bluuebunny/crossref_metadata_2025_split huggingface dataset:
RNA Target Sequences Promote Spreading of RNA Silencing
Authors: Van Houdt Helena , Bleys Annick , Depicker Anna 
Published: January 2003

Abstract
It is generally recognized that a silencing-inducing locus can efficiently reduce the expression of genes that give rise to transcripts partially homologous to those produced by the silencing-inducing locus (primary targets). Interestingly, the expression of genes that produce transcripts without homology to the silencing-inducing locus (secondary targets) can also be decreased dramatically via transitive RNA silencing. This phenomenon requires primary target RNAs that contain sequences homologous to secondary target RNAs. Sequences upstream from the region homologous to the silencing inducer in the primary target transcripts give rise to approximately 22-nucleotide small RNAs, coinciding with the region homologous to the secondary target. The presence of these small RNAs corresponds with reduced expression of the secondary target whose transcripts are not homologous to the silencing inducer. The data suggest that in transgenic plants, targets of RNA silencing are involved in the expansion of the pool of functional small interfering RNAs. Furthermore, methylation of target genes in sequences without homology to the initial silencing inducer indicates not only that RNA silencing can expand across target RNAs but also that methylation can spread along target genes.
Sugar-Regulated Expression of a Putative Hexose Transport Gene in Grape
Authors: Atanassova Rossitza , Leterrier Marina , Gaillard Cécile , Agasse Alice , Sagot Emeric , Coutos-Thévenot Pierre , Delrot Serge 
Published: January 2003

Abstract
Different lengths of the promoter of grape (Vitis vinifera) VvHT1 (Hexose Transporter 1) gene, which encodes a putative hexose transporter expressed during the ripening of grape, have been transcriptionally fused to the β-glucuronidase reporter gene. In transgenic tobacco (Nicotiana tabacum) transformed with these constructs,VvHT1 promoters were clearly responsible for the sink organ preferential expression. The potential sugar effectors ofVvHT1 promoter were studied in tobacco cv Bright-Yellow 2 cells transformed with chimeric constructs. Glucose (56 mm), sucrose (Suc; 58 mm), and the non-transported Suc isomer palatinose doubled the β-glucuronidase activity conferred by the VvHT1 promoter, whereas fructose did not affect it. These effects were the strongest with the 2.4-kb promoter, which contains all putative sugar-responsive elements (activating and repressing), but they were also significant with the 0.3-kb promoter, which contains only activating sugar boxes. The induction of VvHT1 expression by both Suc and palatinose was confirmed in the homologous grape berry cell culture. The data provide the first example of a putative sugar transporter, which is induced by both glucose and Suc in higher plants. Although induction ofVvHT1 expression by Suc does not require transport, the presence of glucosyl moiety is necessary for Suc sensing. These results provide new insights into sugar sensing and signaling in plants.
Divergent Light-, Ascorbate-, and Oxidative Stress-Dependent Regulation of Expression of the Peroxiredoxin Gene Family in Arabidopsis
Authors: Horling Frank , Lamkemeyer Petra , König Janine , Finkemeier Iris , Kandlbinder Andrea , Baier Margarete , Dietz Karl-Josef 
Published: January 2003

Abstract
Peroxiredoxins (prxs) are peroxidases with broad substrate specificity. The seven prx genes expressed in Arabidopsis shoots were analyzed for their expressional response to changing photon fluence rates, oxidative stress, and ascorbate application. The results reveal a highly variable and gene-specific response to reducing and oxidizing conditions. The steady-state transcript amounts of the chloroplast-targeted prxs, namely the two-cysteine (2-Cys) prxs, prx Q andprx II E, decreased upon application of ascorbate.prx Q also responded to peroxides and diamide treatment.prx II B was induced by tertiary butylhydroperoxide, but rather unaffected by ascorbate. The strongest responses were observed for prx II C, which was induced with all treatments. The two Arabidopsis 2-Cys Prxs and four Prx II proteins were expressed heterologously in Escherichia coli. In an in vitro test system, they all showed peroxidase activity, but could be distinguished by their ability to accept dithiothreitol and thioredoxin as electron donor in the regeneration reaction. The midpoint redox potentials (Em′) of Prx II B, Prx II C, and Prx II E were around −290 mV and, thus, less negative than Em′ of Prx II F, 2-Cys Prx A, and 2-Cys Prx B (−307 to −322 mV). The data characterize expression and function of the mitochondrial Prx II F and the chloroplast Prx II E for the first time, to our knowledge. Antibodies directed against 2-Cys Prx and Prx II C showed a slight up-regulation of Prx II protein in strong light and of 2-Cys Prx upon transfer both to high and low light. The results are discussed in context with the subcellular localization of the Prx gene products.
trans-Resveratrol and Grape Disease Resistance. A Dynamical Study by High-Resolution Laser-Based Techniques
Authors: Montero C. , Cristescu S.M. , Jiménez J.B. , Orea J.M. , te Lintel Hekkert S. , Harren F.J.M. , González Ureña A. 
Published: January 2003

AbstractTwo modern laser-based techniques were synchronously applied to study the dynamics of the trans-resveratrol activity in Botrytis cinerea-infected grapes. Direct analysis of trans-resveratrol in both infected and noninfected grapes (Vitis vinifera, Aledo variety) was performed by using an analytical technique incorporating laser desorption coupled with laser resonant ionization and time-of-flight mass spectrometry. On the other hand, one of the most sensitive on-line methods for trace gas detection, laser photoacoustic spectroscopy, was used to investigate the involvement of the plant hormone ethylene (C2H4) in theB. cinerea grapes interaction and its temporal relationship with the trans-resveratrol content upon infection. The trans-resveratrol content and the ethylene released by noninfected grapes showed an opposite behavior. In this case, a high trans-resveratrol content corresponds to a low ethylene emission. For the B. cinerea-infected grapes, ethylene emission rises up after 48 h when the analogous content of trans-resveratrol started to decrease irreversibly. Moreover, the activity of trans-resveratrol as natural pesticide has been investigated by exogenous application on grapes. A short submerge (5 s) of the grapes in 1.6 × 10−4 m solution of trans-resveratrol delays the increase of C2H4 emission with about 48 h and produces a decrease of the C2H4 concentration and its emission rate. The treatment has positive effects on fruit conservation during storage; it doubled the normal shelf-life of grapes at room temperature, maintaining their post-harvest quality within 10 d.
Regulation of Early Tomato Fruit Development by theDiageotropicaGene
Authors: Balbi Virginia , Lomax Terri L. 
Published: January 2003

AbstractThe vegetative phenotype of the auxin-resistantdiageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) includes reduced gravitropic response, shortened internodes, lack of lateral roots, and retarded vascular development. Here, we report that early fruit development is also dramatically altered by the single-genedgt lesion. Fruit weight, fruit set, and numbers of locules and seeds are reduced in dgt. In addition, time to flowering and time from anthesis to the onset of fruit ripening are increased by the dgt lesion, whereas ripening is normal. The dgt mutation appears to affect only the early stages of fruit development, irrespective of allele or genetic background. Expression of members of the LeACS(1-aminocyclopropane-1-carboxylic acid synthase, a key regulatory enzyme of ethylene biosynthesis) and LeIAA(Aux/IAA, auxin-responsive) gene families were quantified via real-time reverse transcriptase-polymerase chain reaction in both dgt and wild-type fruits, providing the first analysis of Aux/IAA gene expression in fruit. Thedgt lesion affects the expression of only certain members of both the LeACS and LeIAAmultigene families. Different subsets of LeIAA gene family members are affected by the dgt mutation in fruits and hypocotyls, indicating that the DGT gene product functions in a developmentally specific manner. The differential expression of subsets of LeIAA and LeACS gene family members as well as the alterations in dgt fruit morphology and growth suggest that the early stages of fruit development in tomato are regulated, at least in part, by auxin- and ethylene-mediated gene expression.
Ethylene Biosynthesis in Detached Young Persimmon Fruit Is Initiated in Calyx and Modulated by Water Loss from the Fruit
Authors: Nakano Ryohei , Ogura Emi , Kubo Yasutaka , Inaba Akitsugu 
Published: January 2003

Abstract
Persimmon (Diospyros kaki Thunb.) fruit are usually classified as climacteric fruit; however, unlike typical climacteric fruits, persimmon fruit exhibit a unique characteristic in that the younger the stage of fruit detached, the greater the level of ethylene produced. To investigate ethylene induction mechanisms in detached young persimmon fruit, we cloned three cDNAs encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (DK-ACS1, 2, and -3) and two encoding ACC oxidase (DK-ACO1 and -2) genes involved in ethylene biosynthesis, and we analyzed their expression in various fruit tissues. Ethylene production was induced within a few days of detachment in all fruit tissues tested, accompanied by temporally and spatially coordinated expression of all theDK-ACS andDK-ACO genes. In all tissues except the calyx, treatment with 1-methylcyclopropene, an inhibitor of ethylene action, suppressed ethylene production and ethylene biosynthesis-related gene expression. In the calyx, one ACC synthase gene (DK-ACS2) exhibited increased mRNA accumulation accompanied by a large quantity of ethylene production, and treatment of the fruit with 1-methylcyclopropene did not prevent either the accumulation of DK-ACS2transcripts or ethylene induction. Furthermore, the alleviation of water loss from the fruit significantly delayed the onset of ethylene production and the expression of DK-ACS2in the calyx. These results indicate that ethylene biosynthesis in detached young persimmon fruit is initially induced in calyx and is modulated by water loss through transcriptional activation ofDK-ACS2. The ethylene produced in the calyx subsequently diffuses to other fruit tissues and acts as a secondary signal that stimulates autocatalytic ethylene biosynthesis in these tissues, leading to a burst of ethylene production.
Metabolism of Sugars in the Endosperm of Developing Seeds of Oilseed Rape
Authors: Hill Lionel M. , Morley-Smith Edward R. , Rawsthorne Stephen 
Published: January 2003

Abstract
The sugars in the endosperm of a developing seed have many potential roles, including the supply of carbon to the developing embryo and controlling gene expression in it. Our understanding of their metabolism is, however, fragmentary and is confined to a very few species (especially Vicia spp.). To develop a quantitative understanding of the regulation of sugars in seeds of oilseed rape (Brassica napus), we measured relevant enzyme activities, the sizes of the pools of sugars in the liquid endosperm, and the flux of sugars from the endosperm into the embryo. The concentrations of hexose sugars in the liquid endosperm decreased, and sucrose (Suc) increased through development. The overall osmotic potential also fell. The timing of the changes was not precise enough to determine whether they signaled the onset of rapid accumulation of storage products. Changes in endosperm invertase activity were complex and quantitatively do not explain the changes in sugars. The embryo can metabolize hexose sugars in addition to Suc, and possibly at higher rates. Therefore, in addition to invertase, the growing embryo itself has a potential to influence the balance of sugars in the endosperm. The activity of Suc synthase in the embryo was greater than that of invertase during development. This observation and a higher activity of fructokinase than glucokinase in the embryo are both consistent with the embryo using Suc as a carbon source.
Modulation of CYP79 Genes and Glucosinolate Profiles in Arabidopsis by Defense Signaling Pathways
Authors: Mikkelsen Michael Dalgaard , Petersen Bent Larsen , Glawischnig Erich , Jensen Anders Bøgh , Andreasson Erik , Halkier Barbara Ann 
Published: January 2003

Abstract
Glucosinolates are natural plant products that function in the defense toward herbivores and pathogens. Plant defense is regulated by multiple signal transduction pathways in which salicylic acid (SA), jasmonic acid, and ethylene function as signaling molecules. Glucosinolate content was analyzed in Arabidopsis wild-type plants in response to single or combinatorial treatments with methyljasmonate (MeJA), 2,6-dichloro-isonicotinic acid, ethylene, and 2,4-dichloro-phenoxyacetic acid, or by wounding. In addition, several signal transduction mutants and the SA-depleted transgenic NahG line were analyzed. In parallel, expression of glucosinolate biosynthetic genes of the CYP79 gene family and the UDPG:thiohydroximate glucosyltransferase was monitored. After MeJA treatment, the amount of indole glucosinolates increased 3- to 4-fold, and the corresponding Trp-metabolizing genes CYP79B2 andCYP79B3 were both highly induced. Specifically, the indole glucosinolateN-methoxy-indol-3-ylmethylglucosinolate accumulated 10-fold in response to MeJA treatment, whereas 4-methoxy-indol-3-ylmethylglucosinolate accumulated 1.5-fold in response to 2,6-dichloro-isonicotinic acid. In general, few changes were seen for the levels of aliphatic glucosinolates, although increases in the levels of 8-methylthiooctyl glucosinolate and 8-methylsulfinyloctyl glucosinolate were observed, particularly after MeJA treatments. The findings were supported by the composition of glucosinolates in the coronatine-insensitive mutantcoi1, the ctr1 mutant displaying constitutive triple response, and the SA-overproducingmpk4 and cpr1 mutants. The present data indicate that different indole glucosinolate methoxylating enzymes are induced by the jasmonate and the SA signal transduction pathways, whereas the aliphatic glucosinolates appear to be primarily genetically and not environmentally controlled. Thus, different defense pathways activate subsets of biosynthetic enzymes, leading to the accumulation of specific glucosinolates.
Functional Mitochondrial Complex I Is Required by Tobacco Leaves for Optimal Photosynthetic Performance in Photorespiratory Conditions and during Transients
Authors: Dutilleul Christelle , Driscoll Simon , Cornic Gabriel , De Paepe Rosine , Foyer Christine H. , Noctor Graham 
Published: January 2003

Abstract
The importance of the mitochondrial electron transport chain in photosynthesis was studied using the tobacco (Nicotiana sylvestris) mutant CMSII, which lacks functional complex I. Rubisco activities and oxygen evolution at saturating CO2showed that photosynthetic capacity in the mutant was at least as high as in wild-type (WT) leaves. Despite this, steady-state photosynthesis in the mutant was reduced by 20% to 30% at atmospheric CO2 levels. The inhibition of photosynthesis was alleviated by high CO2 or low O2. The mutant showed a prolonged induction of photosynthesis, which was exacerbated in conditions favoring photorespiration and which was accompanied by increased extractable NADP-malate dehydrogenase activity. Feeding experiments with leaf discs demonstrated that CMSII had a lower capacity than the WT for glycine (Gly) oxidation in the dark. Analysis of the postillumination burst in CO2 evolution showed that this was not because of insufficient Gly decarboxylase capacity. Despite the lower rate of Gly metabolism in CMSII leaves in the dark, the Gly to Ser ratio in the light displayed a similar dependence on photosynthesis to the WT. It is concluded that: (a) Mitochondrial complex I is required for optimal photosynthetic performance, despite the operation of alternative dehydrogenases in CMSII; and (b) complex I is necessary to avoid redox disruption of photosynthesis in conditions where leaf mitochondria must oxidize both respiratory and photorespiratory substrates simultaneously.
Spatial and Temporal Effects of Free-Air CO2Enrichment (POPFACE) on Leaf Growth, Cell Expansion, and Cell Production in a Closed Canopy of Poplar
Authors: Taylor Gail , Tricker Penny J. , Zhang Fang Z. , Alston Victoria J. , Miglietta Franco , Kuzminsky Elena 
Published: January 2003

Abstract
Leaf expansion in the fast-growing tree,Populus × euramericana was stimulated by elevated [CO2] in a closed-canopy forest plantation, exposed using a free air CO2 enrichment technique enabling long-term experimentation in field conditions. The effects of elevated [CO2] over time were characterized and related to the leaf plastochron index (LPI), and showed that leaf expansion was stimulated at very early (LPI, 0–3) and late (LPI, 6–8) stages in development. Early and late effects of elevated [CO2] were largely the result of increased cell expansion and increased cell production, respectively. Spatial effects of elevated [CO2] were also marked and increased final leaf size resulted from an effect on leaf area, but not leaf length, demonstrating changed leaf shape in response to [CO2]. Leaves exhibited a basipetal gradient of leaf development, investigated by defining seven interveinal areas, with growth ceasing first at the leaf tip. Interestingly, and in contrast to other reports, no spatial differences in epidermal cell size were apparent across the lamina, whereas a clear basipetal gradient in cell production rate was found. These data suggest that the rate and timing of cell production was more important in determining leaf shape, given the constant cell size across the leaf lamina. The effect of elevated [CO2] imposed on this developmental gradient suggested that leaf cell production continued longer in elevated [CO2] and that basal increases in cell production rate were also more important than altered cell expansion for increased final leaf size and altered leaf shape in elevated [CO2].
Alanine Aminotransferase Homologs Catalyze the Glutamate:Glyoxylate Aminotransferase Reaction in Peroxisomes of Arabidopsis
Authors: Liepman Aaron H. , Olsen Laura J. 
Published: January 2003

Abstract
Plant peroxisomal glyoxylate aminotransferases play central roles within the photorespiratory pathway. Genes encoding glyoxylate aminotransferases have been isolated from several animals and microbes, but only recently have plant homologs been identified. Three Arabidopsis homologs of alanine (Ala):glyoxylate aminotransferase 2 (AGT2) contain a putative type 1 peroxisomal targeting signal (PTS1), but the metabolic significance of these AGT2 homologs is unknown. GGT1 and GGT2 are Ala aminotransferase (AlaAT) homologs from Arabidopsis that represent another type of glyoxylate aminotransferase. These proteins are class I aminotransferases, each containing a putative PTS1. GGT1 and GGT2 are members of a small family of AlaATs in Arabidopsis. When expressed as recombinant proteins inEscherichia coli, GGT1 and GGT2 displayed biochemical characteristics very similar to one another, and to the Arabidopsis protein purified from leaves. Four aminotransferase activities were specifically associated with GGT1 and GGT2, using the substrate pairs glutamate (Glu):glyoxylate, Ala:glyoxylate, Glu:pyruvate, and Ala:2-oxoglutarate. GGT1 and GGT2 may have partially redundant functions; transcripts of both genes were detected in many of the same tissues. Although Glu:glyoxylate aminotransferase (GGT) activity has been observed in several locations in different plants and algae, including the cytoplasm and mitochondria, our subcellular fractionation data indicate that GGT activity was exclusively peroxisomal in Arabidopsis. Thus, glyoxylate aminotransferase reactions in plant peroxisomes appear to be catalyzed by at least two distinct types of aminotransferases: an AGT1 homolog with serine:glyoxylate aminotransferase activity (A.H. Liepman, L.J. Olsen [2001] Plant J 25: 487–498), and a pair of closely related, potentially redundant AlaAT homologs with GGT activity.
The Arabidopsis AtIPT8/PGA22 Gene Encodes an Isopentenyl Transferase That Is Involved in De Novo Cytokinin Biosynthesis
Authors: Sun Jiaqiang , Niu Qi-Wen , Tarkowski Petr , Zheng Binglian , Tarkowska Danuse , Sandberg Göran , Chua Nam-Hai , Zuo Jianru 
Published: January 2003

Abstract
Cytokinin plays a critical role in plant growth and development by stimulating cell division and cell differentiation. Despite many years' research efforts, our current understanding of this hormone is still limited regarding both its biosynthesis and signaling. To genetically dissect the cytokinin pathway, we have used a functional screen to identify Arabidopsis gain-of-function mutations that enable shoot formation in the absence of exogenous cytokinins. By using a chemical-inducible activation tagging system, we have identified over 40 putative mutants, designated as pga(plant growth activators), which presumably were affected in key components of cytokinin biosynthesis and signaling pathway. Here, we report a detailed characterization ofpga22, a representative mutant from this collection. A gain-of-function mutation in the PGA22 locus resulted in typical cytokinin responses. Molecular and genetic analyses indicated that PGA22 encodes an isopentenyl transferase (IPT) previously identified as AtIPT8. Plants of the pga22mutant accumulated at remarkably higher levels of isopentenyladenosine-5′-monophosphate and isopentenyladenosine when analyzed by mass spectrometry, suggesting that AtIPT8/PGA22 is a functional IPT that may direct the biosynthesis of cytokinins in planta via an isopentenyladenosine-5′-monophosphate-dependent pathway.
ARAMEMNON, a Novel Database for Arabidopsis Integral Membrane Proteins
Authors: Schwacke Rainer , Schneider Anja , van der Graaff Eric , Fischer Karsten , Catoni Elisabetta , Desimone Marcelo , Frommer Wolf B. , Flügge Ulf-Ingo , Kunze Reinhard 
Published: January 2003

Abstract
A specialized database (DB) for Arabidopsis membrane proteins, ARAMEMNON, was designed that facilitates the interpretation of gene and protein sequence data by integrating features that are presently only available from individual sources. Using several publicly available prediction programs, putative integral membrane proteins were identified among the approximately 25,500 proteins in the Arabidopsis genome DBs. By averaging the predictions from seven programs, approximately 6,500 proteins were classified as transmembrane (TM) candidate proteins. Some 1,800 of these contain at least four TM spans and are possibly linked to transport functions. The ARAMEMNON DB enables direct comparison of the predictions of seven different TM span computation programs and the predictions of subcellular localization by eight signal peptide recognition programs. A special function displays the proteins related to the query and dynamically generates a protein family structure. As a first set of proteins from other organisms, all of the approximately 700 putative membrane proteins were extracted from the genome of the cyanobacterium Synechocystis sp. and incorporated in the ARAMEMNON DB. The ARAMEMNON DB is accessible at the URL http://aramemnon.botanik.uni-koeln.de.