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Ascorbate free radical reductase mRNA levels are induced by wounding
A A Grantz1, D A Brummell, A B Bennett
1Mann Laboratory, Department of Vegetable Crops, University of California, Davis 95616, USA.
Plant Physiology
|May 1, 1995
Summary
Tomato plants possess ascorbate free radical (AFR) reductase, an enzyme crucial for maintaining ascorbic acid levels. Its activity is regulated by mRNA abundance, particularly in response to wounding and low ascorbate conditions.
Area of Science:
- Plant biochemistry
- Molecular biology
- Enzyme kinetics
Background:
- Ascorbate (Vitamin C) is a vital antioxidant in plants, protecting against oxidative stress.
- Ascorbate free radical (AFR) reductase plays a key role in the ascorbate redox cycle.
- Understanding AFR reductase regulation is crucial for plant stress response mechanisms.
Purpose of the Study:
- To isolate and characterize the cDNA encoding tomato AFR reductase.
- To investigate the regulation of AFR reductase gene expression and enzyme activity.
- To correlate AFR reductase levels with ascorbate content and wound response in tomato.
Main Methods:
- cDNA cloning and sequencing of tomato AFR reductase.
- Analysis of mRNA levels using Northern blot or similar techniques.
- Measurement of AFR reductase activity and total ascorbate content in various tomato tissues.
Main Results:
- A cDNA encoding a 433-amino acid protein with putative FAD- and NAD(P)H-binding domains was identified, suggesting a cytosolic AFR reductase.
- A single nuclear gene encodes the tomato AFR reductase.
- AFR reductase mRNA abundance and activity were inversely correlated with total ascorbate content but increased significantly upon wounding.
Conclusions:
- Tomato AFR reductase activity is primarily regulated at the mRNA level.
- Low ascorbate levels or increased ascorbate utilization likely induce AFR reductase expression.
- AFR reductase is important for maintaining ascorbic acid homeostasis and protecting against wound-induced oxidative damage in tomato plants.