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Redox Changes during the Legume-Rhizobium Symbiosis

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Molecular Plant 2009年第3期2卷 370-377页

作者： Christine Chang Isabelle Damiani Alain Puppo Pierre Frendo UMR INRA-Université de Nice-Sophia Antipolis-CNRS 'Interactions Biotiques et Santé Végétale' 400 Route des Chappes BP167 06903 Sophia Antipolis CedexFrance

Reactive Oxygen Species （ROS） are continuously produced as a result of aerobic metabolism or in response to biotic and abiotic stresses. ROS are not only toxic by-products of aerobic metabolism, but are also signaling molecules involved in plant growth and environmental adaptation. Antioxidants can protect the cell from oxidative damage by scavenging the ROS. Thus, they play an important role in optimizing cell function by regulating cellular redox state and modifying gene expression. This article aims to review recent studies highlighting the role of redox signals in establishing and maintaining symbiosis between rhizobia and legumes.

关键词： oxidative and photo-oxidative stress cell differentiation/specialization gene regulation symbiosis legume

Inositol Polyphosphate Phosphatidylinositol 5-Phosphatase9 （At5PTase9） Controls Plant Salt Tolerance by Regulating Endocytosis

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Molecular Plant 2013年第6期6卷 1781-1794页

作者： Yael Golania Yuval Kaye Omri Gilhar Mustafa Ercetin Glenda Gillaspy Alex Levine Department of Plant and Environmental Sciences The Hebrew University of Jerusalem Givat-Ram Campus Jerusalem 91904 Israel Department of Biochemistry and Fralin Biotechn01ogy Center Virginia T'ech Blacksburg VA 24061 USA

Phosphatidylinositol 5-phosphatases （5PTases） components of membrane trafficking system. Recently, we that hydrolyze the 5＇ position of the inositol ring are key reported that mutation in AtSPTase7 gene reduced produc- tion of reactive oxygen species （ROS） and decreased expression of stress-responsive genes, resulting in increased salt sensitivity. Here, we describe an even more salt-sensitive 5ptase mutant, At5ptase9, which also hydrolyzes the 5＇ phos- phate groups specifically from membrane-bound phosphatidylinositides. Interestingly, the mutants were more tolerant to osmotic stress. We analyzed the main cellular processes that may be affected by the mutation, such as production of ROS, influx of calcium, and induction of salt-response genes. The At5ptase9 mutants showed reduced ROS produc- tion and Ca2~ influx, as well as decreased fluid-phase endocytosis. Inhibition of endocytosis by phenylarsine oxide or Tyrphostin A23 in wild-type plants blocked these responses. Induction of salt-responsive genes in wild-type plants was also suppressed by the endocytosis inhibitors. Thus, inhibition of endocytosis in wild-type plants mimicked the salt stress responses, observed in the AtSptase9 mutants. In summary, our results show a key non-redundant role of At5PTase7 and 9 isozymes, and underscore the localization of membrane-bound Ptdlns in regulating plant salt tolerance by coordinating the endocytosis, ROS production, Ca2＋ influx, and induction of stress-responsive genes.

关键词： abiotic/environmental stress oxidative and photo-oxidative stress salinity protein traffic and secretion gene expression Arabidopsis.

The Quaternary Structure of NADPH Thioredoxin Reductase C Is Redox-Sensitive

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Molecular Plant 2009年第3期2卷 457-467页

作者： Juan Manuel Pérez-Ruiz Maricruz Gonzalez Maria Cristina Spinola Luisa Maria Sandalio Francisco Javier Cejudo Instituto de Bioqulmica Vegetal y Fotoslntesis Universidad de Sevilla y CSIC Avda Américo Vespucio 49 41092-Sevilla Spain Present address: Plant Biology Laboratory The Salk Institute 10010 N. Torrey Pines Rd La Jolla CA 92037 USA Estacion Experimental del Zaidin CSIC C/Prof Albareda 1 18008-Granada Spain

NADPH thioredoxin reductase C （NTRC） is a chloroplast enzyme able to conjugate NADPH thioredoxin reductase （NTR） and thioredoxin （TRX） activities for the efficient reduction of 2-Cys peroxiredoxin （2-Cys PRX）. Because NADPH can be produced in chloroplasts during darkness, NTRC plays a key role for plant peroxide detoxification during the night. Here, it is shown that the quaternary structure of NTRC is highly dependent on its redox status. In vitro, most of the enzyme adopted an oligomeric state that disaggregated in dimers upon addition of NADPH, NADH, or DTT. Gel filtration and Western blot analysis of protein extracts from Arabidopsis chloroplast stroma showed that native NTRC forms aggregates, which are sensitive to NADPH and DTT, suggesting that the aggregation state might be a significant aspect of NTRC activity in vivo. Moreover, the enzyme is localized in clusters in Arabidopsis chloroplasts. NTRC triple and double mutants, A164G- V182E-R183F and A164G-R183F, replacing key residues of NADPH binding site, showed reduced activity but were still able to dimerize though with an increase in intermediary forms. Based on these results, we propose that the catalytically active form of NTRC is the dimer, which formation is induced by NADPH.

关键词： Abiotic/environmental stress oxidative and photo-oxidative stress photosynthesis Arabidopsis rice.

Multiple Redox and Non-Redox Interactions Define 2-Cys Peroxiredoxin as a Regulatory Hub in the Chloroplast

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Molecular Plant 2009年第6期2卷 1273-1288页

作者： Meenakumari Muthuramalingam Thorsten Seidel Miriam Laxa Susana M. Nunes de Miranda Florian Gartner Elke Stroher Andrea Kandlbinder Karl-Josef Dietz Biochemistry and Physiology of Plants W5-134 Bielefeld University 33501 Bielefeld Germany

In plants, the highly abundant 2-cysteine peroxiredoxin （2-CysPrx） is associated with the chloroplast and involved in protecting photosynthesis. This work addresses the multiple interactions of the 2-CysPrx in the chloroplast, which depend on its redox state. Transcript co-regulation analysis showed a strong linkage to the peptidyl-prolyl-cis/trans isomerase Cyclophilin 20-3 （Cyp20-3） and other components of the photosynthetic apparatus. Co-expression in protoplasts and quantification of fluorescence resonance energy transfer （FRET） efficiency in vivo confirmed protein interactions of 2-CysPrx with Cyp20-3 as well as NADPH-dependent thioredoxin reductase C （NTRC）, while thioredoxin x （Trx-x） did not form complexes that could enable FRET. Likewise, changes in FRET of fluorescently labeled 2-CysPrx in vitro and in vivo proved redox dependent dynamics of 2-CysPrx. Addition of Cyp20-3 to an in vitro peroxidase assay with 2-CysPrx had no significant effect on peroxide reduction. Also, in the presence of NTRC, addition of Cyp20-3 did not further enhance peroxide reduction. In addition, 2-CysPrx functioned as chaperone and inhibited aggregation of citrate synthase during heat treatment. This activity was partly inhibited by Cyp20-3. As a new interaction partner of decameric 2-CysPrx, photosystem Ⅱ could be identified after chloroplast fractionation and in pull-down assays after reconstitution. In summary, the data indicate a dynamic function of plant 2-CysPrx as redox sensor, chaperone, and regulator in the chloroplast with diverse functions beyond its role as thiol peroxidase.

关键词： oxidative and photo-oxidative stress photosynthesis chloroplast biology Arabidopsis cyclophilin peroxiredoxin thioredoxin.

Differential mRNA Translation in Medicago truncatula Accessions with Contrasting Responses to Ozone-Induced oxidative stress

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Molecular Plant 2012年第1期5卷 187-204页

作者： Michael Puckett Niranjani J. lyer YuhongTang Xin-Bin Dai Patrick Zhao Ramamurthy Mahalingam 246 Noble Research Center Department of Biochemistry and Molecular Biology Oklahoma State University Stillwater OK 74078 USA Samuel Roberts Noble Foundation 2510 Sam Noble Parkway Ardmore OK 73401 USA

Acute ozone is a model abiotic elicitor of oxidative stress and a useful tool for understanding biochemical and molecular events during oxidative signaling. Two Medicago truncatula accessions with contrasting responses to ozone were used to examine translational regulation during ozone stress. In ozone-resistant JE154, significant reduction in ri- bosome loading was observed within one hour of ozone treatment, suggesting energy homeostasis as a vital factor for oxidative stress management. Polysomal RNA-based expression profiling with Affymetrix arrays revealed extensive changes in the translatomes of both accessions. Messenger RNAs with low GC content in their 5＇ and 3＇-UTRs were pref- erentially associated with polysomes during oxidative stress. Genebins analysis revealed extensive changes in various gene ontologies in both accessions. Extensive changes in nicotinate and nicotinamide metabolism genes were corrobo- rated with increased levels of NAD＋ and NADH in JE154. The significantly lower NAD＋：NADH redox status in JE154, in conjunction with higher ATP amounts, provided a cellular milieu conducive for overcoming oxidative stress. Low levels of ATP, NADH, and suppression of antioxidant defense responses, abet build-up of ozone-derived ROS and ultimately lead to oxidative cell death in Jemalong.

关键词： Abiotic/environmental stress oxidative and photo-oxidative stress gene expression Medicago truncatula.

Accumulation of Flavonoids in an ntra ntrb Mutant Leads to Tolerance to UV-C

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Molecular Plant 2009年第2期2卷 249-258页

作者： Talaat Bashandy Ludivine Taconnat Jean-Pierre Renou Yves Meyer Jean-Philippe Reichheld Laboratoire Genome et Developpement des Plantes Universite de Perpignan UMR CNRS 5096 52 avenue Paul Alduy 66860 Perpignan France Unite de Recherche en Genomique Vegetale 91057 Evry cedex France

NADPH-dependent thioredoxin reductases （NTRs） are key regulatory enzymes determining the redox state of thioredoxins. There are two genes encoding NTRs （NTRA and NTRB） in the Arabidopsis genome, each encoding a cytosolic and a mitochondrial isoform. A double ntra ntrb mutant has recently been characterized and shows slower plant growth, slightly wrinkled seeds and a remarkable hypersensitivity to buthionine sulfoximine （BSO）, a specific inhibitor of gluta- thione biosynthesis. In this paper, we demonstrate that this mutant also accumulates higher level of flavonoids. Analysis of transcriptome data showed that several genes of the flavonoid pathway are overexpressed in the ntra ntrb mutant. Accumulation of flavonoids is generally considered a hallmark of plant stress. Nevertheless, no elevation of the expression of genes encoding ROS-detoxification enzymes was observed, suggesting that the ntra ntrb plants do not suffer from oxidative disease. Another hypothesis suggests that flavonoids are specifically synthesized in the ntra ntrb mutant in order to rescue the inactivation of NTR. To test this, the ntra ntrb mutant was crossed with transparent testa 4 （tt4） plants with a mutation in the gene encoding the first enzyme in flavonoid biosynthesis. As ntra ntrb plants are more resistant to UV-C treatment than wild-type plants, this higher resistance was abolished in the ntra ntrb tt4 mutant, suggesting that accumulation of flavonoids in the ntra ntrb mutant protects plants against UV-light.

关键词： abiotic/environmental stress oxidative and photo-oxidative stress secondary metabolism - phenylpropanoidsand phenolics gene expression Arabidopsis.