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Alterations in superoxide dismutase, glutathione, and peroxides in the plasmodial slime mold Physarum polycephalum
Abstract:
Changes in the level of antioxidant defenses and the concentration of free radical by-products were examined in differentiating (M3cVII and LU897 X LU863), non-differentiating (LU887 X LU897), and heterokaryon microplasmodia of the slime mold Physarum polycephalum during spherulation in salts-only medium. As differentiation proceeded, superoxide dismutase activity increased by as much as 46 fold; glutathione concentration and the rate of oxygen consumption decreased; cyanide-resistant respiration, hydrogen peroxide, and organic peroxide concentrations increased. The non-differentiating culture failed to exhibit any of these changes. A heterokaryon obtained by the fusion of differentiating and non-differentiating strains was observed to differentiate at a very retarded rate and to exhibit the changes observed in the spherulating strains at a correspondingly slower rate. These observations suggest that a free radical mechanism may be involved in the differentiation of Physarum microplasmodia into spherules.
Insights
Free radicals and antioxidant defenses shift during Physarum polycephalum differentiation into spherules. These changes, including increased superoxide dismutase, suggest a free radical mechanism drives this developmental process.
Area of Science:
- Cell Biology
- Biochemistry
- Developmental Biology
Background:
- Slime mold Physarum polycephalum undergoes differentiation into sclerotia (spherules).
- The biochemical processes underlying this differentiation are not fully understood.
- Antioxidant defenses and free radical production are critical in cellular processes.
Purpose of the Study:
- To investigate the role of antioxidant defenses and free radical by-products in Physarum polycephalum differentiation.
- To determine if free radical mechanisms are involved in the spherulation process.
Main Methods:
- Examined antioxidant enzyme activity (superoxide dismutase).
- Measured concentrations of glutathione, hydrogen peroxide, and organic peroxides.
- Assessed oxygen consumption and cyanide-resistant respiration.
- Compared differentiating, non-differentiating, and heterokaryon microplasmodia.
Main Results:
- Superoxide dismutase activity increased up to 46-fold during differentiation.
- Glutathione concentration and oxygen consumption rate decreased.
- Hydrogen peroxide, organic peroxide concentrations, and cyanide-resistant respiration increased.
- Non-differentiating cultures showed no significant changes.
- Heterokaryons exhibited a retarded differentiation rate with slower biochemical changes.
Conclusions:
- A free radical mechanism is likely involved in the differentiation of Physarum microplasmodia into spherules.
- Changes in antioxidant status and oxidative stress markers correlate with developmental progression.