bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of particle size characteristics of the Tertiary ‘red clay’ and Pleistocene loess in the Chinese Loess Plateau: implications for origin and sources of the ‘red clay’
Authors: Yang S. L. , Ding Z. L. 
Published: December 2004

AbstractThe origin of the Tertiary ‘red clay’ underlying the Pleistocene loess in the Chinese Loess Plateau remains controversial, although several lines of evidence have suggested a wind‐blown origin. This study examines the particle‐size parameters of the late Miocene and Pliocene ‘red clay’ by comparing it with those of the late Pleistocene loess. The particle‐size distribution of a total of 15 339 loess and 6394 ‘red clay’ samples taken from 12 loess sections along a north–south transect and two ‘red clay’ sequences at Lingtai and Jingchuan was systematically analysed. The median grain size, skewness and kurtosis of the late Pleistocene loess all show a systematic southward change and are principally influenced by distance from source region. The spatial and temporal differentiation of dust deposits is expressed in a skewness–kurtosis–median grain size ternary diagram, from which the distance to the source region can be inferred. The particle‐size characteristics of the Tertiary ‘red clay’ sediments are very similar to those of the palaeosols within the late Pleistocene loess deposits, suggesting an aeolian origin for the ‘red clay’. Based on the comparison of ‘red clay’ and loess in the ternary diagrams, it is inferred that the source–sink distance was greater in the Neogene than in the last and penultimate interglacials, and that the dust source region in north‐western China underwent a progressive expansion during the period from at least 7·0 Ma to the present.
Diagenetic overprinting of the sphaerosiderite palaeoclimate proxy: are records of pedogenic groundwater δ18O values preserved?
Authors: Ufnar David F. , González Luis A. , Ludvigson Greg A. , Brenner Robert L. , Witzke Brian J. 
Published: December 2004

AbstractMeteoric sphaerosiderite lines (MSLs), defined by invariant δ18O and variable δ13C values, are obtained from ancient wetland palaeosol sphaerosiderites (millimetre‐scale FeCO3 nodules), and are a stable isotope proxy record of terrestrial meteoric isotopic compositions. The palaeoclimatic utility of sphaerosiderite has been well tested; however, diagenetically altered horizons that do not yield simple MSLs have been encountered. Well‐preserved sphaerosiderites typically exhibit smooth exteriors, spherulitic crystalline microstructures and relatively pure (> 95 mol% FeCO3) compositions. Diagenetically altered sphaerosiderites typically exhibit corroded margins, replacement textures and increased crystal lattice substitution of Ca2+, Mg2+ and Mn2+ for Fe2+. Examples of diagenetically altered Cretaceous sphaerosiderite‐bearing palaeosols from the Dakota Formation (Kansas), the Swan River Formation (Saskatchewan) and the Success S2 Formation (Saskatchewan) were examined in this study to determine the extent to which original, early diagenetic δ18O and δ13C values are preserved. All three units contain poikilotopic calcite cements with significantly different δ18O and δ13C values from the co‐occurring sphaerosiderites. The complete isolation of all carbonate phases is necessary to ensure that inadvertent physical mixing does not affect the isotopic analyses. The Dakota and Swan River samples ultimately yield distinct MSLs for the sphaerosiderites, and MCLs (meteoric calcite lines) for the calcite cements. The Success S2 sample yields a covariant δ18O vs. δ13C trend resulting from precipitation in pore fluids that were mixtures between meteoric and modified marine phreatic waters. The calcite cements in the Success S2 Formation yield meteoric δ18O and δ13C values. A stable isotope mass balance model was used to produce hyperbolic fluid mixing trends between meteoric and modified marine end‐member compositions. Modelled hyperbolic fluid mixing curves for the Success S2 Formation suggest precipitation from fluids that were < 25% sea water.
Tepee‐shaped agglutinated microbialites: an example from a Famennian carbonate platform on the Lennard Shelf, northern Canning Basin, Western Australia
Authors: Chow Nancy , George Annette D. 
Published: December 2004

AbstractDistinctive, metre‐scale antiformal structures are well developed in a Famennian carbonate platform in the Chedda Cliffs area of the Lennard Shelf reef complexes. The structures are distinguished by chevron‐shaped crests and thickened cores and contain abundant non‐skeletal allochems (ooids/pisoids, peloids and intraclasts) of silt to pebble size and variably developed laminations and fenestrae. The internal morphology and pervasive occurrence of fenestral clotted and wavy laminated fabrics suggest that these structures are microbial mounds composed of agglutinated stromatolites and thrombolites. Microbial fabrics most probably originated through sediment trapping and binding by microbial mats with early lithification involving microbial calcification and cementation of trapped sediment. The facies and stratigraphic context of the mounds support a shallow subtidal, transitional backreef to reef‐flat setting; however, alone these mounds do not provide unequivocal environmental information. Other large antiformal structures in Famennian platforms on the Lennard Shelf, previously described as tepee structures, show morphological similarities to the Chedda Cliffs mounds, which suggests that these other structures may also be microbial mounds. The presence of microbial mounds in platform successions further highlights the importance of microbial communities in the Lennard Shelf reef complexes.
Three‐dimensional modelling of an isolated carbonate buildup (Triassic, Dolomites, Italy)
Authors: Blendinger Wolfgang , Brack Peter , Norborg Arne Kristoffer , Wulff‐Pedersen Erik 
Published: December 2004

AbstractThe Middle Triassic carbonate buildups of the Dolomites show facies similarities with mud mounds but display apparent architectural elements of flat‐topped carbonate platforms. In order to test whether the facies similarities to mounds are also reflected in the internal buildup architecture, a three‐dimensional modelling study of the Middle Triassic Monte Cernera buildup has been carried out. The Cernera buildup exhibits apparent geometries suggesting a mounded platform in the lower and uppermost part of the buildup, separated by an interval with apparent platform geometry and a retrogradational platform interior, which is difficult to explain with a flat top platform model. For this purpose, a number of three‐dimensional models were constructed using the three‐dimensional modelling programme petrelTM. Key geological horizons were constructed based on outcrop measurements, intermediate horizons were calculated in the modelling program, and the intersections of the modelled layers with a digital topography surface were displayed and compared with outcrop photographs. The models were refined stepwise until a best fit with the actual bedding architecture was achieved. The best fit model shows that the mounded geometries in the lower and uppermost part of the buildup are real architectural elements. The intermediate platform stage, about 1·5 km across, had probably retained a mounded top with a relief of up to 50 m, which is difficult to distinguish from an absolutely flat top, but necessary to explain the retrogradational platform interior. The present study shows that Monte Cernera was dominated by mounded geometries at all stages of platform development. The mounded geometry plus facies data suggest that the platform is a deep‐water accumulation, below the zone of intense wave energy, but within the photic zone. The Cernera represents a tropical buildup type, which did not have the capacity to grow into continuously wave‐swept environments because of the small size and the absence of a wave‐resistant energy barrier. Such buildup types are probably common after major crises in earth history, when reef organisms were virtually absent.
Tropical westerlies over Pangaean sand seas
Authors: Loope David B. , Steiner Maureen B. , Rowe Clinton M. , Lancaster Nicholas 
Published: December 2004

AbstractCross‐equatorial, westerly winds are key features of tropical circulation in monsoonal regions. Although prominent in numerical climate models of Pangaea (the supercontinent straddling earth's equator, Late Palaeozoic to Early Mesozoic), such flow has not been confirmed previously by migration directions of ancient dunes. Wind‐blown sandstones that span 100 million years of earth history are widely exposed in south‐western USA. If recent palaeomagnetic data from the Colorado Plateau are used to correct Mesozoic palaeogeographic maps, the Plateau is placed about 10° further south than previously assumed, and the prevailing north‐westerly surface winds recorded by dune‐deposited sandstones are explicable as cross‐equatorial westerlies – the hallmark of modern monsoon circulation. Permian to Early Jurassic dunes were driven by north‐westerlies produced by a steep pressure gradient spanning the supercontinent during December–January–February. Although winds are light in most modern, near‐equatorial settings, the East African Jet accounts for more than half the cross‐equatorial flow in June–July–August. The thicknesses of annual depositional cycles within the Navajo Sandstone indicate that the near‐equatorial, north‐westerly winds that drove these particular dunes were stronger than the modern East African Jet. The Early Jurassic dunes that deposited the thick cycles were positioned west of the dominant (southern hemisphere) thermal low and against highlands to the west – a setting very similar to the East African Jet. The mountains along the western coast of Pangaea not only enhanced wind strength, but also cast a rain shadow that allowed active dunes to extend very close to the palaeoequator.
Methylation of histone H3 in euchromatin of plant chromosomes depends on basic nuclear DNA content
Authors: Houben Andreas , Demidov Dmitri , Gernand Dorota , Meister Armin , Leach Carolyn R. , Schubert Ingo 
Published: December 2004

SummaryStrong methylation of lysine 4 (K4) and low methylation of lysine 9 (K9) have been proposed as modifications of histone H3, typical for transcriptionally active euchromatin and the opposite for inactive heterochromatin. We have analysed the correlation between the global distribution of histone H3, methylated at either lysine 4 or lysine 9, and of microscopically detectable euchromatic or heterochromatic regions in relation to genome size for 24 plant species. Two different distribution patterns of methylated (K9)H3 (Met(K9)H3) were found that depend on genome size. For most species with small genomes (1C <500 Mbp), including Arabidopsis thaliana, strong methylation of (K9)H3 was restricted to constitutive heterochromatin. Species with larger genomes showed a uniform distribution of Met(K9)H3. Contrary to this and regardless of the genome size, methylated (K4)H3 (Met(K4)H3) was found to be enriched within the euchromatin of all species. Transcriptionally less active B chromosomes showed the same patterns as basic A chromosomes. We thus propose that large genomes with high amounts of dispersed repetitive sequences (mainly retroelements) have to silence these sequences and therefore display epigenetic modifications such as methylation of DNA and (K9)H3 also within euchromatic regions.
Antisense inhibition of NADH glutamate synthase impairs carbon/nitrogen assimilation in nodules of alfalfa (Medicago sativa L.)
Authors: Cordoba Elizabeth , Shishkova Svetlana , Vance Carroll P. , Hernández Georgina 
Published: December 2004

SummaryLegumes acquire significant amounts of nitrogen for growth from symbiotic nitrogen fixation. The glutamine synthetase (GS)/NADH‐dependent glutamate synthase (NADH‐GOGAT) cycle catalyzes initial nitrogen assimilation. This report describes the impact of specifically reducing nodule NADH‐GOGAT activity on symbiotic performance of alfalfa (Medicago sativa L.). Four independent transgenic alfalfa lines, designated GA89, GA87, GA88, and GA82 (for GOGATantisense), containing an antisense NADH‐GOGAT cDNA fragment under the control of the soybean leghemoglobin (lbc3) promoter were evaluated. The GA plants were fertile and showed normal growth in non‐symbiotic conditions. The NADH‐GOGAT antisense transgene was heritable and the T1 plants showed phenotypic alterations – similar to primary transformants. Clonally propagated plants were inoculated with Sinorhizobium meliloti after rooting and the symbiotic phenotype was analyzed 21 days post‐inoculation. Nodules of each GA line had reduced NADH‐GOGAT activity, ranging from 33 to 87% of control plants, that was accompanied by comparable decreases in RNA and protein. Plants from the GA89 line, with the lowest NADH‐GOGAT activity (c. 30%), presented a strikingly altered symbiotic phenotype: concomitantly activities of key enzyme for carbon and nitrogen assimilation decreased; nodule amino acids and amides were reduced while sucrose accumulated. Antisense GOGAT plants were chlorotic, reduced in fresh weight, and had a lower N content than control plants. Photosynthesis was also impaired in antisense plants. Specifically, reducing NADH‐GOGAT in nodules resulted in plants having impaired nitrogen assimilation and altered carbon/nitrogen metabolic flux.
A novel protein from Brassica napus has a putative KID domain and responds to low temperature
Authors: Gao Ming‐Jun , Schäfer Ulrike A. , Parkin Isobel A. P. , Hegedus Dwayne D. , Lydiate Derek J. , Hannoufa Abdelali 
Published: December 2004

SummaryTo identify factors that interact with histone deacetylase (HDAC) in Brassica napus, a yeast two‐hybrid library was screened using the Arabidopsis HDA19 as bait. A novel protein, bnKCP1, containing a putative kinase‐inducible domain (KID) was found to interact with HDA19. Southern blot analysis indicated that the bnKCP1 gene belongs to a small gene family of at least three members. Northern blot analysis showed bnKCP1 to be strongly expressed in stems, flowers, roots, and immature siliques, but not in leaf blades of seedlings. The accumulation of bnKCP1 transcript in the leaf blades was induced significantly within 4 h of exposure of B. napus seedlings to cold stress, whereas treatment of leaf blades with inomycin, an ionophore of Ca2+, caused a rapid (30 min) but transient induction of bnKCP1 expression. In contrast to that observed in leaf blades, expression of bnKCP1 in the stems was repressed upon cold treatment. In vitro and in vivo protein‐binding assays showed that bnKCP1 interacts with HDA19 via the KID domain, and that S188 is critical for bnKCP1–HDA19 interaction. BnKCP1 also exerted modest transactivation of the lacZ reporter gene in yeast through its N‐terminal region. These assays suggest that bnKCP1 may function as a transcription factor, which regulates gene expression through interaction with HDA19.
Enhancement of growth by expression of poplar cellulase in Arabidopsis thaliana
Authors: Park Yong Woo , Tominaga Rumi , Sugiyama Junji , Furuta Yuzo , Tanimoto Eiichi , Samejima Masahiro , Sakai Fukumi , Hayashi Takahisa 
Published: December 2004

SummaryTo study the role of cellulose and cellulase in plant growth, we expressed poplar cellulase (PaPopCel1) constitutively in Arabidopsis thaliana. Expression increased the size of the rosettes due to increased cell size. The change in growth was accompanied by changes in biomechanical properties due to cell wall structure indicative of decrease in xyloglucan cross‐linked with cellulose microfibrils by chemical analysis and nuclear magnetic resonance (NMR) spectra. The result supports the concept that the paracrystalline sites of cellulose microfibrils are attacked by poplar cellulase to loosen xyloglucan intercalation and this irreversible wall modification promotes the enlargement of plant cells.
The redistribution of protein sulfur in transgenic rice expressing a gene for a foreign, sulfur‐rich protein
Authors: Hagan N. D. , Upadhyaya N. , Tabe L. M. , Higgins T. J. V. 
Published: December 2004

SummarySulfur amino acid composition is an important determinant of seed protein quality. A chimeric gene encoding sunflower seed albumin (SSA), one of the most sulfur‐rich seed storage proteins identified so far, was introduced into rice (Oryza sativa) in order to modify cysteine and methionine content of the seed. Analysis of a transgenic line expressing SSA at approximately 7% of total seed protein revealed that the mature grain showed little change in the total sulfur amino acid content compared to the parental genotype. This result indicated that the transgenic rice grain was unable to respond to the added demand for cysteine and methionine imposed by the production of SSA. Analysis of the protein composition of the transgenic grain showed changes in the relative levels of the major seed storage proteins, as well as some non‐storage proteins, compared to non‐transgenic controls. Changes observed at the protein level were concomitant with differences in mRNA accumulation but not always with the level of transcription. The limited sulfur reserves appeared to be re‐allocated from endogenous proteins to the new sulfur sink in the transgenic grain. We hypothesize that this response is mediated by a signal transduction pathway that normally modulates seed storage protein composition in response to environmental fluctuations in sulfur availability, via both transcriptional and post‐transcriptional control of gene expression.
Efficient transposition of the Tnt1 tobacco retrotransposon in the model legume Medicago truncatula
Authors: D'Erfurth Isabelle , Cosson Viviane , Eschstruth Alexis , Lucas Helene , Kondorosi Adam , Ratet P. 
Published: December 2004

SummaryThe tobacco element, Tnt1, is one of the few active retrotransposons in plants. Its transposition is activated during protoplast culture in tobacco and tissue culture in the heterologous host Arabidopsis thaliana. Here, we report its transposition in the R108 line of Medicago truncatula during the early steps of the in vitro transformation–regeneration process. Two hundred and twenty‐five primary transformants containing Tnt1 were obtained. Among them, 11.2% contained only transposed copies of the element, indicating that Tnt1 transposed very early and efficiently during the in vitro transformation process, possibly even before the T‐DNA integration. The average number of insertions per transgenic line was estimated to be about 15. These insertions were stable in the progeny and could be separated by segregation. Inspection of the sequences flanking the insertion sites revealed that Tnt1 had no insertion site specificity and often inserted in genes (one out of three insertions). Thus, our work demonstrates the functioning of an efficient transposable element in leguminous plants. These results indicate that Tnt1 can be used as a powerful tool for insertion mutagenesis in M. truncatula.
A novel C‐terminal proteolytic processing of cytosolic pyruvate kinase, its phosphorylation and degradation by the proteasome in developing soybean seeds
Authors: Tang Guo‐Qing , Hardin Shane C. , Dewey Ralph , Huber Steven C. 
Published: December 2004

SummaryCytosolic pyruvate kinase (ATP:pyruvate 2‐O‐phosphotransferase, EC 2.7.1.40) is an important glycolytic enzyme, but the post‐translational regulation of this enzyme is poorly understood. Sequence analysis of the soybean seed enzyme suggested the potential for two phosphorylation sites: site‐1 (FVRKGS220DLVN) and site‐2 (VLTRGGS407TAKL). Sequence‐ and phosphorylation state‐specific antipeptide antibodies established that cytosolic pyruvate kinase (PyrKinc) is phosphorylated at both sites in vivo. However, by SDS–PAGE, the phosphorylated polypeptides were found to be smaller (20–51 kDa) than the full length (55 kDa). Biochemical separations of seed proteins by size exclusion chromatography and sucrose‐density gradient centrifugation revealed that the phosphorylated polypeptides were associated with 26S proteasomes. The 26S proteasome particle in developing seeds was determined to be of approximately 1900 kDa. In vitro, the 26S proteasome degraded associated PyrKinc polypeptides, and this was blocked by proteasome‐specific inhibitors such as MG132 and NLVS. By immunoprecipitation, we found that some part of the phosphorylated PyrKinc was conjugated to ubiquitin and shifted to high molecular mass forms in vivo. Moreover, recombinant wild‐type PyrKinc was ubiquitinated in vitro to a much greater extent than the S220A and S407A mutant proteins, suggesting a link between phosphorylation and ubiquitination. In addition, during seed development, a progressive accumulation of a C‐terminally truncated polypeptide of approximately 51 kDa was observed that was in parallel with a loss of the full‐length 55 kDa polypeptide. Interestingly, the C‐terminal 51 kDa truncation showed not only pyruvate kinase activity but also activation by aspartate. Collectively, the results suggest that there are two pathways for PyrKinc modification at the post‐translational level. One involves partial C‐terminal truncation to generate a 51 kDa pyruvate kinase subunit which might have altered regulatory properties and the other involves phosphorylation and ubiquitin conjugation that targets the protein to the 26S proteasome for complete degradation.
Barley sex6 mutants lack starch synthase IIa activity and contain a starch with novel properties
Authors: Morell Matthew K. , Kosar‐Hashemi Behjat , Cmiel Mark , Samuel Michael S. , Chandler Peter , Rahman Sadequr , Buleon Alain , Batey Ian L. , Li Zhongyi 
Published: December 2004

SummaryAnalysis of barley shrunken grain mutants has identified lines with a novel high amylose starch phenotype. The causal mutation is located at the sex6 locus on chromosome 7H, suggesting the starch synthase IIa (ssIIa) gene as a candidate gene altered by the mutation. Consistent with this hypothesis, no evidence of SSIIa protein expression in either the starch granule or soluble fractions of the endosperm was found. Sequences of the starch synthase IIa gene, ssIIa, from three independent sex6 lines showed the presence of a stop codon preventing translation of the ssIIa transcript in each line. Perfect segregation of the starch phenotype with the presence of stop codons in the ssIIa gene was obtained, providing strong evidence for the lesion in the ssIIa gene being the causal mutation for the sex6 phenotype. The loss of SSIIa activity in barley leads to novel and informative phenotypes. First, a decrease in amylopectin synthesis to less than 20% of the wild‐type levels indicates that SSIIa accounts for the majority of the amylopectin polymer elongation activity in barley. Secondly, in contrast to high amylose starches resulting from branching enzyme downregulation, the sex6 starches have a shortened amylopectin chain length distribution and a reduced gelatinisation temperature. Thirdly, the mutation leads to pleiotropic effects on other enzymes of the starch biosynthesis pathway, abolishing the binding of SSI, branching enzyme IIa and branching enzyme IIb to the starch granules of sex6 mutants, while not significantly altering their expression levels in the soluble fraction.