bluuebunny/crossref_metadata_2025_split huggingface dataset:
Outcrop‐scale acoustic facies analysis and latest Quaternary development of Hueneme and Dume submarine fans, offshore California
Authors: Piper  , Hiscott  , Normark  
Published: March 2003

The uppermost Quaternary deposits of the Hueneme and Dume submarine fans in the Santa Monica Basin have been investigated using a closed‐spaced grid of boomer seismic‐reflection profiles, which give vertical resolution of a few tens of centimetres with acoustic penetration to 50 m. Acoustic facies integrated with geometry define six architectural elements, some with discrete subelements that are of a scale that can be recognized in outcrops of ancient turbidite systems. In the Santa Monica Basin, the relationship of these elements to fan morphology, stratigraphy and sediment source is precisely known.The width of upper Hueneme fan valley has been reduced from 5 km since the last glacial maximum to 1 km at present by construction of laterally confined sandy levees within the main valley. The middle fan comprises three main subelements: thick sand deposits at the termination of the fan valley, low‐gradient sandy lobes typically 5 km long and < 10 m thick, and scoured lobes formed of alternating sand and mud beds with many erosional depressions. The site of thickest lobe sediment accumulation shifts through time, with each sand bed deposited in a previous bathymetric low (i.e. compensation cycles). The lower fan and basin plain consists of sheet‐like alternations of sand and mud with shallow channels and lenses.Variations in the rate of late Quaternary sea level rise initiated changes in sediment facies distribution. At lowstand, and during the approximately 11 ka stillstand in sea level, the Hueneme Fan was fed largely by hyperpycnal flow from the Santa Clara River delta, depositing high sediment waves on the right hand levee and thick sandy lobes on the middle fan. At highstand of sea level, most turbidity currents were generated by failure of silty prodelta muds. In contrast, the smaller Dume Fan was apparently always fed from littoral drift of sand through a single‐canyon point source.
Revised concept of Chrysoperla mediterranea (Hölzel), a green lacewing associated with conifers: courtship songs across 2800 kilometres of Europe (Neuroptera: Chrysopidae)
Authors: Henry Charles S. , Brooks Stephen J. , Johnson James B. , Duelli Peter 
Published: March 2003

SummaryThe Holarctic carnea‐group of Chrysoperla green lacewings consists of numerous cryptic, sibling species, distinguished principally by vibrational courtship songs. A European member of this species‐group, C. mediterranea (Hölzel), was originally diagnosed by its dark green coloration, red band across the front of the head, narrow wings, minute basal dilation of the pretarsus and ecological association with pines. Here we describe its courtship and mating song, which uniquely distinguishes the species from all other members of the carnea‐group in Europe. Males and females both produce a single type of song, characterized by a long train of short, closely spaced volleys and nearly constant carrier frequency. Measured song features are nearly invariant across a large geographical range that extends well outside that previously known for C. mediterranea. Principal components analysis confirms the uniqueness of the mediterranea song in comparison with five other sympatric song species of the carnea‐group. Populations which show the mediterranea song phenotype do not necessarily retain all of the traditional morphological features of the species, particularly in eastern parts of the range. Specifically, the green coloration may be less intense, the wings broader and the pretarsal basal dilation larger, resulting in significant morphological overlap with other song species. Larval morphology and ecophysiology also fail to distinguish C. mediterranea from other song species. Based on unique song phenotype, however, we conclude that C. mediterranea is a valid biological species, which can also be recognized in museum collections when a suite of physical attributes is used.
Macrosiphum on ferns: taxonomy, biology and evolution, including the description of three new species (Hemiptera: Aphididae)
Authors: Jensen Andrew S. , Holman Jaroslav 
Published: March 2003

SummaryThe phytophagous insect fauna of ferns has often been described as depauperate, and some have pointed to the paucity of evidence for adaptive radiation of insect groups feeding specifically on ferns. This paper examines the world's species of fern‐specific Macrosiphum aphids and attempts to determine whether fern‐feeding is a monophyletically derived trait in Macrosiphum. All sixteen species reported to feed on ferns, including three new species, were included in a cladistic analysis, along with fifteen other Macrosiphum species selected to represent the diversity of the genus, Papulaphis sleesmani (Pepper), because of its similarity to fern‐feeding Macrosiphum, and Sitobion avenae (Fabricius), which was used as outgroup. The results gave good support for the monophyly of fifteen of the sixteen fern‐feeders, and also supported a clade consisting of these fifteen fern‐feeders plus Macrosiphum equiseti (Holman), an Equisetum‐specific aphid. One species, Macrosiphum lapponicum Shaposhnikov, from northern Russia, was concluded to be unrelated to other fern‐feeding Macrosiphum. Whether this species truly feeds on a fern requires confirmation. Taxonomic and biological notes are provided for all fern‐feeding Macrosiphum of the world. These include one new combination, Macrosiphum cyatheae (Holman) comb.n., and three new species: Macrosiphum longirostratum sp.n. on Woodsia mollis and Woodsia sp. from Mexico (Michoacán), Macrosiphum miho sp.n. on ‘Aspidium’ sp. from the U.S.A. (Illinois) and Macrosiphum rebecae sp.n. on Adiantum sp. from Mexico (Michoacán). Keys to apterous and alate viviparae of Macrosiphum living on ferns are given.
The marine osmium isotope record
Authors: Peucker‐Ehrenbrink B. , Ravizza G. 
Published: March 2003

Over the past decade the marine osmium isotope record has been developed into a new tracer in palaeoceanographic research. Several analytical developments, particularly in the past few years, have significantly increased our ability to study the behaviour of osmium in the surficial environment. The 187Os/188Os and osmium concentration of seawater, river water, rain, and hydrothermal vent fluids have been measured directly. Recently, the behaviour of osmium in estuaries–critical for estimating the marine residence time of osmium–has been studied. Our knowledge of the surficial osmium cycle has thus significantly improved. In addition, reconstructions of past variations in the marine 187Os/188Os recently have been extended back into the Mesozoic. This review attempts to summarize our current understanding of the marine osmium system–present and past.The 187Os/188Os of seawater during the Cenozoic to first order mimics the marine 87Sr/86Sr record. It is therefore tempting to interpret both records as reflecting increased input of radiogenic osmium and strontium resulting from enhanced continental weathering regulated by climatic/tectonic processes. However, the marine osmium isotope system differs fundamentally from the marine strontium isotope system. This review emphasizes three important differences. First, large impacts are capable of resetting the 187Os/188Os to unradiogenic values without significantly affecting the marine strontium system. Second, organic‐rich sediments are characterized by high 187Re/188Os; resulting 187Os/188Os ingrowth‐trajectories are similar to the average slope of the Cenozoic 187Os/188Os seawater record. Trends towards more radiogenic 187Os/188Os seawater therefore can be caused by weathering of organic‐rich sediments at a constant rate. Third, the marine residence time of osmium is sufficiently short to capture short‐periodic (glacial‐interglacial) fluctuations that are inaccessible to the buffered marine strontium isotope system. This offers the opportunity to discriminate between high‐frequency (climatic) and low‐frequency (tectonic) forcing.
Stringent repression and homogeneous de‐repression by tetracycline of a modified CaMV 35S promoter in intact transgenic tobacco plants
Authors: Gatz Christiane , Frohberg Claus , Wendenburg Regina 
Published: March 2003

SummaryA cauliflower mosaic virus (CaMV) 35S promoter derivative, which is tightly repressed by the Tn 10 encoded Tet repressor in a transient expression system as well as in transgenic plants has been constructed. After treatment of transgenic plants with tetracycline (Tc) the activity of the reporter enzyme β‐glucuronidase (GUS) increased up to 500‐fold in tissue culture as well as under greenhouse conditions. Efficient derepression was achieved by Tc uptake through the roots as well as by Tc treatment of leaves of intact plants. As Tc is not very stable in the plants, this system can also be used for a transient expression of a transgene. This system provides a unique tool for regenerating transgenic plants carrying a repressed transgene and for efficiently de‐repressing its activity by a specific inducer at any time point of further development.
Complementation of Saccharomyces cerevisiae auxotrophic mutants by Arabidopsis thaliana cDNAs
Authors: Minet Michéle , Dufour Marie‐Elisabeth , Lacroute François 
Published: March 2003

SummaryAn Arabidopsis thaliana cDNA bank has been constituted in a Saccharomyces cerevisiae expression vector based on the phosphoglycerate kinase (PGK) promoter and terminator. This bank was used to complement eight S. cerevisiae auxotrophic markers. All of them were corrected. These results confirm the quality of the bank and the feasibility of cloning plant genes by yeast mutant complementation. The cDNA complementing the ura1 yeast mutant was sequenced, analysed and shown to encode a dihydroorotic (DHO) dehydrogenase sequence.
Analysis of the role of the late‐flowering locus, GI, in the flowering of Arabidopsis thaliana
Authors: Araki Takashi , Komeda Yoshibumi 
Published: March 2003

SummaryThe mutation gigantea (gi) is recessive and belongs to the late‐flowering mutations in Arabidopsis thaliana. The late‐flowering mutations result in a pronounced delay in flowering due to a prolonged phase of vegetative growth, which is manifested by an increased number of primary foliage leaves in the rosette (i.e. vegetative nodes). To examine the nature of the gi mutation, detailed phenotypic analysis was carried out for three representative mutant alleles. The results indicate that gi mutants have a defect in the promotion of the floral induction process by long‐day photoperiods and not in the flowering process per se. Temperature‐shift experiments using a partially conditional allele were employed to determine the timing of the functional requirement for the product of the GI locus. The end of the deduced functional period corresponds to the period at which transition of the apical meristem from the vegetative to the reproductive phase occurs. Such timing is in good agreement with the postulated role of the GI locus. These results demonstrate that the GI locus is involved in the promotion of floral initiation (entrance of the meristem into the transitional stage) by long‐day photoperiods.
Fertile transgenic wheat from microprojectile bombardment of scutellar tissue
Authors: Becker D. , Brettschneider R. , Lörz H. 
Published: March 2003

A reproducible transformation system for hexaploid wheat was developed based on particle bombardment of scutellar tissue of immature embryos. Particle bombardment was carried out using a PDS 1000/He gun. Plant material was bombarded with the plasmid pDB1 containing the β‐glucuronidase gene (uidA) under the control of the actin‐1 promoter of rice, and the selectable marker gene bar (phosphinothricin acetyltransferase) under the control of the CaMV 35S promoter. Selection was carried out using the herbicide Basta (Glufosinate‐ammonium). From a total number of 1050 bombarded immature embryos, in seven independent transformation experiments, 59 plants could be regenerated. Putative transformants were screened for enzyme activity by the histochemical GUS assay using cut leaf material and by spraying the whole plants with an aqueous solution of the herbicide Basta. Twelve regenerants survived Basta spraying and showed GUS‐activity. Southern‐blot analysis indicated the presence of introduced foreign genes in the genomic DNA of the transformants and both marker genes were present in all plants analysed.To date, four plants have been grown to maturity and set seed. Histochemically stained pollen grains showed a 1:1 segregation of the uidA gene in all plants tested. A 3:1 segregation of the introduced genes was demonstrated by enzyme activity tests and Southern blot analysis of R1 plants.
Benzothiadiazole induces disease resistance in Arabidopsis by activation of the systemic acquired resistance signal transduction pathway
Authors: Lawton Kay A. , Friedrich Leslie , Hunt Michelle , Weymann Kris , Delaney Terrance , Kessmann Helmut , Staub Theodor , Ryals John 
Published: March 2003

SummaryBenzothiadiazole (BTH) is a novel chemical activator of disease resistance in tobacco, wheat and other important agricultural plants. In this report, it is shown that BTH works by activating SAR in Arabidopsis thaliana. BTH‐treated plants were resistant to infection by turnip crinkle virus, Pseudomonas syringae pv ‘tomato’ DC3000 and Peronospora parasitica. Chemical treatment induced accumulation of mRNAs from the SAR‐associated genes, PR‐1, PR‐2 and PR‐5. BTH treatment induced both PR‐1 mRNA accumulation and resistance against P. parasitica in the ethylene response mutants, etr1 and ein2, and in the methyl jasmonate‐insensitive mutant, jar1, suggesting that BTH action is independent of these plant hormones. BTH treatment also induced both PR‐1 mRNA accumulation and P. parasitica resistance in transgenic Arabidopsis plants expressing the nahG gene, suggesting that BTH action does not require salicylic acid accumulation. However, because BTH‐treatment failed to induce either PR‐1 mRNA accumulation or P. parasitica resistance in the non‐inducible immunity mutant, nim1, it appears that BTH activates the SAR signal transduction pathway.
Cloning of a Ca2+‐ATPase gene and the role of cytosolic Ca2+ in the gibberellin‐dependent signaling pathway in aleurone cells
Authors: Chen Xiongfong , Chang Menchi , Wang Baiyang , Wu Ray 
Published: March 2003

SummaryThe ultimate goal of this investigation was to identify intermediary steps in the gibberellin (GA)‐dependent signaling pathway in rice aleurone cells. By using a differential display approach, a number of putative GA‐responsive genes were isolated. One of them, a GA‐responsive Ca2+‐ATPase gene, was identified and partially characterized. A genomic clone and a cDNA clone were isolated and sequenced. The deduced amino acid sequence showed that this protein resembles an endoplasmic reticulum membrane Ca2+‐ATPase. In a transient assay in rice aleurone cells, expression of the introduced Ca2+‐ATPase cDNA bypassed the GA requirement for stimulating the expression of a major target gene, the α‐amylase c gene (Osamy‐c). This result suggests that GA‐dependent expression of this Ca2+‐ATPase gene (OsCa‐atpase) plays an important role in the GA‐dependent signal‐transduction pathway. To investigate the possible involvement of other proteins and genes that may affect the intracellular Ca2+ level, compounds which can block different putative steps in the signal‐transduction pathway were introduced into rice aleurone cells, and then the level of the OsCa‐atpase transcript or the Osamy‐c transcript was monitored. In the presence of GA, the rice Ca2+‐ATPase and the Ca2+ channels appeared to co‐regulate the local concentration of cytosolic Ca2+. The release of Ca2+ from the internal stores to the cytoplasm was presumably initiated by inositol‐1,4,5‐triphosphate which reached a peak level within 25 min after GA induction. As a second messenger, Ca2+ binds to calmodulin (CaM), and the Ca2+/CaM complex regulates the cytosolic Ca2+ by affecting expression of the OsCa‐atpase. Finally, a working model is proposed for the GA‐dependent signaling pathway in aleurone cells.
Transformation of Arabidopsis thaliana with the codA gene for choline oxidase; accumulation of glycinebetaine and enhanced tolerance to salt and cold stress
Authors: Hayashi Hidenori , Alia  , Mustardy Laszlo , Deshnium Patchraporn , Ida Miki , Murata Norio 
Published: March 2003

SummaryGlycinebetaine is one of the compatible solutes that accumulate in the chloroplasts of certain halotolerant plants when these plants are exposed to salt or cold stress. The codA gene for choline oxidase, the enzyme that converts choline into glycinebetaine, has previously been cloned from a soil bacterium, Arthrobacter globiformis. Transformation of Arabidopsis thaliana with the cloned codA gene under the control of the 35S promoter of cauliflower mosaic virus enabled the plant to accumulate glycinebetaine and enhanced its tolerance to salt and cold stress. At 300 mM NaCl, considerable proportions of seeds of transformed plants germinated well, whereas seeds of wild‐type plants failed to germinate. At 100 mM NaCl, transformed plants grew well whereas wild‐type plants did not do so. The transformed plants tolerated 200 mM NaCl, which was lethal to wild‐type plants. After plants had been incubated with 400 mM NaCl for two days, the photosystem II activity of wild‐type plants had almost completely disappeared, whereas that of transformed plants remained at more than 50% of the original level. When exposed to a low temperature in the light, leaves of wild‐type plants exhibited symptoms of chlorosis, whereas those of transformed plants did not. These observations demonstrate that the genetic modification of Arabidopsis thaliana that allowed it to accumulate glycinebetaine enhanced its ability to tolerate salt and cold stress.
Post‐transcriptional β‐1,3‐glucanase gene silencing involves increased transcript turnover that is translation‐independent
Authors: Jacobs John J.M.R. , Litière Katia , Van Dijk Victor , Van Eldik Gerben J. , Van Montagu Marc , Cornelissen Marc 
Published: March 2003

SummaryIn tobacco line T17, basic β‐1,3‐glucanases are silenced when a β‐1,3‐glucanase (gn1) transgene of Nicotiana plumbaginifolia is present in a homozygous condition. Co‐suppression of endogenous and transgenic basic β‐1,3‐glucanases occurs via a post‐transcriptional process. This study shows that silencing correlates with a reduced stability of the transcripts encoded by gn1 and the co‐suppressed endogenous glucanase genes. The observed decreases in mRNA stability at least partially explain the reductions in mRNA level. Furthermore, the results show that the enhanced, silencing‐related turnover of gn1 mRNA does not require continued protein synthesis. The implications of these findings for the mechanism of gene silencing are discussed.
The maize gene empty pericarp‐2 is required for progression beyond early stages of embryogenesis
Authors: Scanlon Michael J. , Myers Alan M. , Schneeberger Richard G. , Freeling Michael 
Published: March 2003

SummaryThe defective kernel mutation empty pericarp2‐R (emp2‐R) causes retardation and subsequent abortion of maize kernel development. Analyses of genetic aneuploid kernels indicate that the embryo phenotype is not dependent on the endosperm genotype; the mutation conditions embryo defects even in the presence of a normal endosperm. Embryos reach an abnormal coleoptilar stage before aborting and disintegrating. The mutants form primary embryonic organs only; the scutellum and coleoptile develop, but no leaves are formed. Immunohisto‐localization studies utilized KNOX homeodomain proteins as markers of meristem formation and identity. These analyses indicate that the shoot meristem forms in emp2‐R mutant embryos, but does not mature to a tunica‐corpus shape. No evidence of leaf founder cell initialization was revealed in the mutant meristems. These data indicate that the emp2 gene may be required for embryogenic patterning beyond the coleoptilar stage of development.
Structural analysis of elements contributing to 5′ splice site selection in plant pre‐mRNA transcripts
Authors: Egoavil Cesar , Marton Heather A. , Baynton Clair E. , McCullough Andrew J. , Schuler Mary A. 
Published: March 2003

Summary In vivo analyses of the cis‐acting sequence requirements for pre‐mRNA splicing in tobacco nuclei have previously demonstrated that 5′ splice sites are selected by their position relative to AU‐rich sequences within plant introns and by their degree of complementarity to the 5′ end of U1 snRNA. To identify the specific nucleotide sequences promoting recognition of the 5′ exon‐intron boundary, multiple mutations have been introduced into a 22 nt AU‐rich block positioned between two competing 5′ splice sites in a derivative of pea rbcS3A intron 1. Transient expression of these mutant transcripts has delineated a 9 nt element positioned 30–38 nt downstream from the 5′ splice site whose sequence composition affects 5′ splice site choice. Uridine substitutions within this element do not alter 5′ splice selection patterns, and, in fact, enhance recognition of the upstream +1wt 5′ splice site slightly. Guanosine substitutions in this region, specifically creating an AG‐rich AAAGGAGAGGCAGA motif (mutations shown underlined), reduce recognition of the upstream +1wt 5′ splice site and enhance recognition of the downstream +106E 5′ splice site. Cytosine substitutions at homologous positions marginally reduce recognition of the upstream 5′ splice site. Additional mutations in this 9 nt element suggest that the AAAGGAGAGGCAGA motif acts as an specific 5′ exon‐defining element promoting recognition of downstream 5′ splice sites, while AU‐rich motifs promote recognition of upstream 5′ splice sites. Mutations in an adjacent AU‐rich region attenuate the effects of mutations in this short element but are not in themselves sufficient to alter 5′ splice site selection. It is concluded that specific elements on both sides of the exon‐intron boundary define the 5′ splice site in this plant transcript.
Calcium signalling in Arabidopsis thaliana responding to drought and salinity
Authors: Knight Heather , Trewavas Anthony J. , Knight Marc R. 
Published: March 2003

SummaryChanges in cytosolic free calcium concentration ([Ca2+]cyt) in response to mannitol (drought) and salt treatments were detected in vivo in intact whole Arabidopsis seedlings. Transient elevations of [Ca2+]cyt to around 1.5 µM were observed, and these were substantially inhibited by pretreatment with the calcium‐channel blocker lanthanum and to a lesser extent, the calcium‐chelator EGTA. The expression of three genes, p5cs, which encodes Δ1‐pyrroline‐5‐carboxylate synthetase (P5CS), the first enzyme of the proline biosynthesis pathway, rab18 and Iti78 which both encode proteins of unknown function, was induced by mannitol and salt treatments. The induction of all three genes by mannitol was inhibited by pretreatment with lanthanum. Salt‐induced p5cs, but not rab18 and Iti78, expression was also inhibited by lanthanum. Induction of p5cs by mannitol was also inhibited by the calcium channel‐blockers gadolinium and verapamil and the calcium chelator EGTA, further suggesting the involvement of calcium signalling in this response. Mannitol induced greater levels of p5cs gene expression than an isoosmolar concentration of salt, at both relatively high and low concentrations. However, calcium transients were of a similar magnitude and duration in response to both mannitol and isoosmolar concentrations of salt, suggesting that a factor other than calcium is involved in the discrimination between drought and salinity signals in Arabidopsis. In order to gauge the involvement of the vacuole as an intracellular calcium store in the response of Arabidopsis to mannitol, [Ca2+]cyt was measured at the microdomain adjacent to the vacuolar membrane. The results obtained were consistent with a significant calcium release from the vacuole contributing to the overall mannitol‐induced [Ca2+]cyt response. Data obtained by using inhibitors of inositol signalling suggested that this release was occurring through IP3‐dependent calcium channels.