Regulation pattern of carotenoid biosynthesis induced by low light stress in Dunaliella

This research aims to explore the response mechanism of carotenoid synthesis in Dunaliella bardawil under low light stress (≤13.5 µmol·m^-2·s^-1). We analyzed carotenoid composition and its correlation with carotenogenic genes (CRTs) differential expression, promoter regulatory elements and transcription factors. DbPDS and DbZDS were significantly up-regulated under low light stress. Mutation experiments showed ACE, ASF1, CCACA-box, and CCAAT-box in DbZDS promoter key for low light regulation. In addition, CONSTANS (DbCO) and nuclear transcription factor YB (DbNF-YB) had a weak interaction and could bind to DbZDS gene promoter, whereas there was no interaction between DbZDS promoter and DbHY5 (ELONGATED HYPOCOTYL 5). We constructed a DbCO gene overexpressing strain, which significantly enhanced carotenoid content, notably increasing β-carotene levels to 2.3 times. These results significantly enhance our understanding of the regulation of low light stress in microalgae.