.56-fold higher biomass concentration, lipid concentration, and lipid productivity, respectively, was recorded compared to the control. To understand mechanisms underlying higher biomass and lipid production, de novo transcriptome analysis was performed. The transcriptome analysis revealed that the genes responsible for cell proliferation (transcription factor Dp-1, CDC48E) and NADPH production were significantly up-regulated under treated condition. Further, starch synthase showed significant down-regulation that illustrates a shift of carbon-flux for the biosynthesis of lipid. This study unravels the mechanisms influencing rapid growth and lipid accumulation under treated condition and provides new genetic targets for strain improvement of biodiesel-producing microalgae.