bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Chloroplast Small Heat-Shock Protein Oligomer Is Not Phosphorylated and Does Not Dissociate during Heat Stress in Vivo1
Authors: Suzuki Teri Chizue , Krawitz Denise C. , Vierling Elizabeth 
Published: July 2002

Abstract
Plants synthesize several classes of small (15- to 30-kD monomer) heat-shock proteins (sHSPs) in response to heat stress, including a nuclear-encoded, chloroplast-localized sHSP (HSP21). Cytosolic sHSPs exist as large oligomers (approximately 200–800 kD) composed solely or primarily of sHSPs. Phosphorylation of mammalian sHSPs causes oligomer dissociation, which appears to be important for regulation of sHSP function. We examined the native structure and phosphorylation of chloroplast HSP21 to understand this protein's basic properties and to compare it with cytosolic sHSPs. The apparent size of native HSP21 complexes was &gt; 200 kD and they did not dissociate during heat stress. We found no evidence that HSP21 or the plant cytosolic sHSPs are phosphorylated in vivo. A partial HSP21 complex purified from heat-stressed pea (Pisum sativum L.) leaves contained no proteins other than HSP21. Mature recombinant pea andArabidopsis thaliana HSP21 were expressed inEscherichia coli, and purified recombinant Arabidopsis HSP21 assembled into homo-oligomeric complexes with the same apparent molecular mass as HSP21 complexes observed in heat-stressed leaf tissue. We propose that the native, functional form of chloroplast HSP21 is a large, oligomeric complex containing nine or more HSP21 subunits, and that plant sHSPs are not regulated by phosphorylation-induced dissociation.
Wound Signaling in Tomato Plants1
Authors: Birkenmeier Guy F. , Ryan Clarence A. 
Published: July 2002

Abstract
The effects of abscisic acid (ABA) on the accumulation of proteinase inhibitors I (Inh I) and II (Inh II) in young, excised tomato (Lycopersicon esculentum L.) plants were investigated. When supplied to excised plants through the cut stems, 100 μm ABA induced the activation of the ABA-responsive le4 gene. However, under the same conditions of assay, ABA at concentrations of up to 100 μm induced only low levels of proteinase-inhibitor proteins or mRNAs, compared with levels induced by systemin or jasmonic acid over the 24 h following treatment. In addition, ABA only weakly induced the accumulation of mRNAs of several other wound-response proteins. Assays of the ABA concentrations in leaves following wounding indicated that the ABA levels increased preferentially near the wound site, suggesting that ABA may have accumulated because of desiccation. The evidence suggests that ABA is not a component of the wound-inducible signal transduction pathway leading to defense gene activation but is likely involved in the general maintenance of a healthy plant physiology that facilitates a normal wound response.
Control of Meristem Development by CLAVATA1 Receptor Kinase and Kinase-Associated Protein Phosphatase Interactions1
Authors: Stone Julie M. , Trotochaud Amy E. , Walker John C. , Clark Steven E. 
Published: July 2002

Abstract
TheCLAVATA1 (CLV1) gene encodes a putative receptor kinase required for the proper balance between cell proliferation and differentiation in Arabidopsis shoot and flower meristems. Impaired CLV1 signaling results in masses of undifferentiated cells at the shoot and floral meristems. Although many putative receptor kinases have been identified in plants, the mechanism of signal transduction mediated by plant receptor-like kinases is largely unknown. One potential effector of receptor kinase signaling is kinase-associated protein phosphatase (KAPP), a protein that binds to multiple plant receptor-like kinases in a phosphorylation-dependent manner. To examine a possible role for KAPP in CLV1-dependent plant development, the interaction of CLV1 and KAPP was investigated in vitro and in vivo. KAPP binds directly to autophosphorylated CLV1 in vitro and co-immunoprecipitates with CLV1 in plant extracts derived from meristematic tissue. Reduction ofKAPP transcript accumulation in an intermediateclv1 mutant suppresses the mutant phenotype, and the degree of suppression is inversely correlated with KAPPmRNA levels. These data suggest that KAPP functions as a negative regulator of CLV1 signaling in plant development. This may represent a general model for the interaction of KAPP with receptor kinases.
A Model for Signal Transduction during Gamete Release in the Fucoid Alga Pelvetia compressa1
Authors: Pearson Gareth Anthony , Howard Brawley Susan 
Published: July 2002

Abstract
Fucoid algae release gametes into seawater following an inductive light period (potentiation), and gamete expulsion from potentiated receptacles ofPelvetia compressa began about 2 min after a light-to-dark transition. Agitation of the medium reversed potentiation, with an exponential time course completed in about 3 h. Light regulated two signaling pathways during potentiation and gamete expulsion: a photosynthetic pathway and a photosynthesis-independent pathway in which red light was active but blue light was not. Uptake of K+ appears to have an important role in potentiation, because a 50% inhibition of potentiation occurred in the presence of the tetraethylammonium ion, a K+-channel blocker. A central role of anion channels in the maintenance of potentiation is suggested by the premature release of gametes in the light when receptacles were incubated with inhibitors of slow-type anion channels. An inhibitor of tyrosine kinases, tyrphostin A63, also inhibited potentiation. A model for gamete release fromP. compressa is presented that proposes that illumination results in the accumulation of ions (e.g. K+) throughout the cells of the receptacle during potentiation, which then move into the extracellular matrix during gamete expulsion to generate osmomechanical force, resulting in gamete release.
New ArabidopsiscueMutants Suggest a Close Connection between Plastid- and Phytochrome Regulation of Nuclear Gene Expression
Authors: López-Juez Enrique , Paul Jarvis R. , Takeuchi Atsuko , Page Anton M. , Chory Joanne 
Published: July 2002

AbstractWe searched for new components that are involved in the positive regulation of nuclear gene expression by light by extending a screen for Arabidopsis cue(chlorophyll a/b-binding [CAB] protein-underexpressed) mutants (H.-M. Li, K. Culligan, R.A. Dixon, J. Chory [1995] Plant Cell 7: 1599–1610). cue mutants display reduced expression of the CAB3 gene, which encodes light-harvesting chlorophyll protein, the main chloroplast antenna. The new mutants can be divided into (a) phytochrome-deficient mutants (hy1and phyB), (b) virescent or delayed-greening mutants (cue3, cue6, and cue8), and (c) uniformly pale mutants (cue4 andcue9). For each of the mutants, the reduction inCAB expression correlates with the visible phenotype, defective chloroplast development, and reduced abundance of the light-harvesting chlorophyll protein. Levels of protochlorophyllide oxidoreductase (POR) were reduced to varying degrees in etiolated mutant seedlings. In the dark, whereas the virescent mutants displayed reduced CAB expression and the lowest levels of POR protein, the other mutants expressed CAB and accumulated POR at near wild-type levels. All of the mutants, with the exception ofcue6, were compromised in their ability to derepressCAB expression in response to phytochrome activation. Based on these results, we propose that the previously postulated plastid-derived signal is closely involved in the pathway through which phytochrome regulates the expression of nuclear genes encoding plastid proteins.
Extragenic Suppressors of the Arabidopsis gaiMutation Alter the Dose-Response Relationship of Diverse Gibberellin Responses1
Authors: Peng Jinrong , Richards Donald E. , Moritz Thomas , Caño-Delgado Ana , Harberd Nicholas P. 
Published: July 2002

Abstract
Active gibberellins (GAs) are endogenous factors that regulate plant growth and development in a dose-dependent fashion. Mutant plants that are GA deficient, or exhibit reduced GA responses, display a characteristic dwarf phenotype. Extragenic suppressor analysis has resulted in the isolation of Arabidopsis mutations, which partially suppress the dwarf phenotype conferred by GA deficiency and reduced GA-response mutations. Here we describe detailed studies of the effects of two of these suppressors,spy-7 and gar2–1, on several different GA-responsive growth processes (seed germination, vegetative growth, stem elongation, chlorophyll accumulation, and flowering) and on the in planta amounts of active and inactive GA species. The results of these experiments show that spy-7 and gar2–1affect the GA dose-response relationship for a wide range of GA responses and suggest that all GA-regulated processes are controlled through a negatively acting GA-signaling pathway.
A Cross-Polarization, Magic-Angle-Spinning,13C-Nuclear-Magnetic-Resonance Study of Polysaccharides in Sugar Beet Cell Walls1
Authors: Renard Catherine M.G.C. , Jarvis Michael C. 
Published: July 2002

Abstract
Solid-state nuclear magnetic resonance relaxation experiments were used to study the rigidity and spatial proximity of polymers in sugar beet (Beta vulgaris) cell walls. ProtonT1ρ decay and cross-polarization patterns were consistent with the presence of rigid, crystalline cellulose microfibrils with a diameter of approximately 3 nm, mobile pectic galacturonans, and highly mobile arabinans. A direct-polarization, magic-angle-spinning spectrum recorded under conditions adapted to mobile polymers showed only the arabinans, which had a conformation similar to that of beet arabinans in solution. These cell walls contained very small amounts of hemicellulosic polymers such as xyloglucan, xylan, and mannan, and no arabinan or galacturonan fraction closely associated with cellulose microfibrils, as would be expected of hemicelluloses. Cellulose microfibrils in the beet cell walls were stable in the absence of any polysaccharide coating.
Transformation of the Collateral Vascular Bundles into Amphivasal Vascular Bundles in an Arabidopsis Mutant1
Authors: Zhong Ruiqin , Taylor Jennifer J. , Ye Zheng-Hua 
Published: July 2002

Abstract
Arabidopsis inflorescence stems develop a vascular pattern similar to that found in most dicots. The arrangement of vascular tissues within the bundle is collateral, and vascular bundles in the stele are arranged in a ring. Although auxin has been shown to be an inducer of vascular differentiation, little is known about the molecular mechanisms controlling vascular pattern formation. By screening ethyl methanesufonate-mutagenized populations of Arabidopsis, we have isolated an avb1(amphivasal vascular bundle) mutant with a novel vascular pattern. Unlike the collateral vascular bundles seen in the wild-type stems, the vascular bundles in theavb1 stems were similar to amphivasal bundles, i.e. the xylem completely surrounded the phloem. Furthermore, branching vascular bundles in the avb1 stems abnormally penetrated into the pith, which resulted in a disruption in the ring-like arrangement of vascular bundles in the stele. The avb1 mutation did not affect leaf venation pattern and root vascular organization. Auxin polar transport assay indicated that the avb1 mutation did not disrupt the auxin polar transport activity in inflorescence stems. The avb1 mutation also exhibited pleiotropic phenotypes, including curled stems and extra cauline branches. Genetic analysis indicated that the avb1 mutation was monogenic and partially dominant. The avb1 locus was mapped to a region between markers mi69 and ASB2, which is covered by a yeast artificial chromosome clone, CIC9E2, on chromosome 5. Isolation of theavb1 mutant provides a novel means to study the evolutionary mechanisms controlling the arrangement of vascular tissues within the bundle, as well as the mechanisms controlling the arrangement of vascular bundles in the stele.
Nodule-Inducing Activity of Synthetic Sinorhizobium meliloti Nodulation Factors and Related Lipo-Chitooligosaccharides on Alfalfa.Importance of the Acyl Chain Structure1
Authors: Demont-Caulet Nathalie , Maillet Fabienne , Tailler Denis , Jacquinet Jean-Claude , Promé Jean-Claude , Nicolaou Kyriacos C. , Truchet Georges , Beau Jean-Marie , Dénarié Jean 
Published: July 2002

Abstract
Sinorhizobium meliloti nodulation factors (NFs) elicit a number of symbiotic responses in alfalfa (Medicago sativa) roots. Using a semiquantitative nodulation assay, we have shown that chemically synthesized NFs trigger nodule formation in the same range of concentrations (down to 10−10m) as natural NFs. The absence of O-sulfate orO-acetate substitutions resulted in a decrease in morphogenic activity of more than 100-fold and approximately 10-fold, respectively. To address the question of the influence of the structure of the N-acyl chain, we synthesized a series of sulfated tetrameric lipo-chitooligosaccharides (LCOs) having fatty acids of different lengths and with unsaturations either conjugated to the carbonyl group (2E) or located in the middle of the chain (9Z). A nonacylated, sulfated chitin tetramer was unable to elicit nodule formation. Acylation with short (C8) chains rendered the LCO active at 10−7m. The optimal chain length was C16, with the C16-LCO being more than 10-fold more active than the C12- and C18-LCOs. Unsaturations were important, and the diunsaturated 2E,9Z LCO was more active than the monounsaturated LCOs. We discuss different hypotheses for the role of the acyl chain in NF perception.
Cloning and Expression of a Hexose Transporter Gene Expressed during the Ripening of Grape Berry1
Authors: Fillion Laurent , Ageorges Agnès , Picaud Sarah , Coutos-Thévenot Pierre , Lemoine Rémi , Romieu Charles , Delrot Serge 
Published: July 2002

AbstractThe ripening of grape (Vitis vinifera L.) is characterized by massive sugar import into the berries. The events triggering this process and the pathways of assimilate transport are still poorly known. A genomic cloneVvht1 (Vitisvinifera hexose transporter1) and the corresponding cDNA encoding a hexose transporter whose expression is induced during berry ripening have been isolated. Vvht1is expressed mainly in the berries, with a first peak of expression at anthesis, and a second peak about 5 weeks after véraison (a viniculture term for the inception of ripening). Vvht is strictly conserved between two grape cultivars (Pinot Noir and Ugni-Blanc). The organization of the Vvht1 genomic sequence is homologous to that of the Arabidopsis hexose transporter, but differs strongly from that of the Chlorella kessleri hexose transporter genes. The Vvht1 promoter sequence contains several potential regulating cis elements, including ethylene-, abscisic acid-, and sugar-responsive boxes. Comparison of the Vvht1 promoter with the promoter of grape alcohol dehydrogenase, which is expressed at the same time during ripening, also allowed the identification of a 15-bp consensus sequence, which suggests a possible co-regulation of the expression of these genes. The expression of Vvht1 during ripening indicates that sucrose is at least partially cleaved before uptake into the flesh cells.
Cloning and First Functional Characterization of a Plant Cyclic Nucleotide-Gated Cation Channel
Authors: Leng Qiang , Mercier Richard W. , Yao Weizhe , Berkowitz Gerald A. 
Published: July 2002

Abstract
Cyclic nucleotide-gated (cng) non-selective cation channels have been cloned from a number of animal systems. These channels are characterized by direct gating upon cAMP or cGMP binding to the intracellular portion of the channel protein, which leads to an increase in channel conductance. Animal cng channels are involved in signal transduction systems; they translate stimulus-induced changes in cytosolic cyclic nucleotide into altered cell membrane potential and/or cation flux as part of a signal cascade pathway. Putative plant homologs of animal cng channels have been identified. However, functional characterization (i.e. demonstration of cyclic-nucleotide-dependent ion currents) of a plant cng channel has not yet been accomplished. We report the cloning and first functional characterization of a plant member of this family of ion channels. The Arabidopsis cDNA AtCNGC2 encodes a polypeptide with deduced homology to the α-subunit of animal channels, and facilitates cyclic nucleotide-dependent cation currents upon expression in a number of heterologous systems. AtCNGC2 expression in a yeast mutant lacking a low-affinity K+ uptake system complements growth inhibition only when lipophilic cyclic nucleotides are present in the culture medium. Voltage clamp analysis indicates that Xenopus laevis oocytes injected with AtCNGC2 cRNA demonstrate cyclic-nucleotide-dependent, inward-rectifying K+ currents. Human embryonic kidney cells (HEK293) transfected with AtCNGC2 cDNA demonstrate increased permeability to Ca2+ only in the presence of lipophilic cyclic nucleotides. The evidence presented here supports the functional classification of AtCNGC2 as a cyclic-nucleotide-gated cation channel, and presents the first direct evidence (to our knowledge) identifying a plant member of this ion channel family.
Apoplastic pH and Fe3+ Reduction in Intact Sunflower Leaves
Authors: Kosegarten Harald U. , Hoffmann Bernd , Mengel Konrad 
Published: July 2002

AbstractIt has been hypothesized that under NO3 − nutrition a high apoplastic pH in leaves depresses Fe3+ reductase activity and thus the subsequent Fe2+ transport across the plasmalemma, inducing Fe chlorosis. The apoplastic pH in young green leaves of sunflower (Helianthus annuus L.) was measured by fluorescence ratio after xylem sap infiltration. It was shown that NO3 − nutrition significantly increased apoplastic pH at distinct interveinal sites (pH ≥ 6.3) and was confined to about 10% of the whole interveinal leaf apoplast. These apoplastic pH increases presumably derive from NO3 −/proton cotransport and are supposed to be related to growing cells of a young leaf; they were not found in the case of sole NH4 + or NH4NO3 nutrition. Complementary to pH measurements, the formation of Fe2+-ferrozine from Fe3+-citrate was monitored in the xylem apoplast of intact leaves in the presence of buffers at different xylem apoplastic pH by means of image analysis. This analysis revealed that Fe3+reduction increased with decreasing apoplastic pH, with the highest rates at around pH 5.0. In analogy to the monitoring of Fe3+ reduction in the leaf xylem, we suggest that under alkaline nutritional conditions at interveinal microsites of increased apoplastic pH, Fe3+ reduction is depressed, inducing leaf chlorosis. The apoplastic pH in the xylem vessels remained low in the still-green veins of leaves with intercostal chlorosis.
Patterns of Protein Synthesis and Tolerance of Anoxia in Root Tips of Maize Seedlings Acclimated to a Low-Oxygen Environment, and Identification of Proteins by Mass Spectrometry
Authors: Chang William W.P. , Huang Lan , Shen Min , Webster Cecelia , Burlingame Alma L. , Roberts Justin K.M. 
Published: July 2002

Abstract
Tolerance of anoxia in maize root tips is greatly improved when seedlings are pretreated with 2 to 4 h of hypoxia. We describe the patterns of protein synthesis during hypoxic acclimation and anoxia. We quantified the incorporation of [35S]methionine into total protein and 262 individual proteins under different oxygen tensions. Proteins synthesized most rapidly under normoxic conditions continued to account for most of the proteins synthesized during hypoxic acclimation, while the production of a very few proteins was selectively enhanced. When acclimated root tips were placed under anoxia, protein synthesis was depressed and no “new” proteins were detected. We present evidence that protein synthesis during acclimation, but not during subsequent anoxia, is crucial for acclimation. The complex and quantitative changes in protein synthesis during acclimation necessitate identification of large numbers of individual proteins. We show that mass spectrometry can be effectively used to identify plant proteins arrayed by two-dimensional gel electrophoresis. Of the 48 protein spots analyzed, 46 were identified by matching to the protein database. We describe the expression of proteins involved in a wide range of cellular functions, including previously reported anaerobic proteins, and discuss their possible roles in adaptation of plants to low-oxygen stress.
Purification, Enzymatic Characterization, and Nucleotide Sequence of a High-Isoelectric-Point α-Glucosidase from Barley Malt
Authors: Frandsen Torben Peter , Lok Finn , Mirgorodskaya Ekaterina , Roepstorff Peter , Svensson Birte 
Published: July 2002

Abstract
High-isoelectric-point (pI) α-glucosidase was purified 7,300-fold from an extract of barley (Hordeum vulgare) malt by ammonium sulfate fractionation, ion-exchange, and butyl-Sepharose chromatography. The enzyme had high activity toward maltose (k cat = 25 s−1), with an optimum at pH 4.5, and catalyzed the hydrolysis by a retaining mechanism, as shown by nuclear magnetic resonance. Acarbose was a strong inhibitor (K i = 1.5 μm). Molecular recognition revealed that all OH-groups in the non-reducing ring and OH-3 in the reducing ring of maltose formed important hydrogen bonds to the enzyme in the transition state complex. Mass spectrometry of tryptic fragments assigned the 92-kD protein to a barley cDNA (GenBank accession no. U22450) that appears to encode an α-glucosidase. A corresponding sequence (HvAgl97; GenBank accession no. AF118226) was isolated from a genomic phage library using a cDNA fragment from a barley cDNA library. HvAgl97 encodes a putative 96.6-kD protein of 879 amino acids with 93.8% identity to the protein deduced from U22450. The sequence contains two active site motifs of glycoside hydrolase family 31. Three introns of 86 to 4,286 bp interrupt the coding region. The four exons vary from 218 to 1,529 bp. Gene expression analysis showed that transcription reached a maximum 48 h after the start of germination.
A Family of at Least Seven β-Galactosidase Genes Is Expressed during Tomato Fruit Development
Authors: Smith David L. , Gross Kenneth C. 
Published: July 2002

Abstract
During our search for a cDNA encoding β-galactosidase II, a β-galactosidase/exogalactanase (EC 3.2.1.23) present during tomato (Lycopersicon esculentum Mill.) fruit ripening, a family of seven tomato β-galactosidase (TBG) cDNAs was identified. The shared amino acid sequence identity among the seven TBG clones ranged from 33% to 79%. All contained the putative active site-containing consensus sequence pattern G-G-P-[LIVM]-x-Q-x-E-N-E-[FY] belonging to glycosyl hydrolase family 35. Six of the seven single-copy genes were mapped using restriction fragment length polymorphisms of recombinant inbred lines. RNA gel-blot analysis was used to evaluate TBG mRNA levels throughout fruit development, in different fruit tissues, and in various plant tissues. RNA gel-blot analysis was also used to reveal TBG mRNA levels in fruit of the rin, nor, and Nr tomato mutants. The TBG4-encoded protein, known to correspond to β-galactosidase II, was expressed in yeast and exo-galactanase activity was confirmed via a quantified release of galactosyl residues from cell wall fractions containing β(1→4)-d-galactan purified from tomato fruit.