Inhibiting Lycopene Cyclases to Accumulate Lycopene in High β-Carotene-Accumulating Dunaliella bardawil

Dunaliella bardawil is characterized as a mass accumulator of β-carotene through lycopene cyclization by lycopene cyclase catalysis. The present research tried to inhibit the formation of β-carotene in D. bardawil to accumulate lycopene using triethylamine, a lycopene cyclase inhibitor. Results showed that 50 ∼ 100 ppm triethylamine could steadily trigger lycopene production, and 150 ppm triethylamine treatment for 3 days led to maximum proportion of lycopene with lowest proportion of β-carotene. The upstream genes (GGPS, PSY, PDS, and ZDS) involved in lycopene biosynthesis of D. bardawil were upregulated after triethylamine treatment for 3 days. While the transcription levels of the downstream genes (LycB, LycE, and ChyB) were decreased at high triethylamine concentration (50 ∼ 150 ppm). Triethylamine seemed to increase lycopene metabolic flow by inhibiting the expressions of LycB and LycE, which stimulated the expression levels of the upstream genes. The increased expression of upstream genes resulting from the inhibition of lycopene cyclases in D. bardawil provides a new insight into the desired pathway of carotenoid synthesis in algae and plants.