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Tovuu, Altanzaya,Zulfugarov, Ismayil S.,Lee, Choon‐,Hwan Blackwell Publishing Ltd 2013 Physiologia Plantarum Vol.147 No.4
<P>To monitor changes in membrane fluidity in Arabidopsis leaves and thylakoid membranes, we investigated the temperature dependence of a chlorophyll fluorescence parameter, minimum fluorescence (Fo), and calculated the threshold temperature [T(Fo)] at which the rise of the fluorescence level Fo was considered to be started. For the modification of membrane fluidity we took three different approaches: (1) an examination of wild‐type leaves initially cultured at room temperature (22°C), then exposed to either a lower (4°C) or higher (35°C) temperature for 5 days; (2) measurements of the shift in T(Fo) by two mutants deficient in fatty acid desaturase genes – <I>fad7</I> and <I>fad7fad8</I> and (3) an evaluation of the performance of wild‐type plants when leaves were infiltrated with chemicals that modify fluidity. When wild‐type plants were grown at 22°C, the T(Fo) was 48.3 ± 0.3°C. Plants that were then transferred to a chamber set at 4 or 35°C showed a shift in their T(Fo) to 42.7 ± 0.9°C or 48.9 ± 0.1°C, respectively. Under low‐temperature acclimation, the decline in this putative transition temperature was significantly less in <I>fad7</I> and <I>fad7fad8</I> mutants compared with the wild‐type. In both leaf and thylakoid samples, values for T(Fo) were reduced in samples treated with benzyl alcohol, a membrane fluidizer, whereas T(Fo) rose in samples treated with dimethylsulfoxide, a membrane rigidifier. These results indicate that the heat‐induced rise of chlorophyll fluorescence is strongly correlated with the fluidity of thylakoid membranes.</P>
Detection of Reactive Oxygen Species in Higher Plants
Ismayil S. Zulfugarov,Altanzaya Tovuu,Jin-Hong Kim,이춘환 한국식물학회 2011 Journal of Plant Biology Vol.54 No.6
Formed during the reduction of molecular oxygen or water oxidation, reactive oxygen species (ROS) are produced by a variety of enzymes and redox reactions in almost every compartment of the plant cell. In addition to causing cellular damage, these ROS play a role in signaling networks. Many factors contribute to and, simultaneously,control their metabolism, and it is difficult to detect individual ROS accurately. This is due to several challenges inherent to ROS—their relatively short half-lives, low intracellular concentrations, enzymatic and non-enzymatic scavenging capacity of the cells, and the absence of absolutely selective probes for ROS. Here, we describe the common approaches taken for detecting primary ROS,singlet oxygen, superoxide, and hydrogen peroxide as we discuss their advantages and limitations. We can conclude that using two or more independent methods that yield similar results for detection is a reliable means for studying ROS in intact plant tissues.
Enhanced resistance of PsbS-deficient rice (Oryza sativa L.) to fungal and bacterial pathogens
Ismayil S. Zulfugarov,Altanzaya Tovuu,김치열,Kieu Thi Xuan Vo,고수연,Michael Hall,석혜연,김연기,Oscar Skogstrom,문용환,Stefan Jansson,전종성,이춘환 한국식물학회 2016 Journal of Plant Biology Vol.59 No.6
The 22-kDa PsbS protein of Photosystem II is involved in nonphotochemical quenching (NPQ) of chlorophyll fluorescence. Genome-wide analysis of the expression pattern in PsbS knockout (KO) rice plants showed that a lack of this protein led to changes in the transcript levels of 406 genes, presumably a result of superoxide produced in the chloroplasts. The top Gene Ontology categories, in which expression was the most differential, included ‘Immune response’, ‘Response to jasmonic acid’, and ‘MAPK cascade’. From those genes, we randomly selected nine that were up-regulated. Our microarray results were confirmed by quantitative RT-PCR analysis. The KO and PsbS RNAi (knockdown) plants were more resistant to pathogens Magnaporthe oryzae PO6-6 and Xanthomonas oryzae pv. oryzae than either the wild-type plants or PsbS-overexpressing transgenic line. These findings suggest that superoxide production might be the reason that these plants have greater pathogen resistance to fungal and bacterial pathogens in the absence of energy-dependent NPQ. For example, a high level of cell wall lignification in the KO mutants was possibly due to enhanced superoxide production. Our data indicate that certain abiotic stress-induced reactive oxygen species can promote specific signaling pathways, which then activate a defense mechanism against biotic stress in PsbS-KO rice plants.
Zulfugarov, Ismayil S.,Tovuu, Altanzaya,Dogsom, Bolormaa,Lee, Chung Yeol,Lee, Choon-Hwan Royal Society of Chemistry 2010 Photochemical & photobiological sciences Vol.9 No.5
<P>The PsbS protein of photosystem II is necessary for the development of energy-dependent quenching of chlorophyll (Chl) fluorescence (qE), and PsbS-deficient <I>Arabidopsis</I> plant leaves failed to show qE-specific changes in the steady-state 77 K fluorescence emission spectra observed in wild-type leaves. The difference spectrum between the quenched and un-quenched states showed a negative peak at 682 nm. Although the level of qE development in the zeaxanthin-less <I>npq1</I>-<I>2</I> mutant plants, which lacked violaxanthin de-epoxidase enzyme, was only half that of wild type, there were no noticeable changes in this qE-dependent difference spectrum. This zeaxanthin-independent ΔF682 signal was not dependent on state transition, and the signal was not due to photobleaching of pigments either. These results suggest that ΔF682 signal is formed due to PsbS-specific conformational changes in the quenching site of qE and is a new signature of qE generation in higher plants.</P> <P>Graphic Abstract</P><P>The PsbS-specific zeaxanthin-independent ΔF682 signal in 77 K fluorescence emission spectrum was formed due to PsbS-specific conformational changes in the quenching site of qE and is a new signature of qE generation in higher plants that is dependent neither on state transition nor on photobleaching of pigments. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b9pp00132h'> </P>
MOON, Yu Ran,LEE, Min Hee,TOVUU, Altanzaya,LEE, Choon-Hwan,CHUNG, Byung Yeoup,PARK, Youn-Il,KIM, Jin-Hong Journal of Radiation Research Editorial Committee 2011 Journal of radiation research Vol.52 No.2
<P>To characterize a change in NPQ upon exposure to ultraviolet-B (UV-B), the xanthophyll cycle-dependent and -independent NPQs were compared in <I>Cucumis sativus</I>, <I>Lycopersicum esculentum</I>, and <I>Arabidopsis thaliana</I> leaves. The xanthophyll cycle-dependent NPQ was dramatically but reversibly suppressed by UV-B radiation. This suppression was correlated more strongly with a marked decrease in photosynthetic electron transport rather than changes in xanthophyll cycle enzymes such as violaxanthin de-epoxidase and zeaxanthin epoxidase. Accordingly, the UV-B-induced suppression of NPQ cannot be attributed to changes in expressions of VDE and ZEP. However, suppression of the xanthophyll cycle-dependent NPQ could only account for the 77 K fluorescence emission spectra of thylakoid membranes and the increased level of <SUP>1</SUP>O<SUB>2</SUB> production, but not for the decreased levels of •O<SUB>2</SUB><SUP>–</SUP> production and H<SUB>2</SUB>O<SUB>2</SUB> scavenging. These results suggest that a gradual reduction of H<SUB>2</SUB>O<SUB>2</SUB> scavenging activity as well as a transient and reversible suppression of thermal energy dissipation may contribute differentially to increased photooxidative damages in cucumber, tomato, and Arabidopsis plants after acute exposure to UV-B radiation.</P>