@Article{IPB-1625, author = {Flores, R. and Gas, M.-E. and Molina-Serrano, D. and Nohales, M.-?. and Carbonell, A. and Gago, S. and De la Peña, M. and Daròs, J.-A. and}, title = {{Viroid Replication: Rolling-Circles, Enzymes and Ribozymes}}, year = {2009}, pages = {317-334}, journal = {Viruses}, doi = {10.3390/v1020317}, volume = {1}, abstract = {Viroids, due to their small size and lack of protein-coding capacity, must rely essentially on their hosts for replication. Intriguingly, viroids have evolved the ability to replicate in two cellular organella, the nucleus (family Pospiviroidae) and the chloroplast (family Avsunviroidae). Viroid replication proceeds through an RNA-based rolling-circle mechanism with three steps that, with some variations, operate in both polarity strands: i) synthesis of longer-than-unit strands catalyzed by either the nuclear RNA polymerase II or a nuclear-encoded chloroplastic RNA polymerase, in both instances redirected to transcribe RNA templates, ii) cleavage to unit-length, which in the family Avsunviroidae is mediated by hammerhead ribozymes embedded in both polarity strands, while in the family Pospiviroidae the oligomeric RNAs provide the proper conformation but not the catalytic activity, and iii) circularization. The host RNA polymerases, most likely assisted by additional host proteins, start transcription from specific sites, thus implying the existence of viroid promoters. Cleavage and ligation in the family Pospiviroidae is probably catalyzed by an RNase III-like enzyme and an RNA ligase able to circularize the resulting 5’ and 3’ termini. Whether a chloroplastic RNA ligase mediates circularization in the family Avsunviroidae, or this reaction is autocatalytic, remains an open issue.} } @Article{IPB-1618, author = {Dufour, D. and De la Peña, M. and Gago, S. and Flores, R. and Gallego, J. and}, title = {{Structure–function analysis of the ribozymes of chrysanthemum chlorotic mottle viroid: a loop–loop interaction motif conserved in most natural hammerheads}}, year = {2009}, pages = {368-381}, journal = {Nucleic Acids Res.}, doi = {10.1093/nar/gkn918}, volume = {37}, abstract = {Loop–loop tertiary interactions play a key role in the folding and catalytic activity of natural hammerhead ribozymes. Using a combination of NMR spectroscopy, site-directed mutagenesis and kinetic and infectivity analyses, we have examined the structure and function of loops 1 and 2 of the (\+) and (–) hammerheads of chrysanthemum chlorotic mottle viroid RNA. In both hammerheads, loop 1 is a heptanucleotide hairpin loop containing an exposed U at its 5′ side and an extrahelical U at its 3′-side critical for the catalytic activity of the ribozyme in vitro and for viroid infectivity in vivo , whereas loop 2 has a key opened A at its 3′-side. These structural features promote a specific loop–loop interaction motif across the major groove. The essential features of this tertiary structure element, base pairing between the 5′ U of loop 1 and the 3′ A of loop 2, and interaction of the extrahelical pyrimidine of loop 1 with loop 2, are likely shared by a significant fraction of natural hammerheads.} } @Article{IPB-1615, author = {Clarke, S. M. and Cristescu, S. M. and Miersch, O. and Harren, F. J. M. and Wasternack, C. and Mur, L. A. J. and}, title = {{Jasmonates act with salicylic acid to confer basal thermotolerance in Arabidopsis thaliana}}, year = {2009}, pages = {175-187}, journal = {New Phytol.}, doi = {10.1111/j.1469-8137.2008.02735.x}, volume = {182}, abstract = {The cpr5‐1 Arabidopsis thaliana mutant exhibits constitutive activation of salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) signalling pathways and displays enhanced tolerance of heat stress (HS).cpr5‐1 crossed with jar1‐1 (a JA‐amino acid synthetase) was compromised in basal thermotolerance, as were the mutants opr3 (mutated in OPDA reductase3) and coi1‐1 (affected in an E3 ubiquitin ligase F‐box; a key JA‐signalling component). In addition, heating wild‐type Arabidopsis led to the accumulation of a range of jasmonates: JA, 12‐oxophytodienoic acid (OPDA) and a JA‐isoleucine (JA‐Ile) conjugate. Exogenous application of methyl jasmonate protected wild‐type Arabidopsis from HS.Ethylene was rapidly produced during HS, with levels being modulated by both JA and SA. By contrast, the ethylene mutant ein2‐1 conferred greater thermotolerance.These data suggest that JA acts with SA, conferring basal thermotolerance while ET may act to promote cell death.} } @Article{IPB-1672, author = {Ziegler, J. and Brandt, W. and Geißler, R. and Facchini, P. J. and}, title = {{Removal of Substrate Inhibition and Increase in Maximal Velocity in the Short Chain Dehydrogenase/Reductase Salutaridine Reductase Involved in Morphine Biosynthesis}}, year = {2009}, pages = {26758-26767}, journal = {J. Biol. Chem.}, doi = {10.1074/jbc.M109.030957}, volume = {284}, abstract = {Salutaridine reductase (SalR, EC 1.1.1.248) catalyzes the stereospecific reduction of salutaridine to 7(S)-salutaridinol in the biosynthesis of morphine. It belongs to a new, plant-specific class of short-chain dehydrogenases, which are characterized by their monomeric nature and increased length compared with related enzymes. Homology modeling and substrate docking suggested that additional amino acids form a novel α-helical element, which is involved in substrate binding. Site-directed mutagenesis and subsequent studies on enzyme kinetics revealed the importance of three residues in this element for substrate binding. Further replacement of eight additional residues led to the characterization of the entire substrate binding pocket. In addition, a specific role in salutaridine binding by either hydrogen bond formation or hydrophobic interactions was assigned to each amino acid. Substrate docking also revealed an alternative mode for salutaridine binding, which could explain the strong substrate inhibition of SalR. An alternate arrangement of salutaridine in the enzyme was corroborated by the effect of various amino acid substitutions on substrate inhibition. In most cases, the complete removal of substrate inhibition was accompanied by a substantial loss in enzyme activity. However, some mutations greatly reduced substrate inhibition while maintaining or even increasing the maximal velocity. Based on these results, a double mutant of SalR was created that exhibited the complete absence of substrate inhibition and higher activity compared with wild-type SalR.} } @Article{IPB-1671, author = {Ziegler, J. and Facchini, P. J. and Geißler, R. and Schmidt, J. and Ammer, C. and Kramell, R. and Voigtländer, S. and Gesell, A. and Pienkny, S. and Brandt, W. and}, title = {{Evolution of morphine biosynthesis in opium poppy}}, year = {2009}, pages = {1696-1707}, journal = {Phytochemistry}, doi = {10.1016/j.phytochem.2009.07.006}, volume = {70}, abstract = {Benzylisoquinoline alkaloids (BIAs) are a group of nitrogen-containing plant secondary metabolites comprised of an estimated 2500 identified structures. In BIA metabolism, (S)-reticuline is a key branch-point intermediate that can be directed into several alkaloid subtypes with different structural skeleton configurations. The morphinan alkaloids are one subclass of BIAs produced in only a few plant species, most notably and abundantly in the opium poppy (Papaver somniferum). Comparative transcriptome analysis of opium poppy and several other Papaver species that do not accumulate morphinan alkaloids showed that known genes encoding BIA biosynthetic enzymes are expressed at higher levels in P. somniferum. Three unknown cDNAs that are co-ordinately expressed with several BIA biosynthetic genes were identified as enzymes in the pathway. One of these enzymes, salutaridine reductase (SalR), which is specific for the production of morphinan alkaloids, was isolated and heterologously overexpressed in its active form not only from P. somniferum, but also from Papaver species that do not produce morphinan alkaloids. SalR is a member of a class of short chain dehydrogenase/reductases (SDRs) that are active as monomers and possess an extended amino acid sequence compared with classical SDRs. Homology modelling and substrate docking revealed the substrate binding site for SalR. The amino acids residues conferring salutaridine binding were compared to several members of the SDR family from different plant species, which non-specifically reduce (−)-menthone to (\+)-neomenthol. Previously, it was shown that some of these proteins are involved in plant defence. The recruitment of specific monomeric SDRs from monomeric SDRs involved in plant defence is discussed.} } @Article{IPB-1657, author = {Serra, P. and BANI HASHEMIAN, S. M. and PENSABENE-BELLAVIA, G. and Gago, S. and DURAN-VILA, N. and}, title = {{An artificial chimeric derivative of Citrus viroid V involves the terminal left domain in pathogenicity}}, year = {2009}, pages = {515-522}, journal = {Mol. Plant Pathol.}, doi = {10.1111/j.1364-3703.2009.00553.x}, volume = {10}, abstract = {The recently described Citrus viroid V (CVd‐V) induces, in Etrog citron, mild stunting and very small necrotic lesions and cracks, sometimes filled with gum. As Etrog citron plants co‐infected with Citrus dwarfing viroid (CDVd) and CVd‐V show synergistic interactions, these host–viroid combinations provide a convenient model to identify the pathogenicity determinant(s). The biological effects of replacing limited portions of the rod‐like structure of CVd‐V with the corresponding portions of CDVd are reported. Chimeric constructs were synthesized using a novel polymerase chain reaction‐based approach, much more flexible than those based on restriction enzymes used in previous studies. Of the seven chimeras (Ch) tested, only one (Ch5) proved to be infectious. Plants infected with Ch5 showed no symptoms and, although this novel chimera was able to replicate to relatively high titres in singly infected plants, it was rapidly displaced by either CVd‐V or CDVd in doubly infected plants. The results demonstrate that direct interaction(s) between structural elements in the viroid RNA (in this case, the terminal left domain) and as yet unidentified host factors play an important role in modulating viroid pathogenicity. This is the first pathogenic determinant mapped in species of the genus Apscaviroid.} } @Article{IPB-1655, author = {Santner, A. and Calderon-Villalobos, L. I. A. and Estelle, M. and}, title = {{Plant hormones are versatile chemical regulators of plant growth}}, year = {2009}, pages = {301-307}, journal = {Nat. Chem. Biol.}, doi = {10.1038/nchembio.165}, volume = {5}, abstract = {The plant hormones are a structurally unrelated collection of small molecules derived from various essential metabolic pathways. These compounds are important regulators of plant growth and mediate responses to both biotic and abiotic stresses. During the last ten years there have been many exciting advances in our understanding of plant hormone biology, including new discoveries in the areas of hormone biosynthesis, transport, perception and response. Receptors for many of the major hormones have now been identified, providing new opportunities to study the chemical specificity of hormone signaling. These studies also reveal a surprisingly important role for the ubiquitin-proteasome pathway in hormone signaling. In addition, recent work confirms that hormone signaling interacts at multiple levels during plant growth and development. In the future, a major challenge will be to understand how the information conveyed by these simple compounds is integrated during plant growth.} } @Article{IPB-1652, author = {Quint, M. and Barkawi, L. S. and Fan, K.-T. and Cohen, J. D. and Gray, W. M. and}, title = {{Arabidopsis IAR4 Modulates Auxin Response by Regulating Auxin Homeostasis}}, year = {2009}, pages = {748-758}, journal = {Plant Physiol.}, doi = {10.1104/pp.109.136671}, volume = {150}, abstract = {In a screen for enhancers of tir1-1 auxin resistance, we identified two novel alleles of the putative mitochondrial pyruvate dehydrogenase E1α-subunit, IAA-Alanine Resistant4 (IAR4). In addition to enhancing the auxin response defects of tir1-1, iar4 single mutants exhibit numerous auxin-related phenotypes including auxin-resistant root growth and reduced lateral root development, as well as defects in primary root growth, root hair initiation, and root hair elongation. Remarkably, all of these iar4 mutant phenotypes were rescued when endogenous indole-3-acetic acid (IAA) levels were increased by growth at high temperature or overexpression of the YUCCA1 IAA biosynthetic enzyme, suggesting that iar4 mutations may alter IAA homeostasis rather than auxin response. Consistent with this possibility, iar4 mutants exhibit increased Aux/IAA stability compared to wild type under basal conditions, but not in response to an auxin treatment. Measurements of free IAA levels detected no significant difference between iar4-3 and wild-type controls. However, we consistently observed significantly higher levels of IAA-amino acid conjugates in the iar4-3 mutant. Furthermore, using stable isotope-labeled IAA precursors, we observed a significant increase in the relative utilization of the Trp-independent IAA biosynthetic pathway in iar4-3. We therefore suggest that the auxin phenotypes of iar4 mutants are the result of altered IAA homeostasis.} } @Article{IPB-1651, author = {Pienkny, S. and Brandt, W. and Schmidt, J. and Kramell, R. and Ziegler, J. and}, title = {{Functional characterization of a novel benzylisoquinoline O-methyltransferase suggests its involvement in papaverine biosynthesis in opium poppy (Papaver somniferum L)}}, year = {2009}, pages = {56-67}, journal = {Plant J.}, doi = {10.1111/j.1365-313X.2009.03937.x}, volume = {60}, abstract = {The benzylisoquinoline alkaloids are a highly diverse group of about 2500 compounds which accumulate in a species‐specific manner. Despite the numerous compounds which could be identified, the biosynthetic pathways and the participating enzymes or cDNAs could be characterized only for a few selected members, whereas the biosynthesis of the majority of the compounds is still largely unknown. In an attempt to characterize additional biosynthetic steps at the molecular level, integration of alkaloid and transcript profiling across Papaver species was performed. This analysis showed high expression of an expressed sequence tag (EST) of unknown function only in Papaver somniferum varieties. After full‐length cloning of the open reading frame and sequence analysis, this EST could be classified as a member of the class II type O ‐methyltransferase protein family. It was related to O ‐methyltransferases from benzylisoquinoline biosynthesis, and the amino acid sequence showed 68% identical residues to norcoclaurine 6‐O ‐methyltransferase. However, rather than methylating norcoclaurine, the recombinant protein methylated norreticuline at position seven with a K m of 44 μm using S ‐adenosyl‐l ‐methionine as a cofactor. Of all substrates tested, only norreticuline was converted. Even minor changes in the benzylisoquinoline backbone were not tolerated by the enzyme. Accordingly, the enzyme was named norreticuline 7–O ‐methyltransferase (N7OMT). This enzyme represents a novel O ‐methyltransferase in benzylisoquinoline metabolism. Expression analysis showed slightly increased expression of N7OMT in P. somniferum varieties containing papaverine, suggesting its involvement in the partially unknown biosynthesis of this pharmaceutically important compound.} } @Article{IPB-1650, author = {Parry, G. and Calderon-Villalobos, L. I. and Prigge, M. and Peret, B. and Dharmasiri, S. and Itoh, H. and Lechner, E. and Gray, W. M. and Bennett, M. and Estelle, M. and}, title = {{Complex regulation of the TIR1/AFB family of auxin receptors}}, year = {2009}, pages = {22540-22545}, journal = {Proc. Natl. Acad. Sci. U.S.A.}, doi = {10.1073/pnas.0911967106}, volume = {106}, abstract = {Auxin regulates most aspects of plant growth and development. The hormone is perceived by the TIR1/AFB family of F-box proteins acting in concert with the Aux/IAA transcriptional repressors. Arabidopsis plants that lack members of the TIR1/AFB family are auxin resistant and display a variety of growth defects. However, little is known about the functional differences between individual members of the family. Phylogenetic studies reveal that the TIR1/AFB proteins are conserved across land plant lineages and fall into four clades. Three of these subgroups emerged before separation of angiosperms and gymnosperms whereas the last emerged before the monocot-eudicot split. This evolutionary history suggests that the members of each clade have distinct functions. To explore this possibility in Arabidopsis, we have analyzed a range of mutant genotypes, generated promoter swap transgenic lines, and performed in vitro binding assays between individual TIR1/AFB and Aux/IAA proteins. Our results indicate that the TIR1/AFB proteins have distinct biochemical activities and that TIR1 and AFB2 are the dominant auxin receptors in the seedling root. Further, we demonstrate that TIR1, AFB2, and AFB3, but not AFB1 exhibit significant posttranscriptional regulation. The microRNA miR393 is expressed in a pattern complementary to that of the auxin receptors and appears to regulate TIR1/AFB expression. However our data suggest that this regulation is complex. Our results suggest that differences between members of the auxin receptor family may contribute to the complexity of auxin response.} } @Article{IPB-1648, author = {Mugford, S. G. and Yoshimoto, N. and Reichelt, M. and Wirtz, M. and Hill, L. and Mugford, S. T. and Nakazato, Y. and Noji, M. and Takahashi, H. and Kramell, R. and Gigolashvili, T. and Flügge, U.-I. and Wasternack, C. and Gershenzon, J. and Hell, R. and Saito, K. and Kopriva, S. and}, title = {{Disruption of Adenosine-5′-Phosphosulfate Kinase in Arabidopsis Reduces Levels of Sulfated Secondary Metabolites}}, year = {2009}, pages = {910-927}, journal = {Plant Cell}, doi = {10.1105/tpc.109.065581}, volume = {21}, abstract = {Plants can metabolize sulfate by two pathways, which branch at the level of adenosine 5′-phosphosulfate (APS). APS can be reduced to sulfide and incorporated into Cys in the primary sulfate assimilation pathway or phosphorylated by APS kinase to 3′-phosphoadenosine 5′-phosphosulfate, which is the activated sulfate form for sulfation reactions. To assess to what extent APS kinase regulates accumulation of sulfated compounds, we analyzed the corresponding gene family in Arabidopsis thaliana. Analysis of T-DNA insertion knockout lines for each of the four isoforms did not reveal any phenotypical alterations. However, when all six combinations of double mutants were compared, the apk1 apk2 plants were significantly smaller than wild-type plants. The levels of glucosinolates, a major class of sulfated secondary metabolites, and the sulfated 12-hydroxyjasmonate were reduced approximately fivefold in apk1 apk2 plants. Although auxin levels were increased in the apk1 apk2 mutants, as is the case for most plants with compromised glucosinolate synthesis, typical high auxin phenotypes were not observed. The reduction in glucosinolates resulted in increased transcript levels for genes involved in glucosinolate biosynthesis and accumulation of desulfated precursors. It also led to great alterations in sulfur metabolism: the levels of sulfate and thiols increased in the apk1 apk2 plants. The data indicate that the APK1 and APK2 isoforms of APS kinase play a major role in the synthesis of secondary sulfated metabolites and are required for normal growth rates.} } @Article{IPB-1640, author = {Lee, C.-W. and Efetova, M. and Engelmann, J. C. and Kramell, R. and Wasternack, C. and Ludwig-Müller, J. and Hedrich, R. and Deeken, R. and}, title = {{Agrobacterium tumefaciens Promotes Tumor Induction by Modulating Pathogen Defense in Arabidopsis thaliana}}, year = {2009}, pages = {2948-2962}, journal = {Plant Cell}, doi = {10.1105/tpc.108.064576}, volume = {21}, abstract = {Agrobacterium tumefaciens causes crown gall disease by transferring and integrating bacterial DNA (T-DNA) into the plant genome. To examine the physiological changes and adaptations during Agrobacterium-induced tumor development, we compared the profiles of salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and auxin (indole-3-acetic acid [IAA]) with changes in the Arabidopsis thaliana transcriptome. Our data indicate that host responses were much stronger toward the oncogenic strain C58 than to the disarmed strain GV3101 and that auxin acts as a key modulator of the Arabidopsis–Agrobacterium interaction. At initiation of infection, elevated levels of IAA and ET were associated with the induction of host genes involved in IAA, but not ET signaling. After T-DNA integration, SA as well as IAA and ET accumulated, but JA did not. This did not correlate with SA-controlled pathogenesis-related gene expression in the host, although high SA levels in mutant plants prevented tumor development, while low levels promoted it. Our data are consistent with a scenario in which ET and later on SA control virulence of agrobacteria, whereas ET and auxin stimulate neovascularization during tumor formation. We suggest that crosstalk among IAA, ET, and SA balances pathogen defense launched by the host and tumor growth initiated by agrobacteria.} } @Article{IPB-1633, author = {Hause, B. and Wasternack, C. and Strack, D. and}, title = {{Jasmonates in stress responses and development}}, year = {2009}, pages = {1483-1484}, journal = {Phytochemistry}, doi = {10.1016/j.phytochem.2009.07.004}, volume = {70}, } @Article{IPB-1632, author = {Halim, V. A. and Altmann, S. and Ellinger, D. and Eschen-Lippold, L. and Miersch, O. and Scheel, D. and Rosahl, S. and}, title = {{PAMP-induced defense responses in potato require both salicylic acid and jasmonic acid}}, year = {2009}, pages = {230-242}, journal = {Plant J.}, doi = {10.1111/j.1365-313X.2008.03688.x}, volume = {57}, abstract = {To elucidate the molecular mechanisms underlying pathogen‐associated molecular pattern (PAMP)‐induced defense responses in potato (Solanum tuberosum ), the role of the signaling compounds salicylic acid (SA) and jasmonic acid (JA) was analyzed. Pep‐13, a PAMP from Phytophthora , induces the accumulation of SA, JA and hydrogen peroxide, as well as the activation of defense genes and hypersensitive‐like cell death. We have previously shown that SA is required for Pep‐13‐induced defense responses. To assess the importance of JA, RNA interference constructs targeted at the JA biosynthetic genes, allene oxide cyclase and 12‐oxophytodienoic acid reductase, were expressed in transgenic potato plants. In addition, expression of the F‐box protein COI1 was reduced by RNA interference. Plants expressing the RNA interference constructs failed to accumulate the respective transcripts in response to wounding or Pep‐13 treatment, neither did they contain significant amounts of JA after elicitation. In response to infiltration of Pep‐13, the transgenic plants exhibited a highly reduced accumulation of reactive oxygen species as well as reduced hypersensitive cell death. The ability of the JA‐deficient plants to accumulate SA suggests that SA accumulation is independent or upstream of JA accumulation. These data show that PAMP responses in potato require both SA and JA and that, in contrast to Arabidopsis, these compounds act in the same signal transduction pathway. Despite their inability to fully respond to PAMP treatment, the transgenic RNA interference plants are not altered in their basal defense against Phytophthora infestans .} } @Article{IPB-1628, author = {Gago, S. and Elena, S. F. and Flores, R. and Sanjuan, R. and}, title = {{Extremely High Mutation Rate of a Hammerhead Viroid}}, year = {2009}, pages = {1308-1308}, journal = {Science}, doi = {10.1126/science.1169202}, volume = {323}, abstract = {The mutation rates of viroids, plant pathogens with minimal non-protein-coding RNA genomes, are unknown. Their replication is mediated by host RNA polymerases and, in some cases, by hammerhead ribozymes, small self-cleaving motifs embedded in the viroid. By using the principle that the population frequency of nonviable genotypes equals the mutation rate, we screened for changes that inactivated the hammerheads of Chrysanthemum chlorotic mottle viroid. We obtained a mutation rate of 1/400 per site, the highest reported for any biological entity. Such error-prone replication can only be tolerated by extremely simple genomes such as those of viroids and, presumably, the primitive replicons of the RNA world. Our results suggest that the emergence of replication fidelity was critical for the evolution of complexity in the early history of life.} } @Article{IPB-1627, author = {Fonseca, S. and Chini, A. and Hamberg, M. and Adie, B. and Porzel, A. and Kramell, R. and Miersch, O. and Wasternack, C. and Solano, R. and}, title = {{(\+)-7-iso-Jasmonoyl-L-isoleucine is the endogenous bioactive jasmonate}}, year = {2009}, pages = {344-350}, journal = {Nat. Chem. Biol.}, doi = {10.1038/nchembio.161}, volume = {5}, abstract = {Hormone-triggered activation of the jasmonate signaling pathway in Arabidopsis thaliana requires SCFCOI1-mediated proteasome degradation of JAZ repressors. (−)-JA-L-Ile is the proposed bioactive hormone, and SCFCOI1 is its likely receptor. We found that the biological activity of (−)-JA-L-Ile is unexpectedly low compared to coronatine and the synthetic isomer (\+)-JA-L-Ile, which suggests that the stereochemical orientation of the cyclopentanone-ring side chains greatly affects receptor binding. Detailed GC-MS and HPLC analyses showed that the (−)-JA-L-Ile preparations currently used in ligand binding studies contain small amounts of the C7 epimer (\+)-7-iso-JA-L-Ile. Purification of each of these molecules demonstrated that pure (−)-JA-L-Ile is inactive and that the active hormone is (\+)-7-iso-JA-L-Ile, which is also structurally more similar to coronatine. In addition, we show that pH changes promote conversion of (\+)-7-iso-JA-L-Ile to the inactive (−)-JA-L-Ile form, thus providing a simple mechanism that can regulate hormone activity through epimerization.} } @Article{IPB-1667, author = {Weigelt, K. and Küster, H. and Rutten, T. and Fait, A. and Fernie, A. R. and Miersch, O. and Wasternack, C. and Emery, R. J. N. and Desel, C. and Hosein, F. and Müller, M. and Saalbach, I. and Weber, H. and}, title = {{ADP-Glucose Pyrophosphorylase-Deficient Pea Embryos Reveal Specific Transcriptional and Metabolic Changes of Carbon-Nitrogen Metabolism and Stress Responses}}, year = {2009}, pages = {395-411}, journal = {Plant Physiol.}, doi = {10.1104/pp.108.129940}, volume = {149}, abstract = {We present a comprehensive analysis of ADP-glucose pyrophosphorylase (AGP)-repressed pea (Pisum sativum) seeds using transcript and metabolite profiling to monitor the effects that reduced carbon flow into starch has on carbon-nitrogen metabolism and related pathways. Changed patterns of transcripts and metabolites suggest that AGP repression causes sugar accumulation and stimulates carbohydrate oxidation via glycolysis, tricarboxylic acid cycle, and mitochondrial respiration. Enhanced provision of precursors such as acetyl-coenzyme A and organic acids apparently support other pathways and activate amino acid and storage protein biosynthesis as well as pathways fed by cytosolic acetyl-coenzyme A, such as cysteine biosynthesis and fatty acid elongation/metabolism. As a consequence, the resulting higher nitrogen (N) demand depletes transient N storage pools, specifically asparagine and arginine, and leads to N limitation. Moreover, increased sugar accumulation appears to stimulate cytokinin-mediated cell proliferation pathways. In addition, the deregulation of starch biosynthesis resulted in indirect changes, such as increased mitochondrial metabolism and osmotic stress. The combined effect of these changes is an enhanced generation of reactive oxygen species coupled with an up-regulation of energy-dissipating, reactive oxygen species protection, and defense genes. Transcriptional activation of mitogen-activated protein kinase pathways and oxylipin synthesis indicates an additional activation of stress signaling pathways. AGP-repressed embryos contain higher levels of jasmonate derivatives; however, this increase is preferentially in nonactive forms. The results suggest that, although metabolic/osmotic alterations in iAGP pea seeds result in multiple stress responses, pea seeds have effective mechanisms to circumvent stress signaling under conditions in which excessive stress responses and/or cellular damage could prematurely initiate senescence or apoptosis.} } @Article{IPB-1666, author = {Wasternack, C. and Hause, B. and}, title = {{Emerging complexity: jasmonate-induced volatiles affect parasitoid choice}}, year = {2009}, pages = {2451-2453}, journal = {J. Exp. Bot.}, doi = {10.1093/jxb/erp197}, volume = {60}, } @Article{IPB-1664, author = {Vandenborre, G. and Miersch, O. and Hause, B. and Smagghe, G. and Wasternack, C. and Van Damme, E. J. and}, title = {{Spodoptera littoralis-Induced Lectin Expression in Tobacco}}, year = {2009}, pages = {1142-1155}, journal = {Plant Cell Physiol.}, doi = {10.1093/pcp/pcp065}, volume = {50}, abstract = {The induced defense response in plants towards herbivores is mainly regulated by jasmonates and leads to the accumulation of so-called jasmonate-induced proteins. Recently, a jasmonate (JA) inducible lectin called Nicotiana tabacum agglutinin or NICTABA was discovered in tobacco (N. tabacum cv Samsun) leaves. Tobacco plants also accumulate the lectin after insect attack by caterpillars. To study the functional role of NICTABA, the accumulation of the JA precursor 12-oxophytodienoic acid (OPDA), JA as well as different JA metabolites were analyzed in tobacco leaves after herbivory by larvae of the cotton leafworm (Spodoptera littoralis) and correlated with NICTABA accumulation. It was shown that OPDA, JA as well as its methyl ester can trigger NICTABA accumulation. However, hydroxylation of JA and its subsequent sulfation and glucosylation results in inactive compounds that have lost the capacity to induce NICTABA gene expression. The expression profile of NICTABA after caterpillar feeding was recorded in local as well as in systemic leaves, and compared to the expression of several genes encoding defense proteins, and genes encoding a tobacco systemin and the allene oxide cyclase, an enzyme in JA biosynthesis. Furthermore, the accumulation of NICTABA was quanti-fied after S. littoralis herbivory and immunofluorescence microscopy was used to study the localization of NICTABA in the tobacco leaf.} } @Article{IPB-1662, author = {Ticconi, C. A. and Lucero, R. D. and Sakhonwasee, S. and Adamson, A. W. and Creff, A. and Nussaume, L. and Desnos, T. and Abel, S. and}, title = {{ER-resident proteins PDR2 and LPR1 mediate the developmental response of root meristems to phosphate availability}}, year = {2009}, pages = {14174-14179}, journal = {Proc. Natl. Acad. Sci. U.S.A.}, doi = {10.1073/pnas.0901778106}, volume = {106}, abstract = {Inadequate availability of inorganic phosphate (Pi) in the rhizosphere is a common challenge to plants, which activate metabolic and developmental responses to maximize Pi acquisition. The sensory mechanisms that monitor environmental Pi status and regulate root growth via altered meristem activity are unknown. Here, we show that phosphate deficiency response 2 (PDR2) encodes the single P5-type ATPase of Arabidopsis thaliana. PDR2 functions in the endoplasmic reticulum (ER) and is required for proper expression of scarecrow (SCR), a key regulator of root patterning, and for stem-cell maintenance in Pi-deprived roots. We further show that the multicopper oxidase encoded by low phosphate root 1 (LPR1) is targeted to the ER and that LPR1 and PDR2 interact genetically. Because the expression domains of both genes overlap in the stem-cell niche and distal root meristem, we propose that PDR2 and LPR1 function together in an ER-resident pathway that adjusts root meristem activity to external Pi. Our data indicate that the Pi-conditional root phenotype of pdr2 is not caused by increased Fe availability in low Pi; however, Fe homeostasis modifies the developmental response of root meristems to Pi availability.} } @INBOOK{IPB-103, author = {Dorka, R. and Miersch, O. and Hause, B. and Weik, P. and Wasternack, C. and}, title = {{Die Mistel in der Tumortherapie 2. Aktueller Stand der Forschung und klinische Anwendung}}, year = {2009}, pages = {49-66}, chapter = {{Chronobiologische Phänomene und Jasmonatgehalt bei Viscum album L.}}, }