Journal Article

Similar Stress Responses are Elicited by Copper and Ultraviolet Radiation in the Aquatic Plant <i>Lemna gibba</i>: Implication of Reactive Oxygen Species as Common Signals

T. Sudhakar Babu, Tariq A. Akhtar, Mark A. Lampi, Sridevi Tripuranthakam, D. George Dixon and Bruce M. Greenberg

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 12, pages 1320-1329
Published in print December 2003 | ISSN: 0032-0781
Published online December 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg160
Similar Stress Responses are Elicited by Copper and Ultraviolet Radiation in the Aquatic Plant Lemna gibba: Implication of Reactive Oxygen Species as Common Signals

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Metals and ultraviolet (UV) radiation are two environmental stressors that can cause damage to plants. These two types of stressors often impact simultaneously on plants and both are known to promote reactive oxygen species (ROS) production. However, little information is available on the potential parallel stress responses elicited by metals and UV radiation. Using the aquatic plant Lemna gibba, we found that copper and simulated solar radiation (SSR, a light source containing photosynthetically active radiation (PAR) and UV radiation) induced similar responses in the plants. Both copper and SSR caused ROS formation. The ROS levels were higher when copper was combined with SSR than when applied with PAR. Higher concentrations of copper plus PAR caused toxicity as monitored by diminished growth and chlorophyll content. This toxicity was more pronounced when copper was combined with SSR. Because the generation of ROS was also higher when copper was combined with SSR, we attributed this enhanced toxicity to elevated levels of ROS. In comparison to PAR-grown plants, SSR treated plants exhibited elevated levels of superoxide dismutase (SOD) and glutathione reductase (GR). These enzyme levels were further elevated under both PAR and SSR when copper was added at concentrations that generated ROS. Interestingly, copper treatment in the absence of SSR (i.e. copper plus PAR) induced synthesis of the same flavonoids as those observed in SSR without copper. Finally, addition of either dimethyl thiourea or GSH (two common ROS scavengers) lowered in vivo ROS production, alleviated toxicity and diminished induction of GR as well as accumulation of UV absorbing compounds. Thus, the potential of ROS being a common signal for acclimation to stress by both copper and UV can be considered.

Keywords: Keywords: Chalcone synthase — Flavonoids — Glutathione reductase — Oxidative stress — Reactive oxygen species — Superoxide dismutase.; Abbreviations: CHS, chalcone synthase; DMF, dimethylformamide; DMTU, dimethyl thiourea; DTNB, 5,5′-dithiobis-2-nitrobenzoic acid; H2DCFDA, 2′,7′-dichlorodihydrofluorescein diacetate; GR, glutathione reductase; GSSG, oxidized glutathione; PAR, photosynthetically active radiation; RO, reverse osmosis; SOD, superoxide dismutase; SSR, simulated solar radiation; ROS, reactive oxygen species.

Journal Article.  8031 words.  Illustrated.

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

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