bluuebunny/crossref_metadata_2025 huggingface dataset:
The link between oxygen isotope resetting, partial melting, and fluid flow in metamorphic terrains
Authors: Cartwright  , Buick
Published: March 2003

A correlation between the style of partial melting and synmeta‐morphic fluid flow exists in metapelites from the Mount Lofty Ranges, Reynolds Range, and Omeo Zone (Australia). Mount Lofty Ranges migmatites comprise granitic leucosomes in rocks that are still biotite rich, with no indications of other mafic minerals being formed along with the melts. By contrast, in the Reynolds and Omeo migmatites, garnet, cordierite, and/or spinel formed along with the melts. Oxygen isotope data are most consistent with the Mount Lofty Ranges undergoing significant fluid–rock interaction during regional metamorphism, which may have fluxed fluid‐present partial melting. By contrast regional metamorphic fluid flow in the Reynolds Range and Omeo Zone was limited, leading to partial melting via fluid‐absent reactions. The style of melting reactions may help to constrain the timing of isotopic resetting and fluid flow in metamorphic terrains, which is currently a contentious issue.
Steep bending of continental lithosphere without its stretching or plate collision: an indication for lithospheric failure and phase transitions
Authors: Artyushkov
Published: March 2003

The Black Sea and Peri‐Caspian basin include steep slopes which are 4–10 km high and only 20–30 km wide. They formed without extension‐related normal faulting beneath the slopes and convergence in the adjacent regions. In the Peri‐Caspian basin a steep bending of the lithosphere was associated with rapid crustal subsidence which evolved over a few million years. The large intensity and high rate of the deformations indicate a temporary loss of high rigidity in the lithospheric layer which occurred independently of plate‐boundary‐related processes. The origin of this phenomenon presents a special problem. A tentative explanation is that a lithospheric failure in cool intraplate regions can result from infiltration of volatiles from the asthenosphere and rapid metamorphism in mafic rocks in the lower crust.
Extensional tectonics in the Gorringe Bank rocks, Eastern Atlantic ocean: evidence of an oceanic ultra‐slow mantellic accreting centre
Authors: Girardeau  , Cornen  , Beslier  , Le Gall  , Monnier  , Agrinier  , Dubuisson  , Pinheiro  , Ribeiro  , Whitechurch
Published: March 2003

The Gorringe Bank corresponds to an upper mantle peridotite ridge enclosing a 500‐m thick/ 50‐km long laccolith‐like body of gabbro, locally cut and poorly covered by tholeiitic rocks. Strain and kinematic analysis of orientated gabbros and peridotites sampled during the GORRINGE diving cruise (1996) provides new kinematic constraints on extensional high‐temperature deformation recorded at deep levels during stretching, near an accreting centre axis of a mantle‐dominant oceanic lithosphere. It is argued that the Gorringe Bank lithosphere formed at an oceanic ultra‐slow, N010°–020°‐trending accreting centre, mostly by passive tectonic denudation of the mantle, without any synchronous large magmatism. This peculiar lithosphere may be representative of the Iberia oceanic domain located between the continent and the J anomaly ridge, which likely marks the beginning of true spreading at an oceanic spreading ridge.
Discriminating between tectonic and eustatic controls on the stratigraphic record in the Paris basin
Authors: Robin  , Guillocheau  , Gaulier
Published: March 2003

The quantification of tectonic and eustatic factors in the control of the sedimentary record is one of the main questions in sedimentary basin dynamics. We propose two methods allowing: (i) 3D measurement of accommodation at basin scale and (ii) to decipher between local (10–100 km wavelength) and basin‐scale accommodation. The local signal is necessarily of tectonic origin, the basin‐scale signal is of both eustatic and large tectonic origin. The measurement of accommodation requires (a) high‐resolution time‐lines calibrated in ages (sequence stratigraphy on well‐logs and biostratigraphy on cores), (b) decompacted lithologies (well‐logs), and (c) palaeodepth/palaeoaltitude (sedimentology and well‐logs). Application of these methods to the intracratonic Paris basin during the Lias (early Jurassic) suggests a tectonic origin for the 1–5 Myr stratigraphic cycles, with basin‐scale flexure during transgressive half‐cycles, and 10–100 km uplift of basement units, during regressive half‐cycles.
New estimates of carbon transfer to terrestrial ecosystems between the last glacial maximum and the Holocene
Authors: Beerling
Published: March 2003

Ice core records of atmospheric CO2 show an ≈ 80 ppm rise between the last glacial maximum (LGM) and the mid‐Holocene during a corresponding world‐wide expansion of the terrestrial biomass and changes in ocean chemistry. Therefore, the absolute amount of carbon transferred to the atmosphere, probably from the oceans, remains uncertain. To address this issue, I evaluated changes in terrestrial ecosystem carbon storage and isotopic fractionations between the LGM and the mid‐Holocene using a process‐based terrestrial carbon cycle model forced with two general circulation model (GCM) simulations of each interval. The results indicate that global carbon storage in terrestrial ecosystems (vegetation and soils) increased by 668 Gt C during the last glacial–interglacial transition, a value within the range obtained from a revised global carbon isotope mass‐balance analysis (550–680 Gt C), and consistent with independent estimates from the marine isotopic record.
The Gargano Promontory: a Neogene contractional belt within the Adriatic plate
Authors: Bertotti  , Casolari  , Picotti
Published: March 2003

The Gargano Promontory lies on the Adriatic plate between the Dinaride and Apennine fold‐and‐thrust belts and associated foredeeps. Neogene sediments and structures in the Gargano Promontory demonstrate the existence of significant contrac‐tional structures which have not been reported previously. Beginning in early Miocene times, the future Gargano Promontory experienced shortening along NW‐trending, mainly SW‐vergent folds and thrusts. Deformation persisted until the Tortonian, and, most likely, until the Messinian. Limited NW‐directed contraction affected the Promontory probably during Pliocene times. Morphological relief was minimal until the Messinian but from the middle Pliocene onwards, it was substantially similar to the present‐day one partly as a consequence of extension along NE–SW‐trending normal faults. The along‐strike projection of kinematic relationships and quantities observed in the Gargano might call for a re‐interpretation of previously underestimated structures NW and SE of the Promontory.
Late Quaternary rapid climate change in northern Chile
Authors: Lamy  , Klump  , Hebbeln  , Wefer
Published: March 2003

Analyses of terrigenous sediments from the Chilean continental slope off the southern border of the Atacama desert (27.5°S), focusing on illite crystallinity and the Fe:Al ratio of the sediments, reveal a high‐frequency variability of the position of the Southern Westerlies, which is very similar to the coeval short‐term climatic events known from Greenland ice cores and from North Atlantic sediments. Besides showing dominantly precession‐driven variability in precipitation over the Andes, these analyses also reveal rapid changes in weathering intensity along the Chilean Coastal Range during the last 80,000 years. These rapid changes occur at much shorter timescales than the 19–100 kyr orbital forcing of the Milankovitch cycles.
Nutrients, sea level and tectonics: constrains for the facies architecture of a Miocene carbonate ramp in central Italy
Authors: Brandano Marco , Corda Laura
Published: March 2003

ABSTRACT In the western part of the central Apennines, Lower–Middle Miocene carbonates were deposited on a tropical–subtropical carbonate ramp. They record two long‐term cycles, the first of which is illustrated in this paper. Between 21 and 17.5 Ma, Miocene carbonates, paraconformably overlying the Cretaceous limestones, record a transgressive event during a time of global (2nd order) sea‐level lowstand. It is postulated that this deviation is related to an increase in tectonic subsidence. Between 17.5 Ma and 16–15 Ma, with a progressive relative sea‐level rise, the inner–middle ramp facies belt stepped back, whereas the bryozoan‐dominated outer ramp facies belt stepped back but simultaneously prograded. This bloom of suspension‐feeding organisms is interpreted to reflect an increased nutrient availability, hence a change from oligotrophic to eutrophic conditions. Strontium‐isotope dates constrain correlation of the second phase with a eutrophic event possibly linked to the influence of the neighbouring Apenninic accretionary wedge and foredeep system.
The Cretaceous megabreccias of the Gargano Promontory (Apulia, southern Italy): their stratigraphic and genetic meaning in the evolutionary framework of the Apulia Carbonate Platform
Authors: Graziano Roberto
Published: March 2003

Huge megabreccias occur at the eastern margin of the Cretaceous Apulia Carbonate Platform (Gargano Promontory, southern Italy). Their stratigraphic and genetic meaning are controversial in the debated geological evolution of the Apulia Platform. New stratigraphic analyses have revealed that three distinct megabreccia levels occur within the coarse debrites that were previously interpreted to be the result of repeated collapses of a scalloped platform margin during the late Albian–Cenomanian. Each level has peculiar chronostratigraphic distribution, geometry, composition and genetic features. They are the Posta Manganaro Megabreccias (late early Aptian to late Albian pp.), Monte S. Angelo Megabreccias (early–middle Cenomanian) and Belvedere di Ruggiano Megabreccias (middle Turonian). These deposits overlie regional, tectonically enhanced unconformities of late early Aptian, late Albian and late Cenomanian age. These megabreccias, which were formed, respectively, during drowning, prograding and exposure events of the Apulia Platform, reflect important turning points in its Cretaceous geodynamic evolution.
Stress orientations found in north‐east Germany differ from the West European trend
Authors: Roth F. , Fleckenstein P.
Published: March 2003

Knowledge about the acting stresses is of crucial importance for understanding the tectonics of a region. Data about the stress field in north‐eastern Germany used to be very rare. In general, it was assumed that the orientation of the larger horizontal principal stress (SH) is similar to that found for western Germany and central West‐Europe, i.e. NW–SE. To check this, several borehole logs of the late 1980s were analysed for information on the principal horizontal stress orientations: they include Four‐Arm‐Dipmeter and borehole televiewer data from 15 boreholes. The depth range of our stress results reaches from 1500 to 6700 m. They were compared to a few other data, especially from hydraulic fracturing, and to recent findings on the stresses in the Northwest German basin. In contrast to expectation, SH derived from breakout orientations below the salt layers displayed N to NE orientation. The latter was found at 10 locations spread over the NE‐German basin from Berlin to the Baltic sea, from the Polish border to the former border between East and West Germany. Moreover, this stress rotation in the subsaline formations seems to be the continuation of a trend found in the NW German basin.
The lower crust beneath cratonic north‐east Europe: isotopic constraints from garnet granulite xenoliths
Authors: Downes Hilary , Markwick Andrew J. W. , Kempton Pamela D. , Thirlwall Matthew F.
Published: March 2003

Lower crustal garnet‐bearing mafic granulite xenoliths from beneath the cratonic areas of NE Europe (NW Russia, Belarus, Finland) have unradiogenic 143Nd/144Nd ratios that differ strongly from those of xenoliths from beneath Phanerozoic regions of the European plate and worldwide, but closely resemble xenoliths from other cratonic regions of the world. Phanerozoic lower crustal xenoliths worldwide also show a very limited range of Pb isotope compositions whereas most cratonic lower crustal xenoliths have more varied but usually unradiogenic Pb isotope compositions, plotting to the left of the Geochron. However, many of the xenoliths from beneath NE Europe plot on the right‐hand side of the Geochron and also have more radiogenic 208Pb/204Pb ratios. Thus, the lower crust of NE Europe shows characteristics of both cratonic lower crust (unradiogenic Nd isotopes) and Phanerozoic lower crust (radiogenic Pb isotopes). Its present‐day low U/Pb and Th/Pb ratios indicate that it has been depleted in heat‐producing elements, but the radiogenic Pb isotope ratios show that this depletion occurred relatively recently.
High slip rate for a low seismicity along the Palu‐Koro active fault in central Sulawesi (Indonesia)
Authors: Bellier Olivier , Sébrier Michel , Beaudouin Thierry , Villeneuve Michel , Braucher Régis , Bourlès Didier , Siame Lionel , Putranto Eka , Pratomo Indyo
Published: March 2003

In eastern Indonesia, the Central Sulawesi fault system consists of complex left‐lateral strike‐slip fault zones located within the triple junction area between the Pacific, Indo‐Australian and Eurasian plates. Seismicity in Central Sulawesi documents low‐magnitude shallow earthquakes related, from NW to SE, to the NNW‐trending Palu‐Koro (PKF) and WNW‐trending Matano fault zones. Study of the active fault traces indicates a northward growing complexity in the PKF segmentation. Left‐lateral displacement of 370 ± 10 m of streams incised within fans, whose deposition has been dated at 11 000 ± 2300 years, yields a calculated PKF horizontal slip rate of 35 ± 8 mm yr−1. This geologically determined long‐term slip rate agrees with the far‐field strike‐slip rate of 32–45 mm yr−1previously proposed from GPS measurements and confirms that the PKF is a fast slipping fault with a relatively low level of seismicity.
Widespread fluid expulsion along the seafloor of the Costa Rica convergent margin
Authors: Bohrmann Gerhard , Heeschen Katja , Jung Carmen , Weinrebe Willi , Baranov Boris , Cailleau Béatrice , Heath Richard , Hühnerbach Veit , Hort Matthias , Masson Douglas , Trummer Irmgard
Published: March 2003

Active fluid and gas transport were measured and observed along more than 200 km of the convergent margin of Costa Rica during cruise SO144‐2 aboard RV Sonne. Ten profiles were run with the TV‐sled OFOS, eight of which detected the dense occurrence of cold vent sites. This discovery shows that seafloor fluid expulsion is widely spread along the Pacific margin of Costa Rica. Surficial evidence of fluid expulsion is indicated by the appearance of chemosynthetic vent organisms such as bacterial mats, vesicomyid, solemyid and mytilid bivalves and tubeworms. Numerous active vents were indicated by elevated methane concentrations (≤ 200 nmol L–) in the bottom water. Although fluid‐venting activity was known previously from a small area south of Nicoya Peninsula, the present study documents active seepage at landslides, headwall scarps related to seamount subduction, morphological intersections of faults and mid‐slope mud volcanoes.
Negative and positive regulation of a novel proline‐rich protein mRNA by fungal elicitor and wounding.
Authors: Sheng J , D'Ovidio R , Mehdy MC
Published: March 2003

The structure and expression of a cDNA clone (PvPRP1) isolated from a cDNA library prepared from bean (Phaseolus vulgaris) cells treated with fungal elicitor have been characterized. Sequence analysis of the 1.1 kb insert revealed a complete open reading frame which encodes a 32 kDa protein. The protein resembles other proline‐rich proteins in plants but possesses several unique features: (i) the N‐terminal half of the protein is proline rich and contains three identical repeats of Pro‐Val‐ His‐Pro‐Pro‐Val‐Lys‐Pro‐Pro‐Val and six related repeats; (ii) the proline‐rich region contains two tracts of six histidine residues; and (iii) the C‐terminal half is low in proline and lacks repeats. Genomic blotting experiments suggest the presence of a single PvPRP1 gene as well as more distantly related genes within the bean genome. A dramatic decrease in PvPRP1 mRNA levels occurs within 2 h of elicitor treatment of cell cultures. The PvPRP1 mRNA is present at a moderate level in hypocotyls. Upon wounding, the mRNA level initially decreases over 5 h and then accumulates over 25 h to levels which are higher than the basal level in unwounded hypocotyls. Based on the similarity to other proline‐rich proteins with repeated motifs, including the presence of a putative signal peptide, it is likely that the PvPRP1 protein is targetted to the cell wall. The expression of the PvPRP1 gene appears to be integrated with the remodeling of the plant cell wall during the defense response.
Construction and expression of nonsense suppressor tRNAs which function in plant cells
Authors: Franklin Scott , Lin Tsai Yun , Folk William R.
Published: March 2003

An Arabidopsis thaliana L. DNA containing the tRNATrpUGG gene was isolated and altered to encode the amber suppressor tRNATrpUAG or the ochre suppressor tRNATrpUAA. These DNAs were electroporated into carrot protoplasts and tRNA expression was demonstrated by the translational suppression of amber and ochre nonsense mutations in the chloramphenicol acetyltransferase (CAT) reporter gene. DNAs encoding tRNATrpUAG and tRNATrpUAA nonsense suppressor tRNAs caused suppression of their cognate nonsense codons in CAT mRNAs, with the tRNATrpUAG gene exhibiting the greater suppression under optimal conditions for expression of CAT. The development of these translational suppressors which function in plant cells facilitates the study of plant tRNA gene expression and will make possible the manipulation of plant protein structure and function.
A gibberellin‐regulated gene from wheat with sequence homology to cathepsin B of mammalian cells
Authors: Cejudo Francisco J. , Murphy George , Chinoy Catherine , Baulcombe David C.
Published: March 2003

A previous report described several cDNAs corresponding to mRNAs which accumulated in wheat aleurone layers treated with gibberellic acid (GA) (Baulcombe and Buffard, 1983). The protein sequence deduced from one of these clones (2529) has extensive similarity to the thiol protease, cathepsin B from mammalian cells. Southern analysis of wheat DNA has shown that the 2529 mRNA is encoded by a small family of genes carried on the group 4 chromosome. The nucleotide sequence of a member of the gene family expressed at a low level in aleurone layers and the use of a primer extension assay to identify a clone of a member of the gene family producing an abundant mRNA are reported. The 2529 mRNA accumulates in the scutellum and the aleurone layer of germinating grains where its expression is regulated by GA. In the scutellum the expression was restricted to the parenchyma, suggesting that the 2529 product may have a role other than for mobilization of the endosperm.
The root‐knot nematode resistance gene (Mi) in tomato: construction of a molecular linkage map and identification of dominant cDNA markers in resistant genotypes
Authors: Ho Jeong‐Yau , Weide Rob , Ma Helen M. , van Wordragen Monique F. , Lambert Kris N. , Koornneef Maarten , Zabel Pim , Williamson Valerie M.
Published: March 2003

A dominant allele at the Mi locus on chromosome 6 of tomato (Lycopersicon esculentum Mill) confers resistance to three species of root‐knot nematodes (Meloidogyne). The resistance, which is associated with a localized necrotic response, was originally introduced into tomato from the wild species Lycopersicon peruvianum. As a step towards the molecular cloning of Mi, we have identified closely linked DNA markers from both cDNA and genomic DNA libraries as restriction fragment length polymorphisms (RFLPs). DNA from tomato populations segregating for nematode resistance was analyzed to generate a highresolution genetic map of this region. Additional information on gene order was obtained by comparing the size of the introgressed L. peruvianum chromosomal segment within a collection of nematode‐resistant tomato lines. Among the four cDNA markers that are tightly linked to Mi, three are dominant, i.e. L. peruvianum‐specific. One cDNA marker corresponds to a gene family comprising 20–30 members, one of which is diagnostic for all nematode‐resistant genotypes tested. The presence of non‐homologous sequences around the Mi gene may contribute to the suppression of recombination in this region of the genome in crosses heterozygous for Mi. The potential of ‘walking’ from closely linked markers to Mi is discussed.
3′‐end processing of the maize 27 kDa zein mRNA
Authors: Wu Lin , Ueda Takashi , Messing Joachim
Published: March 2003

Cis‐regulatory elements involved in the mRNA 3′‐end processing of the 27 kDa zein gene have been investigated by deletion and site‐directed mutagenesis analyses. In the 3′ flanking region of the 27 kDa zein gene, several AATAAA‐like sequences and a sequence resembling the mammalian GT‐rich sequence are present around the polyadenylation sites. Among the multiple AATAAA‐like sequences, the duplicated AATGAA motifs, located 30–40 bp upstream from the polyadenylation sites, have been shown to play roles as polyadenylation signals. Although either of the two AATGAA motifs can function as a polyadenylation signal in chimeric gene constructs, the one proximal to the polyadenylation sites is likely to be the functional polyadenylation signal in the 27 kDa zein gene. Deletion of the downstream GT‐rich sequence as well as alteration of the sequence surrounding the poly‐adenylation sites has little effect on the mRNA 3′‐end processing. However, the sequence elements located upstream from the polyadenylation signals are essential for the mRNA 3′‐end processing. Mutations in the AATGAA motifs or the upstream sequences reduced the level of a reporter gene expression. A model depicting the mechanism involved in the 3′‐end processing of the 27 kDa zein mRNA is presented.
The ubiquitous presence of exopolygalacturonase in maize suggests a fundamental cellular function for this enzyme
Authors: Dubald Manuel , Barakate Abdellah , Mandaron Paul , Mache Régis
Published: March 2003

Exopolygalacturonase (exoPG) is a pectin‐degrading enzyme abundant in maize pollen. Using immunochemistry and in situ hybridization it is shown that in addition to its presence in pollen, exoPG is also present in sporophytic tissues, such as the tapetum and mesophyll cells. The enzyme is located in the cytoplasm of pollen and of some mesophyll cells. In other mesophyll cells, the tapetum and the pollen tube, exoPG is located in the cell wall. The measurement of enzyme activity shows that exoPG is ubiquitous in the vegetative organs. These results suggest a general function for exoPG in cell wall edification or degradation. ExoPG is encoded by a closely related multigene family. The regulation of the expression of one of the exoPG genes was analyzed in transgenic tobacco. Reporter GUS activity was detected in anthers, seeds and stems but not in leaves or roots of transgenic plants. This strongly suggests that the ubiquitous presence of exoPG in maize is the result of the expression of different exoPG genes.
Four members of the maize β‐tubulin gene family are expressed in the male gametophyte
Authors: Rogers H.J. , Greenland A.J. , Hussey P.J.
Published: March 2003

Four different β‐tubulin cDNA clones have been identified in maize pollen cDNA libraries. Three of the four cDNA clones represent new maize β‐tubulin genes that have been designated tub3, tub4 and tub5. It is shown that the β‐tubulin gene family in maize is more complex than originally anticipated and more complex than those in vertebrates. In the maize β‐tubulin gene family the tub3, tub4 and tub5 genes are shown to represent small β‐tubulin gene subfamilies. Differences in the abundance of the tub3, tub4 and tub5 transcripts are seen among vegetative and reproductive tissues. The tub3 and tub4 transcripts are most abundant in pollen. In spikelet development, abundance of the tub3 transcript increases markedly from the 0.7 cm to the 1.0 cm spikelets whilst the levels of tub4 transcript closely resemble those of total β‐tubulin transcript in the organs examined. The tub3 and tub4 genes appear to have diverged recently in the evolution of the maize β‐tubulin gene family. The tub5 gene is expressed in pollen but its transcript is most abundant in maize vegetative tissues.
Light‐regulated and endogenous fluctuations of chloroplast transcript levels in Chlamydomonas. Regulation by transcription and RNA degradation
Authors: Salvador Maria L. , Klein Uwe , Bogorad Lawrence
Published: March 2003

Changes in the relative sizes of pools of transcripts of organelle genes during plastid development are common in flowering plants, but technical difficulties have prevented direct determinations of the effects of changes in rates of transcription and degradation on such fluctuations. It has been possible to follow both rates in Chlamydomonas reinhardtii. In synchronous or asynchronous cultures of cells grown in 12 h light/12 h dark periods, sizes of pools of transcripts of the chloroplast genes atpA, atpB, tufA, and psaB fluctuate. Differences in chloroplast transcript abundances in light/dark cycles were found to be cell cycle‐independent but controlled by either an endogenous rhythm (atpA, atpB, and tufA) or by light (psaB). In vivo labeling experiments showed that transcriptional regulation and light/dark‐regulated degradation both contribute, in gene‐specific manners, to the level of transcripts of individual C. reinhardtii chloroplast genes in cells grown in alternating light/dark cycles.
Transposition of the maize Ds element from a viral vector to the rice genome
Authors: Sugimoto Kazuhiko , Otsuki Yoshiaki , Saji Shoko , Hirochika Hirohiko
Published: March 2003

The geminivirus miscanthus streak virus (MiSV) was used as a gene vector to study the transposition of the maize Ds element in rice protoplasts. Efficient excision of the Ds from the MISV vector was observed only when the MiSV vector was allowed to replicate and the plasmid expressing the transposase gene encoded by Ac was co‐transfected. Under the same condition, the Ds carrying a hygromycin phosphotransferase gene (Ds::HPT) was also efficiently excised. Hygromycin‐resistant calli were obtained by culturing these transfected protoplasts in order to examine the transposition of the excised Ds::HPT into the rice genome. In five out of 16 calli examined, the Ds::HPT, but not the vector sequence, was integrated into the rice genome and 8 bp target site duplication typical of Ac/Ds transposition was generated. These results show that the Ds::HPT inserted in the MISV vector transposed directly into the rice genome. This demonstrates the direct transposition of a cloned plant transposable element into the plant genome. Implications of these finding are discussed.
Synergism between CACGTG (G‐box) and CACCTG cis‐elements is required for activation of the bean seed storage protein β‐phaseolin} gene†
Authors: Kawagoe Yasushi , Campell Bruce R. , Murai Norimoto
Published: March 2003

Expression of bean seed storage protein phaseolin is under strict developmental control. Four distinct nuclear proteins recognize in vitro the proximal, β‐phaseolin} promoter (−295/+45) which confers spatial and temporal regulation of the native gene. Functional significance of these protein‐binding sites was evaluated by substitution mutation of the motifs in the promoter, which was fused to GUS reporter gene, and subsequent transient gene expression assay using protoplasts from developing bean cotyledons. DNA‐binding protein CAN binds three CANNTG motifs, CACGTG (−248/−243), CACCTG (−163/−158), and CATATG (−100/−95). Substitution mutation of the CACGTG motif, which is commonly known as G‐box, reduced the −295 promoter activity by 75%, indicating that the G‐box is a major positive cis‐element. Mutation analyses also demonstrated that the CACCTG and CATATG motifs act as positive and negative cis‐elements, respectively. Substitution mutation of all three CANNTG motifs essentially eliminated the −295 promoter activity. A construct containing the G‐box and CACCTG motif resulted in a transcriptional level that is much greater than the sum of the transcriptional levels from the individual cis‐elements, demonstrating that the G‐box and CACCTG act synergistically. Substitution mutations of two AT‐rich sequences, to which a nuclear protein AG‐1 binds, showed that these sites function as major negative (−376/−367, −356/−347) or positive (−191/−182) cis‐elements, and that the effect of the two AG‐1 binding sites was counteractive in the −391 promoter. These results indicate that the three CANNTG motifs and two AG‐1‐binding sites play critical roles in transcription of the {β‐phaseolin} gene in cotyledons.
Cell‐cycle regulation of hydroxyproline‐rich glycoprotein HRGPnt3 gene expression during the initiation of lateral root meristems
Authors: Vera Pablo , Lamb Chris , Doerner Peter W.
Published: March 2003

Analysis of transgenic tobacco plants containing a tobacco hydroxyproline‐rich glycoprotein HRGPnt3 gene promoter‐β‐glucuronidase (GUS) gene fusion (HRGPnt3‐uidA) showed that this promoter is active not only in the early stages of initiation of lateral roots as previously described, but also in the initiation of adventitious roots, with similar selective expression in a subset of pericycle cells. HRGPnt3 is also induced during initiation of hairy roots following transformation by Agrobacterium rhizogenes. The auxin indole acetic acid (IAA) induces an increase in the number of characteristic discrete sites of HRGP‐nt3 expression. It is shown that these sites are destined to form new root primordia from pericycle cells of both adventitious and main roots. Dose‐dependent induction of root meristems by auxin overcomes the limitations of this naturally stochastic process and makes lateral root initiation amenable to biochemical analysis. Quiescent pericycle cells, which are developmentally arrested in the G2 phase of the cell cycle, rapidly progress into M phase upon mitogenic stimulation. Colchicine and nocodazole, which block completion of mitosis, inhibited the activation of the HRGPnt3 promoter but did not block auxin induction of parA, a marker for de‐differentiation in leaf mesophyll cell‐derived protoplasts. Hydroxyurea, which inhibits cell‐cycle progression at the G1/S‐phase transition and also blocks lateral root initiation, did not inhibit HRGPnt3 induction. Thus, HRGPnt3 induction precedes completion of the first cell division during primordium formation, and is one of the initial steps in a sequential program of gene expression activated upon stimulation of cell division for the development of a new meristem during lateral root initiation.
Primed in situ labelling facilitates flow sorting of similar sized chromosomes
Authors: Pich Uta , Meister Armin , Macas Jiří , Doležel Jaroslav , Lucretti Sergio , Schubert Ingo
Published: March 2003

Flow karyotyping and sorting of individual chromosome types is difficult when chromosomes of a complement do not differ sufficiently in DNA content. A strategy for sorting chromosomes of similar size has been developed. For this purpose oligonucleotide primed in situ (PRINS)‐labelling was adapted to field bean chromosomes in suspension. With a primer designed according to a tandemly repetitive sequence (Fokl element) PRINS‐labelling resulted in fluorescence signals specific in position and intensity for each chromosome. A bivariate sorting mode combining fluorescence pulse areas obtained from propidium iodide staining (representing DNA content) and fluorescein isothiocyanate signals (representing chromosome‐specific label) allowed chromosomes deviating in length by less than 1% of the haploid metaphase complement to be sorted. The average purity of sorted fractions was 95%. This technique should be applicable also to chromosomes of other species for obtaining chromosome‐specific painting probes, for construction of chromosome‐specific libraries (both without additional DNA amplification), and for gene mapping.
Simultaneous targeting of pea glutathione reductase and of a bacterial fusion protein to chloroplasts and mitochondria in transgenic tobacco
Authors: Creissen Gary , Reynolds Helen , Xue Yongbiao , Mullineaux Phil
Published: March 2003

N‐terminal presequences from cDNAs encoding mitochondrion‐ or chloroplast‐specific proteins are able, with variable efficiencies, to target preproteins to their respective organelles. In the few cases studied in which a nuclear‐encoded protein is found in both these organelles, each compartment‐specific isoform is encoded by a separate gene. Glutathione reductase (GR) from peas is encoded by a single nuclear gene and yet GR is distributed between chloroplasts, mitochondria and the cytosol. Previous sequence analysis of a full‐length GR cDNA revealed the presence of a putative plastid transit peptide. However, expression of this cDNA in transgenic tobacco resulted in substantially elevated GR activities in both chloroplasts and mitochondria in four independent lines examined. There was no effect on expression of the endogenous tobacco GR genes. Replacement of the GR presequence with presequences from pea rbcS (chloroplast) and Nicotiana plumbaginifolia Mn‐SOD (mitochondrion) resulted in targeting of GR only into the appropriate organelle. Expression of a fusion protein between the amino terminal region of GR and phosphinothricin acetyl transferase resulted in targeting of the foreign protein to chloroplasts and mitochondria. Thus, the pea GR presequence is capable of co‐targeting this enzyme or a foreign protein to chloroplasts and mitochondria in vivo. This is the first example of co‐targeting by a higher plant preprotein.
Oxidative stress responses in transgenic tobacco containing altered levels of glutathione reductase activity
Authors: Broadbent P. , Creissen G.P. , Kular B. , Wellburn A.R. , Mullineaux P.M.
Published: March 2003

A pea glutathione reductase cDNA was expressed in tobacco. Three classes of construct were used which gave a range of elevated levels of glutathione reductase (GR) activity in the cytosol (GR32), chloroplasts (GR36), or in both chloroplasts and mitochondria (GR46). In some transgenic progeny (T2) from self‐fertilized GR32 and GR36 primary transformants, having approximately twofold elevation of GR activity as compared with recessive siblings, there was an amelioration of the effect on leaf discs of up to 15 µM paraquat. However, lines with similarly elevated levels of GR activity showed no decreased sensitivity to the herbicide. None of the GR32 and GR36 lines was less sensitive to ozone. Conversely, T2 progeny of GR46 lines, with greater than 4.5‐fold elevations of GR activity, showed no reduced sensitivity to paraquat but two out of four of these lines were less sensitive to ozone fumigation. The differential response to stress co‐segregated with the presence of the transgene but there was no relationship between the degree of stress response and the level of GR activity. There was an elevation in the total glutathione pool in all lines showing increased GR activity but there was no change in the ratio of oxidized to reduced glutathione. These results demonstrate that the mechanisms of protection against ozone and paraquat are different although both can be mediated by elevated GR activity.
Isolation of Arabidopsis mutants altered in the light‐regulation of chalcone synthase gene expression using a transgenic screening approach
Authors: Jackson Jennie A. , Fuglevand Geeta , Brown Bobby A. , Shaw Morgan J. , Jenkins Gareth I.
Published: March 2003

Transgenic Arabidopsis expressing β‐glucuronidase (GUS) driven by a chalcone synthase gene (CHS) promoter were produced. GUS activity in the leaves increased with increasing fluence rates of white light in parallel with endogenous CHS transcript levels. An isogenic line homozygous for the transgene was obtained and mutagenized seedlings of this line were screened for altered light‐induction of the transgene. Putative mutants with low GUS activity were not altered in the light‐induction of endogenous CHS transcripts and are therefore not regulatory mutants. Two mutant lines (A12 and C10) with elevated levels of GUS activity in the light show a corresponding increase in CHS transcript levels. The A12 mutant was focussed upon and designated icx1 (increased chalcone synthase expression). This mutant has enhanced light‐stimulation of CHS expression since CHS transcript levels in darkness in icx1 are very low, as in the wild‐type. The transcript levels of two other genes involved in flavonoid biosynthesis are elevated in the light in icx1 as is anthocyanin formation. However, there is no alteration in LHCII chlorophyll a/b‐binding protein gene (CAB) transcript levels under the same conditions. The altered gene expression phenotype of icx1 co‐segregates with several other phenotypic characteristics, including fewer leaf trichomes and alterations to the seed coat. On the basis of these data and comparison with the Arabidopsis ttg (transparent testa glabra) mutant, it is suggested that the ICX1 gene product may be concerned both with the light‐regulation of gene expression and with developmental processes occurring in the epidermis.
Comparison of the effects of N6‐methyldeoxyadenosine and N5‐methyldeoxycytosine on transcription from nuclear gene promoters in barley
Authors: Rogers John C. , Rogers Sally W.
Published: March 2003

Methylation of deoxycytosine residues in plant nuclear DNA at CpG dinucleotides is generally assumed to suppress transcription, while deoxyadenosine methylation on recombinant reporter gene constructs transiently introduced into plant cells increases expression by uncharacterized mechanisms. A particle bombardment transient expression system was used in intact barley aleurone layers to quantitate the effects of CpG and A methylation on transcription from well‐characterized hormone‐regulated α‐amylase promoters. Methylation of C in all CpG pairs had little effect on transcription. In contrast, the presence of methylated A residues in the sequence GATC scattered in the reporter plasmid outside of the promoter increased transcription two‐ to fivefold, regardless of the strength of the promoter, and proper hormonal regulation of transcription was maintained. The methyl‐dA effect was similar when the amount of reporter construct DNA used was varied over a 20‐fold range, beginning with an amount that gave only a small increment of expression above background. Similar enhancing effects for methyl‐dA were seen with the CaMV 35S, maize Adh1, and maize ubiquitin promoters, though the magnitude varied for each individual promoter. Methyl‐dA did not detectably affect plasmid DNA stability in aleurone cells in transient expression experiments because the enhancing effect of methyl‐dA on expression was the same regardless of whether the assay was performed at 12 h or 40 h. Several proteins in wheat germ nuclear extracts bound preferentially to methylated DNA as assessed by gel retardation assays; one showed preferential binding to methyl‐dA rather than methyl‐CpG residues. The data indicate that the presence of methyl‐dA in the vicinity of active promoters enhances transcription of nuclear genes in barley in a manner independent of the strength of the promoter. This effect may be mediated by a methyl‐dA‐binding protein.
Sequence‐based identification of T‐DNA insertion mutations in Arabidopsis: actin mutants act2‐1 and act4‐1
Authors: McKinney Elizabeth C. , Ali Nazeem , Traut Alice , Feldmann Kenneth A. , Belostotsky Dmitry A. , McDowell John M. , Meagher Richard B.
Published: March 2003

A method is presented to facilitate the isolation of mutations in plant genes, which requires knowledge of the target gene or protein sequence, and is independent of mutant phenotype. The polymerase chain reaction was used to amplify the junctions between a T‐DNA insert and the gene of interest from pools of mutant plant lines. The approach was used to identify mutations in Arabidopsis thaliana actin genes. The Arabidopsis genome encodes 10 actins in six ancient subclasses each with distinct expression patterns. Primers in the T‐DNA border and highly degenerate actin primers, designed from conserved amino acid motifs, were used to prime the amplification. The PCR products were transferred to filters and probed for actin at low stringency. Thus, mutations in all 10 actin genes were screened for simultaneously. Mutations in the vegetative constitutive actin gene, ACT2, and the pollen‐specific actin gene, ACT4, were identified in a population of 5300 lines containing approximately 1.5 T‐DNA insertions per line. The screen was sensitive enough that actin insertion alleles were easily distinguished among pools of 100 plant lines. PCR techniques were used which accelerated the purification of mutant lines, and segregation, physical mapping, and sequencing of the act2‐1 and act4‐1 mutations. This strategy should be generally useful in screening mutant libraries made with a variety of plant insertion elements for mutations in any known sequence.
Metabolic regulation of asparagine synthetase gene expression in maize (Zea mays L.) root tips
Authors: Chevalier Christian , Bourgeois Emmanuelle , Just Daniel , Raymond Philippe
Published: March 2003

Differential hybridization of a cDNA library constructed with poly(A)+ mRNA from 24 h starved maize (Zea mays L.) root tips, resulted in the isolation of a cDNA (called pZSS1) that was highly induced during glucose deprivation. The nucleotide sequence analysis of the full‐length cDNA allowed its identification by comparison with sequence data bases. The 586 amino acid sequence encoded by pZSS1 was shown to be about 60% identical to sequences of asparagine synthetases (EC 6.3.5.4) from Asparagus officinalis, Pisum sativum, Arabidopsis thaliana and Brassica oleracea. Southern blot analysis of maize genomic DNA showed that asparagine synthetase may be encoded by at least two genes. The use of a specific probe for the 3′ untranslated region of pZSS1 in Northern blot experiments, revealed that the isolated AS gene was essentially expressed in roots of maize seedlings. Time course analysis revealed that maximal expression of the gene corresponding to pZSS1 occurs between 18 and 24 h after the onset of the starvation treatment. The steady‐state levels of transcripts in maize root tips were found to change under various incubation conditions. Exogenous supply of metabolizable sugars downregulated the gene expression, while carbohydrate deprivation or feeding with non‐metabolizable sugars resulted in the induction of gene expression. In addition to carbohydrate deprivation, the effects of nitrogen metabolite supply and stress conditions indicate that gene expression might be under metabolic control in maize root tips. The intracellular nitrogen to carbon ratio might be an important factor for the regulation of asparagine synthetase gene expression.
Identification of a membrane glycoprotein in pollen of Papaver rhoeas which binds stigmatic self‐incompatibility (S‐) proteins
Authors: Hearn Melanie J. , Franklin F. Christopher H. , Ride Jon P.
Published: March 2003

Recombinant stigmatic self‐incompatibility (S‐) proteins from Papaver rhoeas have previously been shown to be biologically functional, inhibiting only pollen of the same S‐genotype. In an attempt to identify molecules in pollen which interact with these proteins, Western ligand blotting was used, with the recombinant S‐proteins as probes followed by immunodetection of the bound S‐protein. This revealed that pollen of all S‐genotypes tested contained a 70–120 kDa protein which bound the S1, S3 and S8 proteins in an indistinguishable manner. Binding was destroyed by pretreatment of blots with periodate, implicating a glycoprotein with activity being dependent on the glycan moiety. The activity completely partitioned into the detergent phase on condensation with Triton X‐114, indicating an integral membrane protein. On aqueous two‐phase partition of microsomal membrane preparations, the majority of the binding activity partitioned into the upper phase, suggesting that the molecule is located in the plasma membrane.

No equivalent binding could be detected in extracts of leaves, stems, roots or stigmas of P. rhoeas, nor in immature anthers. Identical activity was detected in pollen of some other Papaver species, but not in pollen of Brassica oleracea, Nicotiana tabacum or Petunia hybrida. The presence in mature pollen of P. rhoeas of a plasma membrane glycoprotein which binds S‐proteins from the stigma of the same species, albeit in a non S‐allele‐specific manner, strongly suggests that this molecule has a role somewhere in the interaction of the stigma proteins with pollen. The activity is not that expected of an S‐specific receptor, but by analogy with certain mammalian systems the molecule may act as an accessory receptor, or co‐receptor, the presence of which may be essential for a functional interaction with an S‐specific receptor.
Regulation of a carotenoid biosynthesis gene promoter during plant development
Authors: Corona Vittorio , Aracri Benedetto , Kosturkova Georgina , Bartley Glenn E. , Pitto Letizia , Giorgetti Lucia , Scolnik Pablo A. , Giuliano Giovanni
Published: March 2003

Carotenoids are terpenoid pigments which are accumulated in the chloroplasts of leaves and in the chromoplasts of many flowers and fruits. Phytoene desaturase (Pds), the second dedicated enzyme in carotenoid biosynthesis, is encoded in tomato by a single copy gene. A 2 kb fragment from the tomato Pds gene, comprising 1.5 kb from the promoter and 0.5 kb from the 5′ non‐translated region, is able to drive developmentally regulated expression of the GUS reporter gene in transgenic tomato and tobacco plants. In tomato, high levels of Pds/GUS expression are found in organs and at stages of development where chromoplasts are formed: petals, anthers and ripening fruits. Tobacco petals and fruits, which do not contain chromoplasts, show instead low levels of Pds/GUS expression. Transgenic tobacco seedlings were subjected to treatment with a range of inhibitors of carotenoid and chlorophyll biosynthesis. The results indicate that, in green tissues, carotenoid and chlorophyll levels are tightly co‐regulated and that a chemically induced arrest in pigment biosynthesis results in activation of the Pds promoter. The promoter is also induced in etiolated seedlings, which contain much lower carotenoid levels than light‐grown seedlings. These data suggest that in green tissues Pds gene transcription may respond to end‐product regulation.
Expression and cellular localization of rab28 mRNA and Rab28 protein during maize embryogenesis
Authors: Niogret Marie Françoise , Culiáñez‐Macià Francisco A. , Goday Adela , Albà M. Mar , Pagès Montserrat
Published: March 2003

The maize abscisic acid (ABA) responsive gene rab28, has been shown to be ABA‐inducible in embryos and vegetative tissues. A polyclonal antiserum was raised against Rab28 protein. Using immunoblotting and immunoprecipitation, the antiserum specifically recognized a protein of about 30 kDa and pl 6 which is in close agreement with the molecular weight and pl predicted by the deduced amino acid sequence. The rab28 gene product accumulated during late embryogenesis. In vegetative tissues, dehydration stress induced rab28 gene expression both in the light and in the dark. The spatial and temporal pattern of rab28 mRNA expression during embryogenesis was investigated by in situ hybridization using digoxigenin‐labelled rab28 probes, and the immunochemical localization of Rab28 protein using anti‐Rab28 antibodies. Expression of rab28 mRNA is restricted to provascular tissues in young embryos, and at later stages of development the most prevalent accumulation occurred in meristem and in the vascular elements of the plumule, root and scutellum. Using immunoelectron microscopy the Rab28 protein has been located in the nucleolus of different cell types. In light of these results the stress regulation of rab28 and a likely role for this protein during late embryogenesis are discussed.