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Changes in ascorbate peroxidase activities during fruit ripening in Capsicum annum
M L Schantz1, H Schreiber, P Guillemaut
1Institut de Biologie Moléculaire des Plantes, C.N.R.S., Université Louis Pasteur, Strasbourg, France.
FEBS Letters
|January 23, 1995
Summary
Capsicum annum fruit ripening involves significant changes in ascorbate peroxidase (APX) activity, particularly within organelles during the chloroplast-chromoplast transition. This study identified distinct APX isoforms and a cytosolic APX transcript that increases during ripening.
Area of Science:
- Biochemistry
- Plant Physiology
- Molecular Biology
Background:
- Ascorbate peroxidase (APX) is a key enzyme in plant antioxidant systems.
- Fruit ripening involves complex biochemical and physiological changes, including alterations in enzyme activity.
Purpose of the Study:
- To investigate the ascorbate peroxidase (APX) system in Capsicum annum during fruit ripening.
- To characterize APX isoforms and their activity changes during the chloroplast-chromoplast transition.
Main Methods:
- Enzyme activity assays on total fruit extracts and isolated organelles.
- Native gel electrophoresis to separate APX isoforms.
- cDNA cloning and sequencing of a cytosolic APX gene.
- Transcript analysis using Northern blotting or similar techniques.
Main Results:
- A significant increase in organelle APX activity was observed during chloroplast-chromoplast transition.
- Distinct patterns of APX isoforms were found in total fruit extracts and isolated organelles between red and green fruit.
- Six isozymes were identified in isolated organelles, with notable differences in patterns.
- A cDNA encoding cytosolic APX was cloned, and its transcript showed a 3-4 fold increase during ripening.
Conclusions:
- The APX system undergoes substantial changes during Capsicum annum fruit ripening, with organelle-localized APX being particularly dynamic.
- Specific APX isoforms and the cytosolic APX transcript play important roles in the ripening process.