chlorophyll-a and 1-3-dihydroxy-4-4-5-5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole

Various nitric oxide (NO) regulators [including the NO donor sodium nitroprusside (SNP), the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), the NO-synthase inhibitor N (G)-nitro-L-Arg-methyl ester (L-NAME), and the SNP analogues sodium nitrite/nitrate and sodium ferrocyanide] were investigated to elucidate the role of NO in white clover (Trifolium repens L.) plants after long-term (5 days) exposure to cadmium (Cd). A dose of 100 μM Cd stress significantly restrained plant growth and decreased the concentrations of chlorophyll and NO in vivo, whereas it disrupted the balance of stress-related hormones and enhanced the accumulation of Cd, thereby inducing reactive oxygen species (ROS) burst. However, the inhibition of plant growth was relieved by 50 μM SNP through its stimulation of ROS-scavenging compounds (ascorbic acid, ascorbate peroxidase, catalase, glutathione reductase, non-protein thiol, superoxide dismutase, and total glutathione), regulation of H(+)-ATPase activity of proton pumps, and increasing jasmonic acid and proline but decreasing ethylene in plant tissues. Even so, the alleviating effect of SNP on plant growth was counteracted by cPTIO and L-NAME and was not observed with SNP analogues, suggesting that the protective roles of SNP are related to the induction of NO. These results suggest that NO may improve the Cd tolerance of white clover plants by eliminating oxidative damage, re-establishing ATPase activity, and maintaining hormone equilibrium. Improving our understanding of the role of NO in white clover plants is key to expanding the plantations to various regions and the recovery of pasture species in the future.

Topics: Adenosine Triphosphatases; Ascorbate Peroxidases; Ascorbic Acid; Benzoates; Cadmium; Catalase; Chlorophyll; Glutathione; Imidazoles; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Plant Growth Regulators; Reactive Oxygen Species; Soil Pollutants; Superoxide Dismutase; Trifolium

To better understand nitric oxide (NO) responsive proteins, we investigated the proteomic differences between untreated (control), sodium nitroprusside (SNP) treated, and carboxy-PTIO potassium salt (cPTIO, NO scavenger) followed by SNP treated cotton plants. This is the first study to examine the effect of different concentrations of NO on the leaf proteome in cotton using a label-free approach based on nanoscale ultraperformance liquid chromatography-electrospray ionization (ESI)-low/high-collision energy MS analysis (MS(E)). One-hundred and sixty-six differentially expressed proteins were identified. Forty-seven of these proteins were upregulated, 82 were downregulated, and 37 were expressed specifically under different conditions. The 166 proteins were functionally divided into 17 groups and localized to chloroplast, Golgi apparatus, cytoplasm, and so forth. The pathway analysis demonstrated that NO is involved in various physiological activities and has a distinct influence on carbon fixation in photosynthetic organisms and photosynthesis. In addition, this is the first time proteins involved in ethylene synthesis were identified to be regulated by NO. The characterization of these protein networks provides a better understanding of the possible regulation mechanisms of cellular activities occurring in the NO-treated cotton leaves and offers new insights into NO responses in plants.

Topics: Benzoates; Chlorophyll; Chloroplasts; Cytoplasm; Databases, Protein; Ethylenes; Gene Expression Regulation, Plant; Golgi Apparatus; Gossypium; Imidazoles; Nitric Oxide; Nitroprusside; Photosynthesis; Plant Leaves; Plant Proteins; Protein Biosynthesis; Proteome; Proteomics; Seeds; Spectrometry, Mass, Electrospray Ionization

Iron deficiency impairs chlorophyll biosynthesis and chloroplast development. In leaves, most of the iron must cross several biological membranes to reach the chloroplast. The components involved in the complex internal iron transport are largely unknown. Nitric oxide (NO), a bioactive free radical, can react with transition metals to form metal-nitrosyl complexes. Sodium nitroprusside, an NO donor, completely prevented leaf interveinal chlorosis in maize (Zea mays) plants growing with an iron concentration as low as 10 microM Fe-EDTA in the nutrient solution. S-Nitroso-N-acetylpenicillamine, another NO donor, as well as gaseous NO supply in a translucent chamber were also able to revert the iron deficiency symptoms. A specific NO scavenger, 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, blocked the effect of the NO donors. The effect of NO treatment on the photosynthetic apparatus of iron-deficient plants was also studied. Electron micrographs of mesophyll cells from iron-deficient maize plants revealed plastids with few photosynthetic lamellae and rudimentary grana. In contrast, in NO-treated maize plants, mesophyll chloroplast appeared completely developed. NO treatment did not increase iron content in plant organs, when expressed in a fresh matter basis, suggesting that root iron uptake was not enhanced. NO scavengers 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and methylene blue promoted interveinal chlorosis in iron-replete maize plants (growing in 250 microM Fe-EDTA). Even though results support a role for endogenous NO in iron nutrition, experiments did not establish an essential role. NO was also able to revert the chlorotic phenotype of the iron-inefficient maize mutants yellow stripe1 and yellow stripe3, both impaired in the iron uptake mechanisms. All together, these results support a biological action of NO on the availability and/or delivery of metabolically active iron within the plant.

Topics: Benzoates; Chlorophyll; Chloroplasts; DNA, Chloroplast; Free Radical Scavengers; Imidazoles; Iron; Light-Harvesting Protein Complexes; Microscopy, Electron; Mutation; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Phenotype; Photosynthetic Reaction Center Complex Proteins; RNA, Messenger; S-Nitroso-N-Acetylpenicillamine; Zea mays