The biosynthesis and accumulation of β-carotene in Dunaliella salina proceed via the glyceraldehyde 3-phosphate/pyruvate pathway

In Dunaliella salina, we studied the early steps in the isoprenoid pathway for the biosynthesis of carotenoids and β-carotene and the effects of metabolic inhibitors. When D. salina was grown under carotenogenic and non-carotenogenic conditions, mevinolin did not inhibit growth or the accumulation of carotenoids, β-carotene or chlorophyll. In contrast, fosmidomycin progressively inhibited cell growth and the biosynthesis of carotenoids, β-carotene and chlorophyll. In this work, we reported for the first time that in D. salina, β-carotene biosynthesis does not proceed via the classical acetate/mevalonate pathway but via the novel glyceraldehyde 3-phosphate/pyruvate pathway. This favours the yield of C5 isoprenoid units for synthesis of isopentenyl diphosphate, the precursor in the biosynthesis of C20 compounds, including geranylgeranyl diphosphate. Consequently, this pathway promotes carotenogenesis and the biosynthesis of C40 β-carotene in D. salina.