bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation and Characterization of Soluble Boron Complexes in Higher Plants (The Mechanism of Phloem Mobility of Boron)
Authors: Hu H. , Penn S. G. , Lebrilla C. B. , Brown P. H. 
Published: July 2002

Abstract
Boron (B) polyol complexes have been isolated and characterized from the phloem sap of celery (Apium graveolens L.) and the extra-floral nectar of peach (Prunus persica L.). In celery the direct analysis of untreated phloem sap by matrix-assisted laser desorption-Fourier transform mass spectrometry, with verification by high-performance liquid chromagraphy and gas chromatography-mass spectrometry, revealed that B is present in the phloem as the mannitol-B-mannitol complex. Molecular modeling further predicted that this complex is present in the 3,4 3[prime],4[prime] bis-mannitol configuration. In the extrafloral nectar of peach, B was present as a mixture of sorbitol-B-sorbitol, fructose-B-fructose, or sorbitol-B-fructose. To our knowledge, these findings represent the first successful isolation and characterization of soluble B complexes from higher plants and provide a mechanistic explanation for the observed phloem B mobility in these species.
Independent Genetic Control of Maize Starch-Branching Enzymes IIa and IIb (Isolation and Characterization of a Sbe2a cDNA)
Authors: Gao M. , Fisher D. K. , Kim K. N. , Shannon J. C. , Guiltinan M. J. 
Published: July 2002

Abstract
In maize (Zea mays L.) three isoforms of starch-branching enzyme (SBEI, SBEIIa, and SBEIIb) are involved in the synthesis of amylopectin, the branched component of starch. To isolate a cDNA encoding SBEIIa, degenerate oligonucleotides based on domains highly conserved in Sbe2 family members were used to amplify Sbe2-family cDNA from tissues lacking SBIIb activity. The predicted amino acid sequence of a Sbe2a cDNA matches the N-terminal sequence of SBIIa protein purified from maize endosperm. The size of the mature protein deduced from the cDNA also matches that of SBEIIa Features of the predicted protein are most similar to members of the SBEII family; however, it differs from maize SBEIIb in having a 49-amino acid N-terminal extension and a region of substantial sequence divergence. Sbe2a mRNA levels are 10-fold higher in embryonic than in endosperm tissue, and are much lower than Sbe2b in both tissues. Unlike Sbe2b, Sbe2a-hybridizing mRNA accumulates in leaf and other vegetative tissues, consistent with the known distribution of SBEIIa and SBEIIb activities.
Membrane Lipid Unsaturation Modulates Processing of the Photosystem II Reaction-Center Protein D1 at Low Temperatures
Authors: Kanervo E. , Tasaka Y. , Murata N. , Aro E. M. 
Published: July 2002

Abstract
The role of membrane lipid unsaturation in the restoration of photosystem II (PSII) function and in the synthesis of the D1 protein at different temperatures after photoinhibition was studied in wild-type cells and a mutant of Synechocystis sp. PCC 6803 with genetically inactivated desaturase genes. We show that posttranslational carboxyl-terminal processing of the precursor form of the D1 protein is an extremely sensitive reaction in the PSII repair cycle and is readily affected by low temperature. Furthermore, the threshold temperature at which perturbations in D1-protein processing start to emerge is specifically dependent on the extent of thylakoid membrane lipid unsaturation, as indicated by comparison of wild-type cells with the mutant defective in desaturation of 18:1 fatty acids of thylakoid membranes. When the temperature was decreased from 33[deg]C (growth temperature) to 18[deg]C, the inability of the fatty acid mutant to recover from photoinhibition was accompanied by a failure to process the newly synthesized D1 protein, which accumulated in considerable amounts as an unprocessed precursor D1 protein. Precursor D1 integrated into PSII monomer and dimer complexes even at low temperatures, but no activation of oxygen evolution occurred in these complexes in mutant cells defective in fatty acid unsaturation.
Construction of a Lotus japonicus Late Nodulin Expressed Sequence Tag Library and Identification of Novel Nodule-Specific Genes
Authors: Szczyglowski K. , Hamburger D. , Kapranov P. , de Bruijn F. J. 
Published: July 2002

Abstract
A range of novel expressed sequence tags (ESTs) associated with late developmental events during nodule organogenesis in the legume Lotus japonicus were identified using mRNA differential display; 110 differentially displayed polymerase chain reaction products were cloned and analyzed. Of 88 unique cDNAs obtained, 22 shared significant homology to DNA/protein sequences in the respective databases. This group comprises, among others, a nodule-specific homolog of protein phosphatase 2C, a peptide transporter protein, and a nodule-specific form of cytochrome P450. RNA gel-blot analysis of 16 differentially displayed ESTs confirmed their nodule-specific expression pattern. The kinetics of mRNA accumulation of the majority of the ESTs analyzed were found to resemble the expression pattern observed for the L. japonicus leghemoglobin gene. These results indicate that the newly isolated molecular markers correspond to genes induced during late developmental stages of L. japonicus nodule organogenesis and provide important, novel tools for the study of nodulation.
Differential Gene Expression in Ripening Banana Fruit
Authors: Clendennen S. K. , May G. D. 
Published: July 2002

Abstract
During banana (Musa acuminata L.) fruit ripening ethylene production triggers a developmental cascade that is accompanied by a massive conversion of starch to sugars, an associated burst of respiratory activity, and an increase in protein synthesis. Differential screening of cDNA libraries representing banana pulp at ripening stages 1 and 3 has led to the isolation of 11 nonredundant groups of differentially expressed mRNAs. Identification of these transcripts by partial sequence analysis indicates that two of the mRNAs encode proteins involved in carbohydrate metabolism, whereas others encode proteins thought to be associated with pathogenesis, senescence, or stress responses in plants. Their relative abundance in the pulp and tissue-specific distribution in greenhouse-grown banana plants were determined by northern-blot analyses. The relative abundance of transcripts encoding starch synthase, granule-bound starch synthase, chitinase, lectin, and a type-2 metallothionein decreased in pulp during ripening. Transcripts encoding endochitinase, β-1,3-glucanase, a thaumatin-like protein, ascorbate peroxidase, metallothionein, and a putative senescence-related protein increased early in ripening. The elucidation of the molecular events associated with banana ripening will facilitate a better understanding and control of these processes, and will allow us to attain our long-term goal of producing candidate oral vaccines in transgenic banana plants.
Accumulation of Salicylic Acid and 4-Hydroxybenzoic Acid in Phloem Fluids of Cucumber during Systemic Acquired Resistance Is Preceded by a Transient Increase in Phenylalanine Ammonia-Lyase Activity in Petioles and Stems1
Authors: Smith-Becker Jennifer , Marois Eric , Huguet Elisabeth J. , Midland Sharon L. , Sims James J. , Keen Noel T. 
Published: July 2002

AbstractCucumber (Cucumis sativa) leaves infiltrated withPseudomonas syringae pv. syringae cells produced a mobile signal for systemic acquired resistance between 3 and 6 h after inoculation. The production of a mobile signal by inoculated leaves was followed by a transient increase in phenylalanine ammonia-lyase (PAL) activity in the petioles of inoculated leaves and in stems above inoculated leaves; with peaks in activity at 9 and 12 h, respectively, after inoculation. In contrast, PAL activity in inoculated leaves continued to rise slowly for at least 18 h. No increases in PAL activity were detected in healthy leaves of inoculated plants. Two benzoic acid derivatives, salicylic acid (SA) and 4-hydroxybenzoic acid (4HBA), began to accumulate in phloem fluids at about the time PAL activity began to increase, reaching maximum concentrations 15 h after inoculation. The accumulation of SA and 4HBA in phloem fluids was unaffected by the removal of all leaves 6 h after inoculation, and seedlings excised from roots prior to inoculation still accumulated high levels of SA and 4HBA. These results suggest that SA and 4HBA are synthesized de novo in stems and petioles in response to a mobile signal from the inoculated leaf.
Effects of Xylem pH on Transpiration from Wild-Type andflaccaTomato Leaves1
Authors: Wilkinson Sally , Corlett Janet E. , Oger Ludovic , Davies William J. 
Published: July 2002

AbstractThe pH of xylem sap from tomato (Lycopersicon esculentum) plants increased from pH 5.0 to 8.0 as the soil dried. Detached wild-type but notflacca leaves exhibited reduced transpiration rates when the artificial xylem sap (AS) pH was increased. When a well-watered concentration of abscisic acid (0.03 μm) was provided in the AS, the wild-type transpirational response to pH was restored toflacca leaves. Transpiration from flaccabut not from wild-type leaves actually increased in some cases when the pH of the AS was increased from 6.75 to 7.75, demonstrating an absolute requirement for abscisic acid in preventing stomatal opening and excessive water loss from plants growing in many different environments.
Does a Low Nitrogen Supply Necessarily Lead to Acclimation of Photosynthesis to Elevated CO2?
Authors: Farage Peter K. , McKee Ian F. , Long Steve P. 
Published: July 2002

Abstract
Long-term exposure of plants to elevated partial pressures of CO2 (pCO2) often depresses photosynthetic capacity. The mechanistic basis for this photosynthetic acclimation may involve accumulation of carbohydrate and may be promoted by nutrient limitation. However, our current knowledge is inadequate for making reliable predictions concerning the onset and extent of acclimation. Many studies have sought to investigate the effects of N supply but the methodologies used generally do not allow separation of the direct effects of limited N availability from those caused by a N dilution effect due to accelerated growth at elevated pCO2. To dissociate these interactions, wheat (Triticum aestivum L.) was grown hydroponically and N was added in direct proportion to plant growth. Photosynthesis did not acclimate to elevated pCO2 even when growth was restricted by a low-N relative addition rate. Ribulose-1, 5-bisphosphate carboxylase/oxygenase activity and quantity were maintained, there was no evidence for triose phosphate limitation of photosynthesis, and tissue N content remained within the range recorded for healthy wheat plants. In contrast, wheat grown in sand culture with N supplied at a fixed concentration suffered photosynthetic acclimation at elevated pCO2 in a low-N treatment. This was accompanied by a significant reduction in the quantity of active ribulose-1, 5-bisphosphate carboxylase/oxygenase and leaf N content.
Purification and Characterization of a NADPH-Dependent Aldehyde Reductase from Mung Bean That Detoxifies Eutypine, a Toxin from Eutypa lata1
Authors: Colrat Ségolène , Latché Alain , Guis Monique , Pech Jean-Claude , Bouzayen Mondher , Fallot Jean , Roustan Jean-Paul 
Published: July 2002

Abstract
Eutypine (4-hydroxy-3-[3-methyl-3-butene-1-ynyl] benzaldehyde) is a toxin produced by Eutypa lata, the causal agent of eutypa dieback in the grapevine (Vitis vinifera). Eutypine is enzymatically converted by numerous plant tissues into eutypinol (4-hydroxy-3-[3-methyl-3-butene-1-ynyl] benzyl alcohol), a metabolite that is nontoxic to grapevine. We report a four-step procedure for the purification to apparent electrophoretic homogeneity of a eutypine-reducing enzyme (ERE) from etiolated mung bean (Vigna radiata) hypocotyls. The purified protein is a monomer of 36 kD, uses NADPH as a cofactor, and exhibits aKm value of 6.3 μm for eutypine and a high affinity for 3- and 4-nitro-benzaldehyde. The enzyme failed to catalyze the reverse reaction using eutypinol as a substrate. ERE detoxifies eutypine efficiently over a pH range from 6.2 to 7.5. These data strongly suggest that ERE is an aldehyde reductase that could probably be classified into the aldo-keto reductase superfamily. We discuss the possible role of this enzyme in eutypine detoxification.
Molecular Cloning and Characterization of Apricot Fruit Polyphenol Oxidase
Authors: Chevalier Tony , de Rigal David , Mbéguié-A-Mbéguié Didier , Gauillard Frédéric , Richard-Forget Florence , Fils-Lycaon Bernard R. 
Published: July 2002

Abstract
A reverse transcriptase-polymerase chain reaction experiment was done to synthesize a homologous polyphenol oxidase (PPO) probe from apricot (Prunus armeniaca var Bergeron) fruit. This probe was further used to isolate a full-length PPO cDNA, PA-PPO (accession no.AF020786), from an immature-green fruit cDNA library.PA-PPO is 2070 bp long and contains a single open reading frame encoding a PPO precursor peptide of 597 amino acids with a calculated molecular mass of 67.1 kD and an isoelectric point of 6.84. The mature protein has a predicted molecular mass of 56.2 kD and an isoelectric point of 5.84. PA-PPO belongs to a multigene family. The gene is highly expressed in young, immature-green fruit and is turned off early in the ripening process. The ratio of PPO protein to total proteins per fruit apparently remains stable regardless of the stage of development, whereas PPO specific activity peaks at the breaker stage. These results suggest that, in addition to a transcriptional control of PPO expression, other regulation factors such as translational and posttranslational controls also occur.
Phloem Transport of d,l-Glufosinate and Acetyl-l-Glufosinate in Glufosinate-Resistant and -Susceptible Brassica napus
Authors: Beriault Jennifer N. , Horsman Geoff P. , Devine Malcolm D. 
Published: July 2002

Abstract
Phloem transport of d,l-[14C]glufosinate,d-[14C]glufosinate, and acetyl-l-[14C]glufosinate was examined in the susceptible Brassica napus cv Excel and a glufosinate-resistant genotype (HCN27) derived by transformation of cv Excel with the phosphinothricin-N-acetyltransferase (pat) gene. Considerably more 14C was exported from an expanded leaf in HCN27 than in cv Excel following application of d,l-[14C]glufosinate (25% versus 6.3% of applied, respectively, 72 h after treatment). The inactive isomer, d-glufosinate, was much more phloem mobile in cv Excel than racemicd,l-glufosinate. Foliar or root supplementation with 1 mm glutamine increasedd,l-[14C]glufosinate translocation in cv Excel but only transiently, suggesting that glutamine depletion is not the major cause of the limited phloem transport. Acetyl-l-[14C]glufosinate (applied as such or derived from l-glufosinate in pattransformants) was translocated extensively in the phloem of both genotypes. Acetyl-l-[14C]glufosinate was readily transported into the floral buds and flowers, and accumulated in the anthers in both genotypes. These results suggest that phloem transport of d,l-glufosinate is limited by rapid physiological effects of the l-isomer in source leaf tissue. The accumulation of acetyl-l-glufosinate in the anthers indicates that it is sufficiently phloem mobile to act as a foliar-applied chemical inducer of male sterility in plants expressing a deacetylase gene in the tapetum, generating toxic concentrations ofl-glufosinate in pollen-producing tissues.
Auxin Biosynthesis in Maize Kernels
Authors: Glawischnig Erich , Tomas Adriana , Eisenreich Wolfgang , Spiteller Peter , Bacher Adelbert , Gierl Alfons 
Published: July 2002

Abstract
Auxin biosynthesis was analyzed in a maize (Zea mays) kernel culture system in which the seeds develop under physiological conditions similar to the in vivo situation. This system was modified for precursor feeding experiments. Tryptophan (Trp) is efficiently incorporated into indole-3-acetic acid (IAA) with retention of the 3,3′ bond. Conversion of Trp to IAA is not competed by indole. Labeling with the general precursors [U-13C6]glucose and [1,2-13C2]acetate followed by retrobiosynthetic analysis strongly suggest that Trp-dependent IAA synthesis is the predominant route for auxin biosynthesis in the maize kernel. The synthesis of IAA from indole glycerol phosphate and IAA formation via condensation of indole with an acetyl-coenzyme A or phosphoenolpyruvate derived metabolite can be excluded.
β-Cyanoalanine Synthase Is a Mitochondrial Cysteine Synthase-Like Protein in Spinach and Arabidopsis
Authors: Hatzfeld Yves , Maruyama Akiko , Schmidt Ahlert , Noji Masaaki , Ishizawa Kimiharu , Saito Kazuki 
Published: July 2002

Abstract
β-Cyano-alanine synthase (CAS; EC 4.4.1.9) plays an important role in cyanide metabolism in plants. Although the enzymatic activity of β-cyano-Ala synthase has been detected in a variety of plants, no cDNA or gene has been identified so far. We hypothesized that the mitochondrial cysteine synthase (CS; EC 4.2.99.8) isoform, Bsas3, could actually be identical to CAS in spinach (Spinacia oleracea) and Arabidopsis. An Arabidopsis expressed sequence tag database was searched for putative Bsas3homologs and four new CS-like isoforms, ARAth;Bsas1;1,ARAth;Bsas3;1, ARAth;Bsas4;1, andARAth;Bsas4;2, were identified in the process. ARAth;Bsas3;1 protein was homologous to the mitochondrial SPIol;Bsas3;1 isoform from spinach, whereas ARAth;Bsas4;1 and ARAth;Bsas4;2 proteins defined a new class within the CS-like proteins family. In contrast to spinach SPIol;Bsas1;1 and SPIol;Bsas2;1 recombinant proteins, spinach SPIol;Bsas3;1 and Arabidopsis ARAth;Bsas3;1 recombinant proteins exhibited preferred substrate specificities for the CAS reaction rather than for the CS reaction, which identified these Bsas3 isoforms as CAS. Immunoblot studies supported this conclusion. This is the first report of the identification of CAS synthase-encoding cDNAs in a living organism. A new nomenclature for CS-like proteins in plants is also proposed.
RSF1, an Arabidopsis Locus Implicated in Phytochrome A Signaling
Authors: Fankhauser Christian , Chory Joanne 
Published: July 2002

AbstractIn Arabidopsis, phytochrome A (phyA) is the major photoreceptor both for high irradiance responses to far-red light and broad spectrum very low fluence responses, but little is known of its signaling pathway(s). rsf1 was isolated as a recessive mutant with reduced sensitivity to far-red inhibition of hypocotyl elongation. At the seedling stage rsf1 mutants are affected, to various degrees, in all described phyA-mediated responses. However, in adultrsf1 plants, the photoperiodic flowering response is normal. The rsf1 mutant has wild-type levels of phyA suggesting that RSF1 is required for phyA signaling rather than phyA stability or biosynthesis. RSF1 thus appears to be a major phyA signaling component in seedlings, but not in adult, Arabidopsis plants.
Cloning and Expression Pattern of a Gene Encoding an α-Xylosidase Active against Xyloglucan Oligosaccharides from Arabidopsis
Authors: Sampedro Javier , Sieiro Carmen , Revilla Gloria , González-Villa Tomás , Zarra Ignacio 
Published: July 2002

Abstract
An α-xylosidase active against xyloglucan oligosaccharides was purified from cabbage (Brassica oleracea var. capitata) leaves. Two peptide sequences were obtained from this protein, the N-terminal and an internal one, and these were used to identify an Arabidopsis gene coding for an α-xylosidase that we propose to callAtXYL1. It has been mapped to a region of chromosome I between markers at 100.44 and 107.48 cM. AtXYL1comprised three exons and encoded a peptide that was 915 amino acids long, with a potential signal peptide of 22 amino acids and eight possible N-glycosylation sites. The protein encoded byAtXYL1 showed the signature regions of family 31 glycosyl hydrolases, which comprises not only α-xylosidases, but also α-glucosidases. The α-xylosidase activity is present in apoplastic extractions from Arabidopsis seedlings, as suggested by the deduced signal peptide. The first eight leaves from Arabidopsis plants were harvested to analyze α-xylosidase activity and AtXYL1expression levels. Both increased from older to younger leaves, where xyloglucan turnover is expected to be higher. When this gene was introduced in a suitable expression vector and used to transformSaccharomyces cerevisiae, significantly higher α-xylosidase activity was detected in the yeast cells. α-Glucosidase activity was also increased in the transformed cells, although to a lesser extent. These results show thatAtXYL1 encodes for an apoplastic α-xylosidase active against xyloglucan oligosaccharides that probably also has activity againstp-nitrophenyl-α-d-glucoside.
Multidimensional molecular replacement
Authors: Glykos Nicholas M. , Kokkinidis Michael 
Published: July 2002

A method is described which attempts to simultaneously and independently determine the positional and orientational parameters of all molecules present in the asymmetric unit of a target crystal structure. This is achieved through a reverse Monte Carlo optimization of a suitable statistic (such as the R factor or the linear correlation coefficient between the observed and calculated amplitudes of the structure factors) in the 6n-dimensional space defined by the rotational and translational parameters of the n search models. Results from the application of this stochastic method – obtained with a space-group-general computer program which has been developed for this purpose – indicate that with present-day computing capabilities the method may be applied successfully to molecular-replacement problems for which the target crystal structure contains up to three molecules per asymmetric unit. It is also shown that the method may be useful in cases where the assumption of topological segregation of the self- and cross-vectors in the Patterson function is violated (as may happen, for example, in closely packed crystal structures).
Structural basis of pheromone binding to mouse major urinary protein (MUP‐I)
Authors: Timm David E. , Baker L.J. , Mueller Heather , Zidek Lukas , Novotny Milos V. 
Published: July 2002

AbstractThe mouse major urinary proteins are pheromone‐binding proteins that function as carriers of volatile effectors of mouse physiology and behavior. Crystal structures of recombinant mouse major urinary protein‐I (MUP‐I) complexed with the synthetic pheromones, 2‐sec‐butyl‐4,5‐dihydrothiazole and 6‐hydroxy‐6‐methyl‐3‐heptanone, have been determined at high resolution. The purification of MUP‐I from mouse liver and a high‐resolution structure of the natural isolate are also reported. These results show the binding of 6‐hydroxy‐6‐methyl‐3‐heptanone to MUP‐I, unambiguously define ligand orientations for two pheromones within the MUP‐I binding site, and suggest how different chemical classes of pheromones can be accommodated within the MUP‐I β‐barrel.