Journal Article

Redox Changes in the Chloroplast and Hydrogen Peroxide are Essential for Regulation of C<sub>3</sub>–CAM Transition and Photooxidative Stress Responses in the Facultative CAM Plant <i>Mesembryanthemum crystallinum</i> L.

Ireneusz Slesak, Barbara Karpinska, Ewa Surówka, Zbigniew Miszalski and Stanislaw Karpinski

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 6, pages 573-581
Published in print June 2003 | ISSN: 0032-0781
Published online June 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg073
Redox Changes in the Chloroplast and Hydrogen Peroxide are Essential for Regulation of C3–CAM Transition and Photooxidative Stress Responses in the Facultative CAM Plant Mesembryanthemum crystallinum L.

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Mesembryanthemum crystallinum, a facultative halophyte and C3–Crassulacean acid metabolism (CAM) intermediate plant, has become a favoured plant for studying stress response mechanisms during C3–CAM shifts. One hour of exposure to excess light (EL) caused inhibition of photosynthetic electron transport in M. crystallinum leaves as indicated by chlorophyll a fluorescence measurements. This was accompanied by an increase in NADP-malic enzyme (ME), one of the key cytosolic enzymes involved in CAM, and by a general increase in superoxide dismutase (SOD) activity. In contrast, NAD-ME activity (the mitochondrial form of ME) was not affected by EL. Exposure to EL and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) treatment of a whole plant in low light induced hydrogen peroxide (H2O2) and C3 to CAM transition. In contrast, treatment with 3-3,4-dichlorophenyl-1,1-dimethyl urea (DCMU) has blocked high light-induced H2O2 accumulation and C3–CAM transition. Moreover, the abundance of transcripts encoding different SODs, ascorbate peroxidase and SOD activity was differently regulated by DCMU and DBMIB. Results of applying EL or high light, H2O2 and photosynthetic electron transport inhibitors suggest that the redox events in the vicinity of PSII and/or PSI and photo-produced H2O2 play a major role in the regulation of C3–CAM transition and photooxidative stress responses in M. crystallinum.

Keywords: Keywords: gene expression — Hydrogen peroxide — Mesembryanthemum crystallinum — Photoinhibition — photooxidative stress — Redox signalling.; Abbreviations: APX, ascorbate peroxidase; CAM, Crassulacean acid metabolism; DBMIB, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone; DCMU, 3-3,4-dichlorophenyl-1,1-dimethyl urea; EL, excess light; Fm, maximum chlorophyll a fluorescence yield; recorded during a short pulse of very high light intensity (less than 1 s and several thousand µmol s–1 m–2); F0, minimum chlorophyll a fluorescence yield recorded at very low light intensity (less than 1 µmol s–1 m–2); F′m and F′0, are light adapted equivalent terms; Fv, is the difference between Fm and F0; ΦPSII, is used as a proxy of quantum yield of electron transport from water trough PSII; Fv/Fm, the quantum efficiency of open photosystem II centres; H2O2, hydrogen peroxide; HL, high light; LL, low light; ME, malic enzyme; NPQ, non-photochemical quenching, it informs which part of light energy is dissipated as a heat; PQ, plastoquinone; qp, coefficient of photochemical quenching, is use for estimation of PSII centres at the open state (oxidised QA); QA, primary quinone electron acceptor of photosystem II; QB, secondary quinone electron acceptor of photosystem II; SOD, superoxide dismutase; ROS, reactive oxygen species.

Journal Article.  6716 words.  Illustrated.

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

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