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Comparative Study
. 2012;7(6):e37578.
doi: 10.1371/journal.pone.0037578. Epub 2012 Jun 4.

Comparative analysis on the key enzymes of the glycerol cycle metabolic pathway in Dunaliella salina under osmotic stresses

Hui Chen  1 , Yan Lu, Jian-Guo Jiang
Affiliations
Comparative Study

Comparative analysis on the key enzymes of the glycerol cycle metabolic pathway in Dunaliella salina under osmotic stresses

Hui Chen et al. PLoS One. 2012.

Erratum in

  • PLoS One. 2012;7(9). doi:10.1371/annotation/4e0ada11-9c9b-44d7-9fd0-cfe5b45c42b1

Abstract

The glycerol metabolic pathway is a special cycle way; glycerol-3-phosphate dehydrogenase (G3pdh), glycerol-3-phosphate phosphatase (G3pp), dihydroxyacetone reductase (Dhar), and dihydroxyacetone kinase (Dhak) are the key enzymes around the pathway. Glycerol is an important osmolyte for Dunaliella salina to resist osmotic stress. In this study, comparative activities of the four enzymes in D. salina and their activity changes under various salt stresses were investigated, from which glycerol metabolic flow direction in the glycerol metabolic pathway was estimated. Results showed that the salinity changes had different effects on the enzymes activities. NaCl could stimulate the activities of all the four enzymes in various degrees when D. salina was grown under continuous salt stress. When treated by hyperosmotic or hypoosmotic shock, only the activity of G3pdh in D. salina was significantly stimulated. It was speculated that, under osmotic stresses, the emergency response of the cycle pathway in D. salina was driven by G3pdh via its response to the osmotic stress. Subsequently, with the changes of salinity, other three enzymes started to respond to osmotic stress. Dhar played a role of balancing the cycle metabolic pathway by its forward and backward reactions. Through synergy, the four enzymes worked together for the effective flow of the cycle metabolic pathways to maintain the glycerol requirements of cells in order to adapt to osmotic stress environments.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. The pathway of glycerol metabolism in Dunaliella.
Figure 2
Figure 2. (NAD+)-dependent G3pdh activity in D. salina cells under different salinity stresses.
(A): Cells grown chronically at various salinities; (B): Cells treated by hyperosmotic or hypoosmotic shock. Columns represent the means of three replicated studies in each sample, with the SD of the means (T test, P<0.01). The significance of the differences between the control (2.0) and test values were tested by using one-way ANOVA. *, P<0.05 vs control.
Figure 3
Figure 3. G3pp activity in D. salina cells under different salinity stresses.
Columns represent the means of three replicated studies in each sample, with the SD of the means (T test, P<0.05). The significance of the differences between the control (2.0) and test values were tested by using one-way ANOVA. *, P<0.05 vs control.
Figure 4
Figure 4. NADPH-specific Dhar activity in D. salina cells under different salinity stresses.
(A): Cells grown chronically at various salinities; (B): Cells treated by hyperosmotic or hypoosmotic shock. Columns represent the means of three replicated studies in each sample, with the SD of the means (T test, P<0.05). The significance of the differences between the control (2.0) and test values were tested by using one-way ANOVA. *, P<0.05 vs control.
Figure 5
Figure 5. Dhak activity in D. salina cells under different salinity stresses.
Columns represent the means of three replicated studies in each sample, with the SD of the means (T test, P<0.05). The significance of the differences between the control (2.0) and test values were tested by using one-way ANOVA. *, P<0.05 vs control.
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