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Thioredoxin Reductase Type C （NTRC） Orchestrates Enhanced thermotolerance.to Arabidopsis by Its Redox-Dependent Holdase Chaperone Function

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Molecular Plant 2013年第2期6卷 323-336页

作者： Ho Byoung Chae Jeong Chan Moon Mi Rim Shin Yong Hun Chi Young Jun Jung Sun Yong Lee Ganesh M. Nawkar Hyun Suk Jung Jae Kyung Hyun Woe Yeon Kim Chang Ho Kang Dae-Jin Yun Kyun Oh Lee Sang Yeol Lee Division of Applied Life Science (BK21 Program) and PMBBRC Gyeongsang National University 501 Jinju-daero Jinju 660-701 Korea Division of Electron Microscopic Research Korea Basic Science Institute 113 Gwahangno Yuse0ng-guDaejeon 303-333 Korea

Genevestigator analysis has indicated heat shock induction of transcripts for NADPH-thioredoxin reduc-tase, type C （NTRC） in the light. Here we show overexpression of NTRC in Arabidopsis （NTRC°E） resulting in enhanced tolerance to heat shock, whereas NTRC knockout mutant plants （ntrcl） exhibit a temperature sensitive phenotype. To investigate the underlying mechanism of this phenotype, we analyzed the protein＇s biochemical properties and protein structure. NTRC assembles into homopolymeric structures of varying complexity with functions as a disulfide reductase, a foldase chaperone, and as a holdase chaperone. The multiple functions of NTRC are closely correlated with protein structure.. Complexes of higher molecular weight （HMW） showed stronger activity as a holdase chaperone, while low molecular weight （LMW） species exhibited weaker holdase chaperone activity but stronger disulfide reductase and fol-dase chaperone activities. Heat shock converted LMW proteins into HMW complexes. Mutations of the two active site Cys residues of NTRC into Ser （C217/454S-NTRC） led to a complete inactivation of its disulfide reductase and foldase chaperone functions, but conferred only a slight decrease in its holdase chaperone function. The overexpression of the mutated C217/454S-NTRC provided Arabidopsis with a similar degree of thermotolerance.compared with that of NTRC°E plants. However, after prolonged incubation under heat shock, NTRC°E plants tolerated the stress to a higher degree than C217/454S-NTRC°E plants. The results suggest that the heat shock-mediated holdase chaperone function of NTRC is responsible for the increased thermotolerance.of Arabidopsis and the activity is significantly supported by NADPH.

关键词： NADPH-thioredoxin reductase type C （NTRC） oligomeric complexes disulfide reductase foldase and holdasechaperone functions redox thermotolerance.

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Improved Growth and Stress Tolerance in the Arabidopsis oxtl Mutant Triggered by Altered Adenine Metabolism

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Molecular Plant 2012年第6期5卷 1310-1332页

作者： Suchada Sukrong Kil-Young Yun Patrizia Stadler Charan Kumar Tony Facciuolo Barbara A.Moffatt Deane L.Falconec Department of Plant and Soil Science University of KentuckyLexingtonKY 40546USA Present address:Department of Pharmacognosy Faculty of Pharmaceutical SciencesChulalongkorn UniversityBangkokThailand Department of Biological Sciences University of MassachusettsOne University AvenueLowellMA 01854USA Present address:Fungi and Plant Co.Ltd Chungcheongbuk-doRepublic of Korea Department of Biology University of WaterlooWaterlooOntarioCanada

Plants perceive and respond to environmental stresses with complex mechanisms that are often associ- ated with the activation of antioxidant defenses. A genetic screen aimed at isolating oxidative stress-tolerant lines of Arabidopsis thaliana has identified oxtl, a line that exhibits improved tolerance to oxidative stress and elevated temperature but displays no apparent deleterious growth effects under non-stress conditions. Oxtl harbors a muta- tion that arises from the altered expression of a gene encoding adenine phosphoribosyltransferase （APT1）, an enzyme that converts adenine to adenosine monophosphate （AMP）, indicating a link between purine metabolism, whole-plant growth responses, and stress acclimation. The oxtl mutation results in decreased APT1 expression that leads to reduced enzymatic activity. Correspondingly, oxtl plants possess elevated levels of adenine. Decreased APT enzyme activity dir- ectly correlates with stress resistance in transgenic lines that ectopically express APT1. The metabolic alteration in oxtl plants also alters the expression of several antioxidant defense genes and the response of these genes to oxidative chal- lenge. Finally, it is shown that manipulation of adenine levels can induce stress tolerance to wild-type plants. Collectively, these results show that alterations in cellular adenine levels can trigger stress tolerance and improve growth, leading to increases in plant biomass. The results also suggest that adenine might play a part in the signals that modulate responses to abiotic stress and plant growth.

关键词： abiotic/oxidative environmental stress acclimation priming purine signaling salvage pathway thermotolerance.

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Interactive Effects of Elevated CO_2 and Growth Temperature on the Tolerance of Photosynthesis to Acute Heat Stress in C_3 and C_4 Species

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Journal of Integrative Plant Biology 2008年第11期50卷 1375-1387页

作者： E. William Hamilton III Scott A. Heckathorn Puneet Joshi Dan Wang Deepak Barua Department of Biology Washington and Lee University Lexington Virginia USA Department of Environmental Sciences University of Toledo Toledo Ohio USA

Determining effects of elevated CO2 on the tolerance of photosynthesis to acute heat-stress （heat wave） is necessary for predicting plant responses to global warming, as photosynthesis is thermolabile and acute heat-stress and atmospheric CO2 will increase in the future. Few studies have examined this, and past results are variable, which may be due to methodological variation. To address this, we grew two C3 and two C4 species at current or elevated CO2 and three different growth temperatures （GT）. We assessed photosynthetic thermotolerance.in both unacclimated （basal tolerance） and preheat-stressed （preHS = acclimated） plants. In C3 species, basal thermotolerance.of net photosynthesis （Pn） was increased in high CO2, but in C4 species, Pn thermotlerance was decreased by high CO2 （except Zea mays at low GT）; CO2 effects in preHS plants were mostly small or absent, though high CO2 was detrimental in one C3 and one C4 species at warmer GT. Though high CO2 generally decreased stomatal conductance, decreases in P, during heat stress were mostly due to non-stomatal effects. Photosystem Ⅱ （PSⅡ） efficiency was often decreased by high CO2 during heat stress, especially at high GT; CO2 effects on post-PSⅡ electron transport were variable. Thus, high CO2 often affected photosynthetic theromotolerance, and the effects varied with photosynthetic pathway, growth temperature, and acclimation state. Most importantly, in heat-stressed plants at normal or warmer growth temperatures, high CO2 may often decrease, or not benefit as expected, tolerance of photosynthesis to acute heat stress. Therefore, interactive effects of elevated CO2 and warmer growth temperatures on acute heat tolerance may contribute to future changes in plant productivity, distribution, and diversity.

关键词： carbon dioxide global climate change photosynthesis thermotolerance.

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Identification and Characterization of Proteins Associated with Plant Tolerance to Heat Stress

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Journal of Integrative Plant Biology 2008年第10期50卷 1230-1237页

作者： Bingru Huang Chenping Xu Department of Plant Biology and Pathology Rutgers University New Brunswick NJ 08901 USA

Heat stress is a major abiotic stress limiting plant growth and productivity in many areas of the world. Understanding mechanisms of plant adaptation to heat stress would facilitate the development of heat-tolerant cultivars for improving productivity in warm climatic regions. Protein metabolism involving protein synthesis and degradation is one of the most sensitive processes to heat stress. Changes in the level and expression pattern of some proteins may play an important role in plant adaptation to heat stress. The identification of stress-responsive proteins and pathways has been facilitated by an increasing number of tools and resources, including two-dimensional electrophoresis and mass spectrometry, and the rapidly expanding nucleotide and amino acid sequence databases. Heat stress may induce or enhance protein expression or cause protein degradation. The induction of heat-responsive proteins, particularly heat shock proteins （HSPs）, plays a key role in plant tolerance to heat stress. Protein degradation involving various proteases is also important in regulating plant responses to heat stress. This review provides an overview of recent research on proteomic profiling for the identification of heat-responsive proteins associated with heat tolerance, heat induction and characteristics of HSPs, and protein degradation in relation to plant responses to heat stress.

关键词： heat shock proteins heat stress proteomics stress response thermotolerance.

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Effects of Heat Shock on Glucocorticoid Receptor

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Science China Chemistry 1994年第5期37卷 557-562页

作者：宋亮年 Department of Pathophysiology Second Military Medical University Shanghai 200433 PRC

The changes of glucocorticoid receptor (GR) during the heat shock response have been studied using a human osteosarcoma cell line (HOS-8603) as the model. The expression of the heat shock protein 70 (hsp70) mRNA in HOS-8603 cells has been enhanced markedly after a heat treatment at 43 ℃ for 30 min. A mild thermal pretreatment (42℃ for 1 h) protects the HOS-8603 cells against a subsequent heat challenge (46℃). This induced thermotolerance.is reflected by the increase of cell viability of HOS-8603 cells. The GR binding activity in HOS-8603 cells decreased rapidly after the heat treatment at 43℃; only 42. 61% of controls were detected 60 min after the heat treatment. However, there was no significant change in the dissociation constant value (Kd). These results indicate that the heat shock induce not only the heat shock mRNA expression, but also the rapid reduction in GR binding activity, suggesting that there might be a functional relationship between GR action and the heat shock response.

关键词： heat shock proteins mRNA glucocorticoids glucocorticold receptor thermotolerance.

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Relationship between the induction of heat shock proteins and the decrease in glucocorticoid receptor during heat shock response in human osteosarcoma cells

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Science China Chemistry 1995年第12期38卷 1473-1481页

作者：宋亮年 Department of Pathophysiology Second Military Medical UniversityShanghai 200433China

Previously,it has been found that glucocorticoid receptor(GR)binding activity decreasedrapidly during heat shock response in HOS-8603,a human osteosarcorna cell line.In this study,Therelationship between the induction of heat shock proteins(HSPs)and the decrease in GR was furtherstudied in the same cell line.It was found that even though quercetin could specifically inhibit the ex-pression of hsp90α and hsp70 mRNA,it could not prevent GR from the decrease in response to the heatshock treatment.This represents the first reported evidence that the induction of HSPs and the decrease inGR during heat shock response were 2 independent biological events.The results of the present study furthershowed that although the heat shock treatment alone had no effects on alkaline phosphatase(AKP)activity,itcould completely block the induction of AKP activity in HOS-8603 cells by dexamethasone(Dex),a syntheticglucocorticoid.These results demonstrate that the heat shock-induced alteration in GR was accompanied by adecrease in GR functional activity.Furthermore,when the induction of HSPs was inhibited by the treatmentof cells with quercetin,the stimulatory effects of Dex on AKP activity could still be inhibited completely bythe heat shock treatment.The results of this part,on the basis of GR functional activity,further demonstratethat quercetin could not inhibit the heat shock-induced decrease in GR,even though it could inhibit the induc-tion of HSPs.To clarify further the effects of quercetin alone on GR binding activity in HOS-8603 cells,theregulation of GR by quercetin was also studied.It was found for the first time that quercetin coulddown-regulate GR in a time-dependent manner significantly,and that the down-regulation of GR by quercetinin HOS-8603 cells paralelled with a decrease in glucocorticoid-mediated functional responses,suggesting thatthe down-regulation of GR by quercetin is of biological significance.

关键词： heat shock protein glucocorticoid receptor alkaline phosphatase quercetin osteosarcoma cells thermotolerance.

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