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.

Keywords: β-Carotene, Dunaliella salina, Gene Expression, Light, Salinity

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