bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scattering of High-Velocity Neutral Particles. XII. He–CH4; He–CF4. CH4–CH4 and CF4–CF4 Interactions
Authors: Amdur I. , Longmire M. S. , Mason E. A. 
Published: July 2004

Collision cross sections have been measured for helium atoms with energies between 500 and 2100 ev, scattered in room-temperature CH4 and CF4. The results have been analyzed to obtain the average potential between a helium atom and a CH4 molecule, 〈V(r)〉Av=602/r9.43ev,for r between 1.92 and 2.37 A, and the average potential between a helium atom and a CF4 molecule, 〈V(r)〉Av=6.18×106/r17.51ev,for r between 2.43 and 2.74 A. This He–CH4 potential is consistent with one valid at larger separation distances which has been obtained by combining potentials derived from high-temperature viscosity and second virial coefficients of helium, and from high-temperature viscosity coefficients of methane.
A procedure which assumes the centers of force to reside in the peripheral H or F atoms has been used to analyze these average atom-molecule interactions in terms of the effective He–H and He–F interatomic potentials. These interatomic potentials have been combined with the potential previously determined for He–He to obtain effective H–H and F–F potentials for atoms in different CH4 and CF4 molecules. These effective interatomic potentials were then summed and averaged over all molecular orientations to yield the average potential between two CH4 molecules, 〈V(r)〉Av=5.64×106/r15.47ev,for r between 2.47 and 3.06 A, and the average potential between two CF4 molecules, 〈V(r)〉Av=1.17×1022/r39.27ev,for r between 3.43 and 3.77 A. This CH4–CH4 potential is consistent with one valid at larger separation distances which has been derived from measurements on gaseous viscosity at high temperatures.
Molecular-Weight Dependence of the Viscoelastic Properties of Whole Polymers
Authors: Peticolas Warner L. , Menefee Emory 
Published: July 2004

A method has been developed by which it is possible to determine the type of molecular weight averaging upon which viscoelastic properties of polymers may depend and which may be used to verify the normal-coordinate theory of viscoelasticity for various types of polymers. The method is extraordinarily simple to carry out since it involves only measurement of the property on whole polymers and mixtures of whole polymers. Neither fractionation nor molecular-weight measurements themselves are required.
Methods of determining the correct average-molecular-weight dependence of melt viscosity and steady-state elastic compliance have been worked out in detail and are illustrated with data on linear polyethylenes.
The method is also applicable to other polymer properties which are molecular-weight dependent.
The Effect of Impurities on the Molecular Weight Distributions of Anionic Polymers
Authors: Orofino T. A. , Wenger F. 
Published: July 2004

The deactivating influence of impurities in anionic polymerizations is considered from the point of view of the ultimate molecular weight distributions obtained with various systems.
With the assumption that initiation is much faster than propagation, theoretical expressions for the weight distribution functions and the weight-to-number average chain length ratios are derived for the cases in which mono- and bifunctional growing chains are subjected throughout the course of polymerization to given, fixed ratios of monomer to impurity concentrations. The relationships obtained are shown to be applicable to systems of practical interest.
The molecular weight distributions of both mono- and bifunctional anionic polymers derived from the foregoing model are found to broaden with increasing impurity content in the monomer supply. The molecular weight distributions for the latter are narrower than those for the former at corresponding levels of impurity content. For moderate degrees of deactivation, the weight distribution function for bifunctional polymers exhibits the characteristic maximum as well as the rudiments of a second relative maximum at lower molecular weight.
Novel Expression Pattern of Cytosolic Gln Synthetase in Nitrogen-Fixing Root Nodules of the Actinorhizal Host, Datisca glomerata
Authors: Berry Alison M. , Murphy Terence M. , Okubara Patricia A. , Jacobsen Karin R. , Swensen Susan M. , Pawlowski Katharina 
Published: July 2004

Abstract
Gln synthetase (GS) is the key enzyme of primary ammonia assimilation in nitrogen-fixing root nodules of legumes and actinorhizal (Frankia-nodulated) plants. In root nodules of Datisca glomerata (Datiscaceae), transcripts hybridizing to a conserved coding region of the abundant nodule isoform, DgGS1-1, are abundant in uninfected nodule cortical tissue, but expression was not detectable in the infected zone or in the nodule meristem. Similarly, the GS holoprotein is immunolocalized exclusively to the uninfected nodule tissue. Phylogenetic analysis of the full-length cDNA of DgGS1-1 indicates affinities with cytosolic GS genes from legumes, the actinorhizal species Alnus glutinosa, and nonnodulating species, Vitis vinifera and Hevea brasilensis. The D. glomerata nodule GS expression pattern is a new variant among reported root nodule symbioses and may reflect an unusual nitrogen transfer pathway from the Frankia nodule microsymbiont to the plant infected tissue, coupled to a distinctive nitrogen cycle in the uninfected cortical tissue. Arg, Gln, and Glu are the major amino acids present in D. glomerata nodules, but Arg was not detected at high levels in leaves or roots. Arg as a major nodule nitrogen storage form is not found in other root nodule types except in the phylogenetically related Coriaria. Catabolism of Arg through the urea cycle could generate free ammonium in the uninfected tissue where GS is expressed.
Microarray Analyses of Gene Expression during Adventitious Root Development in Pinus contorta
Authors: Brinker Monika , van Zyl Leonel , Liu Wenbin , Craig Deborah , Sederoff Ronald R. , Clapham David H. , von Arnold Sara 
Published: July 2004

Abstract
In order to investigate the gene expression pattern during adventitious root development, RNA of Pinus contorta hypocotyls, pulse-treated with the auxin indole-3-butyric acid and harvested at distinct developmental time points of root development, was hybridized to microarrays containing 2,178 cDNAs from Pinus taeda. Over the period of observation of root development, the transcript levels of 220 genes changed significantly. During the root initiation phase, genes involved in cell replication and cell wall weakening and a transcript encoding a PINHEAD/ZWILLE-like protein were up-regulated, while genes related to auxin transport, photosynthesis, and cell wall synthesis were down-regulated. In addition, there were changes in transcript abundance of genes related to water stress. During the root meristem formation phase the transcript abundances of genes involved in auxin transport, auxin responsive transcription, and cell wall synthesis, and of a gene encoding a B-box zinc finger-like protein, increased, while those encoding proteins involved in cell wall weakening decreased. Changes of transcript abundance of genes related to water stress during the root meristem formation and root formation phase indicate that the plant roots had become functional in water transport. Simultaneously, genes involved in auxin transport were up-regulated, while genes related to cell wall modification were down-regulated. Finally, during the root elongation phase down-regulation of transcripts encoding proteins involved in cell replication and stress occurred. Based on the observed changes in transcript abundances, we suggest hypotheses about the relative importance of various physiological processes during the auxin-induced development of roots in P. contorta.
Autophosphorylation and Subcellular Localization Dynamics of a Salt- and Water Deficit-Induced Calcium-Dependent Protein Kinase from Ice Plant
Authors: Chehab E. Wassim , Patharkar O. Rahul , Hegeman Adrian D. , Taybi Tahar , Cushman John C. 
Published: July 2004

Abstract
A salinity and dehydration stress-responsive calcium-dependent protein kinase (CDPK) was isolated from the common ice plant (Mesembryanthemum crystallinum; McCPK1). McCPK1 undergoes myristoylation, but not palmitoylation in vitro. Removal of the N-terminal myristate acceptor site partially reduced McCPK1 plasma membrane (PM) localization as determined by transient expression of green fluorescent protein fusions in microprojectile-bombarded cells. Removal of the N-terminal domain (amino acids 1–70) completely abolished PM localization, suggesting that myristoylation and possibly the N-terminal domain contribute to membrane association of the kinase. The recombinant, Escherichia coli-expressed, full-length McCPK1 protein was catalytically active in a calcium-dependent manner (K 0.5 = 0.15 μ m). Autophosphorylation of recombinant McCPK1 was observed in vitro on at least two different Ser residues, with the location of two sites being mapped to Ser-62 and Ser-420. An Ala substitution at the Ser-62 or Ser-420 autophosphorylation site resulted in a slight increase in kinase activity relative to wild-type McCPK1 against a histone H1 substrate. In contrast, Ala substitutions at both sites resulted in a dramatic decrease in kinase activity relative to wild-type McCPK1 using histone H1 as substrate. McCPK1 undergoes a reversible change in subcellular localization from the PM to the nucleus, endoplasmic reticulum, and actin microfilaments of the cytoskeleton in response to reductions in humidity, as determined by transient expression of McCPK1-green fluorescent protein fusions in microprojectile-bombarded cells and confirmed by subcellular fractionation and western-blot analysis of 6× His-tagged McCPK1.
Isolation and Characterization of a TERMINAL FLOWER Homolog and Its Correlation with Juvenility in Citrus
Authors: Pillitteri Lynn Jo , Lovatt Carol J. , Walling Linda L. 
Published: July 2004

Abstract
TERMINAL FLOWER is a key regulator of floral timing in Arabidopsis and other herbaceous species. A homolog of this gene, CsTFL, was isolated from the hybrid perennial tree crop Washington navel orange (Citrus sinensis L. Osbeck). The deduced amino acid sequence of CsTFL was 65% identical to the Arabidopsis TFL1 protein. Wild-type Arabidopsis plants ectopically expressing CsTFL showed late-flowering phenotypes similar to those described for overexpression of Arabidopsis TFL1. In addition, the 35S:CsTFL transgene complemented the tfl1-2 mutant. The severity of the overexpression phenotypes correlated with the amount of CsTFL transcript that accumulated. Unlike many model systems that have been studied, C. sinensis maintains two distinguishable CsTFL alleles. CsTFL transcripts from either allele were not detected in adult vegetative tissues using reverse transcription-PCR, but CsTFL RNAs were detected in all floral organs. In addition, real-time PCR determined that juvenility in citrus was positively correlated with CsTFL transcript accumulation and negatively correlated with the floral-regulatory genes, LEAFY and APETALA1, RNA levels.
Down-Regulation of Metallothionein, a Reactive Oxygen Scavenger, by the Small GTPase OsRac1 in Rice
Authors: Wong Hann Ling , Sakamoto Tsuyoshi , Kawasaki Tsutomu , Umemura Kenji , Shimamoto Ko 
Published: July 2004

Abstract
Metallothioneins are small, ubiquitous Cys-rich proteins known to be involved in reactive oxygen species (ROS) scavenging and metal homeostasis. We found that the expression of a metallothionein gene (OsMT2b) was synergically down-regulated by OsRac1 and rice (Oryza sativa) blast-derived elicitors. Transgenic plants overexpressing OsMT2b showed increased susceptibility to bacterial blight and blast fungus. OsMT2b-overexpressing cells showed reduced elicitor-induced hydrogen peroxide production. In contrast, homozygous OsMT2b::Tos17-inserted mutant and OsMT2b-RNAi-silenced transgenic cells showed significantly higher elicitor-induced hydrogen peroxide production than the wild-type cells. In vitro assay showed that recombinant OsMT2b protein possessed superoxide- and hydroxyl radical-scavenging activities. Taken together, these results showed that OsMT2b is an ROS scavenger and its expression is down-regulated by OsRac1, thus potentiating ROS, which function as signals in resistance response. The results suggest that OsRac1 plays a dual role as an inducer of ROS production and a suppressor of ROS scavenging.
Phylogenetic Analyses inCornusSubstantiate Ancestry of Xylem Supercooling Freezing Behavior and Reveal Lineage of Desiccation Related Proteins
Authors: Karlson Dale T. , Xiang (Jenny) Qiu-Yun , Stirm Vicki E. , Shirazi A.M. , Ashworth Edward N. 
Published: July 2004

AbstractThe response of woody plant tissues to freezing temperature has evolved into two distinct behaviors: an avoidance strategy, in which intracellular water supercools, and a freeze-tolerance strategy, where cells tolerate the loss of water to extracellular ice. Although both strategies involve extracellular ice formation, supercooling cells are thought to resist freeze-induced dehydration. Dehydrin proteins, which accumulate during cold acclimation in numerous herbaceous and woody plants, have been speculated to provide, among other things, protection from desiccative extracellular ice formation. Here we use Cornus as a model system to provide the first phylogenetic characterization of xylem freezing behavior and dehydrin-like proteins. Our data suggest that both freezing behavior and the accumulation of dehydrin-like proteins in Cornus are lineage related; supercooling and nonaccumulation of dehydrin-like proteins are ancestral within the genus. The nonsupercooling strategy evolved within the blue- or white-fruited subgroup where representative species exhibit high levels of freeze tolerance. Within the blue- or white-fruited lineage, a single origin of dehydrin-like proteins was documented and displayed a trend for size increase in molecular mass. Phylogenetic analyses revealed that an early divergent group of red-fruited supercooling dogwoods lack a similar protein. Dehydrin-like proteins were limited to neither nonsupercooling species nor to those that possess extreme freeze tolerance.
The Putative Arabidopsis Homolog of Yeast Vps52p Is Required for Pollen Tube Elongation, Localizes to Golgi, and Might Be Involved in Vesicle Trafficking
Authors: Lobstein Eglantine , Guyon Anouchka , Férault Madina , Twell David , Pelletier Georges , Bonhomme Sandrine 
Published: July 2004

Abstract
The screening of the Versailles collection of Arabidopsis T-DNA transformants allowed us to identify several male gametophytic mutants, including poky pollen tube (pok). The pok mutant, which could only be isolated as a hemizygous line, exhibits very short pollen tubes, explaining the male-specific transmission defect observed in this line. We show that the POK gene is duplicated in the Arabidopsis genome and that the predicted POK protein sequence is highly conserved from lower to higher eukaryotes. The putative POK homolog in yeast (Saccharomyces cerevisiae), referred to as Vps52p/SAC2, has been shown to be located at the late Golgi and to function in a complex with other proteins, Vps53p, Vps54p, and Vps51p. This complex is involved in retrograde trafficking of vesicles between the early endosomal compartment and the trans-Golgi network. We present the expression patterns of the POK gene and its duplicate P2 in Arabidopsis, and of the putative Arabidopsis homologs of VPS53 and VPS54 of yeast. We show that a POK::GFP fusion protein localizes to Golgi in plant cells, supporting the possibility of a conserved function for Vps52p and POK proteins. These results, together with the expression pattern of the POK::GUS fusion and the lack of plants homozygous for the pok mutation, suggest a more general role for POK in polar growth beyond the pollen tube elongation process.
Tomato Phospholipid Hydroperoxide Glutathione Peroxidase Inhibits Cell Death Induced by Bax and Oxidative Stresses in Yeast and Plants
Authors: Chen Shaorong , Vaghchhipawala Zarir , Li Wei , Asard Han , Dickman Martin B. 
Published: July 2004

Abstract
Using a conditional life or death screen in yeast, we have isolated a tomato (Lycopersicon esculentum) gene encoding a phospholipid hydroperoxide glutathione peroxidase (LePHGPx). The protein displayed reduced glutathione-dependent phospholipid hydroperoxide peroxidase activity, but differs from counterpart mammalian enzymes that instead contain an active seleno-Cys. LePHGPx functioned as a cytoprotector in yeast (Saccharomyces cerevisiae), preventing Bax, hydrogen peroxide, and heat stress induced cell death, while also delaying yeast senescence. When tobacco (Nicotiana tabacum) leaves were exposed to lethal levels of salt and heat stress, features associated with mammalian apoptosis were observed. Importantly, transient expression of LePHGPx protected tobacco leaves from salt and heat stress and suppressed the apoptotic-like features. As has been reported, conditional expression of Bax was lethal in tobacco, resulting in tissue collapse and membrane permeability to Evans blue. When LePHGPx was coexpressed with Bax, little cell death and no vital staining were observed. Moreover, stable expression of LePHGPx in tobacco conferred protection against the fungal phytopathogen Botrytis cinerea. Taken together, our data indicated that LePHGPx can protect plant tissue from a variety of stresses. Moreover, functional screens in yeast are a viable tool for the identification of plant genes that regulate cell death.
Computational Identification and Characterization of Novel Genes from Legumes
Authors: Graham Michelle A. , Silverstein Kevin A.T. , Cannon Steven B. , VandenBosch Kathryn A. 
Published: July 2004

Abstract
The Fabaceae, the third largest family of plants and the source of many crops, has been the target of many genomic studies. Currently, only the grasses surpass the legumes for the number of publicly available expressed sequence tags (ESTs). The quantity of sequences from diverse plants enables the use of computational approaches to identify novel genes in specific taxa. We used BLAST algorithms to compare unigene sets from Medicago truncatula, Lotus japonicus, and soybean (Glycine max and Glycine soja) to nonlegume unigene sets, to GenBank's nonredundant and EST databases, and to the genomic sequences of rice (Oryza sativa) and Arabidopsis. As a working definition, putatively legume-specific genes had no sequence homology, below a specified threshold, to publicly available sequences of nonlegumes. Using this approach, 2,525 legume-specific EST contigs were identified, of which less than three percent had clear homology to previously characterized legume genes. As a first step toward predicting function, related sequences were clustered to build motifs that could be searched against protein databases. Three families of interest were more deeply characterized: F-box related proteins, Pro-rich proteins, and Cys cluster proteins (CCPs). Of particular interest were the &gt;300 CCPs, primarily from nodules or seeds, with predicted similarity to defensins. Motif searching also identified several previously unknown CCP-like open reading frames in Arabidopsis. Evolutionary analyses of the genomic sequences of several CCPs in M. truncatula suggest that this family has evolved by local duplications and divergent selection.
Expansins Abundant in Secondary Xylem Belong to Subgroup A of the α-Expansin Gene Family
Authors: Gray-Mitsumune Madoka , Mellerowicz Ewa J. , Abe Hisashi , Schrader Jarmo , Winzéll Anders , Sterky Fredrik , Blomqvist Kristina , McQueen-Mason Simon , Teeri Tuula T. , Sundberg Björn 
Published: July 2004

Abstract
Differentiation of xylem cells in dicotyledonous plants involves expansion of the radial primary cell walls and intrusive tip growth of cambial derivative cells prior to the deposition of a thick secondary wall essential for xylem function. Expansins are cell wall-residing proteins that have an ability to plasticize the cellulose-hemicellulose network of primary walls. We found expansin activity in proteins extracted from the cambial region of mature stems in a model tree species hybrid aspen (Populus tremula × Populus tremuloides Michx). We identified three α-expansin genes (PttEXP1, PttEXP2, and PttEXP8) and one β-expansin gene (PttEXPB1) in a cambial region expressed sequence tag library, among which PttEXP1 was most abundantly represented. Northern-blot analyses in aspen vegetative organs and tissues showed that PttEXP1 was specifically expressed in mature stems exhibiting secondary growth, where it was present in the cambium and in the radial expansion zone. By contrast, PttEXP2 was mostly expressed in developing leaves. In situ reverse transcription-PCR provided evidence for accumulation of mRNA of PttEXP1 along with ribosomal rRNA at the tips of intrusively growing xylem fibers, suggesting that PttEXP1 protein has a role in intrusive tip growth. An examination of tension wood and leaf cDNA libraries identified another expansin, PttEXP5, very similar to PttEXP1, as the major expansin in developing tension wood, while PttEXP3 was the major expansin expressed in developing leaves. Comparative analysis of expansins expressed in woody stems in aspen, Arabidopsis, and pine showed that the most abundantly expressed expansins share sequence similarities, belonging to the subfamily A of α-expansins and having two conserved motifs at the beginning and end of the mature protein, RIPVG and KNFRV, respectively. This conservation suggests that these genes may share a specialized, not yet identified function.
Contrasting Modes of Diversification in the Aux/IAA and ARF Gene Families
Authors: Remington David L. , Vision Todd J. , Guilfoyle Thomas J. , Reed Jason W. 
Published: July 2004

Abstract
The complete genomic sequence for Arabidopsis provides the opportunity to combine phylogenetic and genomic approaches to study the evolution of gene families in plants. The Aux/IAA and ARF gene families, consisting of 29 and 23 loci in Arabidopsis, respectively, encode proteins that interact to mediate auxin responses and regulate various aspects of plant morphological development. We developed scenarios for the genomic proliferation of the Aux/IAA and ARF families by combining phylogenetic analysis with information on the relationship between each locus and the previously identified duplicated genomic segments in Arabidopsis. This analysis shows that both gene families date back at least to the origin of land plants and that the major Aux/IAA and ARF lineages originated before the monocot-eudicot divergence. We found that the extant Aux/IAA loci arose primarily through segmental duplication events, in sharp contrast to the ARF family and to the general pattern of gene family proliferation in Arabidopsis. Possible explanations for the unusual mode of Aux/IAA duplication include evolutionary constraints imposed by complex interactions among proteins and pathways, or the presence of long-distance cis-regulatory sequences. The antiquity of the two gene families and the unusual mode of Aux/IAA diversification have a number of potential implications for understanding both the functional and evolutionary roles of these genes.