Blackwell Publishing Journal Backfiles 1879-2005
The effects of the treatment of different tissues of three bean cultivars (Pinto, Vilmorin and Arroz) with ultra-violet (UV) UV-B and UV-C radiation and red light on the activity, quantity and RNA levels of NADP-malic enzyme (NADP-ME) were determined. Exposure to UV-B radiation for 8 h caused a marked increase of NADP-ME from leaves, stems and roots in the three cultivars studied. A similar induction was observed in the leaves and stems after 8 h of exposure under UV-C, but not in the roots, suggesting that a different signal might be acting to induce the expression of NADP-ME after UV-B and UV-C exposure. In contrast, red light was ineffective in inducing NADP-ME in either tissue, so the regulation of the expression of this enzyme is phytocrome-independent. The activity of superoxide dismutase, ascorbate peroxidase, catalase and peroxidase was also different in plants treated with UV-B, UV-C and photosynthetically active radiation, suggesting that various pathways may be acting in the regulation of these enzymes by UV-B and UV-C. Reactive oxygen species (ROS) were also required for UV-B induction of NADP-ME, as the addition of ascorbic acid before UV-B treatment prevented NADP-ME induction, whereas salicylic acid was not effective in inducing the enzyme, showing that NADP-ME induction by UV-B is ROS dependent but salicylic acid independent.
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