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Farmer E.E.,University of Lausanne | Mueller M.J.,Julius von Sachs Institute for Biosciences
Annual Review of Plant Biology | Year: 2013

Nonenzymatic lipid oxidation is usually viewed as deleterious. But if this is the case, then why does it occur so frequently in cells? Here we review the mechanisms of membrane peroxidation and examine the genesis of reactive electrophile species (RES). Recent evidence suggests that during stress, both lipid peroxidation and RES generation can benefit cells. New results from genetic approaches support a model in which entire membranes can act as supramolecular sinks for singlet oxygen, the predominant reactive oxygen species (ROS) in plastids. RES reprogram gene expression through a class II TGA transcription factor module as well as other, unknown signaling pathways. We propose a framework to explain how RES signaling promotes cell "REScue" by stimulating the expression of genes encoding detoxification functions, cell cycle regulators, and chaperones. The majority of the known biological activities of oxygenated lipids (oxylipins) in plants are mediated either by jasmonate perception or through RES signaling networks. © Copyright ©2013 by Annual Reviews. All rights reserved.

Sogabe Y.,Kanazawa University | Nakamura H.,Chiba University | Nakagawa T.,Kanazawa University | Hasegawa S.,Kanazawa University | And 6 more authors.
Plant Signaling and Behavior | Year: 2011

It is known that wounding systemically activates the expression of various defense-related genes in plants. However, most studies of wound-induced systemic response are concerned with a leaf-toleaf response. We have recently reported that the long distance signaling was also observed in the shoots of Arabidopsis seedling with wounded roots. We identified early and late root-to-shoot responsive (RtS) genes that were upregulated in the shoots of root-wounded seedlings at 30 min and 6 h post-injury, respectively. It is likely that the primary signals were rapidly transfered from injured roots to shoots, and then these signals were converted into chemical signals. In fact, increase of JA and OPDA content activated the expression of early and late RtS genes in shoots, respectively. In addition, we visualized wound-induced root-to-shoot response by using RtS promoter- luciferase (Luc) transgenic plants. Analysis of the AtERF13 promoter::Luc transgenic plants clearly shows that the wound-induced root-to-shoot signaling was rapidly activated via the vascular systems. © 2011 Landes Bioscience.

Gupta K.J.,University of Rostock | Gupta K.J.,Julius von Sachs Institute for Biosciences | Igamberdiev A.U.,Memorial University of Newfoundland | Manjunatha G.,University of Horticultural science | And 5 more authors.
Plant Science | Year: 2011

In recent years nitric oxide (NO) has been recognized as an important signal molecule in plants. Both, reductive and oxidative pathways and different subcellular compartments appear involved in NO production. The reductive pathway uses nitrite as substrate, which is exclusively generated by cytosolic nitrate reductase (NR) and can be converted to NO by the same enzyme. The mitochondrial electron transport chain is another site for nitrite to NO reduction, operating specifically when the normal electron acceptor, O 2, is low or absent. Under these conditions, the mitochondrial NO production contributes to hypoxic survival by maintaining a minimal ATP formation. In contrast, excessive NO production and concomitant nitrosative stress may be prevented by the operation of NO-scavenging mechanisms in mitochondria and cytosol. During pathogen attacks, mitochondrial NO serves as a nitrosylating agent promoting cell death; whereas in symbiotic interactions as in root nodules, the turnover of mitochondrial NO helps in improving the energy status similarly as under hypoxia/anoxia. The contribution of NO turnover during pathogen defense, symbiosis and hypoxic stress is discussed in detail. © 2011 Elsevier Ireland Ltd.

Gupta K.J.,Julius von Sachs Institute for Biosciences | Gupta K.J.,Max Planck Institute of Molecular Plant Physiology | Kaiser W.M.,Julius von Sachs Institute for Biosciences
Plant and Cell Physiology | Year: 2010

We examined whether root mitochondria and mitochondrial membranes produce nitric oxide (NO) exclusively by reduction of nitrite or also via a nitric oxide synthase (NOS), and to what extent direct NO measurements could become undetectable due to NO oxidation. Chemiluminescence detection of NO in the gas phase was used to monitor NO emission from suspensions (i.e. direct chemiluminescence). For comparison, diaminofluorescein (DAF) and diaminorhodamine (DAR) were used as NO indicators. NO oxidation to nitrite and nitrate was quantified after reduction of nitrite nitrate to NO by vandium (III) with subsequent chemiluminescence detection (i.e. indirect chemiluminescence). Nitrite and NADH consumption were also measured. Anaerobic nitrite-dependent NO emission was exclusively associated with the membrane fraction, without participation of matrix components. Rates of nitrite and NADH consumption matched, whereas the rate of NO emission was lower. In air, mitochondria apparently produced no nitrite-dependent NO, and no NOS activity was detected by direct or indirect chemiluminescence. In contrast, with DAF-2 or DAR-4M, an l-arginine-dependent fluorescence increase took place. However, the response of this apparent low NOS activity to inhibitors, substrates and cofactors was untypical when compared with commercial inducible NOS (iNOS), and the existence of NOS in root mitochondria is therefore doubtful. In a solution of commercial iNOS, about two-thirds of the NO (measured as NADPH consumption) were oxidized to nitrite nitrate. Addition of mitochondria to iNOS decreased the apparent NO emission, but without a concomitant increase in nitrite nitrate formation. Thus, mitochondria appeared to accelerate oxidation of NO to volatile intermediates. © 2010 The Author.

Gupta K.J.,Julius von Sachs Institute for Biosciences | Gupta K.J.,Max Planck Institute of Molecular Plant Physiology | Igamberdiev A.U.,Memorial University of Newfoundland | Kaiser W.M.,Julius von Sachs Institute for Biosciences
Plant Signaling and Behavior | Year: 2010

Considerable evidence has appeared over the past few years that nitric oxide (NO) is an important anoxic metabolite and a potent signal molecule in plants. Several pathways operative in different cell compartments, lead to NO production. Mitochondria, being a major NO producing compartment, can generate it by either nitrite reduction occurring at nearly anoxic conditions or by the oxidative route via nitric oxide synthase (NOS). Recently we compared both pathways by ozone collision chemiluminescence and by DAF fluorescence. We found that nitrite reduction to NO is associated with the mitochondrial membrane fraction but not with the matrix. In case of the nitric oxide synthase pathway, an L-arginine dependent fluorescence was detected but its response to NOS inhibitors and substrates was untypical. Therefore the existence of NOS or NOS-like activity in barley root mitochondria is very doubtful. We also found that mitochondria scavenge NO. In addition, we found indirect evidence that mitochondria are able to convert NO to gaseous intermediates like NO 2, N 2O and N 2O 3. © 2010 Landes Bioscience.

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