Synthesis of 0-carotene in Dunaliella: From genome analysis to metabolic engineering

Dunaliella is well known for its ability to survive under environmental stress conditions responding with the production of added value compounds like glycerol, polyunsaturated fatty acids, and a high percentage of 0-carotene that stands out for its antioxidant properties. In this review, we systematically searched all available publications regarding gene expression of 0-carotene synthesis in Dunaliella using Clarivate's Web of Science search engine. In addition, we performed a bioinformatic analysis of their promoter region using the available Dunaliella genome sequence in The Plant Comparative Genomics portal Phytozome using The Plant Promoter Analysis Navigator PlantPan. We found that the current research mainly focuses on the first and last steps of 0-carotene syntheses, such as phytoene synthase, phytoene desaturase, and lycopene cyclases, respectively, in both gene expression and engineering approaches. In contrast, other steps like isomerization are still limited in Dunaliella. Gene expression under different stress conditions, as well as the activation of the transcription factorbinding sites found, is discussed, as well as genetic and metabolic engineering approaches available to increase 0-carotene synthesis.