Related Experiment Videos
Mannitol Protects against Oxidation by Hydroxyl Radicals.
B. Shen1, R. G. Jensen, H. J. Bohnert
1Department of Plant Sciences (B.S., R.G.J., H.J.B.), Department of Biochemistry (R.G.J., H.J.B.), and Department of Molecular and Cellular Biology (H.J.B.), The University of Arizona, Tucson, Arizona 85721.
Plant Physiology
|September 12, 2002
Summary
Mannitol protects plants from oxidative stress by shielding key enzymes like phosphoribulokinase (PRK) from hydroxyl radical damage. This finding highlights mannitol
Area of Science:
- Plant Physiology
- Biochemistry
- Oxidative Stress Research
Background:
- Hydroxyl radicals are implicated in oxidative damage during plant stress conditions like drought and chilling.
- Mannitol has been previously shown to protect plants against hydroxyl radical-induced oxidative damage.
Purpose of the Study:
- To identify specific enzymes protected by mannitol from hydroxyl radical damage.
- To elucidate the protective mechanisms of mannitol in plant stress responses.
Main Methods:
- Isolated thylakoids were used to generate hydroxyl radicals via Fe2+ and detected by phenylalanine conversion to tyrosine.
- Enzyme activity assays were performed on phosphoribulokinase (PRK) and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) under hydroxyl radical-generating conditions.
- The protective effects of mannitol, sodium formate, catalase, superoxide dismutase, and glycine betaine were evaluated.
Main Results:
- Hydroxyl radicals significantly reduced phosphoribulokinase (PRK) activity by 65% in illuminated thylakoids.
- Mannitol, sodium formate, and catalase effectively protected PRK activity against hydroxyl radical-induced inactivation.
- Superoxide dismutase and glycine betaine did not protect PRK, while RuBisCO activity remained unaffected.
Conclusions:
- Mannitol protects thiol-regulated enzymes, such as PRK, from inactivation by hydroxyl radicals.
- The stress-protective role of mannitol may involve shielding susceptible enzymes and redox-active molecules like thioredoxin, ferredoxin, and glutathione.
- These findings provide a molecular basis for mannitol's role in mitigating oxidative stress in plants.