Carotenoid Biosynthesis in Dunaliella (Chlorophyta)

Carotenoids are mostly 40-carbon isoprenoids that are integral and essential components of photosynthetic pigment-protein complexes, but also membranes. In response to environmental stress, some species of Dunaliella accumulate high amounts of specific carotenoids, such as β-carotene and zeaxanthin. Specifically, in response to environmental stress, cells of the species Dunaliella salina Teodoresco can overaccumulate β-carotene as a secondary carotenoid in lipid vesicles in the chloroplast stroma. The process of this over-accumulation of β-carotene is called carotenogenesis. Although the external environmental stimuli (high salt concentration, excess light, or nitrogen deficiency) leading to carotenogenesis have been identified, very little is known about the signal perception and signal transduction pathways that result in over-accumulation of carotenoids. This chapter reviews the current information about the carotenoid biosynthesis pathway and regulation of carotenogenesis in the alga Dunaliella.