Expression analysis of Dunaliella salina key genes involved in β-carotene biosynthesis under various salinity and light conditions

Dunaliella salina، a unicellular green microalga with ability of large quantity β-carotene accumulation، was used as a proper model for analysis of expression of the pds and lyc genes، involved in β-carotene biosynthesis pathway، under different light intensities and salinity concentrations. For this purpose، an experiment with two factors، light intensities (200 and 1000 µmol m-2s-1) and salinity (2 and 4 M NaCl) were performed in completely randomized factorial design. During 4 days، the steady-state levels of transcripts encoding phytoen desaturase increased substantially in 200-4 and 1000-2 treatments، while lycopene beta cyclase transcripts increased in 200-2، 1000-2 and 1000-4 treatments. As an enhancement effect of increased expression of both genes، the β-carotene reached to its maximum amount in 1000-2 treatment. These results indicated that light intensity induced the expression of the above indicated β-carotene biosynthesis pathway genes. The accumulation of β-carotene could be considered as a protection mechanism of the algae against oxidative stress originated from primary light stress.