title: Redox changes in the chloroplast and hydrogen peroxide are essential for regulation of C(3)-CAM transition and photooxidative stress responses in the facultative CAM plant Mesembryanthemum crystallinum L.
abstract: Mesembryanthemum crystallinum, a facultative halophyte and C(3)-Crassulacean acid metabolism (CAM) intermediate plant, has become a favoured plant for studying stress response mechanisms during C(3)-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 (H(2)O(2)) and C(3) to CAM transition. In contrast, treatment with 3-3,4-dichlorophenyl-1,1-dimethyl urea (DCMU) has blocked high light-induced H(2)O(2) accumulation and C(3)-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, H(2)O(2) and photosynthetic electron transport inhibitors suggest that the redox events in the vicinity of PSII and/or PSI and photo-produced H(2)O(2) play a major role in the regulation of C(3)-CAM transition and photooxidative stress responses in M. crystallinum.
authors.affiliation: Department of Botany, Stockholm University, Lilla Frescativ 5, SE-106 91 Stockholm, Sweden.
authors.forename: Ireneusz
authors.initials: I
authors.lastname: Slesak
authors.forename: Barbara
authors.initials: B
authors.lastname: Karpinska
authors.forename: Ewa
authors.initials: E
authors.lastname: Surówka
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Miszalski
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Karpinski
mesh_terms: D002736:Chloroplasts / Q000201:enzymology* / Q000528:radiation effects; D003991:Dibromothymoquinone / Q000494:pharmacology; D004237:Diuron / Q000494:pharmacology; D004579:Electron Transport / Q000502:physiology / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000502:physiology / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008291:Malate Dehydrogenase / Q000378:metabolism / Q000528:radiation effects; D035723:Mesembryanthemum / Q000166:cytology / Q000201:enzymology* / Q000528:radiation effects; D010084:Oxidation-Reduction / Q000528:radiation effects; D018384:Oxidative Stress / Q000502:physiology* / Q000528:radiation effects; D010775:Photic Stimulation; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects; D013482:Superoxide Dismutase / Q000378:metabolism / Q000528:radiation effects
chemical_list: D003991:Dibromothymoquinone; D004237:Diuron; D006861:Hydrogen Peroxide; D008291:Malate Dehydrogenase; C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+); D013482:Superoxide Dismutase