bluuebunny/crossref_metadata_2025 huggingface dataset:
Marine cements in mid‐Tertiary cool‐water shelf limestones of New Zealand and southern Australia
Authors: Nelson Campbell S. , James Noel P.
Published: March 2003

Large areas of southern Australia and New Zealand are covered by mid‐Tertiary limestones formed in cool‐water, shelf environments. The generally destructive character of sea‐floor diagenesis in such settings precludes ubiquitous inorganic precipitation of carbonates, yet these limestones include occasional units with marine cements: (1) within rarein situbiomounds; (2) within some stacked, cross‐bedded sand bodies; (3) at the top of metre‐scale, subtidal, carbonate cycles; and (4) most commonly, associated with certain unconformities. The marine cements are dominated by isopachous rinds of fibrous to bladed spar, interstitial homogeneous micrite and interstitial micropeloidal micrite, often precipitated sequentially in that order. Internal sedimentation of microbioclastic micrite may occur at any stage. The paradox of marine‐cemented limestone units in an overall destructive cool‐water diagenetic regime may be explained by the precipitation of cement as intermediate Mg‐calcite from marine waters undersaturated with respect to aragonite. In some of the marine‐cemented limestones, aragonite biomoulds may include marine cement/sediment internally, suggesting that dissolution of aragonite can at times be wholly marine and not always involve meteoric influences. We suggest that marine cementation occurred preferentially, but not exclusively, during periods of relatively lowered sea level, probably glacio‐eustatically driven in the mid‐Tertiary. At times of reduced sea level, there was a relative increase in both the temperature and the carbonate saturation state of the shelf waters, and the locus of carbonate sedimentation shifted towards formerly deeper shelf sites, which now experienced increased swell wave and/or tidal energy levels, fostering sediment abrasion and reworking, reduced sedimentation rates and freer exchange of sediment pore‐waters. Energy levels were probably also enhanced by increased upwelling of cold, deep waters onto the Southern Ocean margins of the Australasian carbonate platforms, where water‐mass mixing, warming and loss of CO2locally maintained critical levels of carbonate saturation for sea‐floor cement precipitation and promoted the phosphate‐glauconite mineralization associated with some of the marine‐cemented limestone units.
Isotopic signature of burial diagenesis and primary lithological contrasts in periplatform carbonates (Miocene, Great Bahama Bank)
Authors: Frank Tracy D. , Bernet Karin
Published: March 2003

The stable isotope geochemistry of Miocene sediments from the leeward margin of the Great Bahama Bank was examined to investigate burial diagenetic processes in periplatform carbonates. Data indicate that, in addition to differences in bulk proportions of neritic and pelagic carbonate along the slope, rhythmic variation in primary carbonate content has controlled patterns of burial diagenesis and associated geochemical signatures throughout much of the succession examined. The present study focuses on Ocean Drilling Program Sites 1006 and 1007, the most distal of five sites drilled from marginal to deep basin environments during Leg 166. These Miocene sections are characterized by their cyclic appearance, manifest as decimetre‐ to metre‐scale alternations between light‐coloured ooze/chalk/limestone and dark‐coloured marl/marlstone. The section at Site 1006 contains a high proportion of pelagic carbonate and is unlithified to a subbottom depth of ∼675 m. Fluctuations in δ18O and δ13C values at this site are independent of lithological variation and reflect primary conditions. At Site 1007, located at the toe‐of‐slope and composed of a mixture of bank‐derived and pelagic carbonate, limestones are densely cemented, show little evidence of compaction and have δ18O values up to 2‰ higher than coeval sediments at Site 1006. Marlstones at Site 1007 are poorly cemented, exhibit an increase in compaction‐related features with depth and have lower and more variable δ18O values that are similar to those of coeval sediments at Site 1006. Isotopic and petrographic characteristics of limestone interbeds result from cement precipitation from cold sea water during the first ∼100 m of burial. Higher proportions of insoluble materials and pelagic carbonate seem to have inhibited diagenetic alteration in adjacent marlstones; in spite of significant compaction and pressure solution during burial, original isotopic compositions appear to be best preserved in these intervals at Site 1007. The documented contrasts in petrographic and isotopic patterns illustrate the role of primary sediment composition in controlling lithification processes in periplatform carbonates and stress the importance of considering such factors when interpreting geochemical data from ancient shelf and slope limestones.
Fault‐controlled dolomitization at Swan Hills Simonette oil field (Devonian), deep basin west‐central Alberta, Canada
Authors: Duggan James P. , Mountjoy Eric W. , Stasiuk Lavern D.
Published: March 2003

The partly dolomitized Swan Hills Formation (Middle‐Upper Devonian) in the Simonette oil field of west‐central Alberta underwent a complex diagenetic history, which occurred in environments ranging from near surface to deep (>2500 m) burial. Five petrographically and geochemically distinct dolomites that include both cementing and replacive varieties post‐date stylolites in limestones (depths >500 m). These include early planar varieties and later saddle dolomites. Fluid inclusion data from saddle dolomite cements (Th=137–190 °C) suggest that some precipitated at burial temperatures higher than the temperatures indicated by reflectance data (Tpeak=160 °C). Thus, at least some dolomitizing fluids were ‘hydrothermal’. Fluorescence microscopy identified three populations of primary hydrocarbon‐bearing fluid inclusions and confirms that saddle dolomitization overlapped with Upper Cretaceous oil migration. The source of early dolomitizing fluids probably was Devonian or Mississippian seawater that was mixed with a more 87Sr‐rich fluid. Fabric‐destructive and fabric‐preserving dolostones are over 35 m thick in the Swan Hills buildup and basal platform adjacent to faults, thinning to less than 10 cm thick in the buildup between 5 and 8 km away from the faults. This ‘plume‐like’ geometry suggests that early and late dolomitization events were fault controlled. Late diagenetic fluids were, in part, derived from the crystalline basement or Palaeozoic siliciclastic aquifers, based on 87Sr/86Sr values up to 0·7370 from saddle dolomite, calcite and sphalerite cements, and 206Pb/204Pb of 22·86 from galena samples. Flow of dolomitizing and mineralizing fluids occurred during burial greater than 500 m, both vertically along reactivated faults and laterally in the buildup along units that retained primary and/or secondary porosity.
Diagenetic trends of fluorine concentration in Negev phosphorites, Israel: implications for carbonate fluorapatite composition during phosphogenesis
Authors: Soudry David , Nathan Yaacov
Published: March 2003

An electron probe and chemical study of bulk phosphorite samples and separated constituents from various Negev deposits was carried out together with XRD, FTIR spectroscopy and textural analysis. The results allow a better understanding of the distribution of fluorine in these Upper Cretaceous phosphorite sequences and shed light on variations in the composition of the carbonate fluorapatite (CFA) phase during phosphogenesis. Two facies are recognized: (1) a pristine, microbially generated phosphorite facies; (2) a recycled, peloidal and biodetrital facies. Fluorine distribution in the Negev phosphorites is facies controlled: F/P2O5is much lower in the pristine facies (0·090–0·107) than in the recycled facies (0·107–0·120). In addition, F/P2O5varies considerably between the various constituents of the phosphate fraction; F‐poor francolites (F/P2O5as low as 0·080) co‐exist with F‐rich francolites (F/P2O5as high as 0·135) in the same phosphorite bulk sample. A lower F/P2O5in francolite is associated with higher Cd and Zn concentrations in the phosphorite, an increase in Fe‐rich smectites in the clay fraction and the presence of structural OH in the francolite. The lower F/P2O5ratios in the pristine facies are attributed to high organic deposition rates during the formation of these matted sediments, leading to rapid burial of thein situ‐forming CFA. This is possibly coupled with diffusion of F from sea water into bottom sediments being hampered by microbial mat coatings. These conditions resulted in O2‐depleted porefluids, inducing the precipitation of Cd‐rich Zn sulphides and the formation of Fe‐rich smectites. F‐enrichment probably takes place when the earlier formed F‐poor ‘primary’ CFA is relocated close to the sea floor and bathed with interstitial sea water solutions of higher F concentrations. Oxidation and removal of the sulphide‐bound Cd and Zn apparently occurred together with enrichment in F of the francolite. Combining chemical data with XRD and FTIR results suggests a multistage growth for the Negev phosphate constituents in shifting formational sites and porefluids of varying F concentrations. This multiphase growth is reflected in the patchy distribution of F in the Negev constituents and might explain the inverse correlation between mean CO2/F and F/P2O5ratios of the analysed phosphorites in the two facies. It also suggests that CFA (or an amorphous precursor) initially formed with some OH groups in the apatite structure, which were subsequently substituted by F ions in recycled francolite through re‐equilibration with porefluids of higher F concentrations.
New species of mole crickets of the Gryllotalpa gryllotalpa group (Orthoptera: Gryllotalpidae) from Israel, based on morphology, song recordings, chromosomes and cuticular hydrocarbons, with comments on the distribution of the group in Europe and the Mediterranean region
Authors: BROZA MEIR , BLONDHEIM SYRIL , NEVO EVIATAR
Published: March 2003

Two sibling species of mole crickets of the Gryllotalpa gryllotalpa group inhabit Israel. Both are described as new species based on differences in their morphology, acoustic behaviour, chromosome number, cuticular hydrocarbon pattern and habitats. The species with males having 2n = 23 chromosomes, described in the past as the ‘Dead Sea race’, is designated as G. marismortui sp.n. It is an endangered species. In morphology and chromosome number it is similar to G. cossyrensis Bacetti & Capra from Italy, but differs in the composition of cuticular hydrocarbons. Gryllotalpa marismortui occurs in a limited geographical area along the shore of the Dead Sea. Another species, with 2n = 19 chromosomes, is described as G. tali sp.n. and is found throughout Israel. The calling songs of the males of the new species differ markedly. Females of the respective chromosomal numbers discriminate in favour of the homospecific call. Their habitats are strikingly different: G. marismortui lives in hypersaline soil along the Dead Sea shore (total chloride 187.25 meq %), G. tali inhabits freshwater soil (9.31 meq %). The distribution of the twelve known sibling species and one chromosomal race (not yet described) of the G. gryllotalpa group from Europe and the eastern Mediterranean is summarized. The zoogeography and phylogeny of the group are discussed.
Phylogenetic revision ofBonjeaniaIrwin & Lyneborg (Diptera: Therevidae)
Authors: Winterton Shaun L. , Skevington Jeffrey H. , Irwin Michael E. , Yeates David K.
Published: March 2003

The endemic Australian genusBonjeaniaIrwin & Lyneborg is revised. Seven species are described as new:B. angelikaesp.n.,B. clamosissp.n.,B. dynastissp.n.,B. flavofemoralissp.n.,B. irwinaesp.n.,B. orphnesp.n. andB. trilineatasp.n. Three species,B. actuosa(White),B. nitidifrons(Macquart) andB. segnis(White), are redescribed. All species ofBonjeaniawere compared in a cladistic analysis withAgapophytus albobasalisMann and five exemplars of the speciose sister genusParapsilocephalaKröber, and the phylogenetic relationships ofBonjeaniadiscussed. The male genitalic musculature ofB. clamosissp.n. is described and figured, and discussed with respect to previous studies on other Therevidae.
Molecular variation and phylogeny of members of the Minimus Group of Anopheles subgenus Cellia (Diptera: Culicidae)
Authors: Sharpe Rosie G. , Harbach Ralph E. , Butlin Roger K.
Published: March 2003

Intra‐ and interspecific molecular variation were investigated in four members of the Minimus Group ofAnophelessubgenusCellia:An. aconitus,An. varuna,An. minimusA andAn. minimusC. DNA sequence divergence between these species at a mitochondrial locus (cytochrome oxidase II) and at three nuclear loci (ITS2 and D3 regions of rDNA and guanylate cyclase) is reported. The data confirm the presence of two cryptic species, A and C, withinAn. minimusand provide evidence for the existence of a third species.Anopheles minimusA and C are estimated to have diverged 0.57–1.5 million years ago. The discrepancy observed using the guanylate cyclase intron, which is the fastest evolving region known in the Gambiae Complex but is relatively slowly evolving in the Minimus Group, is discussed. The long‐term effective population sizes ofAn. minimusA and C are estimated to be in their millions, with that of species A being approximately twice the size of species C. This implies thatAn. minimusC has a much wider distribution than currently recognized, with possible widespread implications for vector control. No evidence was found for population structuring in either species A or C: there was greater variation of mitochondrial haplotypes within than among localities. The phylogenetic relationships of Oriental members of the Myzomyia Series are reconstructed.
High‐resolution reconstruction of the last ice sheet in NW Scotland
Authors: Ballantyne  , McCarroll  , Nesje  , Dahl  , Stone  , Fifield
Published: March 2003

Reconstructions of the last (late Devensian) British ice sheet have hitherto been based on assumptions regarding its extent and form. Here we employ observational evidence for the maximum altitude of glacial erosion (trimlines) on mountains that protruded through the ice (palaeonunataks) to reconstruct the form of the ice sheet over ≈ 10 000 km2 of NW Scotland. Contrasts in the clay mineralogy of soils and exposure ages of rock surfaces above and below these trimlines confirm that they represent the upper limit of late Devensian glacial erosion. The reconstruction yields realistic values of basal shear stress and is consistent with independent evidence of ice movement directions. The ice sheet reached ≈ 950 m altitude over the present N–S watershed, descended northwards and north‐westwards, was deflected around an ice dome on Skye and an independent Outer Hebrides ice cap, and probably extended across the adjacent shelf on a bed of deforming sediments.
Slip‐partitioning and fore‐arc deformation at the Sunda Trench, Indonesia
Authors: Baroux  , Avouac  , Bellier  , Sébrier
Published: March 2003

Oblique subduction at the Sunda Trench has produced transpressive deformation of the plate leading edge. A major feature is the right‐lateral Great Sumatran Fault (GSF) which probably absorbs a significant fraction of the trench‐parallel shear. The kinematics of Sunda relative to Australia are discussed on the basis of available GPS data, and geologically determined slip rates on the GSF. In spite of the uncertainty on the plate motion, several robust conclusions can be drawn. The predicted obliquity of the convergence increases northward along the Sumatra Trench, up to about 30°. Slip partitioning is nearly complete along the northern segment of the Sumatra Trench, where the GSF probably accommodates most of the trench parallel shear. Along the southern segment, where obliquity is less than about 20°, slip‐partitioning is not complete as indicated by oblique thrusting at the subduction. There, only a fraction of the trench parallel motion of Australia relative to SE Asia is accommodated along the GSF. These observations suggest that the leading edge behaves like a plastic wedge, except that slip‐partitioning, although incomplete, is observed even at low obliquities.
Matching satellite‐derived gravity signatures and seismicity patterns along mid‐ocean ridges
Authors: De Alteriis G. , Gilg‐Capar L. , Olivet J.L.
Published: March 2003

A world‐wide correlation between satellite‐derived gravity signatures and the relative abundance of teledetected earthquakes over mid‐ocean ridges has yielded some unexpected results. Rift valley disappearances along slow‐spreading centres and attendant excess volcanism coincide with seismicity gaps, at times related to nearby hotspots, whereas earthquake clusters along virtually aseismic, faster‐spreading centres systematically indicate the presence of active propagating ridge tips. Therefore, at the world scale of investigation, seismicity fairly well predicts ridge morphology and 2nd order axial discontinuities. The occurrence of a certain degree of seismicity along the ‘ductile’ Reykjanes ridge south of the Iceland hotspot is tentatively explained in terms of prevailing shear stresses due to oblique spreading which accumulate on the available brittle volume on the flanks of the ridge rather than on its crest.
New visualizations of global tectonic plate motions and plate boundary interactions
Authors: Henderson Donald M.
Published: March 2003

Clear understanding of detailed lithospheric plate motions has been impeded by lack of a suitable means of graphical representation. A series of coloured global maps are presented that reveal more detail in the patterns of both absolute and relative global plate motions. The use of continuous colour to represent velocities overcomes the limitations of earlier maps that used isolated vectors at selected points to indicate plate velocities. Velocity magnitudes and directions for entire surfaces of plates were computed at a resolution of 0.5°, and are shown on two separate maps. Relative motions between plates were decomposed into their shear and normal components, and are plotted on separate maps. Continuous colour is again used to indicate both the directions and magnitudes of sinistral/dextral and convergent/divergent motions for all plate boundaries. A final map of normalized velocity magnitudes for all plates reveals a global, fast ‘belt’ of plate motion that parallels a great circle aligned with the fastest portion of the Pacific Plate and orthogonal to the East Pacific Rise.
Growth rate and life span of Eocene/OligoceneNummulitestests: inferences from Sr/Ca ratio
Authors: Sarangi S. , Sarkar A. , Sarin M. M. , Bhattacharya S. K. , Ebihara M. , Ray A. K.
Published: March 2003

The problem of growth rate and life span ofNummulitesforaminifers, attaining giant sizes during the Eocene, has been addressed by analysing their Sr/Ca ratio across the Eocene/Oligocene Boundary (EOB) of Kutch, western India. The Eocene ratio (˜ 1) rapidly decreases during the Oligocene (˜ 0.5) and is coincident with the extinction of most of the EoceneNummulitesspecies, a rapid enrichment of δ18O and decrease in both test size and species diversity across the boundary. The high Sr/Ca ratio in Eocene foraminifers can be explained by their rapid growth under a favourable climatic condition. The climatic deterioration (e.g. δ18O cooling) across the boundary and during the early Oligocene possibly forced theNummulitesto adopt a slower growth rate (and stunted growth). The rapid growth of the EoceneNummulitesindicates that the giant sizes of these protists need not necessarily involve a large life span.
Styles of tectonic inversion within syn‐orogenic basins: examples from the Central Apennines, Italy
Authors: Scisciani V. , Tavarnelli E. , Calamita F.
Published: March 2003

The geometry of several thrust‐related folds in the Central Apennines of Italy results from a switch in deformation regime, from extension to contraction. This switch in tectonic regime occurred during the deposition of syn‐orogenic sediments, and the emplacement and migration of the thrust belt–foredeep system towards the foreland in Neogene time. The styles of positive tectonic inversion result from normal faults that were steepened, rotated and truncated by thrusts, with local development of minor folds due to buttressing. Normal fault‐controlled escarpments are also locally preserved in the forelimbs and backlimbs of thrust‐related anticlines. The location and amplitudes of contractional structures across the belt reflects the distribution of pre‐thrusting normal faults within precursor syn‐orogenic basins, a result that may improve our understanding of the evolution of Apennine, as well as other thrust belt–foredeep systems.
The remarkable Re–Os chronometer in molybdenite: how and why it works
Authors: Stein H. J. , Markey R. J. , Morgan J. W. , Hannah J. L. , Scherstén A.
Published: March 2003

The Re–Os (rhenium–osmium) chronometer applied to molybdenite (MoS2) is now demonstrated to be remarkably robust, surviving intense deformation and high‐grade thermal metamorphism. Successful dating of molybdenite is dependent on proper preparation of the mineral separate and analysis of a critical quantity of molybdenite, unique to each sample, such that recognized spatial decoupling of187Re parent and187Os daughter within individual molybdenite crystals is overcome. Highly precise, accurate and reproducible age results are derived through isotope dilution and negative thermal ion mass spectrometry (ID‐NTIMS). Spatial decoupling of parent–daughter precludes use of the laser ablation ICP‐MS microanalytical technique for Re–Os dating of molybdenite. The use of a reference or control sample is necessary to establish laboratory credibility and for interlaboratory comparisons. The Rb–Sr, K–Ar and40Ar/39Ar chronometers are susceptible to chemical and thermal disturbance, particularly in terranes that have experienced subsequent episodes of hydrothermal/magmatic activity, and therefore should not be used as a basis for establishing accuracy in Re–Os dating of molybdenite, as has been done in the past. Re–Os ages for molybdenite are almost always in agreement with observed geological relationships and, when available, with zircon and titanite U–Pb ages. For terranes experiencing multiple episodes of metamorphism and deformation, molybdenite is not complicated by overgrowths as is common for some minerals used in U–Pb dating (e.g. zircon, monazite, xenotime), nor are Re and Os mobilized beyond the margins of individual crystals during solid‐state recrystallization. Moreover, inheritance of older molybdenite cores, incorporation of common Os, and radiogenic Os loss are exceedingly rare, whereas inheritance, common Pb and Pb loss are common complications in U–Pb dating techniques. Therefore, molybdenite ages may serve as point‐in‐time markers for age comparisons.
The Cretaceous/Tertiary boundary: sedimentology and micropalaeontology at El Mulato section, NE Mexico
Authors: Alegret L. , Arenillas I. , Arz J. A. , Liesa C. , Meléndez A. , Molina E. , Soria A. R. , Thomas E.
Published: March 2003

ABSTRACT In the El Mulato section (NE Mexico), the Upper Cretaceous marly Méndez and the Lower Palaeogene marly Velasco Formations are separated by a clastic unit. Benthic foraminifera from both marly formations indicate lower bathyal depths. The clastic unit, in contrast, contains platform sands, muddy pebbles and neritic (shallow) faunas mixed with microspherules, indicating that it was allochthonously deposited into the deep basin. The diversity and the variability in origin of the components in the clastic unit, and its sedimentological features, support a model of deposition by turbidity currents related to mass‐wasting processes triggered by the Cretaceous/Tertiary (K/T) boundary impact. Planktic foraminifera were affected by a catastrophic extinction at the K/T boundary, whereas benthic foraminifera show reorganization of the community structure rather than significant extinction. The benthic faunal turnover may have resulted from the drop in primary productivity after the asteroid impact at the end of the Cretaceous.
Insight into the nature of Indian crust underthrusting the Himalaya
Authors: Johnson Michael R. W.
Published: March 2003

ABSTRACTThe nature of the Indian crust underthrusting the Himalaya may be studied in xenoliths within Ordovician granites in the external part of the Himalaya. These peraluminous S‐type granites have travelled forc. 200 km in the Main Central (or related) thrust. The granites and xenoliths sample Indian basement now buried beneath the High Himalayan thrust pile. In low‐strain granites the xenoliths reveal polyphase tectonite fabricsolderthan the fabrics in the country rocks. Most xenoliths show greenschist/lower amphibolite facies assemblages; none is typical granulite facies of the Indian Shield. Therefore, the portion of the Indian crust underthrusting the Himalaya may be early/middle Proterozoic reworked Indian Shield, as in peninsular India. Alternatively reworking may be assigned to the Pan‐African (late Proterozoic) orogeny. This prospect is raised by recent work in East Antarctica but evidence in the Himalaya is rather ambiguous. If confirmed, a Pan‐African event calls for reassessment of the geological history of the Himalayan region, particularly with respect to the placing of India in Gondwanaland.
The promoter of the rice gene GOS2 is active in various different monocot tissues and binds rice nuclear factor ASF‐1
Authors: de Pater B. Sylvia , van der Mark Frits , Rueb Saskia , Katagiri Fumiaki , Chua Nam‐Hai , Schilperoort Rob A. , Hensgens Lambert A. M.
Published: March 2003

A single copy gene has been isolated, termed GOS2, from rice. Sequence comparison revealed highly similar genes in mammals and yeast, indicating that GOS2 encodes an evolutionary conserved protein. GOS2 mRNA was detected in all tissues examined. When the upstream region was translationally fused to the reporter gene gusA it was found to drive expression in a variety of rice tissues and in cell suspensions of other monocot species following introduction by particle bombardment. Therefore, the GOS2 promoter is potentially useful for genetic engineering of monocots. A DNA‐binding activity from rice, termed rice ASF‐1, with similar binding specificity as the cloned tobacco transcription factor TGA‐1a, was found to bind to a TGACG sequence motif in the GOS2 promoter. Possible roles for rice ASF‐1 in the transcriptional activation of the GOS2 promoter are discussed.
Alteration of plant growth and development by Rhizobium nodA and nodB genes involved in the synthesis of oligosaccharide signal molecules
Authors: Schmidt Jürgen , Röhrig Horst , John Michael , Wieneke Ursula , Stacey Gary , Koncz Csaba , Schell Jeff
Published: March 2003

The highly conserved Rhizobium nodulation genes nodABC are required to produce lipid‐linked chitooligosaccharide signal molecules which elicit nodule organogenesis in roots of leguminous plants. Recently, it has been shown that NodB deacetylates chitooligosaccharides at the non‐reducing terminus, so that the free amino group of the chitooligosaccharide backbone can then be acylated by a specific fatty acid. The Rhizobium NodA protein together with the nodB encoded chitooligosaccharide deacetylase are involved in generating small, heat‐stable compounds that stimulate mitosis in protoplasts derived from either legumes or other plant species. To test whether these gene products could play a role in regulation of plant development, we introduced and expressed the Rhizobium meliloti nodA and nodB genes singly or in combination under the control of diverse promoters in tobacco. Altered phenotypes correlating with nodA and nodB gene expression in transgenic plants indicate that tobacco contains the necessary substrates for the NodA and NodB proteins to produce signal molecules modulating plant growth and organ development.
Differential gene expression in nematode‐induced feeding structures of transgenic plants harbouring promoter—gusA fusion constructs
Authors: Goddijn Oscar J.M. , Lindsey Keith , van der Lee Fréderique M. , Klap Joke C. , Sijmons Peter C.
Published: March 2003

Sedentary plant‐parasitic nematodes are able to induce specialized feeding structures in the root system of their host plants by triggering a series of dramatic cellular responses. These changes presumably are accompanied by a reprogramming of gene expression. To monitor such changes, a variety of promoter—gusA fusion constructs were introduced into Arabidopsis and tobacco. Transgenic plants were analysed histochemically for GUS activity in the nematode feeding structures after infection with either Heterodera schachtii or Meloidogyne incognita. Promoters of the Cauliflower Mosaic Virus 35S gene, the bacterial nopaline synthase, rooting loci (rol) and T‐cyt genes and the plant‐derived phenylalanine ammonia‐lyase I gene, which are highly active in non‐infected roots, were all downregulated in the feeding structures as indicated by the strong decrease of GUS activity inside these structures. Less stringent down‐regulation was observed with chimeric gusA fusion constructs harbouring truncated rolB and rolC promoter sequences. Similar observations were made with transgenic Arabidopsis lines that carried randomly integrated promoterless gusA constructs to identify regulatory sequences in the plant genome. Most of the lines that were selected for expression in the root vascular cylinder demonstrated local down‐regulation in feeding structures after infection with H. schachtii. The reverse pattern of GUS activity, a blue feeding structure amidst unstained root cells, was also found in several lines. However, GUS activity that was entirely specific for the feeding structures was not observed. Our data show that the expression of a large number of genes is influenced during the development of the nematode feeding structures.
Isolation and characterization of male flower cDNAs from maize
Authors: Wright Susan Y. , Suner Marie‐Marthe , Bell Philip J. , Vaudin Mark , Greenland Andrew J.
Published: March 2003

Differential screening of two libraries made from whole, immature maize tassels was used to isolate six cDNAs which show enhanced levels of expression in male flowers. MFS1, MFS2, MFS4, MFS10 and MFS18, which were isolated from a 5 cm tassel library, are expressed throughout tassel growth up until mature pollen is produced in the anthers. MFS14, which was isolated from a 10–12 cm tassel library, has a narrower window of expression associated with microsporogenesis and declines as mature pollen is produced. MFS18 mRNA accumulates in the glumes and in anther walls, paleas and lemmas of mature florets. MFS18 mRNA is particularly associated with the vascular bundle in the glumes and encodes a polypeptide of 12 kDa, rich in glycine, proline and serine that has similarities with other plant structural proteins. In contrast, MFS14 mRNA accumulates in the tapetum and encodes a polypeptide of 13 kDa that is rich in alanine. The MFS14 and MFS18 proteins are basic (isolectric points of 11.56 and 9.54, respectively) and both have hydrophobic N‐termini which display all the characteristics of signal peptides, indicating that these proteins may be secreted.
Protein phosphatase inhibitors activate anti‐fungal defence responses of soybean cotyledons and cell cultures
Authors: MacKintosh Carol , Lyon Gary D. , MacKintosh Robert W.
Published: March 2003

The application of a variety of structurally different protein phosphatase inhibitors (okadaic acid, acanthifolicin, microcystins, nodularin, tautomycin, calyculin A, cantharidin and endothall) to cut surfaces of soybean cotyledons (Glycine max L.) resulted in the production of isoflavonoid phytoalexins (plant defence compounds). Daidzein was the predominant isoflavonoid produced by soybean cotyledons in response to protein phosphatase inhibitors. In contrast, several isoflavonoid phytoalexins were seen after application of either an elicitor β‐glucan fraction isolated from yeast extract or hepta‐(1→3, 1→6)‐β‐glucoside which is the most potent elicitor‐active component isolated from the soybean pathogen Phytophthora megasperma f. sp. glycinea. Isoflavonoid production in response to either protein phosphatase inhibitors or elicitors reached a maximum after 20–24 h. The addition of protein phosphatase inhibitors to a soybean cell suspension culture induced the expression of phenylalanine ammonia‐lyase (PAL), the first enzyme in the isoflavonoid biosynthetic pathway. Induction of PAL activity was blocked by protein synthesis inhibitors, cycloheximide or anisomysin, and largely prevented by a protein kinase inhibitor, K252a. Another common response of plant cells to fungal elicitation, alkalinization of the soybean cell culture media, was induced within minutes in response to protein phosphatase inhibitors and was largely prevented by K252a.

These studies suggest a direct role for phosphorylation in activation of plasma membrane ion flux(es), whereas the longer‐term effects of protein phosphatase inhibitors on isoflavonoid production and PAL expression could be due to either direct effects of increased protein phosphorylation, or the secondary consequences of other phosphorylation‐induced cellular changes. They also indicate that protein phosphatase inhibitors are likely to be of general use in investigating mechanisms of plant responses to environmental stimuli.
In situ hybridization localizes avocado sunblotch viroid on chloroplast thylakoid membranes and coconut cadang cadang viroid in the nucleus
Authors: Bonfiglioli Roderick G. , McFadden Geoffrey I. , Symons Robert H.
Published: March 2003

Viroids, small single‐stranded circular RNA molecules, are the smallest known infectious agents in Nature. The apparent inability of viroids to encode for proteins means that they must rely fully on host functions for their replication. The specific ultrastructural localization of viroids is fundamental to the determination of their replication strategies. In this paper the first in situ hybridization study to localize viroids within the cell at the electron microscope level is reported. Biotin‐labelled RNA probes were used with subsequent detection by gold‐labelled monoclonal anti‐biotin antibodies to localize avocado sunblotch viroid and coconut cadang cadang viroid. Avocado sunblotch viroid was located in chloroplasts, mostly on the thylakoid membranes of cells from infected leaves of avocado (Persea americana). In contrast, coconut cadang cadang viroid was located in the nucleolus and nucleoplasm of cells of infected leaves of oil palm (Elaeis guineensis), with a higher concentration in the nucleolus. The results provide insight on the potential host RNA polymerases involved in the replication of these two viroids.
Genetic length polymorphisms create size variation in proline‐rich proteins of the cell wall
Authors: Schmidt John Scott , Lindstrom Jon T. , Vodkin Lila O.
Published: March 2003

Two genes, Prp1 and Prp2, encode proline‐rich proteins that are found in different stages of developing seed coats, hypocotyls, and roots of soybeans (Glycine max (L.) Merr.). PRP1 is found in young seed coats and PRP2 is found later during seed dessication. In some soybean varieties, both proteins are smaller as determined by immunoblotting seed coat proteins separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It was found that Prp1 and Prp2 genes are linked to each other by testing seed coat protein extracts from an F2 population of a cross between the cultivar Richland, which exhibits the larger PRP proteins, and Blackhawk, which has the smaller PRP proteins. The Prp1 and Prp2 genes were separated by approximately 13% recombination. Simultaneous expression of soluble PRP2 polypeptides in the maternal seed coat and underlying aleurone layer of the embryo was found. The molecular basis for the size difference between the two varieties was examined using polymerase chain reaction to isolate the Prp genes from Blackhawk, the variety that exhibited the smaller proteins. Both of the genes from Blackhawk contained length polymorphisms that result in omission of some of the repeat units (pro pro val tyr lys) from the proteins. In Prp1, there were two separate deletions in different parts of the gene, each being two tandem repeats in length. In Prp2, there was only one deletion of two tandem repeats. These deletions occur within the coding regions in a manner that conserves the reading frame. The results are the first description of genetic variation in cell wall proteins and its molecular basis. The nature of these genetic length polymorphisms indicates that the basic repeat unit structure is conserved and that the proline‐rich proteins of the cell wall tolerate loss or gain of integral numbers of repeat units.
A self‐stabilizing Ac derivative and its potential for transposon tagging
Authors: Schmitz Gregor , Theres Klaus
Published: March 2003

With the goal of developing a self‐stabilizing transposon tagging system, a derivative of the maize transposable element Ac (Ds303) harbouring a deletion between bp 246 and 736 has been introduced into tomato (Lycopersicon esculentum) by Agrobacterium tumefaciens‐mediated transformation. The deletion removes the major transcription start site, 84 bp of the putative Ac promoter and part of the untranslated leader. Transpositions from the T‐DNA, where Ds303 was inserted between the mannopine synthase 1′ promoter and the GUS gene, were observed in four independent transgenic plants analysed. After transposition the transposed Ds303 elements were stably integrated in the genome and could not transactivate a tester Ds element. However, somatic and germinal transpositions of the transposed Ds303 elements occurred in the presence of a transposase source.
Complementary deletions in expressed potato U2snRNA gene variants support the hypothesis that stem—loop IIb is dispensable for splicing
Authors: Brown John W.S. , Simpson Craig G. , Clark Gillian P. , Waugh Robble
Published: March 2003

A polymerase chain reaction (PCR) strategy designed to amplify DNA sequences between closely linked U2snRNA genes has generated extensive coding and 5′ regulatory sequence information on the potato U2snRNA multigene family. Two of the U2snRNA coding sequences isolated differed substantially from normal U2snRNAs by containing both complementary deletions and regions of novel sequence. However, sequences such as Sm‐binding sites and loops of stem—loops III and IV, which are some of the most highly conserved regions in U2snRNA, remain highly conserved in these genes. The complementary deletions would effectively remove stem—loop IIb which has been shown in yeast to be unnecessary for pre‐mRNA splicing. Transcripts from one of the genes have been detected by reverse transcriptase‐PCR (RT‐PCR) in total RNA. These novel U2snRNA genes represent the first reported example of naturally occurring structural variants and provide support for the proposed non‐essential role of U2snRNA stem—loop IIb.
Targeted recombination in plants using Agrobacterium coincides with additional rearrangements at the target locus
Authors: Risseeuw Eddy , Offringa Remko , Franke‐van Dijk Marry E.I. , Hooykaas Paul J.J.
Published: March 2003

The use of Agrobacterium for gene targeting in plants has been investigated. Leaf protoplasts of five transgenic tobacco lines, containing a T‐DNA insertion with a defective npt‐II gene at different positions in the plant genome, were transformed via Agrobacterium with a T‐DNA containing a npt‐II repair gene. After selection for kanamycin resistance and PCR analysis six recombinants were derived from four of the target lines. The recombination frequencies were similar for the different target lines with one recombinant from approximately 3×105 transformants. Apparently gene targeting is more or less independent of the location of the target construct in the plant genome. Molecular analysis revealed that gene targeting had occurred in five of the six recombinant lines. However precise recombination had occurred in only one line, while in the other four lines restoration of the npt‐II gene was accompanied by a deletion of part of the target locus. The sixth recombinant line showed restoration of the npt‐II gene of the incoming T‐DNA construct which was inserted in the plant genome at a position closely linked to the target locus. The different recombination products favour a model in which recombination is via gene conversion followed by reintegration of the synthesized DNA via homologous or illegitimate recombination rather than a reciprocal exchange of DNA between two cross‐overs.
Multiple serine phosphorylation sites on the 30 kDa TMV cell‐to‐cell movement protein synthesized in tobacco protoplasts
Authors: Haley Ann , Hunter Tony , Kiberstis Paula , Zimmern David
Published: March 2003

p30, the protein required for cell‐to‐cell movement of tobacco mosaic virus (TMV), has a slightly reduced mobility on SDS‐polyacrylamide gels when isolated by immunoprecipitation from TMV‐infected protoplasts compared with that of p30 translated from viral RNA in vitro. Further investigation established a probable cause for the difference in mobility between the two: protoplasts incorporate [32P]orthophosphate into p30 at multiple sites, predominantly as phosphoserine. Tryptic peptide mapping reveals at least five internal phosphopeptides in p30, besides the C‐terminal tryptic phosphopeptide already reported, involving at least two distinct domains of the protein (at residues 61–114 and residues 212–231), which may be substrates for different protein kinases. These structural results are consistent with a three‐domain model for the TMV movement protein with two regulatory domains similar to that recently proposed on genetic grounds for dianthovirus movement proteins.
Cell cycle‐regulated histone gene expression in synchronized plant cells
Authors: Reichheld Jean‐Philippe , Sonobe Seiji , Clément Bernadette , Chaubet Nicole , Gigot Claude
Published: March 2003

The regulation of histone gene expression during the cell cycle has been studied in a synchronized tobacco (BY2) cell suspension. Maximal expression was found in S phase but unlike other eukaryotic organisms the amount of histone mRNA was not coupled to DNA synthesis. Using aphidicolin as an inhibitor of DNA synthesis either before or at mid‐S phase an accumulation of histone mRNAs was found in the absence of any DNA synthesis which was not due to a stabilization of the mRNAs but to actual control at the transcriptional level. At the completion of unperturbed or delayed S phase, histone mRNAs were selectively degraded by a post‐transcriptional mechanism requiring de novo transcription.
Feedback inhibition of fatty acid synthesis in tobacco suspension cells
Authors: Shintani David K. , Ohlrogge John B.
Published: March 2003

The flux through many metabolic pathways is regulated through feedback inhibition on regulatory enzymes by endproducts of the pathway. Whether feedback inhibition occurs in fatty acid synthesis in plants has been investigated. The addition of exogenous oleic acid, in the form of oleoyl‐Tween (Tween‐18:1) caused a three‐ to fivefold decrease in the rate of [1‐14C]acetate incorporation into tobacco suspension cell fatty acids. The decrease in acetate incorporation occurred rapidly upon addition of Tween‐18:1 and appeared to be specific for fatty acid synthesis. In order to elucidate possible regulatory steps involved in the feedback regulation of fatty acid synthesis in plant cells, tobacco cell acyl‐ACP intermediates were analyzed using a combination of [1‐14C]acetate labeling and immunoblot analysis. Within 30 min of exogenous lipid addition, acetyl‐ACP increased and long chain acyl‐ACP decreased, whereas medium chain acyl‐ACP levels remained constant. These acyl‐ACP profiles observed during the feedback inhibition were those predicted to occur under conditions where the flux through fatty acid synthesis is decreased due to limiting levels of malonyl‐CoA and therefore indicated that acetyl‐CoA carboxylase (ACCase) was centrally involved in the feedback regulation of fatty acid synthesis. Immunoblot analysis showed that ACCase protein levels did not change during the feedback inhibition, indicating that the feedback inhibition of fatty acid synthesis in plant cells occurs through biochemical or post‐translational modification of ACCase and possibly other fatty acid synthesis enzymes.
Expression of the early nodulin, ENOD40, in soybean roots in response to various lipo‐chitin signal molecules
Authors: Minami Eiichi , Kouchi Hiroshi , Cohn Jonathan R. , Ogawa Tomoya , Stacey Gary
Published: March 2003

The lipo‐chitin (LCO) nodulation signal (nod signal) purified from Bradyrhizobium japonicum induced nodule primordia on soybean (i.e. Glycine soja) roots. These primordia were characterized by a bifurcated vascular connection, cortical cell division, and the accumulation of mRNA of the early nodulin gene, ENOD40. A chemically synthesized LCO identical in structure to the Nod signal purified from B. japonicum cultures showed the same activity when inoculated on to soybean roots. Surprisingly, synthetic LCO or chitin pentamer, inactive in inducing root hair curling (HAD) or cortical cell division (NOI) in G. soja, induced the transient accumulation of ENOD40 mRNA. In roots inoculated with such LCO, ENOD40 mRNA was abundant at 40 h after inoculation but decreased to the background levels 6 days after inoculation. In contrast, nod signals active in inducing HAD and NOI induced high levels of ENOD40 accumulation at 40 h and 6 days after inoculation. In situ hybridization analysis showed that ENOD40 mRNA accumulated in the pericycle of the vascular bundle at 24 h after root inoculation with nod signal. At 6 days post‐inoculation with nod signal, ENOD40 expression was seen in dividing subepidermal cortical cells. These results provide morphological and molecular evidence that nodule induction in soybean in response to purified or synthetic nod signal is similar, if not identical, to nodule formation induced by bacterial inoculation. Surprisingly, ENOD40 mRNA accumulation occurs in response to non‐specific chitin signals. This suggests that, in the case of ENOD40, nodulation specificity is not determined at the level of initial gene expression.
Characterization of LRP, a leucine‐rich repeat (LRR) protein from tomato plants that is processed during pathogenesis
Authors: Tornero Pablo , Mayda Esther , Gómez María Dolores , Cañas Luis , Conejero Vicente , Vera Pablo
Published: March 2003

This paper describes the isolation and characterization of LRP, a new gene from tomato plants. The deduced amino acid sequence showed that the encoded protein is enriched in leucine, and contains interesting structural motifs. LRP contains four tandem repeats of a canonical 24 amino acid leucine‐rich repeat (LRR) sequence present in different proteins that mediates molecular recognition and/or interaction processes. Genomic organization and intron‐exon arrangement of LRP favor the hypothesis that the LRR domains present in LRP evolved by exon duplication and shuffling. LRP expression analysis and immunohisto‐chemical localization studies of the encoded protein indicate that the gene is under developmental regulation exhibiting tissue‐specificity, particularly in certain cell types of the stele, like phloem fibers, parenchyma cells of the protoxylem, and in the cell files that constitute the rays of the secondary xylem. It is shown that this gene is upregulated in diseased tomato plants infected with citrus exocortis viroid. However, in this pathogenic context, LRP is processed proteolytically to a lower molecular weight form by a host‐induced extracellular protease. The structural characteristics of LRP, its spatio‐temporal pattern of expression, and its post‐translational processing during pathogenesis, suggest this protein as a candidate molecule that may mediate recognition and interaction events taking place in the plant extracellular matrix under normal and/or pathogenesis‐related conditions.