bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photosystem II Cyclic Heterogeneity and Photoactivation in the Diazotrophic, Unicellular CyanobacteriumCyanotheceSpecies ATCC 511421
Authors: Meunier Pascal C. , Colón-López Milagros S. , Sherman Louis A. 
Published: July 2002

Abstract
The unicellular, diazotrophic cyanobacterium Cyanothece sp. ATCC 51142 demonstrated important modifications to photosystem II (PSII) centers when grown under light/dark N2-fixing conditions. The properties of PSII were studied throughout the diurnal cycle using O2-flash-yield and pulse-amplitude-modulated fluorescence techniques. Nonphotochemical quenching (qN) of PSII increased during N2 fixation and persisted after treatments known to induce transitions to state 1. TheqN was high in cells grown in the dark, and then disappeared progressively during the first 4 h of light growth. The photoactivation probability, ε, demonstrated interesting oscillations, with peaks near 3 h of darkness and 4 and 10 h of light. Experiments and calculations of the S-state distribution indicated that PSII displays a high level of heterogeneity, especially as the cells prepare for N2 fixation. We conclude that the oxidizing side of PSII is strongly affected during the period before and after the peak of nitrogenase activity; changes include a lowered capacity for O2 evolution, altered dark stability of PSII centers, and substantial changes in qN.
Polygalacturonase-Mediated Solubilization and Depolymerization of Pectic Polymers in Tomato Fruit Cell Walls1
Authors: Chun Jong-Pil , Huber Donald J. 
Published: July 2002

AbstractThe hydrolysis of cell wall pectins by tomato (Lycopersicon esculentum) polygalacturonase (PG) in vitro is more extensive than the degradation affecting these polymers during ripening. We examined the hydrolysis of polygalacturonic acid and cell walls by PG isozyme 2 (PG2) under conditions widely adopted in the literature (pH 4.5 and containing Na+) and under conditions approximating the apoplastic environment of tomato fruit (pH 6.0 and K+ as the predominate cation). The pH optima for PG2 in the presence of K+ were 1.5 and 0.5 units higher for the hydrolysis of polygalacturonic acid and cell walls, respectively, compared with activity in the presence of Na+. Increasing K+concentration stimulated pectin solubilization at pH 4.5 but had little influence at pH 6.0. Pectin depolymerization by PG2 was extensive at pH values from 4.0 to 5.0 and was further enhanced at high K+levels. Oligomers were abundant products in in vitro reactions at pH 4.0 to 5.0, decreased sharply at pH 5.5, and were negligible at pH 6.0. EDTA stimulated PG-mediated pectin solubilization at pH 6.0 but did not promote oligomer production. Ca2+ suppressed PG-mediated pectin release at pH 4.5 yet had minimal influence on the proportional recovery of oligomers. Extensive pectin breakdown in processed tomato might be explained in part by cation- and low-pH-induced stimulation of PG and other wall-associated enzymes.
Comparison of Binding Properties and Early Biological Effects of Elicitins in Tobacco Cells
Authors: Bourque Stéphane , Ponchet Michel , Binet Marie-Noëlle , Ricci Pierre , Pugin Alain , Lebrun-Garcia Angela 
Published: July 2002

Abstract
Elicitins are a family of small proteins secreted by Phytophthora species that have a high degree of homology and elicit defense reactions in tobacco (Nicotiana tabacum). They display acidic or basic characteristics, the acidic elicitins being less efficient in inducing plant necrosis. In this study we compared the binding properties of four elicitins (two basic and two acidic) and early-induced signal transduction events (Ca2+ influx, extracellular medium alkalinization, and active oxygen species production). The affinity for tobacco plasma membrane-binding sites and the number of binding sites were similar for all four elicitins. Furthermore, elicitins compete with one another for binding sites, suggesting that they interact with the same receptor. The four elicitins induced Ca2+ influx, extracellular medium alkalinization, and the production of active oxygen species in tobacco cell suspensions, but the intensity and kinetics of these effects were different from one elicitin to another. As a general observation the concentrations that induce similar levels of biological activities were lower for basic elicitins (with the exception of cinnamomin-induced Ca2+ uptake). The qualitative similarity of early events induced by elicitins indicates a common transduction scheme, whereas fine signal transduction tuning is different in each elicitin.
Overexpression of Arabidopsis Phytochrome B Inhibits Phytochrome A Function in the Presence of Sucrose1
Authors: Short Timothy W. 
Published: July 2002

Abstract
Overexpression of phytochrome B (phyB) in Arabidopsis has previously been demonstrated to result in dominant negative interference of phytochrome A (phyA)-mediated hypocotyl growth inhibition in far-red (FR) light. This phenomenon has been examined further in this study and has been found to be dependent on the FR fluence rate and on the availability of metabolizable sugars in the growth medium. Poorly metabolized sugars capable of activating the putative hexokinase sensory function were not effective in eliciting the phytochrome interference response. Overexpressed phyB lacking the chromophore-binding site was also effective at inhibiting the phyA response, especially at higher fluence rates of FR. Overexpressed phyB produces the dominant negative phenotype without any apparent effect on phyA abundance or degradation. It is possible that phyA and phyB interact with a common reaction partner but that either the energy state of the cell or a separate sugar-signaling mechanism modulates the phytochrome-signaling interactions.
Transgenic Overexpression of the Transcription FactorAlfin1Enhances Expression of the Endogenous MsPRP2Gene in Alfalfa and Improves Salinity Tolerance of the Plants1
Authors: Winicov Ilga , Bastola Dhundy R. 
Published: July 2002

Abstract
Alfin1cDNA encodes a putative transcription factor associated with NaCl tolerance in alfalfa (Medicago sativa L.). The recombinant protein binds DNA in a sequence-specific manner, including promoter fragments of the NaCl-inducible gene MsPRP2. Alfin1 function was tested in transgenic alfalfa under the control of the 35S promoter in the sense and antisense orientations with the endogenous MsPRP2 as a reporter gene. Calli overexpressing Alfin1 were more resistant to growth inhibition by 171 mm NaCl than vector-transformed controls, whereas calli expressing Alfin1 in the antisense orientation were more sensitive to NaCl inhibition. Transgenic plants overexpressing Alfin1 in the sense orientation grew well. In contrast, the antisense transgenic plants grew poorly in soil, demonstrating that Alfin1 expression is essential for normal plant development. Transgenic calli and plant roots overexpressing Alfin1 showed enhanced levels of endogenous MsPRP2 mRNA accumulation. However,MsPRP2 mRNA accumulation was also regulated in a tissue-specific manner, as shown in leaves of transgenic plants overexpressing Alfin1. These results suggest that Alfin1 acts as a transcriptional regulator in plants and regulatesMsPRP2 expression in alfalfa.Alfin1 overexpressing transgenic plants showed salinity tolerance comparable to one of our NaCl-tolerant plants, indicating that Alfin1 also functions in gene regulation in NaCl tolerance.
Periplasmic Carbonic Anhydrase Structural Gene (Cah1) Mutant in Chlamydomonas reinhardtii1
Authors: Van Kyujung , Spalding Martin H. 
Published: July 2002

Abstract
To survive in various conditions of CO2 availability, Chlamydomonas reinhardtiishows adaptive changes, such as induction of a CO2-concentrating mechanism, changes in cell organization, and induction of several genes, including a periplasmic carbonic anhydrase (pCA1) encoded by Cah1. Among a collection of insertionally generated mutants, a mutant has been isolated that showed no pCA1 protein and no Cah1 mRNA. This mutant strain, designated cah1-1, has been confirmed to have a disruption in the Cah1 gene caused by a singleArg7 insert. The most interesting feature ofcah1-1 is its lack of any significant growth phenotype. There is no major difference in growth or photosynthesis between the wild type andcah1-1 over a pH range from 5.0 to 9.0 even though this mutant apparently lacks Cah1 expression in air. Although the presence of pCA1 apparently gives some minor benefit at very low CO2 concentrations, the characteristics of this Cah1 null mutant demonstrate that pCA1 is not essential for function of the CO2-concentrating mechanism or for growth of C. reinhardtii at limiting CO2 concentrations.
Exposure to Low Irradiances Favors the Synthesis of 9-cis β,β-Carotene in Dunaliella salina (Teod.)
Authors: Orset Sandra Charlotte , Young Andrew John 
Published: July 2002

Abstract
We examined the effect of irradiance on the synthesis of β-carotene and its isomers by Dunaliella salina. Growth irradiance had a marked effect both on growth of the alga (which was suppressed at both low and high irradiances) and on the accumulation of β-carotene. The accumulation of β-carotene but not α-carotene was closely linked to an increase in irradiance. Growth at low irradiances (20–50 μmol m−2s−1) promoted a high ratio of 9-cis to all-trans β-carotene (&gt;2:1), while exposure to high irradiances (200–1,250 μmol m−2 s−1) resulted in a large reduction in this ratio (to &lt;0.45:1). A similar pattern was seen for the geometric isomers of α-carotene, with exposure to low irradiance favoring the accumulation of the 9-cis form. The carotenoid biosynthesis inhibitors 4-chloro-5(methylamino)-2-(α-α-α-trifluoro-m-tolyl)-3-(sH)-pyridazinone and 2-(4-chlorophenylthio)triethylamine caused the accumulation of the precursors phytoene and lycopene, respectively, in D. salina. High-performance liquid chromatography and infrared analysis showed that phytoene adopted the 15-cis and all-trans forms (as in higher plants), and that lycopene primarily adopted the all-trans form. This indicates that isomerization of β-carotene takes place during or after cyclization.
Accumulation ofENOD2-Like Transcripts in Non-Nodulating Woody Papilionoid Legumes
Authors: Foster Carol M. , Horner Harry T. , Graves William R. 
Published: July 2002

AbstractJapanese pagodatree (Styphnolobium japonicum [L.] Schott) and American yellowwood (Cladrastis kentukeaDum.-Cours.) Rudd are the first woody, non-nodulating papilionoid legumes shown to possess putative early nodulin 2 (ENOD2) genes. ENOD2 cDNAs from Japanese pagodatree (807 bp) and American yellowwood (735 bp) have 75% to 79% sequence identity to ENOD2 sequences and encode deduced proteins that possess conserved ENOD2 pentapeptides (PPHEK and PPEYQ). Lower percentages of glucose and higher percentages of histidine and valine suggest that SjENOD2 andCkENOD2 are different from other ENOD2s. Hybridization analyses indicate the clones representENOD2 gene families of two to four genes in Japanese pagodatree and American yellowwood genomes, andENOD2-like transcripts were detected in stems and flowers, as well as roots. Only roots of control species that nodulate,Maackia amurensis Rupr. & Maxim. and alfalfa (Medicago sativa), produced pseudonodules after treatment with zeatin or 2,3,5-triiodobenzoic acid, an auxin transport inhibitor. Accumulation of MaENOD2 transcripts was enhanced during the first 10 d of treatment, but 2,3,5-triiodobenzoic acid and zeatin enhanced transcript accumulation after 30 d in roots of Japanese pagodatree and American yellowwood. Characteristics that distinguish ENOD2 gene families in basal, non-nodulating woody legumes from otherENOD2 genes may provide new information about the function of these genes during symbiotic and non-symbiotic organ development.
Negative Interference of Endogenous Phytochrome B with Phytochrome A Function in Arabidopsis
Authors: Hennig Lars , Poppe Christoph , Sweere Uta , Martin Annette , Schäfer Eberhard 
Published: July 2002

AbstractTo study negative interactions between phytochromes, phytochrome B (phyB) overexpressor lines, the mutants phyA-201,phyB-4, phyB-5, phyD-1,phyA-201 phyB-5, phyA-201 phyD-1, andphyB-5 phyD-1 of Arabidopsis were used. Endogenous phyB, but not phytochrome D (phyD), partly suppressed phytochrome A (phyA)-dependent inhibition of hypocotyl elongation in far-red light (FR). Dichromatic irradiation demonstrated that the negative effect of phyB was largely independent of the photoequilibrium, i.e. far-red light absorbing form of phytochrome formation. Moreover,phyB-4, a mutant impaired in signal transduction, did not show a loss of inhibition of phyA by phyB. Overexpression of phyB, conversely, resulted in an enhanced inhibition of phyA function, even in the absence of supplementary carbohydrates. However, overexpression of a mutated phyB, which cannot incorporate the chromophore, had no detectable effect on phyA action. In addition to seedling growth, accumulation of anthocyanins in FR, another manifestation of the high irradiance response, was strongly influenced by phyB holoprotein. Induction of seed germination by FR, a very low fluence response, was suppressed by both endogenous phyB and phyD. In conclusion, we show that both classical response modes of phyA, high irradiance response, and very low fluence response are subject to an inhibitory action of phyB-like phytochromes. Possible mechanisms of the negative interference are discussed.
Differential Regulation of a Family of Apyrase Genes fromMedicago truncatula
Authors: Cohn Jonathan R. , Uhm Taesik , Ramu Senthil , Nam Yong-Woo , Kim Dong-Jin , Penmetsa R. Varma , Wood Todd C. , Denny Roxanne L. , Young Nevin D. , Cook Douglas R. , Stacey Gary 
Published: July 2002

Abstract
Four putative apyrase genes were identified from the model legumeMedicago truncatula. Two of the genes identified fromM. truncatula (Mtapy1 and Mtapy4) are expressed in roots and are inducible within 3 h after inoculation with Sinorhizobium meliloti. The level of mRNA expression of the other two putative apyrases, Mtapy2and Mtapy3, was unaffected by rhizobial inoculation. Screening of a bacterial artificial chromosome library of M. truncatula genomic DNA showed that Mtapy1,Mtapy3, and Mtapy4 are present on a single bacterial artificial chromosome clone. This apyrase cluster was mapped to linkage group seven. A syntenic region on soybean linkage group J was found to contain at least two apyrase genes. Screening of nodulation deficient mutants of M. truncatula revealed that two such mutants do not express apyrases to any detectable level. The data suggest a role for apyrases early in the nodulation response before the involvement of root cortical cell division leading to the nodule structure.
shygrl1Is a Mutant Affected in Multiple Aspects of Photomorphogenesis
Authors: Santiago-Ong May , Green Rachel M. , Tingay Sonia , Brusslan Judy A. , Tobin Elaine M. 
Published: July 2002

AbstractWe have used a counter-selection strategy based on aberrant phytochrome regulation of an Lhcb gene to isolate an Arabidopsis mutant designated shygrl1(shg1). shg1 seedlings have reduced phytochrome-mediated induction of the Lhcb gene family, but normal phytochrome-mediated induction of several other genes, including the rbcS1a gene. Additional phenotypes observed in shg1 plants include reduced chlorophyll in leaves and additional photomorphogenic abnormalities when the seedlings are grown on medium containing sucrose. Mutations in the TATA-proximal region of the Lhcb1*3 promoter that are known to be important for phytochrome regulation affected reporter gene expression in a manner similar to the shg1 mutation. Our results are consistent with the possibility that the mutation either leads to defective chloroplast development or to aberrant phytochrome regulation. They also add to the evidence of complex interactions between light- and sucrose-regulated pathways.
Cytoplasmic pH Dynamics in Maize Pulvinal Cells Induced by Gravity Vector Changes,
Authors: Johannes Eva , Collings David A. , Rink Jochen C. , Allen Nina Strömgren 
Published: July 2002

Abstract
In maize (Zea mays) and other grasses, changes in orientation of stems are perceived by pulvinal tissue, which responds to the stimulus by differential growth resulting in upward bending of the stem. The amyloplast-containing bundle sheath cells are the sites of gravity perception, although the initial steps of gravity perception and transmission remain unclear. In columella cells of Arabidopsis roots, we previously found that cytoplasmic pH (pHc) is a mediator in early gravitropic signaling (A.C. Scott, N.S. Allen [1999] Plant Physiol 121: 1291–1298). The question arises whether pHc has a more general role in signaling gravity vector changes. Using confocal ratiometric imaging and the fluorescent pH indicator carboxy seminaphtorhodafluor acetoxymethyl ester acetate, we measured pHc in the cells composing the maize pulvinus. When stem slices were gravistimulated and imaged on a horizontally mounted confocal microscope, pHc changes were only apparent within the bundle sheath cells, and not in the parenchyma cells. After turning, cytoplasmic acidification was observed at the sides of the cells, whereas the cytoplasm at the base of the cells where plastids slowly accumulated became more basic. These changes were most apparent in cells exhibiting net amyloplast sedimentation. Parenchyma cells and isolated bundle sheath cells did not show any gravity-induced pHc changes although all cell types responded to external stimuli in the predicted way: Propionic acid and auxin treatments induced acidification, whereas raising the external pH caused alkalinization. The results suggest that pHc has an important role in the early signaling pathways of maize stem gravitropism.
The Properties of the Chlorophyll a/b-Binding Proteins Lhca2 and Lhca3 Studied in Vivo Using Antisense Inhibition
Authors: Ganeteg Ulrika , Strand Åsa , Gustafsson Petter , Jansson Stefan 
Published: July 2002

Abstract
The specific functions of the light-harvesting proteins Lhca2 and Lhca3 were studied in Arabidopsis ecotype Colombia antisense plants in which the proteins were individually repressed. The antisense effect was specific in each plant, but levels of Lhca proteins other than the targeted products were also affected. The contents of Lhca1 and Lhca4 were unaffected, but Lhca3 (in Lhca2-repressed plants) was almost completely depleted, and Lhca2 decreased to about 30% of wild-type levels in Lhca3-repressed plants. This suggests that the Lhca2 and Lhca3 proteins are in physical contact with each other and that they require each other for stability. Photosystem I fluorescence at 730 nm is thought to emanate from pigments bound to Lhca1 and Lhca4. However, fluorescence emission and excitation spectra suggest that Lhca2 and Lhca3, which fluoresce in vitro at 680 nm, also could contribute to far-red fluorescence in vivo. Spectral forms with absorption maxima at 695 and 715 nm, apparently with emission maxima at 702 and 735 nm, respectively, might be associated with Lhca2 and Lhca3.
Effect of pH and salt bridges on structural assembly: Molecular structures of the monomer and intertwined dimer of the Eps8 SH3 domain
Authors: Kishan K.V. Radha , Newcomer Marcia E. , Rhodes Thomas H. , Guilliot Stephen D. 
Published: July 2002

AbstractThe SH3 domain of Eps8 was previously found to form an intertwined, domain‐swapped dimer. We report here a monomeric structure of the EPS8 SH3 domain obtained from crystals grown at low pH, as well as an improved domain‐swapped dimer structure at 1.8 Å resolution. In the domain‐swapped dimer the asymmetric unit contains two “hybrid‐monomers.” In the low pH form there are two independently folded SH3 molecules per asymmetric unit. The formation of intermolecular salt bridges is thought to be the reason for the formation of the dimer. On the basis of the monomer SH3 structure, it is argued that Eps8 SH3 should, in principle, bind to peptides containing a PxxP motif. Recently it was reported that Eps8 SH3 binds to a peptide with a PxxDY motif. Because the “SH3 fold” is conserved, alternate binding sites may be possible for the PxxDY motif to bind. The strand exchange or domain swap occurs at the n‐src loops because the n‐src loops are flexible. The thermal b‐factors also indicate the flexible nature of n‐src loops and a possible handle for domain swap initiation. Despite the loop swapping, the typical SH3 fold in both forms is conserved structurally. The interface of the acidic form of SH3 is stabilized by a tetragonal network of water molecules above hydrophobic residues. The intertwined dimer interface is stabilized by hydrophobic and aromatic stacking interactions in the core and by hydrophilic interactions on the surface.
Small Area Variation in Hospital Admission Rates: Bayesian Adjustment for Primary Care and Hospital Factors
Authors: Congdon Peter , Best Nicky 
Published: July 2002

SUMMARY
Hospital admission rates are often used as a proxy to reflect patterns of morbidity or health need in population subgroups or across geographic areas. This paper considers the estimation of small area variations in relative health need, as measured by routinely collected hospital admissions data, after allowing for variation in general practice (primary care) and hospital (supply) effects. A fully Bayesian hierarchical modelling framework is adopted, using combinations of electoral ward populations and general practice patients’ lists to define catchment groups for analysis. Hospitals create a further stratum, with flows of patients between catchment groups and hospitals being represented by a gravity model. Variations in health outcomes are modelled by using a range of random-effects structures for each cross-classification of strata, together with a consideration of ward, practice, hospital and crossed level covariates. The approach is applied to case-studies of child respiratory and total emergency hospital admissions for residents in a London health authority.
Creep Rupture Due to Material Damage by Cavitation
Authors: Ragab A. R. 
Published: July 2002

Abstract
A phenomenological model to predict creep rupture times, based on material damage due to void growth and coalescence is presented. The model employs the Gurson-Tvergaard yield function together with the Norton-Baily power creep law. Rupture occurs at the end of a tertiary creep stage when the load-carrying capacity of the test-piece vanishes. Formulations for both uniaxial and triaxial conditions are given. Comparisons among the predictions of the present model and experiments for a vast number of data points indicate satisfactory agreement. A relation incorporating steady-state creep rate, rupture strain and rupture time is suggested. Furthermore acceptable correlation of the creep-rupture strength and creep strength to cause a specified creep strain is obtained.
In Vitro Activity of the New Triazole BMS-207147 against
Aspergillus
Species in Comparison with Itraconazole and Amphotericin B
Authors: Moore Caroline B. , Walls Caroline M. , Denning David W. 
Published: July 2002

ABSTRACT

The in vitro activity of BMS-207147 against 80 clinical isolates of
Aspergillus
was compared with that of itraconazole and amphotericin B, using a validated microtiter method. Geometric mean MICs (in μg/ml) were as follows: 1.71 for BMS-207147, 0.67 for itraconazole, and 0.63 for amphotericin B. The range of concentrations of each drug was 0.125 to >16 μg/ml.
Aspergillus fumigatus
was significantly more susceptible to BMS-207147 (
P
< 0.05) than
A. terreus
and
A. flavus
. No BMS-207147-resistant
A. fumigatus
isolates were identified, though eight itraconazole-resistant (MIC, >8 μg/ml) isolates were. BMS-207147 is active against
Aspergillus
spp. at slightly high concentrations compared with itraconazole and amphotericin B.