bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Euphorbia characias Latex Amine Oxidase1
Authors: Padiglia Alessandra , Medda Rosaria , Lorrai Anita , Murgia Barbara , Pedersen Jens Z. , Finazzi Agró Alessandro , Floris Giovanni 
Published: July 2002

Abstract
A copper-containing amine oxidase from the latex of Euphorbia characias was purified to homogeneity and the copper-free enzyme obtained by a ligand-exchange procedure. The interactions of highly purified apo- and holoenzyme with several substrates, carbonyl reagents, and copper ligands were investigated by optical spectroscopy under both aerobic and anaerobic conditions. The extinction coefficients at 278 and 490 nm were determined as 3.78 × 105m−1cm−1 and 6000 m−1cm−1, respectively. Active-site titration of highly purified enzyme with substrates and carbonyl reagents showed the presence of one cofactor at each enzyme subunit. In anaerobiosis the native enzyme oxidized one equivalent substrate and released one equivalent aldehyde per enzyme subunit. The apoenzyme gave exactly the same 1:1:1 stoichiometry in anaerobiosis and in aerobiosis. These findings demonstrate unequivocally that copper-free amine oxidase can oxidize substrates with a single half-catalytic cycle. The DNA-derived protein sequence shows a characteristic hexapeptide present in most 6-hydroxydopa quinone-containing amine oxidases. This hexapeptide contains the tyrosinyl residue that can be modified into the cofactor 6-hydroxydopa quinone.
Blue Light and Abscisic Acid Independently Induce Heterophyllous Switch in Marsilea quadrifolia1
Authors: Lin Bai-Ling , Yang Wen-Jen 
Published: July 2002

Abstract
In natural habitats Marsilea quadrifolia L. produces different types of leaves above and below the water level. In aseptic cultures growth conditions can be manipulated so that leaves of the submerged type are produced continuously. Under such conditions the application of either blue light or an optimal concentration of abscisic acid (ABA) induced the development of aerial-type leaves. When fluridone, an inhibitor of ABA biosynthesis, was added to the culture medium it did not prevent blue light induction of aerial leaf development. During blue light treatment the endogenous ABA level inM. quadrifolia leaves remained unchanged. However, after the plants were transferred to an enriched medium, the ABA level gradually increased, corresponding to a transition in development from the submerged type of leaves to aerial leaves. These results indicate that the blue light signal is not mediated by ABA. Therefore, in the regulation of heterophyllous determination, discrete pathways exist in response to environmental signals.
Purification and Characterization of Caffeine Synthase from Tea Leaves1
Authors: Kato Misako , Mizuno Kouichi , Fujimura Tatsuhito , Iwama Masanori , Irie Masachika , Crozier Alan , Ashihara Hiroshi 
Published: July 2002

AbstractCaffeine synthase (CS), theS-adenosylmethionine-dependentN-methyltransferase involved in the last two steps of caffeine biosynthesis, was extracted from young tea (Camellia sinensis) leaves; the CS was purified 520-fold to apparent homogeneity and a final specific activity of 5.7 nkat mg−1protein by ammonium sulfate fractionation and hydroxyapatite, anion-exchange, adenosine-agarose, and gel-filtration chromatography. The native enzyme was monomeric with an apparent molecular mass of 61 kD as estimated by gel-filtration chromatography and 41 kD as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme displayed a sharp pH optimum of 8.5. The final preparation exhibited 3- and 1-N-methyltransferase activity with a broad substrate specificity, showing high activity toward paraxanthine, 7-methylxanthine, and theobromine and low activity with 3-methylxanthine and 1-methylxanthine. However, the enzyme had no 7-N-methyltransferase activity toward xanthosine and xanthosine 5′-monophosphate. The Km values of CS for paraxanthine, theobromine, 7-methylxanthine, andS-adenosylmethionine were 24, 186, 344, and 21 μm, respectively. The possible role and regulation of CS in purine alkaloid biosynthesis in tea leaves are discussed. The 20-amino acid N-terminal sequence for CS showed little homology with other methyltransferases.
Leucine Aminopeptidase RNAs, Proteins, and Activities Increase in Response to Water Deficit, Salinity, and the Wound Signals Systemin, Methyl Jasmonate, and Abscisic Acid1
Authors: Chao Wun S. , Gu Yong-Qiang , Pautot Véronique , Bray Elizabeth A. , Walling Linda L. 
Published: July 2002

Abstract
LapARNAs, proteins, and activities increased in response to systemin, methyl jasmonate, abscisic acid (ABA), ethylene, water deficit, and salinity in tomato (Lycopersicon esculentum). Salicylic acid inhibited wound-induced increases of LapA RNAs. Experiments using the ABA-deficient flacca mutant indicated that ABA was essential for wound and systemin induction ofLapA, and ABA and systemin acted synergistically to induce LapA gene expression. In contrast,pin2 (proteinase inhibitor 2) was not dependent on exogenous ABA. Whereas both LapA and le4(L. esculentumdehydrin) were up-regulated by increases in ABA, salinity, and water deficit, only LapAwas regulated by octadecanoid pathway signals. Comparison ofLapA expression with that of thePR-1 (pathogenesis-related 1) andGluB (basic β-1,3-glucanase) genes indicated that these PR protein genes were modulated by a systemin-independent jasmonic acid-signaling pathway. These studies showed that at least four signaling pathways were utilized during tomato wound and defense responses. Analysis of the expression of aLapA1:GUS gene in transgenic plants indicated that theLapA1 promoter was active during floral and fruit development and was used during vegetative growth only in response to wounding, Pseudomonas syringae pv tomatoinfection, or wound signals. This comprehensive understanding of the regulation of LapA genes indicated that this regulatory program is distinct from the wound-induced pin2, ABA-responsive le4, and PR protein genes.
The Relationship between Ethylene Binding and Dominant Insensitivity Conferred by Mutant Forms of the ETR1 Ethylene Receptor
Authors: Hall Anne E. , Grace Chen Qianhong , Findell Jennifer L. , Eric Schaller G. , Bleecker Anthony B. 
Published: July 2002

Abstract
Ethylene responses in Arabidopsis are mediated by a small family of receptors, including theETR1 gene product. Specific mutations in the N-terminal ethylene-binding domain of any family member lead to dominant ethylene insensitivity. To investigate the mechanism of ethylene insensitivity, we examined the effects of mutations on the ethylene-binding activity of the ETR1 protein expressed in yeast. Theetr1-1 andetr1-4 mutations completely eliminated ethylene binding, while the etr1-3mutation severely reduced binding. Additional site-directed mutations that disrupted ethylene binding in yeast also conferred dominant ethylene insensitivity when the mutated genes were transferred into wild-type Arabidopsis plants. By contrast, theetr1-2 mutation did not disrupt ethylene binding in yeast. These results indicate that dominant ethylene insensitivity may be conferred by mutations that disrupt ethylene binding or that uncouple ethylene binding from signal output by the receptor. Increased dosage of wild-type alleles in triploid lines led to the partial recovery of ethylene sensitivity, indicating that dominant ethylene insensitivity may involve either interactions between wild-type and mutant receptors or competition between mutant and wild-type receptors for downstream effectors.
A Point Mutation in the Ethylene-Inducing Xylanase Elicitor Inhibits the β-1-4-Endoxylanase Activity But Not the Elicitation Activity
Authors: Furman-Matarasso Noa , Cohen Eitan , Du Quansheng , Chejanovsky Nor , Hanania Uri , Avni Adi 
Published: July 2002

AbstractEthylene-inducing xylanase (EIX) elicits plant defense responses in certain tobacco (Nicotiana tabacum) and tomato cultivars in addition to its xylan degradation activity. It is not clear, however, whether elicitation occurs by cell wall fragments released by the enzymatic activity or by the xylanase protein interacting directly with the plant cells. We cloned the gene encoding EIX protein and overexpressed it in insect cells. To determine the relationship between the two activities, substitution of amino acids in the xylanase active site was performed. Substitution at glutamic acid-86 or -177 with glutamine (Gln), aspartic acid (Asp), or glycine (Gly) inhibited the β-1-4-endoxylanase activity. Mutants having Asp-86 or Gln-177 also lost the ability to induce the hypersensitive response and ethylene biosynthesis. However, mutants having Gln-86, Gly-86, Asp-177, or Gly-177 retained ability to induce ethylene biosynthesis and the hypersensitive response. Our data show that the xylanase activity of EIX elicitor can be separated from the elicitation process, as some of the mutants lack the former but retain the latter.
Cloning and Molecular Analyses of a Gibberellin 20-Oxidase Gene Expressed Specifically in Developing Seeds of Watermelon
Authors: Kang Hong-Gyu , Jun Sung-Hoon , Kim Junyul , Kawaide Hiroshi , Kamiya Yuji , An Gynheung 
Published: July 2002

AbstractTo understand the biosynthesis and functional role of gibberellins (GAs) in developing seeds, we isolatedCv20ox, a cDNA clone from watermelon (Citrullus lanatus) that shows significant amino acid homology with GA 20-oxidases. The complementary DNA clone was expressed inEscherichia coli as a fusion protein, which oxidized GA12 at C-20 to the C19 compound GA9, a precursor of bioactive GAs. RNA-blot analysis showed that the Cv20ox gene was expressed specifically in developing seeds. The gene was strongly expressed in the integument tissues, and it was also expressed weakly in inner seed tissues. In parthenocarpic fruits induced by 1-(2-chloro-4-pyridyl)-3-phenylurea treatment, the expression pattern of Cv20ox did not change, indicating that the GA 20-oxidase gene is expressed primarily in the maternal cells of developing seeds. The promoter ofCv20ox was isolated and fused to the β-glucuronidase (GUS) gene. In a transient expression system, β-glucuronidase staining was detectable only in the integument tissues of developing watermelon seeds.
The Starch-Debranching Enzymes Isoamylase and Pullulanase Are Both Involved in Amylopectin Biosynthesis in Rice Endosperm
Authors: Kubo Akiko , Fujita Naoko , Harada Kyuya , Matsuda Toshiaki , Satoh Hikaru , Nakamura Yasunori 
Published: July 2002

Abstract
The activities of the two types of starch debranching enzymes, isoamylase and pullulanase, were greatly reduced in endosperms of allelic sugary-1 mutants of rice (Oryza sativa), with the decrease more pronounced for isoamylase than for pullulanase. However, the decrease in isoamylase activity was not related to the magnitude of thesugary phenotype (the proportion of the phytoglycogen region of the endosperm), as observed with pullulanase. In the moderately mutated line EM-5, the pullulanase activity was markedly lower in the phytoglycogen region than in the starch region, and isoamylase activity was extremely low or completely lost in the whole endosperm tissue. These results suggest that both debranching enzymes are involved in amylopectin biosynthesis in rice endosperm. We presume that isoamylase plays a predominant role in amylopectin synthesis, but pullulanase is also essential or can compensate for the role of isoamylase in the construction of the amylopectin multiple-cluster structure. It is highly possible that isoamylase was modified in somesugary-1 mutants such as EM-273 and EM-5, since it was present in significant and trace amounts, respectively, in these mutants but was apparently inactive. The results show that theSugary-1 gene encodes the isoamylase gene of the rice genome.
Cloning, Expression, and Molecular Characterization of a Small Pea Gene Family Regulated by Low Levels of Ultraviolet B Radiation and Other Stresses
Authors: Brosché Mikael , Strid Åke 
Published: July 2002

Abstract
A pea (Pisum sativum) DNA fragment (termed MB3) was isolated by differential display of cDNAs obtained from total leaf RNA of ultraviolet B (UV-B) radiation-treated plants. Longer cDNAs were cloned by rapid amplification of cDNA ends in the 3′ to 5′ direction. Three different, but very similar, cDNAs were cloned, sadA, sadB, andsadC, the major difference between them being a 36-bp deletion in the coding region of sadB. Southern blotting confirmed the occurrence of at least three genes in the pea genome. Database comparisons of the SAD protein sequences revealed high identity (46%) and similarity (77%) with a putative tomato (Lycopersicon esculentum) short-chain alcohol dehydrogenase. Very low levels of UV-B radiation (the biologically effective radiation normalized to 300 nm = 0.08 W m−2) was shown to up-regulate expression, a dose considerably lower than that needed to induce expression of the well-known UV-B defensive chalcone synthase and phenylalanine ammonia lyase genes. RNase protection assay revealed that primarilysadA and sadC mRNA accumulation was enhanced by UV-B. In addition to UV-B irradiation, ozone fumigation, wounding, aluminum stress, and salt stress induced increased transcript levels of the sad genes in pea.
Increased Respiratory Restriction during Phosphate-Limited Growth in Transgenic Tobacco Cells Lacking Alternative Oxidase
Authors: Parsons Hannah L. , Yip Justine Y.H. , Vanlerberghe Greg C. 
Published: July 2002

Abstract
We found that mitochondrial alternative oxidase (AOX) protein and the capacity for CN-resistant respiration are dramatically increased in wild-type tobacco (Nicotiana tabacum) suspension-cultured cells in response to growth under P limitation, and antisense (AS8) tobacco cells unable to induce AOX under these conditions have altered growth and metabolism. Specifically, we found that the respiration of AS8 cells was restricted during P-limited growth, when the potential for severe adenylate control of respiration (at the level of C supply to the mitochondrion and/or at the level of oxidative phosphorylation) is high due to the low cellular levels of ADP and/or inorganic P. As a result of this respiratory restriction, AS8 cells had altered growth, morphology, cellular composition, and patterns of respiratory C flow to amino acid synthesis compared with wild-type cells with abundant AOX protein. Also, AS8 cells under P limitation displayed high in vivo rates of generation of active oxygen species compared with wild-type cells. This difference could be abolished by an uncoupler of mitochondrial oxidative phosphorylation. Our results suggest that induction of non-phosphorylating AOX respiration (like induction of adenylate and inorganic P-independent pathways in glycolysis) is an important plant metabolic adaptation to P limitation. By preventing severe respiratory restriction, AOX acts to prevent both redirections in C metabolism and the excessive generation of harmful active oxygen species in the mitochondrion.
The Activity of the Maize Opaque2 Transcriptional Activator Is Regulated Diurnally
Authors: Ciceri Pietro , Locatelli Franca , Genga Annamaria , Viotti Angelo , Schmidt Robert J. 
Published: July 2002

Abstract
The maize (Zea maysL.) Opaque2 (O2) protein is an endosperm-specific transcriptional activator whose DNA-binding activity is regulated diurnally by a phosphorylation/dephosphorylation mechanism. We show that theO2 transcript undergoes pronounced oscillations during the day-night cycle. The highest level of the O2 message is present at midday and the lowest level at midnight. The level ofO2 transcript follows a diurnal rhythm that appears controlled by the circadian clock. Two different endosperm-expressed DNA-binding proteins, PBF (prolamin box-binding factor) and OHP1 (O2-heterodimerizing protein 1), were also analyzed. While thePBF message levels oscillate diurnally, the steady-state levels of OHP1 transcript were constant through the day and night. We present data showing that the seed is not directly involved in the perception of the light signal, but presumably responds to diurnal fluxes of nutrients into the endosperm. Moreover, we show that the O2 protein is not involved in the regulation of its own transcript levels. These data indicate that O2 activity is down-regulated at night by both a reduction in O2transcript and by hyperphosphorylation of residual O2 protein, and suggest that regulatory gene activity during endosperm development may be acutely sensitive to a diurnal signal(s) emanating from the plant and passing into the developing seeds.
A Putative Role for the Tomato Genes DUMPY and CURL-3 in Brassinosteroid Biosynthesis and Response
Authors: Koka Chala V. , Cerny R. Eric , Gardner Randy G. , Noguchi Takahiro , Fujioka Shozo , Takatsuto Suguru , Yoshida Shigeo , Clouse Steven D. 
Published: July 2002

Abstract
Thedumpy (dpy) mutant of tomato (Lycopersicon esculentum Mill.) exhibits short stature, reduced axillary branching, and altered leaf morphology. Application of brassinolide and castasterone rescued the dpyphenotype, as did C-23-hydroxylated, 6-deoxo intermediates of brassinolide biosynthesis. The brassinolide precursors campesterol, campestanol, and 6-deoxocathasterone failed to rescue, suggesting thatdpy may be affected in the conversion of 6-deoxocathasterone to 6-deoxoteasterone, similar to the Arabidopsisconstitutive photomorphogenesis and dwarfism(cpd) mutant. Measurements of endogenous brassinosteroid levels by gas chromatography-mass spectrometry were consistent with this hypothesis. To examine brassinosteroid-regulated gene expression in dpy, we performed cDNA subtractive hybridization and isolated a novel xyloglucan endotransglycosylase that is regulated by brassinosteroid treatment. The curl-3(cu-3) mutant (Lycopersicon pimpinellifolium [Jusl.] Mill.) shows extreme dwarfism, altered leaf morphology, de-etiolation, and reduced fertility, all strikingly similar to the Arabidopsis mutantbrassinosteroid insensitive 1 (bri1). Primary root elongation of wild-type L. pimpinellifoliumseedlings was strongly inhibited by brassinosteroid application, whilecu-3 mutant roots were able to elongate at the same brassinosteroid concentration. Moreover, cu-3 mutants retained sensitivity to indole-3-acetic acid, cytokinins, gibberellin, and abscisic acid while showing hypersensitivity to 2,4-dichlorophenoxyacetic acid in the root elongation assay. Thecu-3 root response to hormones, coupled with itsbri1-like phenotype, suggests that cu-3may also be brassinosteroid insensitive.
Enhancement of Na+ Uptake Currents, Time-Dependent Inward-Rectifying K+ Channel Currents, and K+Channel Transcripts by K+ Starvation in Wheat Root Cells
Authors: Buschmann Peter H. , Vaidyanathan Rama , Gassmann Walter , Schroeder Julian I. 
Published: July 2002

Abstract
Excessive low-affinity Na+ uptake is toxic to the growth of glycophytic plants. Recently, several reports have suggested that the interaction between K+ and Na+ uptake might represent a key factor in determining the Na+ tolerance of plants. We investigated the effects of K+ starvation on Na+ and K+ uptake mechanisms in the plasma membrane of wheat (Triticum aestivum L.) root cortex cells using the patch-clamp technique. Unexpectedly, K+starvation of wheat seedlings was found to enhance the magnitude and frequency of occurrence of time-dependent inward-rectifying K+ channel currents (IK + in). We examined whether the transcription of a wheat root K+ in channel gene is induced by K+ starvation. A cDNA coding for a wheat root K+ channel homolog, TaAKT1 (accession no.AF207745), was isolated. TaAKT1 mRNA levels were up-regulated in roots in response to withdrawal of K+ from the growth medium. Furthermore, K+ starvation caused an enhancement of instantaneous Na+ currents (INa +). Electrophysiological analyses suggested that IK + in and INa + are not mediated by the same transport protein based on: (a) different activation curves, (b) different time dependencies, (c) different sensitivities to external Ca2+, and (d) different cation selectivities. These data implicate a role for INa + in Na+ uptake and stress during K+ starvation, and indicate that K+ in channels may contribute to K+-starvation-induced K+ uptake in wheat roots.
AVP2, a Sequence-Divergent, K+-Insensitive H+-Translocating Inorganic Pyrophosphatase from Arabidopsis
Authors: Drozdowicz Yolanda M. , Kissinger Jessica C. , Rea Philip A. 
Published: July 2002

Abstract
Plant vacuolar H+-translocating inorganic pyrophosphatases (V-PPases; EC 3.6.1.1) have been considered to constitute a family of functionally and structurally monotonous intrinsic membrane proteins. Typified by AVP1 (V. Sarafian, Y. Kim, R.J. Poole, P.A. Rea [1992] Proc Natl Acad Sci USA 89: 1775–1779) from Arabidopsis, all characterized plant V-PPases share greater than 84% sequence identity and catalyze K+-stimulated H+ translocation. Here we describe the molecular and biochemical characterization of AVP2 (accession no. AF182813), a sequence-divergent (36% identical) K+-insensitive, Ca2+-hypersensitive V-PPase active in both inorganic pyrophosphate hydrolysis and H+ translocation. The differences between AVP2 and AVP1 provide the first indication that plant V-PPases from the same organism fall into two distinct categories. Phylogenetic analyses of these and other V-PPase sequences extend this principle by showing that AVP2, rather than being an isoform of AVP1, is but one representative of a novel category of AVP2-like (type II) V-PPases that coexist with AVP1-like (type I) V-PPases not only in plants, but also in apicomplexan protists such as the malarial parasite Plasmodium falciparum.
Cucumber Mosaic Virus Infection Affects Sugar Transport in Melon Plants
Authors: Shalitin Dror , Wolf Shmuel 
Published: July 2002

Abstract
Viral infection often affects carbon assimilation and metabolism in host plants. To better understand the effect of cucumber mosaic virus (CMV) infection on sugar transport, carbohydrate levels and the amounts of the various sugars in the phloem sap were determined in infected melon (Cucumis melo L.) plants. Source leaves infected with CMV were characterized by high concentrations of reducing sugars and relatively low starch levels. The altered level of carbohydrates was accompanied by increased respiration and decreased net photosynthetic rates in the infected leaves. Although stachyose was the predominant sugar in phloem sap collected from petioles of control leaves, sucrose (Suc) was a major sugar in the phloem sap of infected leaves. Moreover, analyses of the newly fixed14CO2 revealed a high proportion of radioactive Suc in the phloem sap of infected leaves 60 min post-labeling. The alteration in phloem sap sugar composition was found in source, but not old, leaves. Moreover, elevations in Suc concentration were also evident in source leaves that did not exhibit symptoms or contain detectable amounts of virus particles. The mode by which CMV infection may cause alterations in sugar transport is discussed in terms of the mechanism by which sugars are loaded into the phloem of cucurbit plants.