Light intensity effects on some molecular and biochemical characteristics of Dunaliella salina

To gain a better understanding of molecular and biochemical events involved in light intensity adaptations of Dunaliella salina, we studied the expression of phytoen synthase (psy) gene; pigments, carbohydrates, proteins and lipids accumulation under two light intensities. The cells were pre-cultured under 50 μmol photon m-2s-1 light intensity and then transferred to two different light intensities of 200 and 1000 μmol photon m-2s-1. The psy gene expression in high light (1000 μmol photon m-2s-1) decreased and remained fairly constant until 48 h however, a more decrease was appeared under the low light (200 μmol photon m-2s-1). After 2 weeks cultivation, the high light led to a considerable decrease of Chl a and Chl b contents, and an increase in carotenoids/total chlorophylls and Chl a/Chl b ratios. Total, soluble and non-soluble (starch) carbohydrates; proteins and lipids contents of cells were increased under the high light conditions. The results suggest that D. salina cells can have light intensity dependent adjustments in gene expressions, photosynthesis apparatus function, and structure as well as biochemical cell composition.