Plant cell physiology

Purine alkaloid catabolism pathways in young, mature and aged leaves of tea (Camellia sinensis L.) were investigated by incubating leaf sections with l4 C-labelled theobromine, caffeine, theophylline and xanthine. Incorporation of label into CO 2 was determined and methanolsoluble metabolites were analysed by high-performance liquid chromatography-radiocounting and thin layer chromatography. The data obtained demonstrate that theobromine is the immediate precursor of caffeine, which accumulates in tea leaves because its conversion to theophylline is the rate limiting step in the purine alkaloid catabolism pathway. The main fate of [8-14 C]theophylline incubated with mature and aged leaves, and to a lesser extent young leaves, is conversion to 3-methylxanthine and onto xanthine which is degraded to 14 CO 2 via the purine catabolism pathway. However, with young leaves, sizable amounts of [8-14 C]theophylline were salvaged for the synthesis of caffeine via a 3-methylxanthine -»• theobromine -* caffeine pathway. Trace amounts of [2-14 C]xanthine were also salvaged for caffeine biosynthesis in young leaves, by conversion to 3methylxanthine, and this was enhanced in the presence of 5 mM allopurinol which inhibits purine catabolism. Feeds of [2-14 C]xanthine to young leaves also indicated that 3methylxanthine, as well as being salvaged for theobromine and caffeine production, is also converted, via TV-l-methylation, to theophylline.

Leaf senescence is a developmentally and environmentally regulated process which includes global changes in gene expression. Using Arabidopsis as a model, we modified Chl arrangement in photosystems by overexpressing the catalytic domain (the C domain) of chlorophyllide a oxygenase (CAO) fused with the linker domain (the B domain) of CAO and green fluorescent protein (GFP). In these plants (referred to as the BCG plants for the B and C domains of CAO and GFP), the Chl a/b ratio was drastically decreased and Chl b was incorporated into core antenna complexes. The BCG plants exhibited a significant delay of both developmental and dark-induced leaf senescence. The photosynthetic apparatus, CO 2 fixation enzymes and the chloroplast structure were lost in wild-type plants during senescence, while BCG plants retained them longer than the wild type. Large-scale quantitative real-time PCR analyses of 1,880 transcription factor (TF) genes showed that 241 TFs are differentially expressed between BCG plants and wild-type plants at senescence, $40% of which are known senescence-associated genes (SAGs). Expression profiling also revealed the down-regulation of a large number of additional non-TF SAGs. In contrast, genes involved in photosynthesis were up-regulated, while those encoding Chl degradation enzymes were down-regulated in BCG plants. These results demonstrate that alteration of pigment composition in the photosynthetic apparatus retards senescence through transcriptional reprogramming.

Le septembre 2008 Titre : Caractérisation moléculaire et physiologique des Facteurs de Réponse à l'Ethylène (ERF) chez la tomate (Solanum lycopersicon) JURY Mr. Jean-Claude PECH Président (INP-ENSAT) Mr. Christophe ROTHAN Rapporteur (INRA Bordeaux) Mr. Guy ALBAGNAC Rapporteur (INRA Montpellier) Mme. Mathilde CAUSSE Examinatrice (INRA Avignon) Mr. Masaru OHME-TAKAGI Examinateur (AIST Tsukuba) Mr. Farid REGAD Examinateur (INP-ENSAT) Mr. Mondher BOUZAYEN Directeur de thèse (INP-ENSAT) Mr. Xavier BERTHET Membre invité (NINSAR Barcelone) Ecole doctorale : Biologie Santé et Biotechnologie Unité de recherche : UMR990 INP-ENSAT/INRA Génomique et Biotechnologie des Fruits Directeur de Thèse : Pr. Mondher BOUZAYEN Je remercie Mondher BOUZ AYEN et Masaru OHME-T AKAGI pour m'avoir acceuilli, encadré et fait confiance pendant ce travail de thèse. Je remercie Farid REGAD pour les discussions scientifiques ainsi que son soutien jusqu'à très tard dans la nuit. Je remercie Jean-Claude PECH et Alain LATCHE pour avoir échangé scientifiquement avec moi. Un merci tout spéciale à Corinne, Isabelle, Simone, Marie, Salma et Benoît pour tous les moments de sciences (ou pas) partagés. Merci à Prassad, Ravi, Wangshu et Lanlan d'avoir participé à cette aventure. Un grand merci à Hélène, Carole, Lydie, Olivie r et Dominique pour la transformation et le suivi des plantes transgéniques (et ce n'est pas peu dire). Un grand merci à l'ensemble des membres du laboratoire pour tous les moments partagés, de sciences, et de convivialité : Christian, Je tiens également à remercier tous les membres du Research Institute of Genome-based Biofactory Miho Ikeda, Akira Iwase, Yoshimi Umemura, Tomotsugu Koyama, Masahito Shikata, Kyoko Matsui, Nobut aka Mitsuda, Naoko Kaneta , sans qui cette thèse n'aurait pas eu le même parfum. ありがとう. Merci aussi à Toshi et Hiroshi Ez ura de m'avoir acceuilli. Merci à mes proches qui m'ont soutenu pendant ces années, mes parents et mon frère. Enfin, je tiens à remercier tout particulièrement Laëtitia qui m'a suivi au bout du monde (au sens propre et au sens figuré), pour son soutien permanent et sans qui ce travail aurait été un peu différent. (2007): Isolation and characterization of a Vitis vinifera transcription factor, VvWRKY1, and its effect on responses to fungal pathogens in transgenic tobacco plants J Exp Bot.;58 (8):

The mechanisms that control polyamine (PA) metabolism in plant cell lines with different embryogenic potential are not well understood. This study involved the use of two Araucaria angustifolia cell lines, one of which was defined as being blocked, in that the cells were incapable of developing somatic embryos, and the other as being responsive, as it could generate somatic embryos. Cellular PA metabolism was modulated by using 5 mM arginine (Arg) or ornithine (Orn) at two time points during cell growth. Two days after subculturing with Arg, an increase in citrulline (Cit) content was observed, followed by a higher expression of genes related to PA catabolism in the responsive cell line; whereas, in the blocked cell line, we only observed an accumulation of PAs. After fourteen days, metabolism was directed towards putrescine accumulation in both cell lines. Exogenous Arg and Orn not only caused a change in cellular contents of PAs, but also altered the abundance of a broader spectru...

Kinetic and structural properties of NADP-malic enzyme (NADP-ME, EC 1.1.1.40) purified from stems and roots of wheat (Triticum aestivum), along with the possible physiological role of the enzyme were examined. Enzyme purification from stems sequentially involved precipitation with crystalline ammonium sulfate, anion-exchange, affinity and size exclusion chromatographies, while anion-exchange chromatography was omitted for the enzyme purification from roots. SDS-PAGE of the purified enzyme showed a single protein band with a molecular mass of 72-kDa. Enzyme activity was dependent on the presence of a bivalent metal cation, Mg 2+ or Mn 2+ . Binding characteristics of each metal ion suggest the existence of at least two different binding sites with distinct affinities. Nonetheless, activity response to NADP + and L-malate exhibited Michaelis-Menten behavior with K m values of 37 and 960 ftM, respectively. The amount and activity of NADP-ME were increased by GSH, cellulase and macerozyme. From these results we suggest that NADP-ME of wheat could be implicated in defense-related deposition of lignin.

Brassinosteroids (BRs) activate the BRI1 and BAK1/SERK3 membrane receptor complex, which leads to a wide range of changes in gene expression, plant growth and development. As an initial step to elucidate additional roles of BAK1, we cloned a BAK1-binding protein, BAK1-Associating Receptor-Like Kinase 1 (BARK1), and characterized its gene expression and root phenotypes. BARK1 is a putative membrane LRR-RLK (leucine-rich repeat receptor-like kinase) protein that specifically binds to BAK1 and its homologs. Careful examination of BARK1 expression using transgenic plants expressing a green fluorescent protein (GFP) reporter under the control of the native BARK1 promoter (BARK1p::GFP) revealed that this gene is ubiquitously expressed in most plant tissues, and shows especially strong expression in the xylem vasculature of primary and lateral roots as well as in mature pollen. Interestingly, the expression of the BARK1 gene was increased in the BR biosynthetic loss-of-function mutant, det2, and a loss-of-function mutant of BR signaling, bak1-3. In contrast, this gene was downregulated in the bzr1-1D plant, which is a BR signal gainof-function mutant. BARK1-overexpressing transgenic plants clearly enhanced primary root growth in a dosedependent manner, and their roots were hypersensitive to BR-induced root growth inhibition. In addition, both the number and density of lateral roots were dramatically increased in the BARK1 transgenic plants in a dose-dependent manner. Together with observations that ARF (AUXIN RESPONSE FACTOR) genes are up-regulated in the BARK1 overexpressor, we suggest that the BARK1 overexpressor phenotype with more lateral roots is partly due to the increased expression of ARF genes in this genetic background. In conclusion, BAK1-interacting BARK1 protein may be involved in BR-mediated plant growth and development such as in lateral roots via auxin regulation.

The effect of treatment of wheat plants with Cd 2+ ions on the photochemical activity of the primary leaves was examined. Three day-old etiolated seedlings were treated with Cd 2+ ions for 24 h in dark, and after this treatment the plants were grown in the light until the primary leaves were fully developed. Cd 2+ ions (30-120 fiu) induced a significant decrease in activities of both photosystem II and photosystem I. The extent of the decrease in PS II activity was much greater than that in the PS I activity. Analysis of changes in the fluorescence yield of chlorophyll a also indicated that Cd 2+ ions drastically affect the photochemistry of photosystem II. Cd 2+ ions induced decrease in the rates of photoreduction of 2,6-dichlorophenol indophenol even in the presence of the exogenous electron donor, hydroxylamine, both in Tris-treated and untreated chloroplasts. This result suggests that the site of inhibition is near the site of donation of electrons by hydroxylamine. Treatment with Cd 2+ ions impairs the electron transport system on the reducing side of PS II. The decrease in the fluorescence yield of Chi a is less than that in the evolution of O 2 mediated by oxidized phenylenediamine. This difference may be a result of inhibition on the reducing side of PS II. In addition to inhibition on the reducing side, Cd 2+ ions may affect the oxidizing side of PS II. A comparative study of the rates of evolution of O 2 with /7-benzoquinone and dichloro-^7-benzoquinone as electron acceptors was performed since the halogenated benzoquinones have been shown to accept electrons from both active and inactive centers of photosystem II while some of the benzoquinones accept electrons only from active centers. The results suggest that Cd 2+ ions induced a marginal increase in the number of inactive reaction centers in PS II. Analysis of light-saturation-kinetics of the evolution of O 2 catalysed by PS II indicates a reduction in the size of the antennae as well as in the concentration of the active (a-type) reaction centers of PS II. Thus, the Cd 2+-induced effects on the photochemistry of PS II involve changes on the reducing side of PS II as well as possible changes in the sizes of the populations of active and inactive centers. Thus, short-term exposure to Cd 2+ ions during establishment of seedlings has a severely detrimental effect on photochemical activities in chloroplasts.

Expression of the GH3 promoter/GUS reporter (GH3/ GUS) gene in transgenic tobacco is silent in most vegetative tissues and organs, but can be specifically induced by auxin in all cell types throughout the plant, indicating that auxin is a limiting factor for activation of the GH3/GUS gene. In the absence of exogenous auxin, expression of the GH3/ GUS gene either correlates with physiological events which are presumably mediated by auxin or occurs in cells where relatively high levels of endogenous auxin are expected. For example, the GH3/GUS gene is expressed in dormant lateral buds, tips of adventitious roots, and stem parenchyma cells where adventitious roots are initiating. The GH3/GUS gene is activated at the cut surface nearest the tip of a leaf from which a strip of tissue has been excised, and in the basal end of an excised shoot segment. Also, the GH3/GUS gene is expressed predominantly in the lower side of a gravistimulated shoot and in the dark side of a unilateral light-stimulated shoot. Furthermore, the expression pattern of the GH3/GUS gene is similar to the distribution pattern of 14 C-IAA that is applied at the apical end of the gravistimulated shoot. Thus, the results reported here provide additional support for a crucial role of auxin in shoot gravi-and photo-tropisms and adventitious root formation. Furthermore, the data presented in this report also indicate that expression of the GH3/GUS gene is an excellent molecular marker for studying auxin transport and for monitoring changes in either auxin concentration or cellular sensitivity to auxin in planta.

eHALOPH (http://www.sussex.ac.uk/affiliates/halophytes/) is a database of salt-tolerant plants - halophytes. Records of plant species tolerant of salt concentrations of around 80 mM sodium chloride or more have been collected along with data on plant type, life form, ecotypes, maximum salinity tolerated, the presence or absence of salt glands, photosynthetic pathway, antioxidants, secondary metabolites, compatible solutes, habitat, economic use and whether there are publications on germination, microbial interactions and mycorrhizal status, bioremediration and of molecular data. The database eHALOPH can be used in the analysis of traits associated with tolerance and for informing choice of species that might be used for saline agriculture, bioremediation or ecological restoration and rehabilitation of degraded wetlands or other areas.

Membrane lipids and fatty acids of Ochromonas danica were analyzed. Of the two betaine lipids, the homoserine lipid DGTS mainly contains 14:0 and 18:2 fatty acids, while the alanine lipid DGTA is enriched in 18:0, 18:2 and 22:5 fatty acids. Of the polar moiety of DGTA, improved NMR data are presented. On incubation of cells with [3,4-14 C]methionine, DGTS as well as DGTA were labelled. With [l-14 qmethionine as a substrate, the label appeared in DGTS only. If double labelled [ 3 H](glycerol)/[ 14 C](polar part)DGTS was used as a precursor, radioactivity was incorporated specifically into DGTA in which the isotope ratio was unchanged compared to the precursor. Thus, the glyceryltrimethylhomoserine part of DGTS acts as the precursor of the polar group of DGTA. Labelling of cells with [l-14 C]oleate in a pulse-chase manner and subsequent analysis of the label in the fatty acids and molecular species of different lipids including DGTS and DGTA, suggested a clearly different role of the two betaine lipids: DGTS acts as a i) primary acceptor for exogenous C 18 monoene acid, ii) substrate for the desaturation of 18:1 to 18:2 acid, and iii) donor of mainly 18:2 fatty acid to be distributed among PE and other membrane lipids. Into DGTA, in contrast, fatty acids are introduced only after elongation and desaturation. As a result, the biosynthesis of DGTA from DGTS involves a decarboxylation and recarboxylation of the polar part and a simultaneous deacylation and reacylation of the glycerol moiety.

Witchweeds ( Striga spp.) and broomrapes ( Orobanche and Phelipanche spp.) are the two most devastating root parasitic plants belonging to the family Orobanchaceae and are causing enormous crop losses throughout the world. Seeds of these root parasites will not germinate unless they are exposed to chemical stimuli, 'germination stimulants' produced by and released from plant roots. Most of the germination stimulants identifi ed so far are strigolactones (SLs), which also function as host recognition signals for arbuscular mycorrhizal fungi and a novel class of plant hormones inhibiting shoot branching. In this review, we focus on SLs as germination stimulants for root parasitic plants. In addition, we discuss how quantitative and qualitative differences in SL exudation among sorghum cultivars infl uence their susceptibility to Striga .

Strawberry, a small fruit crop of great importance throughout the world, has been considered a model plant system for Rosaceae, and is susceptible to a large variety of phytopathogenic organisms. Most components and mechanisms of the strawberry defense network remain poorly understood. However, from current knowledge, it seems clear that the ability of a strawberry plant to respond efficiently to pathogens relies first on the physiological status of injured tissue (pre-formed mechanisms of defense) and secondly on the general ability to recognize and identify the invaders by surface plant receptors, followed by a broad range of induced mechanisms, which include cell wall reinforcement, production of reactive oxygen species, phytoalexin generation and pathogenesis-related protein accumulation. Dissection of these physiological responses at a molecular level will provide valuable information to improve future breeding strategies for new strawberry varieties and to engineer strawberry plants for durable and broad-spectrum disease resistance. In turn, this will lead to a reduction in use of chemicals and in environmental risks. Advances in the understanding of the molecular interplay between plant (mainly those considered model systems) and various classes of microbial pathogens have been made in the last two decades. However, major progress in the genetics and molecular biology of strawberry is still needed to uncover fully the way in which this elaborate plant innate immune system works. These fundamental insights will provide a conceptual framework for rational human intervention through new strawberry research approaches. In this review, we will provide a comprehensive overview and discuss recent advances in molecular research on strawberry defense mechanisms against pathogens.

Gene expression throughout the reproductive process in rice ( Oryza sativa ) beginning with primordia development through pollination/fertilization to zygote formation was analyzed. We analyzed 25 stages/organs of rice reproductive development including early microsporogenesis stages with 57,381 probe sets, and identifi ed around 26,000 expressed probe sets in each stage. Fine dissection of 25 reproductive stages/organs combined with detailed microarray profi ling revealed dramatic, coordinated and fi nely tuned changes in gene expression. A decrease in expressed genes in the pollen maturation process was observed in a similar way with Arabidopsis and maize. An almost equal number of ab initio predicted genes and cloned genes which appeared or disappeared coordinated with developmental stage progression. A large number of organ-/stage-specifi c genes were identifi ed; notably 2,593 probe sets for developing anther, including 932 probe sets corresponding to ab initio predicted genes. Analysis of cell cycle-related genes revealed that several cyclin-dependent kinases (CDKs), cyclins and components of SCF E3 ubiquitin ligase complexes were expressed specifi cally in reproductive organs. Cell wall biosynthesis or degradation protein genes and transcription factor genes expressed specifi cally in reproductive stages were also newly identifi ed. Rice genes homologous to reproduction-related genes in other plants showed expression profi les both consistent and inconsistent with their predicted functions. The rice reproductive expression atlas is likely to be the most extensive and most comprehensive data set available, indispensable for unraveling functions of many specifi c genes in plant reproductive processes that have not yet been thoroughly analyzed.

The nitrogen (N) status of a plant determines the composition of its major components (amino acids, proteins, carbohydrates and organic acids) and, directly or indirectly, affects the quality of agricultural products in terms of their calorific value and taste. Although these effects are guided by changes in metabolic pathways, no overall metabolic analysis has previously been conducted to demonstrate such effects. Here, metabolite profiling using gas chromatography-mass spectrometry (GC-MS) was used to evaluate the effect of N levels on spinach tissue, comparing two cultivars that differed in their ability to use N. Wide variation in N content was observed without any distinct inhibition of growth in either cultivar. Principal component analysis (PCA) and self-organizing mapping (SOM) were undertaken to describe changes in the metabolites of mature spinach leaves. In PCA, the first component accounted for 44.5% of the total variance, the scores of which was positively correlated with the plant's N content, and a close relationship between metabolite profiles and N status was observed. Both PCA and SOM revealed that metabolites could be broadly divided into two types, correlating either positively or negatively with plant N content. The simple and co-coordinated metabolic stream, containing both general and spinach-specific aspects of plant N content, will be useful in future research on such topics as the detection of environmental effects on spinach through comprehensive metabolic profiling.

In recent years a number of legume genes involved in root nodule (RN) symbiosis have been identified in the model legumes, Lotus japonicus (Lotus) and Medicago truncatula. Among them, a distinct set of genes has been categorized as a common symbiosis pathway (CSP), because they are also essential for another mutual interaction, the arbuscular mycorrhiza (AM) symbiosis, which is evolutionarily older than the RN symbiosis and is widely distributed in the plant kingdom. Based on the concept that the legume RN symbiosis has evolved from the ancient AM symbiosis, one issue is whether the CSP is functionally conserved between non-nodulating plants, such as rice, and nodulating legumes. We identified three rice CSP gene orthologs, OsCASTOR, OsPOLLUX and OsCCaMK, and demonstrated the indispensable roles of OsPOLLUX and OsCCaMK in rice AM symbiosis. Interestingly, molecular transfection of either OsCASTOR or OsCCaMK could fully complement symbiosis defects in the corresponding Lotus mutant lines for both the AM and RN symbioses. Our results not only provide a conserved genetic basis for the AM symbiosis between rice and Lotus, but also indicate that the core of the CSP has been well conserved during the evolution of RN symbiosis. Through evolution, CASTOR and CCaMK have remained as the molecular basis for the maintenance of CSP functions in the two symbiosis systems. 1659 by guest on December 30, 2015 http://pcp.oxfordjournals.org/ Downloaded from 1660 Functional analysis of the rice common sym pathway by guest on December 30, 2015 http://pcp.oxfordjournals.org/ Downloaded from Symbiotic phenotypes were examined at 4 wpi with M. loti or G. intraradices. Data are compiled results of more than two independent experiments. AM, arbuscular mycorrhiza infection; Nod, nodule formation; Inf, rhizobial infection into nodule cells. a Plants were transformed with a binary vector harboring the GFP marker only. 1664 Functional analysis of the rice common sym pathway by guest on December 30, 2015 http://pcp.oxfordjournals.org/ Downloaded from 1668 Functional analysis of the rice common sym pathway by guest on December 30, 2015 http://pcp.oxfordjournals.org/ Downloaded from 1670 Functional analysis of the rice common sym pathway by guest on December 30, 2015 http://pcp.oxfordjournals.org/ Downloaded from

Membrane trafficking functions in the delivery of proteins that are newly synthesized in the endoplasmic reticulum (ER) to their final destinations, such as the plasma membrane (PM) and the vacuole, and in the internalization of extracellular components or PM-associated proteins for recycling or degradative regulation. These trafficking pathways play pivotal roles in the rapid responses to environmental stimuli such as challenges by microorganisms. In this review, we provide an overview of the current knowledge of plant membrane trafficking and its roles in plant-microbe interactions. Although there is little information regarding the mechanism of pathogenic modulation of plant membrane trafficking thus far, recent research has identified many membrane trafficking factors as possible targets of microbial modulation.

Oxygen plays an important role in photosynthesis by participating in a number of O 2 -consuming reactions. O 2 inhibits CO 2 fixation by stimulating photorespiration, thus reducing plant production. O 2 interacts with photosynthetic electron transport in the chloroplasts' thylakoids in two main ways: by accepting electrons from PSI (Mehler reaction); and by accepting electrons from reduced plastoquinone (PQ) mediated by the plastid terminal oxidase (PTOX). In this study, we show, using 101 plant species, that there is a difference in the potential for photosynthetic electron flow to O 2 between angiosperms and gymnosperms. We found, from measurements of Chl fluorescence and leaf absorbance at 830 nm, (i) that electron outflow from PSII, as determined by decay kinetics of Chl fluorescence after application of a saturating light pulse, is more rapid in gymnosperms than in angiosperms; (ii) that the reaction center Chl of PSI (P700) is rapidly and highly oxidized in gymnosperms during induction of photosynthesis; and (iii) that these differences are dependent on oxygen. Finally, rates of O 2 uptake measured by mass spectrometry in the absence of photorespiration were significantly promoted by illumination in dark-adapted leaves of gymnosperms, but not in those of angiosperms. The light-stimulated O 2 uptake was around 10% of the maximum O 2 evolution in gymnosperms and 1% in angiosperms. These results suggest that gymnosperms have increased capacity for electron leakage to oxygen in photosynthesis compared with angiosperms. The involvement of the Mehler reaction and PTOX in the electron flow to O 2 is discussed.

... Ethyl methanesulfonate was inacti-vated by the addition of 5% sodium thiosulfate, and the mutagenized cells were collected by centrifugation at 2,500 xg for 15 ... Then, the cell sus-pension was further incubated at 22°C for 2 days in the presence of ampicillin at 100/ig-ml"1 for ...

Rice is becoming a model plant in monocotyledons and a model cereal crop. For better understanding of the rice plant, it is essential to elucidate the developmental programs of the life cycle. To date, several attempts have been made in rice to categorize the developmental processes of some organs into substages. These studies are based exclusively on the morphological and anatomical viewpoints. Recent advancement in genetics and molecular biology has given us new aspects of developmental processes. In this review, we first describe the phasic development of the rice plant, and then describe in detail the developmental courses of major organs, leaf, root and spikelet, and specific organs/ tissues. Also, for the facility of future studies, we propose a staging system for each organ.

The 50 MHz 15N NMR spectra of ~SN-enriched bacteriochlorophyll a were recorded in twelve different solvents. The 15N signals of the four nitrogens in the tetrapyrrole rin~s I, II, llI and IV (signals I, II, Ill and IV) were assigned by the use of correlations with those of the or, 13 and ~ methine H. Signals I and llI appeared in the higher field, while signals II and IV appeared in the lower field; the difference in the chemical shifts within each pair of signals was small. The results indicate an approximate D2h symmetry of the nitrogen environment, with higher electronic density on the ring ! and ring IIl nitrogens. 0009-2614/95/$09.50

Respiratory CO 2 efflux and O 2 uptake rates in leaves change in response to the growth CO 2 concentration ([CO 2 ]). The degrees of change vary depending on the responses of cellular processes such as nitrogen (N) assimilation and accumulation of organic acids to growth [CO 2 ]. However, the underlying mechanisms remain unclear. Here, we examined the respiratory characteristics of mature leaves of two rice varieties with different yield capacities at different growth stages under ambient and elevated [CO 2 ] conditions at a free-air CO 2 enrichment site. We also examined the effect of increased water temperature on leaf respiration. We measured the rates of CO 2 efflux and O 2 uptake, and determined N contents, primary metabolite contents and maximal activities of respiratory enzymes. The leaf CO 2 efflux rates decreased in plants grown at elevated [CO 2 ] in both varieties, and were higher in high-yielding Takanari than in Koshihikari. The leaf O 2 uptake rates showed little change with respect to growth [CO 2 ] and variety. The increased water temperature did not significantly affect the CO 2 efflux and O 2 uptake rates. The N and amino acid contents were significantly higher in Takanari than in Koshihikari. The enhanced N assimilation in Takanari may have consumed more respiratory NADH, leading to higher CO 2 efflux rates. In Koshihikari, the ratio of tricarboxylic acid (TCA) cycle intermediates changed and maximal activities of enzymes in the TCA cycle decreased at elevated [CO 2 ]. Therefore, the decreased rates of CO 2 efflux in Koshihikari may be due to the decreased activities of TCA cycle enzymes at elevated [CO 2 ].

The glycine decarboxylase complex (GDC) plays a critical role in the photorespiratory C 2 cycle of C 3 species by recovering carbon following the oxygenation reaction of ribulose-1,5-bisphosphate carboxylase/oxygenase. Loss of GDC from mesophyll cells (MCs) is considered a key early step in the evolution of C 4 photosynthesis. To assess the impact of preferentially reducing GDC in rice MCs, we decreased the abundance of OsGDCH (Os10g37180) using an artificial microRNA (amiRNA) driven by a promoter that preferentially drives expression in MCs. GDC Hand P-proteins were undetectable in leaves of gdch lines. Plants exhibited a photorespiratory-deficient phenotype with stunted growth, accelerated leaf senescence, reduced chlorophyll, soluble protein and sugars, and increased glycine accumulation in leaves. Gas exchange measurements indicated an impaired ability to regenerate ribulose 1,5-bisphosphate in photorespiratory conditions. In addition, MCs of gdch lines exhibited a significant reduction in chloroplast area and coverage of the cell wall when grown in air, traits that occur during the later stages of C 4 evolution. The presence of these two traits important for C 4 photosynthesis and the non-lethal, down-regulation of the photorespiratory C 2 cycle positively contribute to efforts to produce a C 4 rice prototype.

Similarity of gene expression profiles provides important clues for understanding the biological functions of genes, biological processes and metabolic pathways related to genes. A gene expression network (GEN) is an ideal choice to grasp such expression profile similarities among genes simultaneously. For GEN construction, the Pearson correlation coefficient (PCC) has been widely used as an index to evaluate the similarities of expression profiles for gene pairs. However, calculation of PCCs for all gene pairs requires large amounts of both time and computer resources. Based on correspondence analysis, we developed a new method for GEN construction, which takes minimal time even for large-scale expression data with general computational circumstances. Moreover, our method requires no prior parameters to remove sample redundancies in the data set. Using the new method, we constructed rice GENs from large-scale microarray data stored in a public database. We then collected and integrated various principal rice omics annotations in public and distinct databases. The integrated information contains annotations of genome, transcriptome and metabolic pathways. We thus developed the integrated database OryzaExpress for browsing GENs with an interactive and graphical viewer and principal omics annotations (http://riceball.lab.nig.ac.jp/oryzaexpress/). With integration of Arabidopsis GEN data from ATTED-II, OryzaExpress also allows us to compare GENs between rice and Arabidopsis. Thus, OryzaExpress is a comprehensive rice database that exploits powerful omics approaches from all perspectives in plant science and leads to systems biology.

2-cysteine peroxiredoxins (2-CysPrx) switch between functions as thiol peroxidase, chaperone, interaction partner and possibly proximity-based oxidase in a redox-dependent manner. In photosynthetic eukaryotes 2-CysPrx localizes to the plastid, functions in context of photosynthesis and enables an ascorbate peroxidase-independent water-water cycle for detoxifying H2O2. The high degree of evolutionary conservation of 2-CysPrx suggests that the switching is an essential characteristics and needed to transduce redox information to downstream pathways and regulation. The study aimed at exploring the dissociation behavior of 2-CysPrx and its interactions with cyclophilin in dependence on bulk phase conditions. Isothermal titration microcalorimetry (ITC), dynamic light scattering and size exclusion chromatography proved the previously suggested model that reduced 2-CysPrx below a critical transition concentration (CTC) exists in its dimeric state, and above the CTC adopts the decameric sta...

The ASYMMETRIC LEAVES2 (AS2) gene of Arabidopsis thaliana is involved in the establishment of the leaf venation system, which includes the prominent midvein, as well as in the development of a symmetric lamina. The gene product also represses the expression of class 1 knox homeobox genes in leaves. We have characterized the AS2 gene, which appears to encode a novel protein with cysteine repeats (designated the C-motif) and a leucine-zipper-like sequence in the amino-terminal half of the primary sequence. The Arabidopsis genome contains 42 putative genes that potentially encode proteins with conserved amino acid sequences that include the C-motif and the leucine-zipper-like sequence in the amino-terminal half. Thus, the AS2 protein belongs to a novel family of proteins that we have designated the AS2 family. Members of this family except AS2 also have been designated ASLs (AS2-like proteins). Transcripts of AS2 were detected mainly in adaxial domains of cotyledonary primordia. Green fluorescent protein-fused AS2 was concentrated in plant cell nuclei. Overexpression of AS2 cDNA in transgenic Arabidopsis plants resulted in upwardly curled leaves, which differed markedly from the downwardly curled leaves generated by lossof-function mutation of AS2. Our results suggest that AS2 functions in the transcription of a certain gene(s) in plant nuclei and thereby controls the formation of a symmetric flat leaf lamina and the establishment of a prominent midvein and other patterns of venation.

Changes in gene expression are the main outcome of hormone signaling cascades that widely control plant physiology. In the case of the hormones gibberellins, the transcriptional control is exerted through the activity of the DELLA proteins, which act as negative regulators in the signaling pathway. This review focuses on recent transcriptomic approaches in the context of gibberellin signaling, which have provided useful information on new processes regulated by these hormones such as the regulation of photosynthesis and gravitropism. Moreover, the enrichment of specific cis-elements among DELLA primary targets has also helped extend the view that DELLA proteins regulate gene expression through the interaction with multiple transcription factors from different families.

Distribution of pigments in the reaction center (RC) complex, chlorosomes and chlorosome-free membranes prepared from the green sulfur bacterium, Chlorobium tepidum, was analyzed. The RC complex contained approximately 40 molecules of bacteriochlorophyll (BChl) a per P840, half of which are estimated to be in the Fenna-Matthews-Olson (FMO) protein. Carotenes (2 molecules per P840) occupied only one third of the total carotenoids. The remaining carotenoids (4 to 5 molecules per P840) were OH-chlorobactene glucoside ester and OH-/-carotene glucoside ester. Dihydrochlorobactene was decreased compared with cellular carotenes. Furthermore, approximately 9 C670 and 1 menaquinone-7 per P840 were also found. BChl c and carotenes, whose major component is chlorobactene, were found mainly in chlorosomes, and two kinds of carotenoid glucoside esters were observed in chlorosome-free membranes.

Nitric oxide (•NO) has been shown to participate in plant response against pathogen infection; however, less is known of the participation of other NO-derived molecules designated as reactive nitrogen species (RNS). Using two sunfl ower (Helianthus annuus L.) cultivars with different sensitivity to infection by the pathogen Plasmopara halstedii , we studied key components involved in RNS and ROS metabolism. We analyzed the superoxide radical production, hydrogen peroxide content, L-arginine-dependent nitric oxide synthase (NOS) and S-nitrosoglutathione reductase (GSNOR) activities. Furthermore, we examined the location and contents of •NO, S-nitrosothiols (RSNOs), S-nitrosoglutathione (GSNO) and protein 3-nitrotyrosine (NO 2-Tyr) by confocal laser scanning microscopy (CLSM) and biochemical analyses. In the susceptible cultivar, the pathogen induces an increase in proteins that undergo tyrosine nitration accompanied by an augmentation in RSNOs. This rise of RSNOs seems to be independent of the enzymatic generation of •NO because the L-argininedependent NOS activity is reduced after infection. These results suggest that pathogens induce nitrosative stress in susceptible cultivars. In contrast, in the resistant cultivar, no increase of RSNOs or tyrosine nitration of proteins was observed, implying an absence of nitrosative stress. Therefore, it is proposed that the increase of tyrosine nitration of proteins can be considered a general biological marker of nitrosative stress in plants under biotic conditions.

The ndhBand psaEmutants of the cyanobacterium Synechocystis sp. PCC 6803 are partly deficient in PSIdriven cyclic electron transport. We compared photoinhibition in these mutants to the wild type to test the hypothesis that PSI cyclic electron transport protects against photoinhibition. Photoinhibitory treatment greatly accelerated PSI cyclic electron transport in the wild type and also in both the mutants. The psaEmutant showed rates of PSI cyclic electron transport similar to the wild type under all conditions tested. The ndhBmutant showed much lower rates of PSI cyclic electron transport than the wild type following brief dark adaptation but exceeded wild type rates after exposure to photoinhibitory light. The wild type and both mutants showed similar rates of photoinhibition damage and photoinhibition repair at PSII. Photoinhibition at PSI was much slower than at PSII and was also similar between the wild type and both mutants, despite the known instability of PSI in the psaEmutant. We conclude that photoinhibitory light induces sufficient PSI-driven cyclic electron transport in both the ndhBand psaEmutants to fulfill any role that cyclic electron transport plays in protection against photoinhibition.

Compared to rye plants grown under normal conditions of mineral nutrients, those grown under deficient conditions of mineral nutrients were shown to have a high potential activity of the root vacuolar H + -pyrophosphatase (H + -PPiase), with a low level of PP ( in roots. Immunoblot analysis suggested a qualitative change of the enzyme.

Non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (NP-GAPDH) is a conserved cytosolic protein found in higher plants. In photosynthetic cells, the enzyme is involved in a shuttle transfer mechanism to export NADPH from the chloroplast to the cytosol. To investigate the role of this enzyme in plant tissues, we characterized a mutant from Arabidopsis thaliana having an insertion at the NP-GAPDH gene locus. The homozygous mutant was determined to be null respect to NP-GAPDH, as it exhibited undetectable levels of both transcription of NP-GAPDH mRNA, protein expression and enzyme activity. Transcriptome analysis demonstrated that the insertion mutant plant shows altered expression of several enzymes involved in carbohydrate metabolism. Significantly, cytosolic phosphorylating (NAD-dependent) glyceraldehyde-3-phosphate dehydrogenase mRNA levels are induced in the mutant, which correlates with an increase in enzyme activity. mRNA levels and enzymatic activity of glucose-6-phosphate dehydrogenase were also elevated, correlating with an increase in NADPH concentration. Moreover, increased ROS levels were measured in the mutant plants. Down-regulation of several glycolytic and photosynthetic genes suggests that NP-GAPDH is important for the efficiency of both metabolic processes. The results presented demonstrate that NP-GAPDH has a relevant role in plant growth and development.