Présentation PowerPoint

Présentation PowerPoint

A B Chloroplast O2 O2 1 O2 RuBP CO2 Chloroplast 1 O2 Glycolate PSII RuBP 3 O2 Glycolate PSII PGA PGA NADPH NADPH PSI PSI NADP+ NADP+ O.2 O2 O2. 2 H2O2 O2 Sugar-P Peroxisome Sugar-P H2O2 O2 Glycolate Peroxisome H2O2 CO2 CO2 CO2 CO2 Glyoxylate CO2 CO2 CO2 CO2 CO2 CO2 Glycolate O2 H2O2 1 Glyoxylate CO2 O2 CO2 CO2 CO2 Leaf interior CO2 CO2

CO2 CO2 CO2 CO2 CO2 CO2 CO2 Epidermis Figure 1. Current concepts of how drought increases the generation of reactive oxygen species (ROS) in photosynthesis. A. Cartoon of leaf section in well-watered plants in which relatively high intercellular CO2 concentrations (Ci) allow efficient regeneration of terminal oxidants and limit RuBP oxygenation. B. Drought-induced stomatal closure restricts CO2 uptake, favoring photorespiratory production of H 2O2 in the peroxisome (1) and possibly favoring production of superoxide and H 2O2 (2) or singlet oxygen (3) by the photosynthetic electron transport chain. APOPLAST CYTOSOL Plasma Membrane NADPH NADPH oxidase O2 Superoxide dismutase Flavocytochrome O2-. CuZn NADP+ H2O2 Class III peroxidase O2 Superoxide dismutase Heme O2-. CuZn e- Amine oxidase Putrescine Cadaverine O2 Cu H2O2 Oxalate oxidase Oxalate H2O2 Mn Polyamine oxidase FAD Spermidine Spermine O2 H2O2 O2 H2O2 Figure 2. Multiple ROS-producing enzymes at the cell surface/exterior. Enzymes are shown in blue and their redox cofactors are indicated in yellow. Class III peroxidases may accept electrons from several types of compound to generate superoxide, but in many cases their physiological reductant is not established (reviewed by OBrien et al., 2012). AGI Gene name Redox class At2g29460 At1g17020 At5g35790 At1g06830 At1g35720 At2g28190 At1g08830 At5g17220 At4g02520,At2g02930 At5g06290 At1g56500 At4g39640

At1g78370 At3g03190 At5g18600 GSTU4 glutathione S-transferase TAU4 SRG1 senescence related gene 1 (ascorbate oxidase) G6PD1 glucose-6-phosphate dehydrogenase 1 ROXY6 CC-type glutaredoxin ANNAT1 annexin 1, peroxidase activity CSD2 CuZn superoxide dismutase CSD1 CuZn superoxide dismutase GSTF12 glutathione S-transferase PHI12 GSTF2,GSTF3 glutathione S-transferases PHI2, PHI3 2-cys PrxB 2-cys peroxiredoxin subunit B thioredoxin family protein, suppressor of quenching 1 GGT1 g-glutamyl transpeptidase 1 GSTU20 glutathione S-transferase TAU20 GSTF11 glutathione S-transferase TAU11 ROXY10 CC-type glutaredoxin glutathione ascorbate NADPH glutathione ROS ROS ROS glutathione glutathione thioredoxin thioredoxin glutathione glutathione glutathione glutathione Drought 1 1.49 1.11 -1.02 -3.24 1.33 -2.72 -1.49 4.76 -1.31 -1.56 -1.05 -1.12 -2.27 -2.21 -1.27 Drought 2 4.36 4.94 -1.83 -1.23 1.80 -1.77 -1.18 3.96 -3.25 -2.13 -1.13 -2.44 -2.29 -1.38 -1.21 Salt ABA 1.99 3.92 -1.27 -2.39 1.20 -2.18 -1.36 1.90 -1.55 -1.06 -0.21 -0.64 -0.03 0.53 0.27 Osmotic 3.78 3.47 -2.24 0.41 0.01 -0.15 0.49 0.13 -0.28 -0.48 0.21 -0.24 -0.81 0.99 1.06 2.28 0.60 -0.57 -2.65 0.61 -0.59 0.11 0.52 0.73 -0.12 -0.43 0.02

-0.08 0.18 -0.48 Figure 3. The 15 of the 302 redox-linked genes that respond > 2-fold in the same direction in both drought 1 and drought 2 datasets and their response in related conditions. Data extracted from Genevestigator are shown as log 2 values compared to controls. Red and green indicate induction and repression. Genes are ordered from top according to the number of conditions in which they respond. The full list of genes and their expression values are given in Supplemental Table S1. For details of experiments, see Supplemental Table S2. Thiol-dependent peroxide metabolism Signaling is also possible through antioxidative activity per se Thiol-independent peroxide metabolism Antioxidative systems participate in signaling by their effects on peroxide levels H2O2 2 H2O ROOH APX CAT H2O2 2 H 2O H2O2 O2 ASC MDHA ROH ROOH ROH ROOH ROH GST DHA ASC GSH GSSG PRXII PRXII 2CPRX 2CPRX SH SH SOH SH SH SH SOH SH + GSH MDHAR DHAR GSS NAD(P) + NAD(P)H GSH GSS SH GSH APX functioning independently of glutathione S S SH GSSG GRX Dismutation by catalase 2CPRX PRXII Ascorbate-glutathione GST glutathione pathway peroxidase function GRX SH SH

NTR/TRX SH SH NTR/TRX S S GSSG Glutathione-linked peroxiredoxin Thioredoxin-linked peroxiredoxin Figure 4. Peroxide-removing enzymes: roles as antioxidants, in signaling, or both? Cartoon of the best characterized peroxide-metabolizing enzymes in plants. Other mechanisms are possible and for ease of display reactions are not shown stoichiometrically. APX, ascorbate peroxidase. CAT, catalase. DHAR, dehydroascorbate reductase. GRX, glutaredoxin. GST, glutathione S-transferase. MDHAR, monodehydroascorbate reductase. NTR, NADPH-thioredoxin C. PRXII, type II peroxiredoxin. 2CPRX, 2-cys PRX. TRX, thioredoxin. A B 66 272 37 Total number of drought-induced genes = 375 8 6 4 2 cat2: High CO2 cat2: H2O2 (peroxisome) flu : singlet O2 (chloroplast) External H2O2 (extracellular) ABA DROUGHT 2 Paraquat: O2-, H2O2 (chloroplast) Oxidative stress marker transcripts (log2 treated/control) DROUGHT 1 C ABA Paraquat: O-2, H2O2 (chloroplast) flu: singlet O2 (chloroplast) 246 375 317 129 0 58 External H2O2 (extracellular) cat2: H2O2 (peroxisome) cat2: high CO2 (negative control) 360 354 372 15 21 3 0 Figure 5. Analysis of drought-inducible gene expression in responses to redox perturbation. A. Heatmap of drought-induced genes extracted from Genevestigator and the response of these genes to ABA or oxidative stress (top), and histogram showing expression of oxidative stress marker genes after the different treatments (bottom). Data are shown as log 2 values compared to Col-0 (wild-type or untreated). Experimental details are given in Supplemental Table S2. Red and green on the heatmap indicate induction and repression according to the color scale shown at the top. The five genes for which data are shown in the bottom histogram are (left to right) APX1, GSTU24, UGT75B1, UGT73B5, and GPX6 (for values, see Supplemental Table S3B). B. Overlap of induced genes (cut-off 2-fold) in the two drought experiments. 375 genes were induced >2-fold in at least one of the experiments (Supplemental Table S3A). C. Number of these 375 genes that were induced > 2-fold by the different oxidative stresses (indicated in red circles within the outer blue circles).

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