| Calcium, a universal second messenger, acts as a mediator of stimulus-response coupling in the regulation of diverse cellular functions, including light, gravity, hormones, osmotic stresses. However, the role of calcium in the response of marine algae to environment shock has been seldom reported. Dunaliella salina is known as probably the most halotolerant eukaryotic organism living in various salt habitats, and glycerol metabolism plays an important role in its osmoregulation. In the study, we investigated the growth, intracellular glycerol content and activities of enzymes in glycerol metabolism of D. salina under NaCl stress, and the effects of exogenous calcium, EGTA or La3+ on growth, glycerol metabolism were investigated, respectively.Growth of D. salina was inhibited in solutions containing 4, 3, 0.8, or 0.6 mol/L NaCl. The intracellular glycerol content accumulated and activities of glycerol 3-phosphate phosphatase and dihydroxyacetone reductase catalyzing dihydroxyacetone to glycerol were enhanced in response to hyperosmotic stress. However, glycerol content decreased and the activities of glycerol 3-phosphate phosphatase lost and dihydroxyacetone reductase catalyzing glycerol to dihydroxyacetone increased when adapting to hypoosmotic stress. Exogenous calcium in the solution enhanced the extent of the changes in hyperosmotic stress response, including accumulation of intracellular glycerol, increase of the activities of glycerol 3-phosphate phosphatase and dihydroxyacetone reductase catalyzing dihydroxyacetone to glycerol. However, under hypoosmotic stress, exogenous calcium inhibited the growth of D. salina and the glycerol content change, and reduced the activity dihydroxyacetone reductase catalyzing glycerol to dihydroxyacetone. The effects of exogenous EGTA or La3+ in the solution on the growth, glycerol content, activities of glycerol 3-phosphate phosphatase and dihydroxyacetone reductase were reverse as comparied with the effects of exogenous...
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