Fig 1.
The effects of nutrient deprivation on the cell growth of D. salina.
Cell density was determined for 15 days after exposure to the different treatments. Complete medium (CM), Nitrogen deprivation (-N), Phosphorous deprivation (-P), Sulfur deprivation (-S), Nitrogen and phosphorous deprivation (-N-P), Nitrogen and sulfur deprivation (-N-S), Phosphorous and sulfur deprivation (-P-S), Nitrogen, phosphorous and sulfur deprivation (-N-P-S). The plotted data are the averages ± SE of six replicates.
Fig 2.
Changes in culture color and the morphology of D. salina cells.
The first three rows of this picture demonstrate that the color of the cultures changed gradually during nutrient deprivation. The middle three rows of this picture demonstrate that the color of the cells changed gradually during nutrient deprivation. The last three rows of this picture show that the lipid globules changed during nutrient deprivation. Complete medium (CM), Nitrogen deprivation (-N), Phosphorous deprivation (-P), Sulfur deprivation (-S), Nitrogen and phosphorous deprivation (-N-P), Nitrogen and sulfur deprivation (-N-S), Phosphorous and sulfur deprivation (-P-S), Nitrogen, phosphorous and sulfur deprivation (-N-P-S). Scale bars, 10 μm.
Fig 3.
The chlorophyll contents of D. salina cells during nutrient deprivation.
Changes in the total chlorophyll (A), chlorophyll a (B) and chlorophyll b (C) contents were measured during nutrient deprivation. The ratio of chlorophyll a and chlorophyll b (D) during nutrient deprivation was used to reflect changes in the status of the cells. Complete medium (CM), Nitrogen deprivation (-N), Phosphorous deprivation (-P), Sulfur deprivation (-S), Nitrogen and phosphorous deprivation (-N-P), Nitrogen and sulfur deprivation (-N-S), Phosphorous and sulfur deprivation (-P-S), Nitrogen, phosphorous and sulfur deprivation (-N-P-S). The presented data are the averages ± SE of three replicates.
Fig 4.
The photosynthetic and respiratory rates of D. salina cells during nutrient deprivation.
The photosynthetic and respiratory rates were calculated based on the amount of oxygen consumed and released by D. salina cells under dark and light conditions, respectively. The true photosynthetic rates (A) show the changes in the amount of oxygen released, and the respiratory rates (B) show the changes in the amount of oxygen consumed. Complete medium (CM), Nitrogen deprivation (-N), Phosphorous deprivation (-P), Sulfur deprivation (-S), Nitrogen and phosphorous deprivation (-N-P), Nitrogen and sulfur deprivation (-N-S), Phosphorous and sulfur deprivation (-P-S), Nitrogen, phosphorous and sulfur deprivation (-N-P-S). The presented data are the averages ± SE of three replicates.
Fig 5.
The carotenoid contents of D. salina cells during nutrient deprivation.
The total carotenoid contents (A) were measured using the colorimetric method. The ratio of total colored carotenoids to chlorophyll (B) indirectly reflected the changes in carotenoids and chlorophyll in D. salina cells. The β-carotene contents (C) and the relative contents of lutein (D) were measured via HPLC. Complete medium (CM), Nitrogen deprivation (-N), Phosphorous deprivation (-P), Sulfur deprivation (-S), Nitrogen and phosphorous deprivation (-N-P), Nitrogen and sulfur deprivation (-N-S), Phosphorous and sulfur deprivation (-P-S), Nitrogen, phosphorous and sulfur deprivation (-N-P-S). The presented data are the averages ± SE of three replicates.
Fig 6.
The activities of the antioxidant enzymes of D. salina during nutrient deprivation.
The activities of SOD (A) and CAT (B) in D. salina cells during nutrient deprivation were determined using a colorimetric method. Complete medium (CM), Nitrogen deprivation (-N), Phosphorous deprivation (-P), Sulfur deprivation (-S), Nitrogen and phosphorous deprivation (-N-P), Nitrogen and sulfur deprivation (-N-S), Phosphorous and sulfur deprivation (-P-S), Nitrogen, phosphorous and sulfur deprivation (-N-P-S). The presented data are the averages ± SE of three replicates.
Fig 7.
Steady-state mRNA levels of MEP and carotenoid biosynthesis pathway genes in D. salina.
The cultures were subjected to different types of nutrient deprivation. As negative controls for nutrient deprivation, cultures were maintained in complete medium (CM). The samples used for RNA isolation were harvested 7 days and 14 days after exposure to the different treatments. The steady-state mRNA levels of DXS (A), HDR (B), PSY (C), PDS1 (D), PDS2 (E), PDS3 (F), ZDS (G), LCYB (H) and CHYB (I) were quantified via quantitative real-time PCR, normalized against 18S rRNA, and plotted as the relative transcript levels versus time. Gene expressions of cells cultured in CM for seven days were used as control. Nitrogen deprivation (-N), Phosphorous deprivation (-P), Sulfur deprivation (-S), Nitrogen and phosphorous deprivation (-N-P), Nitrogen and sulfur deprivation (-N-S), Phosphorous and sulfur deprivation (-P-S), Nitrogen, phosphorous and sulfur deprivation (-N-P-S). The presented data are the averages ± SE of three replicates.