Journal Article

Evaluation of the Defense System in Chloroplasts to Photooxidative Stress Caused by Paraquat Using Transgenic Tobacco Plants Expressing Catalase from <i>Escherichia coli</i>

Yoshiko Miyagawa, Masahiro Tamoi and Shigeru Shigeoka

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 41, issue 3, pages 311-320
Published in print March 2000 | ISSN: 0032-0781
Published online March 2000 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/41.3.311
Evaluation of the Defense System in Chloroplasts to Photooxidative Stress Caused by Paraquat Using Transgenic Tobacco Plants Expressing Catalase from Escherichia coli

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We evaluated the defense system in chloroplasts to photooxidative stress imposed by paraquat treatment under illumination in transgenic tobacco plants with increased tolerance to drought stress at a high light intensity produced by catalase from Escherichia coli targeted to chloroplasts [Shikanai et al. (1998) FEBS Lett. 428: 47]. At 24 h after the paraquat application, Chl was destroyed in the wild-type plants, but not in transgenic plants. Photosynthetic activities monitored by CO2 fixation and Chi fluorescence were much less affected by the paraquat treatment in transgenic lines. The activities of chloroplastic ascorbate peroxidase (APX) isoenzymes decreased in parallel with the depletion of ascorbate (AsA) in leaves in both lines. Paraquat treatment had no effect on the transcript level of chloroplastic APX isoenzymes, while it significantly lowered the level of their proteins. These data suggest that the depletion of AsA in chloroplasts under severe stress conditions inactivates and degrades chloroplastic APX isoenzymes.

Keywords: Ascorbate peroxidase; Catalase; Chloroplast; Paraquat treatment; Photooxidative stress; Transgenic tobacco

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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