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Zhou J.,Zhejiang University | Xia X.-J.,Zhejiang University | Zhou Y.-H.,Zhejiang University | Shi K.,Zhejiang University | And 4 more authors.
Journal of Experimental Botany

H2O2 and mitogen-activated protein kinase (MAPK) cascades play important functions in plant stress responses, but their roles in acclimation response remain unclear. This study examined the functions of H 2O2 and MPK1/2 in acclimation-induced cross-tolerance in tomato plants. Mild cold, paraquat, and drought as acclimation stimuli enhanced tolerance to more severe subsequent chilling, photooxidative, and drought stresses. Acclimation-induced cross-tolerance was associated with increased transcript levels of RBOH1 and stress- and defence-related genes, elevated apoplastic H2O2 accumulation, increased activity of NADPH oxidase and antioxidant enzymes, reduced glutathione redox state, and activation of MPK1/2 in tomato. Virus-induced gene silencing of RBOH1, MPK1, and MPK2 or MPK1/2 all compromised acclimation-induced cross-tolerance and associated stress responses. Taken together, these results strongly suggest that acclimation-induced cross-tolerance is largely attributed to RBOH1-dependent H2O2 production at the apoplast, which may subsequently activate MPK1/2 to induce stress responses. © © The Author 2013. Published by Oxford University Press on behalf of the Society for Experimental Biology. Source

Jiang Y.-P.,Zhejiang University | Cheng F.,Zhejiang University | Zhou Y.-H.,Zhejiang University | Xia X.-J.,Zhejiang University | And 6 more authors.
New Phytologist

• Brassinosteroids (BRs) play a vital role in plant growth, stress tolerance and productivity. Here, the involvement of BRs in the regulation of CO 2 assimilation and cellular redox homeostasis was studied. • The effects of BRs on CO 2 assimilation were studied in cucumber (Cucumis sativus) through the analysis of the accumulation of H 2O 2 and glutathione and photosynthesis-related enzyme activities using histochemical and cytochemical detection or a spectrophotometric assay, and Rubisco activase (RCA) using western blot analysis and immunogold labeling. • Exogenous BR increased apoplastic H 2O 2 accumulation, the ratio of reduced to oxidized glutathione (GSH:GSSG) and CO 2 assimilation, whereas a BR biosynthetic inhibitor had the opposite effects. BR-induced CO 2 assimilation was decreased by a H 2O 2 scavenger or inhibition of H 2O 2 generation, GSH biosynthesis and the NADPH-generating pentose phosphate pathway. BR-, H 2O 2- or GSH-induced CO 2 assimilation was associated with increased activity of enzymes in the Benson-Calvin cycle. Immunogold labeling and western blotting showed that BR increased the content of RCA and this effect was blocked by inhibitors of redox homeostasis. • These results strongly suggest that BR-induced photosynthesis involves an H 2O 2-mediated increase in the GSH:GSSG ratio, which may positively regulate the synthesis and activation of redox-sensitive enzymes in carbon fixation. © 2012 The Authors New Phytologist. © 2012 New Phytologist Trust. Source

Xu J.-Y.,Zhejiang University | Wu L.-Y.,Zhejiang University | Zheng X.-Q.,Key Laboratory of Horticultural Plants Growth | Lu J.-L.,Zhejiang University | And 2 more authors.
Investigative Ophthalmology and Visual Science

PURPOSE. To examine the protective effect of green tea polyphenols against ultraviolet B (UVB)-induced damage to retinal pigment epithelial (RPE) cells. METHODS. Green tea polyphenols (GTP) was used to treat RPE cells before or after exposure to UVB. Viability of RPE cells was tested by 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Survivin gene expression was examined by real-time PCR analysis. Ultrastructure of RPE cells was examined by transmission electron microscopy. RESULTS. GTP effectively suppressed the decrease in viability of the UVB stressed RPE cells and the UVB suppression of surviving gene expression level. GTP alleviated mitochondria dysfunction and DNA fragmentation induced by UVB. CONCLUSIONS. GTP protected RPE cells from UVB damage through its increase in the survivin gene expression and its attenuation of mitochondria dysfunction and DNA fragmentation. GTP is a potential candidate for further development as a chemoprotective factor for the primary prevention of agerelated eye diseases such as age-related macular degeneration. © Association for Research in Vision and Ophthalmology. Source

Ahammed G.J.,Zhejiang University | Yuan H.-L.,Zhejiang University | Ogweno J.O.,Zhejiang University | Zhou Y.-H.,Zhejiang University | And 5 more authors.

The present study was carried out to investigate the effects of exogenously applied 24-epibrassinolide (BR) on growth, gas exchange, chlorophyll fluorescence characteristics, lipid peroxidation and antioxidant systems of tomato seedlings grown under different levels (0, 10, 30, 100 and 300μM) of phenanthrene (PHE) and pyrene (PYR) in hydroponics. A concentration-dependent decrease in growth, photosynthetic pigment contents, net photosynthetic rate (Pn), stomatal conductance (Gs), maximal quantum yield of PSII (Fv/Fm), effective quantum yield of PSII (Φ PSII), photochemical quenching coefficient (qP) has been observed following PHE and PYR exposure. By contrast, non-photochemical quenching coefficient (NPQ) was increased. PHE was found to induce higher stress than PYR. However, foliar or root application of BR (50nM and 5nM, respectively) alleviated all those depressions with a sharp improvement in the activity of photosynthetic machinery. The activities of guaicol peroxidase (GPOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) as well as content of malondialdehyde (MDA) were increased in a dose-dependent manner under PHE or PYR treatments. Compared with control the highest increments of GPOD, CAT, APX, GR and MDA by PHE/PYR alone treatments were observed following 300μM concentration, which were 67%, 87%, 53%, 95% and 74% by PHE and 42%, 53%, 30%, 86% and 62% by PYR, respectively. In addition, both reduced glutathione (GSH) and oxidized glutathione (GSSG) were induced by PHE or PYR. Interestingly, BR application in either form further increased enzymatic and non enzymatic antioxidants in tomato roots treated with PHE or PYR. Our results suggest that BR has an anti-stress effect on tomato seedlings contaminated with PHE or PYR and this effect is mainly attributed by increased detoxification activity. © 2011 Elsevier Ltd. Source

Ahammed G.J.,Zhejiang University | Choudhary S.P.,Zhejiang University | Chen S.,Zhejiang University | Xia X.,Zhejiang University | And 4 more authors.
Journal of Experimental Botany

Heavy metal pollution often occurs together with organic contaminants. Brassinosteroids (BRs) induce plant tolerance to several abiotic stresses, including phenanthrene (PHE) and cadmium (Cd) stress. However, the role of BRs in PHE+Cd co-contamination-induced stress amelioration is unknown. Here, the interactive effects of PHE, Cd, and 24-epibrassinolide (EBR; a biologically active BR) were investigated in tomato plants. The application of Cd (100 μM) alone was more phytotoxic than PHE applied alone (100 μM); however, their combined application resulted in slightly improved photosynthetic activity and pigment content compared with Cd alone after a 40 d exposure. Accumulation of reactive oxygen species and membrane lipid peroxidation were induced by PHE and/or Cd; however, the differences in effect were insignificant between Cd and PHE+Cd. The foliar application of EBR (0.1 μM) to PHE- and/or Cd-stressed plants alleviated photosynthetic inhibition and oxidative stress by causing enhancement of the activity of the enzymes and related transcript levels of the antioxidant system, secondary metabolism, and the xenobiotic detoxification system. Additionally, PHE and/or Cd residues were significantly decreased in both the leaves and roots after application of EBR, more specifically in PHE+Cd-stressed plants when treated with EBR, indicating a possible improvement in detoxification of these pollutants. The findings thus suggest a potential interaction of EBR and PHE for Cd stress alleviation. These results advocate a positive role for EBR in reducing pollutant residues for food safety and also strengthening phytoremediation. © 2012 The Author. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved. Source

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