Ozone-Induced Alterations in the Accumulation of Newly Synthesized Proteins in Leaves of Maize

Pino, Mariela; Mudd, J.B.; Bailey‐Serres, Julia

doi:10.1104/pp.108.2.777

Cited by 20 publications

(11 citation statements)

References 23 publications

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“…This has been suggested to occur, in part, from reduced stomatal conductance or accelerated loss of D1 protein affecting photosynthetic activity (Pell et al, 1990;Godde and Buchhold, 1992;Pino et al, 1995). However, despite their higher rate of stomatal conductance and greater accumulation of ROS following a chronic exposure to ozone, DHAR-OX leaves maintained a higher rate of CO 2 assimilation than control leaves, whereas DHAR-KD leaves exhibited a reduced rate of CO 2 assimilation.…”

Section: Discussionmentioning

confidence: 74%

Increasing Tolerance to Ozone by Elevating Foliar Ascorbic Acid Confers Greater Protection against Ozone Than Increasing Avoidance

2005

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Ascorbic acid (Asc) is the most abundant antioxidant in plants and serves as a major contributor to the cell redox state. Exposure to environmental ozone can cause significant damage to plants by imposing conditions of oxidative stress. We examined whether increasing the level of Asc through enhanced Asc recycling would limit the deleterious effects of environmental oxidative stress. Plants overexpressing dehydroascorbate reductase (DHAR), which results in an increase in the endogenous level of Asc, were exposed to acute or chronic levels of ozone. DHAR-overexpressing plants had a lower oxidative load, a lower level of oxidative-related enzyme activities, a higher level of chlorophyll, and a higher level of photosynthetic activity 24 h following an acute exposure (2 h) to 200 ppb ozone than control plants, despite exhibiting a larger stomatal area. Reducing the size of the Asc pool size through suppression of DHAR expression had the opposite effect. Following a chronic exposure (30 d) to 100 ppb ozone, plants with a larger Asc pool size maintained a larger stomatal area and a higher oxidative load, but retained a higher level of photosynthetic activity than control plants, whereas plants suppressed for DHAR had a substantially reduced stomatal area, but also a substantially lower level of photosynthetic activity. Together, these data indicate that, despite a reduced ability to respond to ozone through stomatal closure, increasing the level of Asc through enhanced Asc recycling provided greater protection against oxidative damage than reducing stomatal area.Despite its essential role in supporting life, oxygen can be highly damaging. In the chloroplast, excess light can result in the production of reactive oxygen species (ROS), e.g. reduction of O 2 to superoxide that can occur in PSII or PSI by electrons derived from PSII. O 2 2 is then disproportionated by superoxide dismutase (SOD) to O 2 and H 2 O 2 . The H 2 O 2 is further reduced to H 2 O by ascorbate peroxidase (APX) in the water-water cycle (Asada, 2000). This cycle serves to maintain electron flow through the photosystems. However, exposure to many abiotic stresses, including cold, drought, or high light, can exacerbate ROS production by creating conditions of light stress at lower photon flux density. H 2 O 2 inactivates APX within seconds if ascorbic acid (Asc) recycling is impaired (Miyake and Asada, 1996). H 2 O 2 can also inhibit CO 2 assimilation by inhibiting several Calvin cycle enzymes (Asada, 1999). ROS can also be generated in response to exposure to pollutants, such as ozone (Grimes et al., 1983;Mudd, 1997;Schraudner et al., 1998), which can serve as signaling intermediates in guard cells to promote stomatal closure (Pei et al., 2000;Zhang et al., 2001) or, following a severe exposure, can damage cell membranes or even induce programmed cell death Overmyer et al., 2000;Rao et al., 2000;Loreto et al., 2001;Pasqualini et al., 2002Pasqualini et al., , 2003.Asc is the most abundant antioxidant in plants and serves as the major contributor to the ...

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Section: Discussionmentioning

confidence: 74%

Increasing Tolerance to Ozone by Elevating Foliar Ascorbic Acid Confers Greater Protection against Ozone Than Increasing Avoidance

2005

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“…Electrophoresis was performed in an isoelectric focusing gel apparatus using glass tubes (130 ϫ 3.5 mm; Hoefer Scientific, Richmond, CA) for 26 h at 143 V, with migration toward the cathode. Separation in the second dimension was in an acidic-urea polyacrylamide gel (Krieg et al, 1988) Pino et al, 1995). After the extrusion from the glass tubes, first-dimension gels were incubated in the equilibration buffer for 15 min (0.05 m Tris-HCl, pH 6.8, 5% [v/v] BME, 10% [v/v] …”

Section: Two-dimensional Pagementioning

confidence: 99%

Regulated Phosphorylation of 40S Ribosomal Protein S6 in Root Tips of Maize

et al. 2003

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Ribosomal protein S6 (RPS6) is located in the mRNA binding site of the 40S subunit of cytosolic ribosomes. Two maize (Zea mays) rps6 genes were identified that encode polypeptides (30 kD, 11.4 pI) with strong primary amino acid sequence and predicted secondary structure similarity to RPS6 of other eukaryotes. Maize RPS6 was analyzed by the use of two-dimensional gel electrophoresis systems, in vivo labeling with [ 32 P]P i and immunological detection. Nine RPS6 isoforms were resolved in a two-dimensional basic-urea/sodium dodecyl sulfate-polyacrylamide gel electrophoresis system. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry performed on trypsin-digested isoforms identified four serine (Ser) and one threonine (Thr) residue in the carboxy-terminal region as phosphorylation sites (RRS 238 KLS 241 AAAKAS 247 AAT 250 S 251 A-COOH). Heterogeneity in RPS6 phosphorylation was a consequence of the presence of zero to five phosphorylated residues. Phosphorylated isoforms fell into two groups characterized by (a) sequential phosphorylation of Ser-238 and Ser-241 and (b) the absence of phospho-Ser-238 and presence of phospho-Ser-241. The accumulation of hyper-phosphorylated isoforms with phospho-Ser-238 was reduced in response to oxygen deprivation and heat shock, whereas accumulation of these isoforms was elevated by cold stress. Salt and osmotic stress had no reproducible effect on RPS6 phosphorylation. The reduction in hyper-phosphorylated isoforms under oxygen deprivation was blocked by okadaic acid, a Ser/Thr phosphatase inhibitor. By contrast, the recovery of hyper-phosphorylated isoforms upon re-oxygenation was blocked by LY-294002, an inhibitor of phosphatidylinositol 3-kinases. Thus, differential activity of phosphatase(s) and kinase(s) determine complex heterogeneity in RPS6 phosphorylation.Ribosomal protein S6 (RPS6) assembles onto the 45S rRNA precursor in the nucleolus and is located at the small head region of the cytosolic 40S ribosomal subunit (Nygärd and Nilsson, 1990). RPS6 can be directly cross-linked to mRNA, tRNA, and initiation factors, confirming its location in a region involved in the initiation of translation. RPS6, a 30-kD protein, is the major phosphoprotein of eukaryotic ribosomes. In mammals and fruitfly (Drosophila melanogaster), it is sequentially phosphorylated at five carboxyterminal Ser residues (Krieg et al., 1988;Fumagalli and Thomas, 2000;Radimerski et al., 2000). RPS6 phosphorylation in the nucleolus occurs during active ribosome biogenesis, whereas RPS6 phosphorylation in the cytoplasm is thought to promote the selective translation of a subset of transcripts, primarily ribosomal protein and elongation factor mRNAs with a 5Ј-terminal oligopyrimidine tract (5ЈTOP; Reinhard et al., 1994;Jefferies et al., 1997;Fumagalli and Thomas, 2000). Ribosomes with the highest degree of RPS6 phosphorylation appear to have a selective advantage in mobilization into polysomes (Jefferies and Meyuhas and Hornstein, 2000). RPS6 phosphorylation might not be sufficient to re...

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“…On the basis of the gas-exchange measurements only, we cannot explain where the alteration was localized, since both stomatal limitations and altered mesophyllic CO2 fixation contribute to the decrease in Amax-The decrease in CO2 fixation, as a consequence of ozone exposure, has been attributed by many authors (Farage et al 1991, Nie et al 1993, Pell et al 1994, Pino et al 1995 to a reduction in the activity and the content of Rubisco, resulting in a decrease of the carboxylation rate, which in turn could determine a decline in the photosynthetic electron transport activity (Baker et al 1994). On the basis of the gas-exchange measurements only, we cannot explain where the alteration was localized, since both stomatal limitations and altered mesophyllic CO2 fixation contribute to the decrease in Amax-The decrease in CO2 fixation, as a consequence of ozone exposure, has been attributed by many authors (Farage et al 1991, Nie et al 1993, Pell et al 1994, Pino et al 1995 to a reduction in the activity and the content of Rubisco, resulting in a decrease of the carboxylation rate, which in turn could determine a decline in the photosynthetic electron transport activity (Baker et al 1994).…”

Section: Discussionmentioning

confidence: 96%

“…In both mature and young ozonated pumpkin leaves, the development of non-photochemical quenching allows a decrease in the PSII photochemistry rate. Some report on the stimulation of Dl synthesis and a reduction of its degradation (Lutz et al 1992, Aames et al 1993, some on the increase of both Dl synthesis and degradation (Godde and Buchold 1992), others on a lower rate of synthesis accompanied by a reduced content (Pino et al 1995, Ranieri et al 1995. Moreover, the detection of A at the end of the dark period in both mature and young ozonated tissues, but not in the controls, seems to point to the involvement of the xanthophyll cycle as a direct consequence of ozone exposure.…”

Section: Discussionmentioning

confidence: 99%

CO2 assimilation, xanthophyll cycle pigments and PSII efficiency in pumpkin plants as affected by ozone fumigation

Ciompi¹,

Castagna²,

Ranieri³

et al. 1997

Physiol Plant

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CO2 assimilation, xanthophyll cycle pigments and PSII efficiency in pumpkin plants as affected by ozone fumigation. -Physiol. Plant. 101: 881-889.CO2 assimilation, xanthophyll cycle pigments and PSII efficiency were analyzed in two different ages of pumpkin leaves {Cucurbita pepo L. cv. Ambassador) exposed to 150 nmol moF of ozone (5 days, 5 h day"'). Gas-exchange measurements revealed a reduction in CO2 assimilation and stomatal conductance, accompanied by an increase in the intercellular CO2 concentration both in young and in mature leaves as compared to their respective controls. In both leaves, Fo remained unchanged, while F^ and the Fv/Fjn ratio decreased after O3 fumigation, indicating that ozone may induce an alteration in the capability of photosystem II (PSII) to reduce the primary acceptor QA. In the mature leaves the photochemical quenching (qp) was significantly lowered by the pollutant, but this was not the case in the young leaves where qp did not change. In both mature and young ozonated pumpkin leaves, the development of non-photochemical quenching caused a decrease in the PSII photochemical rate, as shown by the correlation between Fv/F^ and the de-epoxidation state of dark-adapted leaves. Decreases in the Fv/F^ ratio are generally attributed to damage to the PSII reaction centre, apart from the down-regulation ofthe capacity of PSII electron transport. While in young ozonated leaves the decrease in the Fv/Fn, ratio was not associated with damage to the Dl protein, in mature ozonated pumpkin leaves, the decrease in the Fy/Fn, was accompanied by a significant decline in the Dl content. In conclusion, ozone exposure induces alterations in the light reactions of photosynthesis in both young and mature leaves. However, in young leaves the engagement of the xanthophyll cycle appears to counteract ozone effects against the photosynthetic apparatus as demonstrated by the absence of damage to the Dl protein. On the other hand, the loss of Dl protein in mature fumigated leaves suggests that the activation of the xanthophyll cycle is not sufficient to prevent photoinhibition, probably because a physiological state of senescence adds to the oxidative stress.

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Ozone-Induced Alterations in the Accumulation of Newly Synthesized Proteins in Leaves of Maize

Cited by 20 publications

References 23 publications

Increasing Tolerance to Ozone by Elevating Foliar Ascorbic Acid Confers Greater Protection against Ozone Than Increasing Avoidance

Increasing Tolerance to Ozone by Elevating Foliar Ascorbic Acid Confers Greater Protection against Ozone Than Increasing Avoidance

Regulated Phosphorylation of 40S Ribosomal Protein S6 in Root Tips of Maize

CO2 assimilation, xanthophyll cycle pigments and PSII efficiency in pumpkin plants as affected by ozone fumigation

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