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Ozone effects on plants...

Date post: 11-May-2015
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From climate change to molecular response: redox proteomics of ozone-induced responses in soybean
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Joseph Jez Presentation by : Satya Prakash Chaurasia Department of Botany, University of Delhi, [email protected] www.facebook.com/91satya www.twitter.com/Satyapr101991
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Introduction

Tropospheric ozone in northern hemisphere causes significant Agricultural

loss.

Since 90th century, ground level O3 concentrations have doubled.

Regions in India , china and US facing a 10% per year rise.

Soybean, rice , wheat etc.

Climate models predict that mean surface O3 concentrations may rise 20–

25% globally by 2050, with concentrations in India and south Asia reaching

comparable values by 2020 (IPCC 2001; Dentener et al., 2005; Van

Dingenen et al., 2009).

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Basic Protocol O3 treatment. Soybeans were planted at SoyFACE in July, 2009 three different treatments were given[Ambient(36ppb),moderate(58),high(116ppb)]

plants were harvested during reproductive growth in Aug ,2009

leaves and roots were obtained and immediately dipped in liquid N2

• Bradford Assay.Total Protein

• Infrared gas analyzerPhotosynthetic carbon uptake rates

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Protein extraction/redox proteome labeling

Frozen tissues were ground to a fine powder in liquid N2

suspended in extraction buffer( containing NEM)

Sonication and centrifuged supernatant mixed with MeOH,incubation centrifuged pellet washed with MeOH and resuspended in reduction buffer( DDT) Incubation and reprecipitation with MeOH Pellet dried and resuspended in labeling buffer( IAF)

NEM: N-ethylmaleimide ; IAF: 5-iodoacetamidofluorescein

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IEF run and proteomic analysis

proteins absorbed into IEF pH(4-7) strips imaging of gel to detect IAF labeled proteins

gels were fixed, washed and stained with Sypro Ruby to detect total protein image alignment and identification of spots differing significantly

these spots were excised and proteins obtained

LC- MS/MS analysis and Data searched against NCBInr database

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Spectrophotometric Enzyme assays: • Phosphoglycerate Kinase(PGK)• Malate dehydrogenase(MDH)• Glutamine synthase(GS)• Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)• Fructose 1,6-bisphosphate aldolase ( FBA), and • Ribulose 1,5-bisphosphate carboxylase oxygenase ( RuBisCo)

Immunoblot analysis of RuBisCo large subunit: membrane from SDS-PAGE, after TBS incubation, treated with Anti-RuBisCo large subunit antibody treated with secondary antibody conjugated with enzyme

detection by colorimetric detection

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Results

• Total protein content from different plant samples showed no significant difference.

• Photosynthetic carbon uptake showed linear decline with increasing Ozone concentration.

• A total of 1455 spots were identified of which 277 were differentially expressed and/or oxidized.

• Effects vary with length, concentration of Ozone exposure.

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(a)Distribution of proteins across combinations of tissue and O3 concentration. Numbers in overlapping regions of the lobes indicate proteins found in more than one set of conditions.

(b)(b–e) Numbers of differentially oxidized (5-iodoacetamidofluorescein (IAF)) and ⁄ or abundant (Sypro Ruby) proteins between treated samples and controls.

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Panels show the fold changes in oxidation (5-iodoacetamidofluorescein (IAF)) and expression level (Sypro) relative to ambient controls for proteinsidentified by nano-LC ⁄MS⁄ MS.

Summary of fold-changes in total and redox proteomes of soybean root tissue exposed to high (116 ppb) O3 (a); and leaf (b) and root tissues (c) exposed to moderate (58 ppb) O3.

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Fold changes, relative to ambient (37 ppb) O3 sample, in oxidation state (5-iodoacetamidofluorescein (IAF)) and abundance (Sypro) for identified proteins are plotted. Names of representative proteins are shown with highly (> threefold) oxidized (orange box) and oxidized (> threefold) ⁄ expressed (> 1.5-fold) proteins(pink boxes) indicated.

Summary of fold changes in total and redox proteomes of soybean leaf tissue exposed to high (116 ppb) O3.

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Discussion

• Large no. of metabolic pathways are affected:– Amino acid biosynthesis– Nitrogen homeostasis– Carbon metabolism– Starch/sugar mobilization pathway(MDH)– Isoprenoid synthesis pathway– Carotenoid and isoflavanoids pathways– Calvin cycle , glycolysis, citric acid cycle

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• Glutamine synthase(GS) -leaf senescence and recycling of ammonia.

• Malate dehydrogenase(MDH) Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and Fructose 1,6-bisphosphate aldolase ( FBA)• chlorophyll α ⁄ β binding protein, ferredoxin reductase, and a

chlorophyllase-like protein

RuBisCO large and small subunits, RuBisCO activase, RuBisCO-associated protein, and RuBisCO-binding protein showed increased expression and ⁄ or oxidation in this sample.

Oxidation of RuBisCO can reduce the catalytic activity of the enzyme (Marcus et al., 2003); however, alterations in proteins associated with RuBisCO (i.e. the activase) may compensate for possible oxidative changes.

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The proteomic analysis here supports studies demonstrating that redox-protection mechanisms play a critical role in plant responses to O3 exposure (Gillespie et al., 2011), and for the first time directly shows that O3 exposure changes the thiol oxidation state of proteins in various pathways.

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