bluuebunny/crossref_metadata_2025_split huggingface dataset:
Galactosylononitol and Stachyose Synthesis in Seeds of Adzuki Bean1
Authors: Peterbauer Thomas , Richter Andreas 
Published: July 2002

Abstract
Stachyose synthase (STS) (EC 2.4.1.67) was purified to homogeneity from mature seeds of adzuki bean (Vigna angularis). Electrophoresis under denaturing conditions revealed a single polypeptide of 90 kD. Size-exclusion chromatography of the purified enzyme yielded two activity peaks with apparent molecular masses of 110 and 283 kD. By isoelectric focusing and chromatofocusing the protein was separated into several active forms with isoelectric point values between pH 4.7 and 5.0. Purified STS catalyzed the transfer of the galactosyl group from galactinol to raffinose andmyo-inositol. Additionally, the enzyme catalyzed the galactinol-dependent synthesis of galactosylononitol from d-ononitol. The synthesis of a galactosylcyclitol by STS is a new oberservation. Mutual competitive inhibition was observed when the enzyme was incubated with both substrates (raffinose and ononitol) simultaneously. Galactosylononitol could also substitute for galactinol in the synthesis of stachyose from raffinose. Although galactosylononitol was the less-efficient donor, the Michaelis constant value for raffinose was lower in the presence of galactosylononitol (13.2 mm) compared with that obtained in the presence of galactinol (38.6 mm). Our results indicate that STS catalyzes the biosynthesis of galactosylononitol, but may also mediate a redistribution of galactosyl residues from galactosylononitol to stachyose.
The Expression of Light-Regulated Genes in the High-Pigment-1 Mutant of Tomato1
Authors: Peters Janny L. , Széll Márta , Kendrick Richard E. 
Published: July 2002

AbstractThree light-regulated genes, chlorophyll a/b-binding protein (CAB), ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit, and chalcone synthase (CHS), are demonstrated to be up-regulated in the high-pigment-1 (hp-1) mutant of tomato (Lycopersicon esculentum Mill.) compared with wild type (WT). However, the pattern of up-regulation of the three genes depends on the light conditions, stage of development, and tissue studied. Compared with WT, the hp-1 mutant showed higher CAB gene expression in the dark after a single red-light pulse and in the pericarp of immature fruits. However, in vegetative tissues of light-grown seedlings and adult plants, CAB mRNA accumulation did not differ between WT and the hp-1mutant. The ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit mRNA accumulated to a higher level in thehp-1 mutant than WT under all light conditions and tissues studied, whereas CHS gene expression was up-regulated in de-etiolated vegetative hp-1-mutant tissues only. The CAB and CHS genes were shown to be phytochrome regulated and both phytochrome A and B1 play a role in CAB gene expression. These observations support the hypothesis that the HP-1 protein plays a general repressive role in phytochrome signal transduction.
Purification and Characterization of NADP+-Linked Isocitrate Dehydrogenase from Scots Pine
Authors: Palomo Jesús , Gallardo Fernando , Suárez Maria F. , Cánovas Francisco M. 
Published: July 2002

Abstract
NADP+-isocitrate dehydrogenase (NADP+-IDH; EC 1.1.1.42) is involved in the supply of 2-oxoglutarate for ammonia assimilation and glutamate synthesis in higher plants through the glutamine synthetase/glutamate synthase (GS/GOGAT) cycle. Only one NADP+-IDH form of cytosolic localization was detected in green cotyledons of pine (Pinus spp.) seedlings. The pine enzyme was purified and exhibited molecular and kinetic properties similar to those described for NADP+-IDH from angiosperm, with a higher catalytic efficiency (105 m −1s−1) than the deduced efficiencies for GS and GOGAT in higher plants. A polyclonal antiserum was raised against pine NADP+-IDH and used to assess protein expression in the seedlings. Steady-state levels of NADP+-IDH were coordinated with GS during seed germination and were associated with GS/GOGAT enzymes during chloroplast biogenesis, suggesting that NADP+-IDH is involved in the provision of carbon skeletons for the synthesis of nitrogen-containing molecules. However, a noncoordinated pattern of NADP+-IDH and GS/GOGAT was observed in advanced stages of cotyledon development and in the hypocotyl. A detailed analysis in hypocotyl sections revealed that NADP+-IDH abundance was inversely correlated with the presence of GS, GOGAT, and ribulose-1,5-bisphosphate carboxylase/oxygenase but was associated with the differentiation of the organ. These results cannot be explained by the accepted role of the enzyme in nitrogen assimilation and strongly suggest that NADP+-IDH may have other, as-yet-unknown, biological functions.
Comparative Analysis of the Regulation of Expression and Structures of Two Evolutionarily Divergent Genes for Δ1-Pyrroline-5-Carboxylate Synthetase from Tomato
Authors: Fujita Tomomichi , Maggio Albino , Garcia-Rios Mario , Bressan Ray A. , Csonka Laszlo N. 
Published: July 2002

AbstractWe isolated two tomato (Lycopersicon esculentum) cDNA clones, tomPRO1 and tomPRO2, specifying Δ1-pyrroline-5-carboxylate synthetase (P5CS), the first enzyme of proline (Pro) biosynthesis. tomPRO1 is unusual because it resembles prokaryotic polycistronic operons (M.G. Garcı́a-Rı́os, T. Fujita, P.C. LaRosa, R.D. Locy, J.M. Clithero, R.A. Bressan, L.N. Csonka [1997] Proc Natl Acad Sci USA 94: 8249–8254), whereas tomPRO2 encodes a full-length P5CS. We analyzed the accumulation of Pro and the tomPRO1and tomPRO2 messages in response to NaCl stress and developmental signals. Treatment with 200 mm NaCl resulted in a &gt;60-fold increase in Pro levels in roots and leaves. However, there was a &lt;3-fold increase in the accumulation of thetomPRO2 message and no detectable induction in the level of the tomPRO1 message in response to NaCl stress. Although pollen contained approximately 100-fold higher levels of Pro than other plant tissues, there was no detectable increase in the level of either message in pollen. We conclude that transcriptional regulation of these genes for P5CS is probably not important for the osmotic or pollen-specific regulation of Pro synthesis in tomato. Using restriction fragment-length polymorphism mapping, we determined the locations of tomPRO1 and tomPRO2 loci in the tomato nuclear genome. Sequence comparison suggested thattomPRO1 is similar to prokaryotic P5CS loci, whereastomPRO2 is closely related to other eukaryotic P5CS genes.
The First Step of Gibberellin Biosynthesis in Pumpkin Is Catalyzed by at Least Two Copalyl Diphosphate Synthases Encoded by Differentially Regulated Genes
Authors: Smith Maria W. , Yamaguchi Shinjiro , Ait-Ali Tahar , Kamiya Yuji 
Published: July 2002

Abstract
The first step in gibberellin biosynthesis is catalyzed by copalyl diphosphate synthase (CPS) and ent-kaurene synthase. We have cloned from pumpkin (Cucurbita maxima L.) two cDNAs, CmCPS1 and CmCPS2, that each encode a CPS. Both recombinant fusion CmCPS proteins were active in vitro. CPS are translocated into plastids and processed by cleavage of transit peptides. For CmCPS1 andCmCPS2, the putative transit peptides cannot exceed the first 99 and 107 amino acids, respectively, because longer N-terminal deletions abolished activity. Levels of both CmCPStranscripts were strictly regulated in an organ-specific and developmental manner. Both transcripts were almost undetectable in leaves and were abundant in petioles. CmCPS1 transcript levels were high in young cotyledons and low in roots. In contrast,CmCPS2 transcripts were undetectable in cotyledons but present at significant levels in roots. In hypocotyls, apices, and petioles, CmCPS1 transcript levels decreased with age much more rapidly than those of CmCPS2. We speculate that CmCPS1 expression is correlated with the early stages of organ development, whereasCmCPS2 expression is correlated with subsequent growth. In contrast, C. maxima ent-kaurene synthase transcripts were detected in every organ at almost constant levels. Thus,ent-kaurene biosynthesis may be regulated through control of CPS expression.
Arachidonic Acid Alters Tomato HMG Expression and Fruit Growth and Induces 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase-Independent Lycopene Accumulation1
Authors: Rodrı́guez-Concepción Manuel , Gruissem Wilhelm 
Published: July 2002

Abstract
Regulation of isoprenoid end-product synthesis required for normal growth and development in plants is not well understood. To investigate the extent to which specific genes for the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) are involved in end-product regulation, we manipulated expression of theHMG1 and HMG2 genes in tomato (Lycopersicon esculentum) fruit using arachidonic acid (AA). In developing young fruit AA blocked fruit growth, inhibitedHMG1, and activated HMG2 expression. These results are consistent with other reports indicating thatHMG1 expression is closely correlated with growth processes requiring phytosterol production. In mature-green fruit AA strongly induced the expression of HMG2,PSY1 (the gene for phytoene synthase), and lycopene accumulation before the normal onset of carotenoid synthesis and ripening. The induction of lycopene synthesis was not blocked by inhibition of HMGR activity using mevinolin, suggesting that cytoplasmic HMGR is not required for carotenoid synthesis. Our results are consistent with the function of an alternative plastid isoprenoid pathway (the Rohmer pathway) that appears to direct the production of carotenoids during tomato fruit ripening.
The Arabidopsis CBF Gene Family Is Composed of Three Genes Encoding AP2 Domain-Containing Proteins Whose Expression Is Regulated by Low Temperature but Not by Abscisic Acid or Dehydration1
Authors: Medina Joaquı́n , Bargues Mónica , Terol Javier , Pérez-Alonso Manuel , Salinas Julio 
Published: July 2002

Abstract
We have identified two genes from Arabidopsis that show high similarity withCBF1, a gene encoding an AP2 domain-containing transcriptional activator that binds to the low-temperature-responsive element CCGAC and induces the expression of some cold-regulated genes, increasing plant freezing tolerance. These two genes, which we have named CBF2 and CBF3, also encode proteins containing AP2 DNA-binding motifs. Furthermore, like CBF1, CBF2 and CBF3 proteins also include putative nuclear-localization signals and potential acidic activation domains. The CBF2 andCBF3 genes are linked to CBF1,constituting a cluster on the bottom arm of chromosome IV. The high level of similarity among the three CBF genes, their tandem organization, and the fact that they have the same transcriptional orientation all suggest a common origin.CBF1, CBF2, and CBF3 show identical expression patterns, being induced very rapidly by low-temperature treatment. However, in contrast to most of the cold-induced plant genes characterized, they are not responsive to abscisic acid or dehydration. Taken together, all of these data suggest that CBF2 and CBF3 may function as transcriptional activators, controlling the level of low-temperature gene expression and promoting freezing tolerance through an abscisic acid-independent pathway.
Glycerol Is a Suberin Monomer. New Experimental Evidence for an Old Hypothesis1
Authors: Moire Laurence , Schmutz Alain , Buchala Antony , Yan Bin , Stark Ruth E. , Ryser Ulrich 
Published: July 2002

AbstractThe monomer composition of the esterified part of suberin can be determined using gas chromatography-mass spectroscopy technology and is accordingly believed to be well known. However, evidence was presented recently indicating that the suberin of green cotton (Gossypium hirsutum cv Green Lint) fibers contains substantial amounts of esterified glycerol. This observation is confirmed in the present report by a sodium dodecyl sulfate extraction of membrane lipids and by a developmental study, demonstrating the correlated accumulation of glycerol and established suberin monomers. Corresponding amounts of glycerol also occur in the suberin of the periderm of cotton stems and potato (Solanum tuberosum) tubers. A periderm preparation of wound-healing potato tuber storage parenchyma was further purified by different treatments. As the purification proceeded, the concentration of glycerol increased at about the same rate as that of α,ω-alkanedioic acids, the most diagnostic suberin monomers. Therefore, it is proposed that glycerol is a monomer of suberins in general and can cross-link aliphatic and aromatic suberin domains, corresponding to the electron-translucent and electron-opaque suberin lamellae, respectively. This proposal is consistent with the reported dimensions of the electron-translucent suberin lamellae.
Posttranscriptional Gene Silencing in Transgenic Sugarcane. Dissection of Homology-Dependent Virus Resistance in a Monocot That Has a Complex Polyploid Genome1
Authors: Ingelbrecht Ivan L. , Irvine James E. , Mirkov T. Erik 
Published: July 2002

AbstractRNA-mediated, posttranscriptional gene silencing has been determined as the molecular mechanism underlying transgenic virus resistance in many plant virus-dicot host plant systems. In this paper we show that transgenic virus resistance in sugarcane (Saccharum spp. hybrid) is based on posttranscriptional gene silencing. The resistance is derived from an untranslatable form of the sorghum mosaic potyvirus strain SCH coat protein (CP) gene. Transgenic sugarcane plants challenged with sorghum mosaic potyvirus strain SCH had phenotypes that ranged from fully susceptible to completely resistant, and a recovery phenotype was also observed. Clones derived from the same transformation event or obtained after vegetative propagation could display different levels of virus resistance, suggesting the involvement of a quantitative component in the resistance response. Most resistant plants displayed low or undetectable steady-state CP transgene mRNA levels, although nuclear transcription rates were high. Increased DNA methylation was observed in the transcribed region of the CP transgenes in most of these plants. Collectively, these characteristics indicate that an RNA-mediated, homology-dependent mechanism is at the base of the virus resistance. This work extends posttranscriptional gene silencing and homology-dependent virus resistance, so far observed only in dicots, to an agronomically important, polyploid monocot.
Expansins Are Conserved in Conifers and Expressed in Hypocotyls in Response to Exogenous Auxin1
Authors: Hutchison Keith W. , Singer Patricia B. , McInnis Stephanie , Diaz-Sala Carmen , Greenwood Michael S. 
Published: July 2002

Abstract
Differential display reverse transcription-polymerase chain reaction was used to detect the induction of gene expression during adventitious root formation in loblolly pine (Pinus taeda) after treatment with the exogenous auxin indole-3-butyric acid. A BLAST search of the GenBank database using one of the clones obtained revealed very strong similarity to the α-expansin gene family in angiosperms. A near-full-length loblolly pine α-expansin sequence was obtained using 5′- and 3′-rapid amplification of cDNA end cloning, and the deduced amino acid sequence was highly conserved relative to those of angiosperm expansins. Northern analysis indicates that α-expansin mRNA expression increases 50- to 100-fold in the base of hypocotyl stem cuttings from loblolly pine seedlings in response to indole-3-butyric acid, with peak expression occurring 24 to 48 h after induction.
Functional Characterization and Expression Analysis of the Amino Acid Permease RcAAP3 from Castor Bean1
Authors: Neelam Anil , Marvier Allison C. , Hall J.L. , Williams Lorraine E. 
Published: July 2002

Abstract
A polymerase chain reaction-based library screening procedure was used to isolate RcAAP3, an amino acid permease cDNA from castor bean (Ricinus communis). RcAAP3 is 1.7 kb in length, with an open reading frame that encodes a protein with a calculated molecular mass of 51 kD. Hydropathy analysis indicates that the RcAAP3 protein is highly hydrophobic in nature with nine to 11 putative transmembrane domains. RcAAP3-mediated uptake of citrulline in a yeast transport mutant showed saturable kinetics with aKm of 0.4 mm. Transport was higher at acidic pH and was inhibited by the protonophore carbonylcyanide-m-chlorophenylhydrazone, suggesting a proton-coupled transport mechanism. Citrulline uptake was strongly inhibited (72%) by the permeable sulfydryl reagentN-ethylmaleimide, but showed lower sensitivity (30% inhibition) to the nonpermeable reagentp-chloromercuribenzenesulfonic acid. Diethylpyrocarbonate, a histidine modifier, inhibited citrulline uptake by 80%. A range of amino acids inhibited citrulline uptake, suggesting that RcAAP3 may be a broad substrate permease that can transport neutral and basic amino acids with a lower affinity for acidic amino acids. Northern analysis indicated that RcAAP3 is widely expressed in source and sink tissues of castor bean, and that the pattern of expression is distinct from RcAAP1 andRcAAP2.
Gibberellin Biosynthesis in Maize. Metabolic Studies with GA15, GA24, GA25, GA7, and 2,3-Dehydro-GA9
Authors: Davis Gordon , Kobayashi Masatomo , Phinney Bernard O. , Lange Theo , Croker Steve J. , Gaskin Paul , MacMillan Jake 
Published: July 2002

Abstract[17-14C]-Labeled GA15, GA24, GA25, GA7, and 2,3-dehydro-GA9 were separately injected into normal,dwarf-1 (d1), and dwarf-5 (d5) seedlings of maize (Zea mays L.). Purified radioactive metabolites from the plant tissues were identified by full-scan gas chromatography-mass spectrometry and Kovats retention index data. The metabolites from GA15 were GA44, GA19, GA20, GA113, and GA15-15,16-ene (artifact?). GA24 was metabolized to GA19, GA20, and GA17. The metabolites from GA25 were GA17, GA25 16α,17-H2-17-OH, and HO-GA25 (hydroxyl position not determined). GA7was metabolized to GA30, GA3, isoGA3 (artifact?), and trace amounts of GA7-diene-diacid (artifact?). 2,3-Dehydro-GA9was metabolized to GA5, GA7 (trace amounts), 2,3-dehydro-GA10 (artifact?), GA31, and GA62. Our results provide additional in vivo evidence of a metabolic grid in maize (i.e. pathway convergence). The grid connects members of a putative, non-early 3,13-hydroxylation branch pathway to the corresponding members of the previously documented early 13-hydroxylation branch pathway. The inability to detect the sequence GA12 → GA15 → GA24 → GA9 indicates that the non-early 3,13-hydroxylation pathway probably plays a minor role in the origin of bioactive gibberellins in maize.
Physiological Implications of the Kinetics of Maize Leaf Phosphoenolpyruvate Carboxylase
Authors: Tovar-Méndez Alejandro , Mújica-Jiménez Carlos , Muñoz-Clares Rosario A. 
Published: July 2002

Abstract
It has been a common practice to assay phosphoenolpyruvate carboxylase (PEPC) under high, nonphysiological concentrations of Mg2+ and bicarbonate. We have performed kinetic studies on the enzyme from maize (Zea mays) leaves at near physiological levels of free Mg2+ (0.4 mm) and bicarbonate (0.1 mm), and found that both the nonphosphorylated and phosphorylated enzymes exhibited a high degree of cooperativity in the binding of phosphoenolpyruvate, a much lower affinity for this substrate and for activators, and a greater affinity for malate than at high concentrations of these ions. Inhibition of the phosphorylated enzyme by malate was overcome by glycine or alanine but not by glucose-6-phosphate, either in the absence or presence of high concentrations of glycerol, a compatible solute. Alanine caused significant activation at physiological concentrations, suggesting a pivotal role for this amino acid in regulating maize leaf PEPC activity. Our results showed that the maximum enzyme activity attainable in vivo would be less than 50% of that attainable in vitro under optimum conditions. Therefore, the high levels of PEPC protein in the cytosol of C4 mesophyll cells might be an adaptation for sustaining the steady-state rate of flux through the photosynthetic CO2 assimilation pathway despite the limitations imposed by the PEPC kinetic properties and the conditions of its environment.
Internal Conductance to CO2 Diffusion and C18OO Discrimination in C3 Leaves
Authors: Gillon Jim S. , Yakir Dan 
Published: July 2002

Abstract
18O discrimination in CO2 stems from the oxygen exchange between 18O-enriched water and CO2 in the chloroplast, a process catalyzed by carbonic anhydrase (CA). A proportion of this 18O-labeled CO2 escapes back to the atmosphere, resulting in an effective discrimination against C18OO during photosynthesis (Δ18O). By constraining the δ18O of chloroplast water (δe) by analysis of transpired water and the extent of CO2-H2O isotopic equilibrium (θeq) by measurements of CA activity (θeq = 0.75–1.0 for tobacco, soybean, and oak), we could apply measured Δ18O in a leaf cuvette attached to a mass spectrometer to derive the CO2 concentration at the physical limit of CA activity, i.e. the chloroplast surface (c cs). From the CO2 drawdown sequence between stomatal cavities from gas exchange (c i), from Δ18O (c cs), and at Rubisco sites from Δ13C (c c), the internal CO2 conductance (g i) was partitioned into cell wall (g w) and chloroplast (g ch) components. The results indicated that g ch is variable (0.42–1.13 mol m−2 s−1) and proportional to CA activity. We suggest that the influence of CA activity on the CO2 assimilation rate should be important mainly in plants with low internal conductances.
Tissue-Preferential Expression of a Rice α-Tubulin Gene,OsTubA1, Mediated by the First Intron
Authors: Jeon Jong-Seong , Lee Sichul , Jung Ki-Hong , Jun Sung-Hoon , Kim Chanhong , An Gynheung 
Published: July 2002

Abstract
The genomic clone encoding an α-tubulin,OsTubA1, has been isolated from rice (Oryza sativa L.). The gene consists of four exons and three introns. RNA-blot analysis showed that the gene is strongly expressed in actively dividing tissues, including root tips, young leaves, and young flowers. Analysis of chimeric fusions between OsTubA1and β-glucuronidase (GUS) revealed that the intron 1 was required for high-level GUS expression in actively dividing tissues, corresponding with normal expression pattern ofOsTubA1. Fusion constructs lacking the intron 1 showed more GUS staining in mature tissues rather than young tissues. When the intron 1 was placed at the distal region from 5′-upstream region or at the 3′-untranslated region, no enhancement of GUS expression was observed. Sequential deletions of the OsTubA1 intron 1 brought about a gradual reduction of GUS activity in calli. These results suggest that tissue-preferential expression of theOsTubA1 gene is mediated by the intron 1 and that it may be involved in a mechanism for an efficient RNA splicing that is position dependent.