bluuebunny/crossref_metadata_2025_split huggingface dataset:
Indole-3-Acetic Acid Controls Cambial Growth in Scots Pine by Positional Signaling1
Authors: Uggla Claes , Mellerowicz Ewa J , Sundberg Björn 
Published: July 2002

Abstract
The vascular cambium produces secondary xylem and phloem in plants and is responsible for wood formation in forest trees. In this study we used a microscale mass-spectrometry technique coupled with cryosectioning to visualize the radial concentration gradient of endogenous indole-3-acetic acid (IAA) across the cambial meristem and the differentiating derivatives in Scots pine (Pinus sylvestris L.) trees that had different rates of cambial growth. This approach allowed us to investigate the relationship between growth rate and the concentration of endogenous IAA in the dividing cells. We also tested the hypothesis that IAA is a positional signal in xylem development (C. Uggla, T. Moritz, G. Sandberg, B. Sundberg [1996] Proc Natl Acad Sci USA 93: 9282–9286). This idea postulates that the width of the radial concentration gradient of IAA regulates the radial number of dividing cells in the cambial meristem, which is an important component for determining cambial growth rate. The relationship between IAA concentration in the dividing cells and growth rate was poor, although the highest IAA concentration was observed in the fastest-growing cambia. The radial width of the IAA concentration gradient showed a strong correlation with cambial growth rate. The results indicate that IAA gives positional information in plants.
Gibberellins Promote Trichome Formation by Up-RegulatingGLABROUS1in Arabidopsis1
Authors: Perazza Daniel , Vachon Gilles , Herzog Michel 
Published: July 2002

AbstractTrichome development is dependent on gibberellin (GA) signaling inArabidopsis thaliana. Using the GA-deficient mutantga1–3, the GA-response mutant spy-5, and uniconazol (a GA-biosynthesis inhibitor), we show that the GA level response correlates positively with both trichome number and trichome branch number. Two genes, GL1 and TTG, are required for trichome initiation. In ga1–3, coexpression of GL1 and R, the maizeTTG functional homolog, under control of the constitutive 35S promoter, restored trichome development, whereas overexpression of neither GL1 nor R alone was sufficient to significantly suppress the glabrous phenotype. We next focused on GL1 regulation by GAs. In the double mutant the gl1–1 glabrous phenotype is epistatic to thespy-5 phenotype, suggesting that GL1 acts downstream of the GA signal transduction pathway. The activity of a β-glucuronidase reporter gene driven by the GL1promoter was decreased in the wild type grown on uniconazol and showed a clear GA-dependent activation in ga1–3. Finally, quantification of GL1 transcript levels by reverse transcriptase-polymerase chain reaction demonstrated that relative to wild type, ga1–3 plants contained less transcript. These data support the hypothesis that GAs induce trichome development through up-regulation of GL1 and possiblyTTG genes.
Electric Signaling and Pin2 Gene Expression on Different Abiotic Stimuli Depend on a Distinct Threshold Level of Endogenous Abscisic Acid in Several Abscisic Acid-Deficient Tomato Mutants1
Authors: Herde Oliver , Peña Cortés Hugo , Wasternack Claus , Willmitzer Lothar , Fisahn Joachim 
Published: July 2002

Abstract
Experiments were performed on three abscisic acid (ABA)-deficient tomato (Lycopersicon esculentum Mill.) mutants, notabilis,flacca, and sitiens, to investigate the role of ABA and jasmonic acid (JA) in the generation of electrical signals and Pin2 (proteinaseinhibitor II) gene expression. We selected these mutants because they contain different levels of endogenous ABA. ABA levels in the mutant sitiens were reduced to 8% of the wild type, in notabilis they were reduced to 47%, and in flacca they were reduced to 21%. In wild-type and notabilis tomato plants the induction ofPin2 gene expression could be elicited by heat treatment, current application, or mechanical wounding. Inflacca and sitiens only heat stimulation induced Pin2 gene expression. JA levels inflacca and sitiens plants also accumulated strongly upon heat stimulation but not upon mechanical wounding or current application. Characteristic electrical signals evolved in the wild type and in the notabilis andflacca mutants consisting of a fast action potential and a slow variation potential. However, in sitiens only heat evoked electrical signals; mechanical wounding and current application did not change the membrane potential. In addition, exogenous application of ABA to wild-type tomato plants induced transient changes in membrane potentials, indicating the involvement of ABA in the generation of electrical signals. Our data strongly suggest the presence of a minimum threshold value of ABA within the plant that is essential for the early events in electrical signaling and mediation of Pin2 gene expression upon wounding. In contrast, heat-induced Pin2 gene expression and membrane potential changes were not dependent on the ABA level but, rather, on the accumulation of JA.
Differential Expression of Genes for Cyclin-Dependent Protein Kinases in Rice Plants1
Authors: Umeda Masaaki , Umeda-Hara Chikage , Yamaguchi Masatoshi , Hashimoto Junji , Uchimiya Hirofumi 
Published: July 2002

Abstract
Cyclin-dependent protein kinases (CDKs) play key roles in regulating the eukaryotic cell cycle. We have analyzed the expression of four rice (Oryza sativa) CDK genes, cdc2Os1, cdc2Os2,cdc2Os3, and R2, by in situ hybridization of sections of root apices. Transcripts of cdc2Os1,cdc2Os2, and R2 were detected uniformly in the dividing region of the root apex. cdc2Os1 andcdc2Os2 were also expressed in differentiated cells such as those in the sclerenchyma, pericycle, and parenchyma of the central cylinder. By contrast, signals corresponding to transcripts ofcdc2Os3 were distributed only in patches in the dividing region. Counterstaining of sections with 4′,6-diamidino-2-phenylindole and double-target in situ hybridization with a probe for histone H4 transcripts revealed that cdc2Os3 transcripts were abundant from the G2 to the M phase, but were less abundant or absent during the S phase. The levels of the Cdc2Os3 protein and its associated histone H1-kinase activity were reduced by treatment of cultured cells with hydroxyurea, which blocks cycling cells at the onset of the S phase. Our results suggest that domains other than the conserved amino acid sequence (the PSTAIRE motif) have important roles in the function of non-PSTAIRE CDKs in distinct cell-cycle phases.
An Allele of the Ripening-Specific 1-Aminocyclopropane-1-Carboxylic Acid Synthase Gene (ACS1) in Apple Fruit with a Long Storage Life1
Authors: Sunako Tomomi , Sakuraba Wakako , Senda Mineo , Akada Shinji , Ishikawa Ryuji , Niizeki Minoru , Harada Takeo 
Published: July 2002

Abstract
An allele of the 1-aminocyclopropane-1-carboxylic acid (ACC) synthase gene (Md-ACS1), the transcript and translated product of which have been identified in ripening apples (Malus domestica), was isolated from a genomic library of the apple cultivar, Golden Delicious. The predicted coding region of this allele (ACS1-2) showed that seven nucleotide substitutions in the corresponding region ofACS1-1 resulted in just one amino acid transition. A 162-bp sequence characterized as a short interspersed repetitive element retrotransposon was inserted in the 5′-flanking region of ACS1-2 corresponding to position −781 in ACS1-1. TheXhoI site located near the 3′ end of the predicted coding region of ACS1-2 was absent from the reverse transcriptase-polymerase chain reaction product, revealing that exclusive transcription from ACS1-1occurs during ripening of cv Golden Delicious fruit. DNA gel-blot and polymerase chain reaction analyses of genomic DNAs showed clearly that apple cultivars were either heterozygous forACS1-1 andACS1-2 or homozygous for each type. RNA gel-blot analysis of the ACS1-2homozygous Fuji apple, which produces little ethylene and has a long storage life, demonstrated that the level of transcription fromACS1-2 during the ripening stage was very low.
Cucumber Hypocotyls Respond to Cutin Monomers via Both an Inducible and a Constitutive H2O2-Generating System1
Authors: Kauss Heinrich , Fauth Markus , Merten Axel , Jeblick Wolfgang 
Published: July 2002

Abstract
Hypocotyls from etiolated cucumber (Cucumis sativa L.) seedlings were gently abraded at their surface to allow permeation of elicitors. Segments from freshly abraded hypocotyls were only barely competent for H2O2 elicitation with fungal elicitor or hydroxy fatty acids (classical cutin monomers). However, elicitation competence developed subsequent to abrasion, reaching an optimum after about 4 h. This process was potentiated in seedlings displaying acquired resistance to Colletotrichum lagenarium due to root pretreatment with 2,6-dichloroisonicotinic acid or a benzothiadiazole. Induction of competence depended on protein synthesis and could be effected not only by surface abrasion, but also by fungal spore germination on the epidermal surface or by rotating the seedlings in buffer. Inhibitor studies indicated that the inducible mechanism for H2O2 production involves protein phosphorylation, Ca2+ influx, and NAD(P)H oxidase. In contrast, a novel cucumber cutin monomer, dodecan-1-ol, also elicited H2O2 in freshly abraded hypocotyls without previous competence induction. This finding suggests the presence of an additional H2O2-generating system that is constitutive. It is insensitive to inhibitors and has, in addition, a different specificity for alkanols. Thus, dodecan-1-ol might initiate defense before the inducible H2O2-generating system becomes effective.
Glutathione and Homoglutathione Synthesis in Legume Root Nodules
Authors: Matamoros Manuel A. , Moran Jose F. , Iturbe-Ormaetxe Iñaki , Rubio Maria C. , Becana Manuel 
Published: July 2002

Abstract
High-performance liquid chromatography (HPLC) with fluorescence detection was used to study thiol metabolism in legume nodules. Glutathione (GSH) was the major non-protein thiol in all indeterminate nodules examined, as well as in the determinate nodules of cowpea (Vigna unguiculata), whereas homoglutathione (hGSH) predominated in soybean (Glycine max), bean (Phaseolus vulgaris), and mungbean (Vigna radiata) nodules. All nodules had greater thiol concentrations than the leaves and roots of the same plants because of active thiol synthesis in nodule tissue. The correlation between thiol tripeptides and the activities of glutathione synthetase (GSHS) and homoglutathione synthetase (hGSHS) in the nodules of eight legumes, and the contrasting thiol contents and activities in alfalfa (Medicago sativa) leaves (98% hGSH, 100% hGSHS) and nodules (72% GSH, 80% GSHS) indicated that the distribution of GSH and hGSH is determined by specific synthetases. Thiol contents and synthesis decreased with both natural and induced nodule senescence, and were also reduced in the senescent zone of indeterminate nodules. Thiols and GSHS were especially abundant in the meristematic and infected zones of pea (Pisum sativum) nodules. Thiols and γ-glutamylcysteinyl synthetase were also more abundant in the infected zone of bean nodules, but hGSHS was predominant in the cortex. Isolation of full-length cDNA sequences coding for γ-glutamylcysteinyl synthetase from legume nodules revealed that they are highly homologous to those from other higher plants.
Nitric Oxide Modulates the Activity of Tobacco Aconitase
Authors: Navarre Duroy A. , Wendehenne David , Durner Jörg , Noad Robert , Klessig Daniel F. 
Published: July 2002

Abstract
Recent evidence suggests an important role for nitric oxide (NO) signaling in plant-pathogen interactions. Additional elucidation of the role of NO in plants will require identification of NO targets. Since aconitases are major NO targets in animals, we examined the effect of NO on tobacco (Nicotiana tabacum) aconitase. The tobacco aconitases, like their animal counterparts, were inhibited by NO donors. The cytosolic aconitase in animals, in addition to being a key redox and NO sensor, is converted by NO into an mRNA binding protein (IRP, or iron-regulatory protein) that regulates iron homeostasis. A tobacco cytosolic aconitase gene (NtACO1) whose deduced amino acid sequence shared 61% identity and 76% similarity with the human IRP-1 was cloned. Furthermore, residues involved in mRNA binding by IRP-1 were conserved in NtACO1. These results reveal additional similarities between the NO signaling mechanisms used by plants and animals.
Role of Hormones in the Induction of Iron Deficiency Responses in Arabidopsis Roots
Authors: Schmidt Wolfgang , Tittel Julia , Schikora Adam 
Published: July 2002

Abstract
In “strategy I” plants, several alterations in root physiology and morphology are induced by Fe deficiency, although the mechanisms by which low Fe levels are translated into reactions aimed at alleviating Fe shortage are largely unknown. To prove whether changes in hormone concentration or sensitivity are involved in the adaptation to suboptimal Fe availability, we tested 45 mutants of Arabidopsis defective in hormone metabolism and/or root hair formation for their ability to increase Fe(III) chelate reductase activity and to initiate the formation and enlargement of root hairs. Activity staining for ferric chelate reductase revealed that all mutants were responsive to Fe deficiency, suggesting that hormones are not necessary for the induction. Treatment of wild-type plants with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid caused the development of root hairs in locations normally occupied by non-hair cells, but did not stimulate ferric reductase activity. Ectopic root hairs were also formed in −Fe roots, suggesting a role for ethylene in the morphological responses to Fe deficiency. Ultrastructural analysis of rhizodermal cells indicated that neither Fe deficiency nor 1-aminocyclopropane-1-carboxylic acid treatment caused transfer-cell-like alterations in Arabidopsis roots. Our data indicate that the morphological and physiological components of the Fe stress syndrome are regulated separately.
Role of Magnesium Chelatase Activity in the Early Steps of the Tetrapyrrole Biosynthetic Pathway
Authors: Papenbrock Jutta , Mock Hans-Peter , Tanaka Ryouichi , Kruse Elisabeth , Grimm Bernhard 
Published: July 2002

AbstractMagnesium-protoporphyrin IX chelatase (Mg-chelatase) is located at the branchpoint of tetrapyrrole biosynthesis, at which point protoporphyrin IX is distributed for the synthesis of chlorophyll and heme. We investigated the regulatory contribution of Mg-chelatase to the flow of metabolites. In plants, the enzyme complex consists of three subunits, designated CHL D, CHL I, and CHL H. Transgenic tobacco (Nicotiana tabacum) plants expressing antisense RNA for the Mg-chelatase subunit CHL H were analyzed to elucidate further the role of Mg-chelatase in the distribution of protoporphyrin IX into the branched tetrapyrrolic pathway. The transgenic plants displayed a reduced growth rate and chlorophyll deficiency. Both phenotypical properties were correlated with lower Mg-chelatase activity. Unexpectedly, less protoporphyrin IX and heme accumulated, and a decrease in 5-aminolevulinate (ALA)-synthesizing capacity and ALA dehydratase activity paralleled the progressive reduction in Mg-chelatase activity in the transformants compared with control plants. The reduced activities of the early enzymatic steps corresponded with lower levels of transcripts encoding glutamyl-tRNA reductase and ALA-dehydratase. The decreased expression and activities of early enzymes in the pathway could be explained by a feedback-controlled mechanism in response to lower Mg-chelatase activity. We discuss intercompartmental signaling that synchronizes the activities of the first steps in tetrapyrrolic metabolism with the late steps for the synthesis of end products.
Elicitation of Suspension-Cultured Tomato Cells Triggers the Formation of Phosphatidic Acid and Diacylglycerol Pyrophosphate
Authors: van der Luit Arnold H. , Piatti Titus , van Doorn Aveline , Musgrave Alan , Felix Georg , Boller Thomas , Munnik Teun 
Published: July 2002

Abstract
Phosphatidic acid (PA) and its phosphorylated derivative diacylglycerol pyrophosphate (DGPP) are lipid molecules that have been implicated in plant cell signaling. In this study we report the rapid but transient accumulation of PA and DGPP in suspension-cultured tomato (Lycopersicon esculentum) cells treated with the general elicitors,N,N′,N",N‴-tetraacetylchitotetraose, xylanase, and the flagellin-derived peptide flg22. To determine whether PA originated from the activation of phospholipase D or from the phosphorylation of diacylglycerol (DAG) by DAG kinase, a strategy involving differential radiolabeling with [32P]orthophosphate was used. DAG kinase was found to be the dominant producer of PA that was subsequently metabolized to DGPP. A minor but significant role for phospholipase D could only be detected when xylanase was used as elicitor. Since PA formation was correlated with the high turnover of polyphosphoinositides, we hypothesize that elicitor treatment activates phospholipase C to produce DAG, which in turn acts as substrate for DAG kinase. The potential roles of PA and DGPP in plant defense signaling are discussed.
Regulation of Transcript Levels of a Potato Gibberellin 20-Oxidase Gene by Light and Phytochrome B
Authors: Jackson Stephen D. , James Pat E. , Carrera Esther , Prat Salomé , Thomas Brian 
Published: July 2002

Abstract
Up to three gibberellin (GA) 20-oxidase genes have now been cloned from several species including Arabidopsis, bean (Phaseolus vulgaris), and potato (Solanum tuberosum). In each case the GA 20-oxidase genes exhibit different patterns of tissue expression. We have performed extensive northern analysis on one of the potato GA 20-oxidase genes (StGA20ox1), which is the only one that shows significant transcript levels in leaves. We show that levels ofStGA20ox1 transcript are elevated in transgenic antisense plants that have reduced levels of phytochrome B (PHYB) compared with wild-type plants, implicating PHYB in the control of GA biosynthesis. We show that StGA20ox1 transcript levels vary in leaves of different age throughout the plant and cycle throughout the day, furthermore they are up-regulated by light and down-regulated in the dark. The degree of the response to the light-on signal is similar in potato plants deficient in phytochrome A or PHYB and wild-type plants. The induction ofStGA20ox1 by blue light raises the possibility that a blue light receptor may be involved in the control of this gene by light.
Analysis of Oxidative Stress and Wound-Inducible Dinor Isoprostanes F1 (Phytoprostanes F1) in Plants
Authors: Imbusch Ruth , Mueller Martin J. 
Published: July 2002

Abstract
Isoprostanes F2 are arachidonate autoxidation products in mammals that have been shown to be induced during several human disorders associated with enhanced free-radical generation. Isoprostanes F2 represent not only extremely reliable markers of oxidative stress in vivo, but they also exert potent biological effects. Therefore, it has been postulated that isoprostanoids are mediators of oxidant injury in vivo. Higher plants, however, do not synthesize arachidonic acid or isoprostanes. Here we show that a series of isoprostane F2 analogs termed phytoprostanes F1 (previously dinor isoprostanes F1) are formed by an analogous pathway from α-linolenate in plants. High-performance liquid chromatography and gas chromatography-mass spectrometry methods using [18O]3phytoprostanes F1 as internal standard have been developed to quantify phytoprostanes F1. In fresh peppermint (Mentha piperita) leaves, phytoprostanes F1 were found in free form (76 ng/g of dry weight) and at about 150-fold higher levels esterified in lipids. It is notable that these levels of phytoprostanes F1 are more than two orders of magnitude higher than the basal levels of isoprostanes F2 in mammalian tissues. Furthermore, wounding, as well as butyl hydroperoxide or cupric acetate stress triggered a dramatic increase of free and esterified phytoprostanes F1. Thus phytoprostanes F1 may represent a sensitive measure of oxidative damage in plants similar to isoprostanes in mammals. However, one of the most exciting issues to be clarified is the possibility that linolenate-derived phytoprostanes F1 exert biological activities in plants and/or animals.
Mechanism of Arsenate Resistance in the Ericoid Mycorrhizal Fungus Hymenoscyphus ericae
Authors: Sharples Jade M. , Meharg Andrew A. , Chambers Susan M. , Cairney John W.G. 
Published: July 2002

Abstract
Arsenate resistance is exhibited by the ericoid mycorrhizal fungusHymenoscyphus ericae collected from As-contaminated mine soils. To investigate the mechanism of arsenate resistance, uptake kinetics for arsenate (H2AsO4 −), arsenite (H3AsO3), and phosphate (H2PO4 −) were determined in both arsenate-resistant and -non-resistant H. ericae. The uptake kinetics of H2AsO4 −, H3AsO3, and H2PO4 − in both resistant and non-resistant isolates were similar. The presence of 5.0 μm H2PO4 − repressed uptake of H2AsO4 − and exposure to 0.75 mm H2AsO4 −repressed H2PO4 − uptake in bothH. ericae. Mine site H. ericaedemonstrated an enhanced As efflux mechanism in comparison with non-resistant H. ericae and lost approximately 90% of preloaded cellular As (1-h uptake of 0.22 μmol g−1 dry weight h−1 H2AsO4 −) over a 5-h period in comparison with non-resistant H. ericae, which lost 40% of their total absorbed H2AsO4 −. As lost from the fungal tissue was in the form of H3AsO3. The results of the present study demonstrate an enhanced H3AsO3 efflux system operating in mine siteH. ericae as a mechanism for H2AsO4 − resistance. The ecological significance of this mechanism of arsenate resistance is discussed.
Sequences Downstream of the Translation Initiation Codon Are Important Determinants of Translation Efficiency in Chloroplasts
Authors: Kuroda Hiroshi , Maliga Pal 
Published: July 2002

Abstract
The objective of this study was to determine if mRNA sequences downstream of the translation initiation codon are important for translation of plastid mRNAs. We have employed a transgenic approach, measuring accumulation of the neomycin phosphotransferase (NPTII) reporter enzyme translationally fused with 14 N-terminal amino acids encoded in the rbcL or atpB plastid genes. NPTII accumulation from wild-type and mutant rbcLand atpB segments was compared. We report that silent mutations in the rbcL segment reduced NPTII accumulation 35-fold. In contrast, mutations in the atpB mRNA reduced NPTII accumulation only moderately from approximately 7% (w/w) to approximately 4% (w/w) of the total soluble cellular protein, indicating that the importance of sequences downstream of the translation initiation codon are dependent on the individual mRNA. Information provided here will facilitate transgene design for high-level expression of recombinant proteins in chloroplasts by translational fusion with the N-terminal segment of highly expressed plastid genes or by introduction of silent mutations in the N-terminal part of the coding region.