bluuebunny/crossref_metadata_2025 huggingface dataset:
Trade and environmental distortions: coordinated intervention
Authors: ZHAO JINHUA
Published: July 2002

Free trade may not improve welfare when environmental distortions exist. We study the coordination of trade and environmental policies when the distortion is loose property rights governing resources. Using the dual approach of Dixit and Norman (1980), we trade out ‘iso-welfare’ curves in the space of the degree of environment distortion and the level of the import tariff. We use these curves to find necessary and sufficient conditions for disproportionate reforms, piecemeal or discrete, to be welfare improving. We also find that the needed reduction in the distortion to make trade welfare improving increases as the environmental stock increases, the productivity of the environmentally intensive good increases, or when the country is a large exporter of the environmentally intensive good.
Land degradation, agricultural productivity and common property: evidence from Côte d'Ivoire
Authors: AHUJA VINOD
Published: July 2002

This study provides evidence on the effectiveness of community controls in regulating the use of common agricultural land in Côte d'Ivoire and tests for factors such as group size, ethnic and income heterogeneity of the group, income and resource stock levels, in explaining the variation in effectiveness across communities. The results indicate significant deterioration in community controls. These results point towards the need for a comprehensive policy framework towards agriculture in general and land tenure in particular. The study also finds that smaller and ethnically homogenous communities are better able to coordinate their actions, thereby internalizing a higher proportion of the value of land as a factor of agricultural production than their large ethnically heterogenous counterparts. No evidence is, however, found in favour of income heterogeneity hindering or facilitating collective action.
On Admitting Psychotic
Adolescents to Hospital:
Time to Review the
Admission Process
Authors: Dimond Claire , Goldberg David
Published: July 2002

Difficult management issues, frequently involving many agencies,
arise
when psychotic adolescents need admission to hospital. We review the
recent experience of a community-based adolescent team and identify
factors that appeared to inhibit effective management at times when
admission was necessary. Suggestions are made about how to develop the

flexible arrangements necessary to facilitate appropriate management.
WAGE ADJUSTMENT AND EMPLOYMENT PERSISTENCY
Authors: Andersen Torben M. , Hylleberg Svend
Published: July 2002

Persistent high unemployment has fostered the employment persistency hypothesis
according to which employment changes are driven by unanticipated shocks whereas anticipated
shocks that potentially could change employment are absorbed by wage
changes. Empirical tests of the persistency hypothesis fail to distinguish between the
properties of shocks and endogenous propagation mechanism causing persistency. This paper
develops a new test strategy by explicitly distinguishing between these two factors. The
methodology is applied to the manufacturing sector in Denmark, and some support
in favor of an endogenous propagation mechanism causing employment persistency
is found.
Binding of transcriptional activators to sigma 54 in the presence of the transition state analog ADP–aluminum fluoride: insights into activator mechanochemical action
Authors: Chaney Matthew , Grande Ricardo , Wigneshweraraj Siva R. , Cannon Wendy , Casaz Paul , Gallegos Maria-Trinidad , Schumacher Jorg , Jones Susan , Elderkin Sarah , Dago Angel Ernesto , Morett Enrique , Buck Martin
Published: July 2002

Conformational changes in sigma 54 (ς54) and ς54-holoenzyme depend on nucleotide hydrolysis by an activator. We now show that ς54 and its holoenzyme bind to the central ATP-hydrolyzing domains of the transcriptional activators PspF and NifA in the presence of ADP–aluminum fluoride, an analog of ATP in the transition state for hydrolysis. Direct binding of ς54 Region I to activator in the presence of ADP–aluminum fluoride was shown and inferred from in vivo suppression genetics. Energy transduction appears to occur through activator contacts to ς54 Region I. ADP–aluminum fluoride-dependent interactions and consideration of other AAA+ proteins provide insight into activator mechanochemical action.
An mt+ gamete-specific nuclease that targets mt− chloroplasts during sexual reproduction in C. reinhardtii
Authors: Nishimura Yoshiki , Misumi Osami , Kato Ko , Inada Noriko , Higashiyama Tetsuya , Momoyama Yu , Kuroiwa Tsuneyoshi
Published: July 2002

Although the active digestion of mating-type minus (mt−) chloroplast DNA (cpDNA) in young zygotes is considered to be the basis for the uniparental inheritance of cpDNA inChlamydomonas reinhardtii, little is known about the underlying molecular mechanism. One model of active digestion proposes that nucleases are either synthesized or activated to digestmt− cpDNA. We used a native-PAGE/in gelo assay to investigate nuclease activities in chloroplasts from young zygotes, and identified a novel Ca2+-dependent nuclease activity. The timing of activation (∼60–90 min after mating) and the localization of the nuclease activity (in mt− chloroplasts) coincided with the active digestion of mt− cpDNA. Furthermore, the activity of the nuclease was coregulated with the maturation of mating-type plus (mt+) gametes, which would enable the efficient digestion of mt− cpDNA. Based on these observations, we propose that the nuclease (designated as Mt+-specific DNase, MDN) is a developmentally controlled nuclease that is activated inmt+ gametes and participates in the destruction ofmt− cpDNA in young zygotes, thereby ensuring uniparental inheritance of chloroplast traits.
Automated Finishing with Autofinish
Authors: Gordon David , Desmarais Cindy , Green Phil
Published: July 2002

Currently, the genome sequencing community is producing shotgun sequence data at a very high rate, but finishing (collecting additional directed sequence data to close gaps and improve the quality of the data) is not matching that rate. One reason for the difference is that shotgun sequencing is highly automated but finishing is not: Most finishing decisions, such as which directed reads to obtain and which specialized sequencing techniques to use, are made by people. If finishing rates are to increase to match shotgun sequencing rates, most finishing decisions also must be automated. The Autofinishcomputer program (which is part of the Consed computer software package) does this by automatically choosing finishing reads.Autofinish is able to suggest most finishing reads required for completion of each sequencing project, greatly reducing the amount of human attention needed. Autofinish sometimes completely finishes the project, with no human decisions required. It cannot solve the most complex problems, so we recommend thatAutofinish be allowed to suggest reads for the first three rounds of finishing, and if the project still is not finished completely, a human finisher complete the work. We compared thisAutofinish-Hybrid method of finishing against a human finisher in five different projects with a variety of shotgun depths by finishing each project twice—once with each method. This comparison shows that the Autofinish-Hybrid method saves many hours over a human finisher alone, while using roughly the same number and type of reads and closing gaps at roughly the same rate.Autofinish currently is in production use at several large sequencing centers. It is designed to be adaptable to the finishing strategy of the lab—it can finish using some or all of the following: resequencing reads, reverses, custom primer walks on either subclone templates or whole clone templates, PCR, or minilibraries.Autofinish has been used for finishing cDNA, genomic clones, and whole bacterial genomes (see http://www.phrap.org).
Hunting with Traps: Genome-Wide Strategies for Gene Discovery and Functional Analysis
Authors: Durick Kyle , Mendlein John , Xanthopoulos Kleanthis G.
Published: July 2002

With sequence analysis of the human genome well underway, there is an increasingly urgent challenge to understand the fundamental function and interplay of genes that build and maintain an organism. Several approaches will be critical for interpreting gene function, including random cDNA sequencing, expression profiling in different tissues, genetic analysis of human or model organism phenotypes, and creation of transgenic or “knockout” animals. Traditional gene-trapping approaches, in which genes are randomly disrupted with DNA elements inserted throughout the genome, have been used to generate large numbers of mutant organisms for genetic analysis. Recent modifications of gene-trapping methods and their increased use in mammalian systems are likely to result in a wealth of new information on gene function. Various trapping strategies allow genes to be segregated based on criteria like the specific subcellular location of an encoded protein, the tissue expression profile, or responsiveness to specific stimuli. Genome-wide gene-trapping strategies, which integrate gene discovery and expression profiling, can be applied in a massively parallel format to produce living assays for drug discovery.
Effects of Pharmacologically Induced Changes in NMDA-Receptor Activity on Long-Term Memory in Humans
Authors: Rammsayer Thomas H.
Published: July 2002

In a double-blind crossover design, either 30 mg of the noncompetitive NMDA-receptor antagonist memantine or a placebo was administered to 40 healthy male volunteers. Twenty line drawings of objects and 20 photographs of unfamiliar faces were presented on a computer screen. After a retention interval of 80 min, the participants' task was to select the original objects and faces from a set of 80 items. Results were analyzed applying a signal-detection-theory approach. Recognition performance for objects was significantly impaired under memantine as compared to placebo, whereas performance on face recognition was not affected. Findings support the notion of differential effects of NMDA-receptor antagonists on memory functions in humans.
Strain-dependent Differences in LTP and Hippocampus-dependent Memory in Inbred Mice
Authors: Nguyen Peter V. , Abel Ted , Kandel Eric R. , Bourtchouladze Roussoudan
Published: July 2002

Many studies have used “reverse” genetics to produce “knock-out” and transgenic mice to explore the roles of various molecules in long-term potentiation (LTP) and spatial memory. The existence of a variety of inbred strains of mice provides an additional way of exploring the genetic bases of learning and memory. We examined behavioral memory and LTP expression in area CA1 of hippocampal slices prepared from four different inbred strains of mice: C57BL/6J, CBA/J, DBA/2J, and 129/SvEms-+Ter?/J. We found that LTP induced by four 100-Hz trains of stimulation was robust and long-lasting in C57BL/6J and DBA/2J mice but decayed in CBA/J and 129/SvEms-+Ter?/J mice. LTP induced by one 100-Hz train was significantly smaller after 1 hr in the 129/SvEms-+Ter?/J mice than in the other three strains. Theta-burst LTP was shorter lasting in CBA/J, DBA/2J, and 129/SvEms-+Ter?/J mice than in C57BL/6J mice. We also observed specific memory deficits, among particular mouse strains, in spatial and nonspatial tests of hippocampus-dependent memory. CBA/J mice showed defective learning in the Morris water maze, and both DBA/2J and CBA/J strains displayed deficient long-term memory in contextual and cued fear conditioning tests. Our findings provide strong support for a genetic basis for some forms of synaptic plasticity that are linked to behavioral long-term memory and suggest that genetic background can influence the electrophysiological and behavioral phenotypes observed in genetically modified mice generated for elucidating the molecular bases of learning, memory, and LTP.
Molecular Analysis of Signals Controlling Dormancy and Growth in Underground Adventitious Buds of Leafy Spurge
Authors: Horvath David P. , Chao Wun S. , Anderson James V.
Published: July 2002

Dormancy and subsequent regrowth of adventitious buds is a critical physiological process for many perennial plants. We have used the expression of hormone and cell cycle-responsive genes as markers to follow this process in leafy spurge (Euphorbia esula). In conjunction with earlier studies, we show that loss of mature leaves results in decreased sugar levels and increased gibberellin perception in underground adventitious buds. Gibberellin is sufficient for induction of S phase-specific but not M phase-specific gene expression. Loss of both apical and axillary buds or inhibition of polar auxin transport did not result in induction of S phase- or M phase-specific gene expression. Loss of polar auxin transport was necessary for continuation of the cell cycle and further bud development if the S phase was previously initiated.
An Ultraviolet-B-Resistant Mutant with Enhanced DNA Repair in Arabidopsis
Authors: Tanaka Atsushi , Sakamoto Ayako , Ishigaki Yasuhito , Nikaido Osamu , Sun Guakin , Hase Yoshihiro , Shikazono Naoya , Tano Shigemitsu , Watanabe Hiroshi
Published: July 2002

An ultraviolet-B (UV-B)-resistant mutant,uvi1 (UV-B insensitive 1), of Arabidopsis was isolated from 1,280 M1 seeds that had been exposed to ion beam irradiation. The fresh weight ofuvi1 under high-UV-B exposure was more than twice that of the wild type. A root-bending assay indicated that root growth was less inhibited by UV-B exposure in uvi1 than in the wild type. When the seedlings were grown under white light, the UV-B dose required for 50% inhibition was about 6 kJ m−2for the wild type and 9 kJ m−2 for uvi1. When the seedlings were irradiated with UV-B in darkness, the dose required for 50% inhibition was about 1.5 kJ m−2 for the wild type and 4 kJ m−2 for uvi1. An enzyme-linked immunosorbent assay showed that the reduction in levels of cyclobutane pyrimidine dimers (CPDs) under white light and of (6-4) photoproducts in darkness occurred faster in uvi1 than in the wild type. These results indicate that uvi1 had increased photoreactivation of CPDs and dark repair of (6-4) photoproducts, leading to strong UV-B resistance. Furthermore, the transcript levels of PHR1 (CPD photolyase gene) were much higher inuvi1 than in the wild type both under white light and after UV-B exposure. Placing the plants in the dark before UV-B exposure decreases the early reduction of CPDs in the wild type but not inuvi1. Our results suggest that UVI1 is a negative regulator of two independent DNA repair systems.
A Thiol Protease and an Anionic Peroxidase Are Induced by Lowering Cytokinins during Callus Growth in Petunia
Authors: Tournaire C. , Kushnir S. , Bauw G. , Inze D. , de la Serve B. T. , Renaudin J. P.
Published: July 2002

We previously identified a group of proteins that increase early in Petunia hybrida calli subcultured on a low-cytokinin medium, unlike the calli subcultured on a high-cytokinin medium. The calli on the low-cytokinin medium do not regenerate (J.-P. Renaudin, C. Tournaire, B. Teyssendier de la Serve [1991] Physiol Plant 82: 48–56). Two of these proteins, P21 and P17, have been identified by peptide sequencing and cloned. P21 is highly homologous to a group of thiol proteases, including barley aleurain, rice oryzain [gamma], Arabidopsis SAG2, and mammalian cathepsin H. P17 is highly homologous to a group of anionic peroxidases from potato and tomato. A study of their expression in two P. hybrida lines, PC6 and St40, which differ in their ability to regenerate, showed that the genes for P21 and P17 are differentially expressed depending on the type and the age of the organ, with the highest expression in senescing leaves and in aged calli. The data are in favor of these genes being associated with an early step of senescence, which may be due, in part, to a reduction in total cytokinin. The two Petunia lines are, thus, functionally different concerning the action of cytokinin in two developmental phenomena: in vitro organogenesis and senescence.
A Cherry Protein and Its Gene, Abundantly Expressed in Ripening Fruit, Have Been Identified as Thaumatin-Like
Authors: Fils-Lycaon B. R. , Wiersma P. A. , Eastwell K. C. , Sautiere P.
Published: July 2002

A 29-kD polypeptide is the most abundant soluble protein in ripe cherry fruit (Prunus avium L); accumulation begins at the onset of ripening as the fruit turns from yellow to red. This protein was extracted from ripe cherries and purified by size-exclusion and ion-exchange chromatography. Antibodies to the purified protein were used to screen a cDNA library from ripe cherries. Numerous recombinant plaques reacted positively with the antibodies; the DNA sequence of representative clones encoded a polypeptide of 245 amino acid residues. A signal peptide was indicated, and the predicted mature protein corresponded to the purified protein in size (23.3 kD, by mass spectrometry) and isoelectric point (4.2). A search of known protein sequences revealed a strong similarity between this polypeptide and the thaumatin family of pathogenesis-related proteins. The cherry thaumatin-like protein does not have a sweet taste, and no antifungal activity was seen in preliminary assays. Expression of the protein appears to be regulated at the gene level, with mRNA levels at their highest in the ripe fruit.
Identification and Characterization of a Fruit-Specific, Thaumatin-Like Protein That Accumulates at Very High Levels in Conjunction with the Onset of Sugar Accumulation and Berry Softening in Grapes
Authors: Tattersall D. B. , van Heeswijck R. , Hoj P. B.
Published: July 2002

The protein composition of the grape (Vitis vinifera cv Muscat of Alexandria) berry was examined from flowering to ripeness by gel electrophoresis. A protein with an apparent molecular mass of 24 kD, which was one of the most abundant proteins in extracts of mature berries, was purified and identified by amino acid sequence to be a thaumatin-like protein. Combined cDNA sequence analysis and electrospray mass spectrometry revealed that this protein, VVTL1 (for V. vinifera thaumatin-like protein 1), is synthesized with a transient signal peptide as seen for apoplastic preproteins. Apart from the removal of the targeting signal and the formation of eight disulfide bonds, VVTL1 undergoes no other posttranslational modification. Southern, northern, and western analyses revealed that VVTL1 is found in the berry only and is encoded by a single gene that is expressed in conjunction with the onset of sugar accumulation and softening. The exact role of VVTL1 is unknown, but the timing of its accumulation correlates with the inability of the fungal pathogen powdery mildew (Uncinula necator) to initiate new infections of the berry. Western analysis revealed that the presence of thaumatin-like proteins in ripening fruit might be a widespread phenomenon.
Studying Early Nodulin GeneENOD40Expression and Induction by Nodulation Factor and Cytokinin in Transgenic Alfalfa1
Authors: Fang Yiwen , Hirsch Ann M.
Published: July 2002

ENOD40, an early nodulin gene, is expressed following inoculation with Rhizobium meliloti or by adding R. meliloti-produced nodulation (Nod) factors or the plant hormone cytokinin to uninoculated roots. We isolated two MsENOD40 clones, designatedMsENOD40–1 and MsENOD40–2, with distinct promoters from an alfalfa (Medicago sativa cv Chief) genomic library. The promoters were fused to the reporter geneuidA (gus), and the constructs were introduced into alfalfa. We observed that theMsENOD40–1 construct was expressed almost exclusively under symbiotic conditions. The MsENOD40–2 construct was transcribed under both symbiotic and nonsymbiotic conditions and in nonnodular and nodular tissues. Both MsENOD40promoter-gus constructs were similarly expressed as nodules developed, and both were expressed in roots treated with 6-benzylaminopurine or purified Nod factor. However, no blue color was detected in nodule-like structures induced by the auxin transport inhibitor N-1-(naphthyl)phthalamic acid on roots of plants containing the MsENOD40–1 promoter construct, whereas pseudonodules from plants containing theMsENOD40–2 promoter construct stained blue. A 616-bp region at the distal 5′ end of the promoter is important for proper spatial expression of MsENOD40 in nodules and also for Nod-factor and cytokinin-induced expression.
Genes Involved in Osmoregulation during Turgor-Driven Cell Expansion of Developing Cotton Fibers Are Differentially Regulated1
Authors: Smart Lawrence B. , Vojdani Fakrieh , Maeshima Masayoshi , Wilkins Thea A.
Published: July 2002

Cotton (Gossypium hirsutum L.) fibers are single-celled trichomes that synchronously undergo a phase of rapid cell expansion, then a phase including secondary cell wall deposition, and finally maturation. To determine if there is coordinated regulation of gene expression during fiber expansion, we analyzed the expression of components involved in turgor regulation and a cytoskeletal protein by measuring levels of mRNA and protein accumulation and enzyme activity. Fragments of the genes for the plasma membrane proton-translocating ATPase, vacuole-ATPase, proton-translocating pyrophosphatase (PPase), phosphoenolpyruvate carboxylase, major intrinsic protein, and α-tubulin were amplified by polymerase chain reaction and used as probes in ribonuclease protection assays of RNA from a fiber developmental series, revealing two discrete patterns of mRNA accumulation. Transcripts of all but the PPase accumulated to highest levels during the period of peak expansion (+12–15 d postanthesis [dpa]), then declined with the onset of secondary cell wall synthesis. The PPase was constitutively expressed through fiber development. Activity of the two proton-translocating-ATPases peaked at +15 dpa, whereas PPase activity peaked at +20 dpa, suggesting that all are involved in the process of cell expansion but with varying roles. Patterns of protein accumulation and enzyme activity for some of the proteins examined suggest posttranslational regulation through fiber development.
Coordinate Accumulation of Antifungal Proteins and Hexoses Constitutes a Developmentally Controlled Defense Response during Fruit Ripening in Grape1
Authors: Salzman Ron A. , Tikhonova Irina , Bordelon Bruce P. , Hasegawa Paul M. , Bressan Ray A.
Published: July 2002

During ripening of grape (Vitis labruscana L. cv Concord) berries, abundance of several proteins increased, coordinately with hexoses, to the extent that these became the predominant proteins in the ovary. These proteins have been identified by N-terminal amino acid-sequence analysis and/or function to be a thaumatin-like protein (grape osmotin), a lipid-transfer protein, and a basic and an acidic chitinase. The basic chitinase and grape osmotin exhibited activities against the principal grape fungal pathogens Guignardia bidwellii andBotrytis cinerea based on in vitro growth assays. The growth-inhibiting activity of the antifungal proteins was substantial at levels comparable to those that accumulate in the ripening fruit, and these activities were enhanced by as much as 70% in the presence of 1 m glucose, a physiological hexose concentration in berries. The simultaneous accumulation of the antifungal proteins and sugars during berry ripening was correlated with the characteristic development of pathogen resistance that occurs in fruits during ripening. Taken together, accumulation of these proteins, in combination with sugars, appears to constitute a novel, developmentally regulated defense mechanism against phytopathogens in the maturing fruit.
Differential Control of Xanthophylls and Light-Induced Stress Proteins, as Opposed to Light-Harvesting Chlorophyll a/bProteins, during Photosynthetic Acclimation of Barley Leaves to Light Irradiance
Authors: Montané Marie-Hélène , Tardy Florence , Kloppstech Klaus , Havaux Michel
Published: July 2002

Barley (Hordeum vulgare L.) plants were grown at different photon flux densities ranging from 100 to 1800 μmol m−2s−1 in air and/or in atmospheres with reduced levels of O2 and CO2. Low O2 and CO2 partial pressures allowed plants to grow under high photosystem II (PSII) excitation pressure, estimated in vivo by chlorophyll fluorescence measurements, at moderate photon flux densities. The xanthophyll-cycle pigments, the early light-inducible proteins, and their mRNA accumulated with increasing PSII excitation pressure irrespective of the way high excitation pressure was obtained (high-light irradiance or decreased CO2 and O2availability). These findings indicate that the reduction state of electron transport chain components could be involved in light sensing for the regulation of nuclear-encoded chloroplast gene expression. In contrast, no correlation was found between the reduction state of PSII and various indicators of the PSII light-harvesting system, such as the chlorophyll a-to-b ratio, the abundance of the major pigment-protein complex of PSII (LHCII), the mRNA level of LHCII, the light-saturation curve of O2 evolution, and the induced chlorophyll-fluorescence rise. We conclude that the chlorophyll antenna size of PSII is not governed by the redox state of PSII in higher plants and, consequently, regulation of early light-inducible protein synthesis is different from that of LHCII.
Characterization of Source- and Sink-Specific Sucrose/H+ Symporters from Carrot
Authors: Shakya Roshani , Sturm Arnd
Published: July 2002

To understand how sucrose (Suc) is transported from source leaves to developing tap roots of carrot (Daucus carota L.), we cloned two cDNAs (DcSUT1 and DcSUT2) for proteins with homologies to plant Suc/H+ symporters. The deduced polypeptide sequences are 52% identical and have 12 predicted membrane-spanning domains each. Transport activities were confirmed by expression of the clones in yeast cells. Both transporters had optimal activity below pH 5.0 and Michaelis constant values of 0.5 mm. Suc uptake was inhibited by protonophores, suggesting that Suc transport is linked to the proton electrochemical potential across the plasma membrane. DcSUT1 andDcSUT2 had markedly different expression patterns. Transcripts of DcSUT1 were found only in the green parts of plants, with highest levels in the lamina of source leaves, indicating that DcSUT1 is required for the loading of Suc into the phloem. In leaf lamina expression was diurnally regulated, suggesting that Suc export from the leaves is higher during the day than during the night. The mRNA of DcSUT2 was found mainly in sink organs, and no diurnal expression pattern was detected in the storage root. Here, expression was not restricted to the phloem but was much higher in storage parenchyma tissues of phloem and xylem. The close relationship of DcSUT2 with a Suc/H+ symporter from fava bean, which facilitates Suc uptake into the cotyledons of developing seeds, indicates that this carrot Suc transporter may be involved in loading Suc into storage parenchyma cells.
Transgenically Enhanced Sorbitol Synthesis Facilitates Phloem Boron Transport and Increases Tolerance of Tobacco to Boron Deficiency1
Authors: Brown Patrick H. , Bellaloui Nacer , Hu Hening , Dandekar Abhaya
Published: July 2002

The mobility of elements within plants contributes to a plant species' tolerance of nutrient deficiencies in the soil. The genetic manipulation of within-plant nutrient movement may therefore provide a means to enhance plant growth under conditions of variable soil nutrient availability. In these experiments tobacco (Nicotiana tabacum) was engineered to synthesize sorbitol, and the resultant effect on phloem mobility of boron (B) was determined. In contrast to wild-type tobacco, transgenic tobacco plants containing sorbitol exhibit a marked increase in within-plant B mobility and a resultant increase in plant growth and yield when grown with limited or interrupted soil B supply. Growth of transgenic tobacco could be maintained by reutilization of B present in mature tissues or from B supplied as a foliar application to mature leaves. In contrast, B present in mature leaves of control tobacco lines could not be used to provide the B requirements for new plant growth. 10B-labeling experiments verified that B is phloem mobile in transgenic tobacco but is immobile in control lines. These results demonstrate that the transgenic enhancement of within-plant nutrient mobility is a viable approach to improve plant tolerance of nutrient stress.
Regulation and Functional Expression of Cinnamate 4-Hydroxylase from Parsley
Authors: Koopmann Edda , Logemann Elke , Hahlbrock Klaus
Published: July 2002

A previously isolated parsley (Petroselinum crispum) cDNA with high sequence similarity to cinnamate 4-hydroxylase (C4H) cDNAs from several plant sources was expressed in yeast (Saccharomyces cerevisiae) containing a plant NADPH:cytochrome P450 oxidoreductase and verified as encoding a functional C4H (CYP73A10). Low genomic complexity and the occurrence of a single type of cDNA suggest the existence of only oneC4H gene in parsley. The encoded mRNA and protein, in contrast to those of a functionally related NADPH:cytochrome P450 oxidoreductase, were strictly coregulated with phenylalanine ammonia-lyase mRNA and protein, respectively, as demonstrated by coinduction under various conditions and colocalization in situ in cross-sections from several different parsley tissues. These results support the hypothesis that the genes encoding the core reactions of phenylpropanoid metabolism form a tight regulatory unit.
Overexpression of a Novel Arabidopsis Gene Related to Putative Zinc-Transporter Genes from Animals Can Lead to Enhanced Zinc Resistance and Accumulation
Authors: van der Zaal Bert J. , Neuteboom Leon W. , Pinas Johan E. , Chardonnens Agnes N. , Schat Henk , Verkleij Jos A.C. , Hooykaas Paul J.J.
Published: July 2002

We describe the isolation of an Arabidopsis gene that is closely related to the animalZnT genes (Zntransporter). The protein encoded by the ZAT (Zn transporter ofArabidopsisthaliana) gene has 398 amino acid residues and is predicted to have six membrane-spanning domains. To obtain evidence for the postulated function of the Arabidopsis gene, transgenic plants with the ZAT coding sequence under control of the cauliflower mosaic virus 35S promoter were analyzed. Plants obtained with ZAT in the sense orientation exhibited enhanced Zn resistance and strongly increased Zn content in the roots under high Zn exposure. Antisense mRNA-producing plants were viable, with a wild-type level of Zn resistance and content, like plants expressing a truncated coding sequence lacking the C-terminal cytoplasmic domain of the protein. The availability of ZAT can lead to a better understanding of the mechanism of Zn homeostasis and resistance in plants.
A Single Limit Dextrinase Gene Is Expressed Both in the Developing Endosperm and in Germinated Grains of Barley1
Authors: Burton Rachel A. , Zhang Xiao-Qi , Hrmova Maria , Fincher Geoffrey B.
Published: July 2002

The single gene encoding limit dextrinase (pullulan 6-glucanohydrolase; EC 3.2.1.41) in barley (Hordeum vulgare) has 26 introns that range in size from 93 to 822 base pairs. The mature polypeptide encoded by the gene has 884 amino acid residues and a calculated molecular mass of 97,417 D. Limit dextrinase mRNA is abundant in gibberellic acid-treated aleurone layers and in germinated grain. Gibberellic acid response elements were found in the promoter region of the gene. These observations suggest that the enzyme participates in starch hydrolysis during endosperm mobilization in germinated grain. The mRNA encoding the enzyme is present at lower levels in the developing endosperm of immature grain, a location consistent with a role for limit dextrinase in starch synthesis. Enzyme activity was also detected in developing grain. The limit dextrinase has a presequence typical of transit peptides that target nascent polypeptides to amyloplasts, but this would not be expected to direct secretion of the mature enzyme from aleurone cells in germinated grain. It remains to be discovered how the enzyme is released from the aleurone and whether another enzyme, possibly of the isoamylase group, might be equally important for starch hydrolysis in germinated grain.
Characterization of Mutants with Alterations of the Phosphorylation Site in the D2 Photosystem II Polypeptide ofChlamydomonas reinhardtii1
Authors: Fleischmann Mark M. , Rochaix Jean-David
Published: July 2002

We have changed the potential phosphorylation site, a threonine residue at position 2 of the D2 polypeptide of the photosystem II complex of Chlamydomonas reinhardtii, to alanine, valine, aspartate, proline, glycine, or glutamate. Mutants with neutral amino acid changes did not display any phenotype with regard to photoautotrophic growth, light sensitivity, fluorescence transients, or photoinhibition. Pulse labeling of these mutants with 32P indicated that a phosphorylated protein of the same size as D2 is absent in these mutants, suggesting that threonine-2 is indeed the unique phosphorylation site of D2. In contrast, mutants in which threonine-2 has been replaced with acidic residues are deficient in photosystem II. Use of chimeric genes containing the psbD5′-untranslated region revealed that the initiation of translation was not affected in these mutants, but the mutations interfered with a later step of D2 synthesis and accumulation.
Arabidopsis Contains at Least Four Independent Blue-Light-Activated Signal Transduction Pathways1
Authors: Lascève Gérard , Leymarie Juliette , Olney Margaret A. , Liscum Emmanuel , Christie John M. , Vavasseur Alain , Briggs Winslow R.
Published: July 2002

We have investigated the stomatal and phototropic responses to blue light of a number of single and double mutants at various loci that encode proteins involved in blue-light responses in Arabidopsis. The stomatal responses of light-grown mutant plants (cry1, cry2, nph1, nph3, nph4, cry1cry2, andnph1cry1) did not differ significantly from those of their wild-type counterparts. Second positive phototropic responses of etiolated mutant seedlings, cry1, cry2, cry1cry2, andnpq1-2, were also similar to those of their wild-type counterparts. Although npq1 and single and double cry1cry2 mutants showed somewhat reduced amplitude for first positive phototropism, threshold, peak, and saturation fluence values for first positive phototropic responses of etiolated seedlings did not differ from those of wild-type seedlings. Similar to the cry1cry2 double mutants and tonpq1-2, a phyAphyB mutant showed reduced curvature but no change in the position or shape of the fluence-response curve. By contrast, the phototropism mutantnph1-5 failed to show phototropic curvature under any of the irradiation conditions used in the present study. We conclude that the chromoproteins cry1, cry2, nph1, and the blue-light photoreceptor for the stomatal response are genetically separable. Moreover, these photoreceptors appear to activate separate signal transduction pathways.
Identification of a Promoter Sequence from theBETL1Gene Cluster Able to Confer Transfer-Cell-Specific Expression in Transgenic Maize
Authors: Hueros Gregorio , Gomez Elisa , Cheikh Nordine , Edwards Janice , Weldon Marcia , Salamini Francesco , Thompson Richard D.
Published: July 2002

The maize (Zea maysL.) betl1 locus, encoding a basal endosperm transfer layer-specific protein, has been mapped and molecularly cloned in its entirety. The locus is shown to consist of three gene copies in the maize inbred line A69Y. To distinguish the three transcription units from the locus name, we have termed them BETL1a, BETL1b,and BETL1c. Two of the copies are expressed, whereas one is inactive and contains retrotransposon-like insertions in both promoter and intron regions. Based on this information, and a restriction site map covering 17 kb around the BETL1locus, a DNA fragment putatively containing an active promoter sequence was identified. This fragment was tested for its ability to confer transfer-cell-specific expression in transient and stably transformed maize tissues. The transgenic maize plants obtained showed the predicted cell-type specificity of expression restricted to the basal endosperm transfer cells, although there were minor deviations in promoter strength and timing and accumulation of the transgene product from the corresponding BETL-1 endogene expression pattern.
Both phyA and phyB Mediate Light-Imposed Repression ofPHYA Gene Expression in Arabidopsis
Authors: Cantón Francisco R. , Quail Peter H.
Published: July 2002

The negatively photoregulatedPHYA gene has a complex promoter structure in Arabidopsis, with three active transcription start sites. To identify the photoreceptors responsible for regulation of this gene, and to assess the relative roles of the three transcription start sites, we analyzed the changes in PHYA transcript levels in wild-type and photoreceptor mutant seedlings under various irradiation conditions. Continuous far-red or red light exposures each induced a significant decline in transcript levels in wild-type etiolated seedlings. Analysis of mutants specifically lacking either phyA or phyB protein demonstrated that these phytochromes are required for the negative regulation induced by far-red and red light, respectively. Ribonuclease protection experiments showed further that this negative regulation is confined almost exclusively to the shortest, most abundant PHYA transcript, and occurs predominantly in shoots. By contrast, both of the other minor transcripts in shoots, and all three transcripts in roots, exhibit near constitutive expression. This complex expression pattern indicates that the PHYAgene is subject to regulation by multiple signals, including environmental, developmental, and organ-specific signals.
ATMPK4, an Arabidopsis Homolog of Mitogen-Activated Protein Kinase, Is Activated in Vitro by AtMEK1 through Threonine Phosphorylation
Authors: Huang Yafan , Li Hui , Gupta Rajeev , Morris Peter C. , Luan Sheng , Kieber Joseph J.
Published: July 2002

The modulation of mitogen-activated protein kinase (MAPK) activity regulates many intracellular signaling processes. In animal and yeast cells, MAP kinases are activated via phosphorylation by the dual-specificity kinase MEK (MAP kinase kinase). Several plant homologs of MEK and MAPK have been identified, but the biochemical events underlying the activation of plant MAPKs remain unknown. We describe the in vitro activation of an Arabidopsis homolog of MAP kinase, ATMPK4. ATMPK4 was phosphorylated in vitro by an Arabidopsis MEK homolog, AtMEK1. This phosphorylation occurred principally on threonine (Thr) residues and resulted in elevated ATMPK4 kinase activity. A second Arabidopsis MEK isoform, ATMAP2Kα, failed to phosphorylate ATMPK4 in vitro. Tyr dephosphorylation by the Arabidopsis Tyr-specific phosphatase AtPTP1 resulted in an almost complete loss of ATMPK4 activity. Immunoprecipitates of Arabidopsis extracts with anti-ATMPK4 antibodies displayed myelin basic protein kinase activity that was sensitive to treatment with AtPTP1. These results demonstrate that a plant MEK can phosphorylate and activate MAPK, and that Tyr phosphorylation is critical for the catalytic activity of MAPK in plants. Surprisingly, in contrast to the animal enzymes, AtMEK1 may not be a dual-specificity kinase but, rather, the required Tyr phosphorylation on ATMPK4 may result from autophosphorylation.
The Forms and Sources of Cytokinins in Developing White Lupine Seeds and Fruits
Authors: Emery R.J. Neil , Ma Qifu , Atkins Craig A.
Published: July 2002

A comprehensive range of cytokinins (CK) was identified and quantified by gas chromatography-mass spectrometry in tissues of and in xylem and phloem serving developing white lupine (Lupinus albus) fruits. Analyses were initiated at anthesis and included stages of podset, embryogenesis, and seed filling up to physiological maturation 77 d post anthesis (DPA). In the first 10 DPA, fertilized ovaries destined to set pods accumulated CK. The proportion of cis-CK:trans-CK isomers was initially 10:1 but declined to less than 1:1. In ovaries destined to abort, the ratio of cis-isomers to trans-isomers remained high. During early podset, accumulation of CK (30–40 pmol ovary−1) was accounted for by xylem and phloem translocation, both containing more than 90% cis-isomers. During embryogenesis and early seed filling (40–46 DPA), translocation accounted for 1% to 14% of the increases of CK in endosperm (20 nmol fruit−1) and seed coat (15 nmol fruit−1), indicating synthesis in situ. High CK concentrations in seeds (0.6 μmol g−1 fresh weight) were transient, declining rapidly to less than 1% of maximum levels by physiological maturity. These data pose new questions about the localization and timing of CK synthesis, the significance of translocation, and the role(s) of CK forms in reproductive development.
Adenosine Kinase of Arabidopsis. Kinetic Properties and Gene Expression
Authors: Moffatt Barbara A. , Wang Li , Allen Mike S. , Stevens Yvonne Y. , Qin Wensheng , Snider Jamie , von Schwartzenberg Klaus
Published: July 2002

To assess the functional significance of adenosine salvage in plants, the cDNAs and genes encoding two isoforms of adenosine kinase (ADK) were isolated from Arabidopsis. TheADK1- and ADK2-coding sequences are very similar, sharing 92% and 89% amino acid and nucleotide identity, respectively. Each cDNA was overexpressed in Escherichia coli, and the catalytic activity of each isoform was determined. Both ADKs had similar catalytic properties with aK  m andV  max/K  m for adenosine of 0.3 to 0.5 μm and 5.4 to 22 L min−1 mg−1 protein, respectively. TheK  m andV  max/K  m for the cytokinin ribosideN  6(isopentenyl) adenosine are 3 to 5 μm and 0.021 to 0.14 L min−1mg−1 protein, respectively, suggesting that adenosine is the preferred substrate for both ADK isoforms. In Arabidopsis plants, both ADK genes are expressed constitutively, with the highest steady-state mRNA levels being found in stem and root.ADK1 transcript levels were generally higher than those of ADK2. ADK enzyme activity reflected relative ADK protein levels seen in immunoblots for leaves, flowers, and stems but only poorly so for roots, siliques, and dry seeds. The catalytic properties, tissue accumulation, and expression levels of these ADKs suggest that they play a key metabolic role in the salvage synthesis of adenylates and methyl recycling in Arabidopsis. They may also contribute to cytokinin interconversion.
Free and Conjugated Benzoic Acid in Tobacco Plants and Cell Cultures. Induced Accumulation upon Elicitation of Defense Responses and Role as Salicylic Acid Precursors
Authors: Chong Julie , Pierrel Marie-Agnès , Atanassova Rossitza , Werck-Reichhart Danièle , Fritig Bernard , Saindrenan Patrick
Published: July 2002

Salicylic acid (SA) is a key endogenous component of local and systemic disease resistance in plants. In this study, we investigated the role of benzoic acid (BA) as precursor of SA biosynthesis in tobacco (Nicotiana tabacum cv Samsun NN) plants undergoing a hypersensitive response following infection with tobacco mosaic virus or in tobacco cell suspensions elicited with β-megaspermin, an elicitor from Phytophthora megasperma. We found a small pool of conjugated BA in healthy leaves and untreated cell suspensions of tobacco, whereas free BA levels were barely detectable. Infection of plants with tobacco mosaic virus or elicitation of cells led to a rapid de novo synthesis and accumulation of conjugated BA, whereas free BA was weakly induced. In presence of diphenylene iodonium, an inhibitor of superoxide anion formation, SA accumulation was abolished in elicited cells and much higher BA levels were concomitantly induced, mainly as a conjugated form. Furthermore, piperonylic acid, an inhibitor of cinnamate-4-hydroxylase was used as a powerful tool to redirect the metabolic flow from the main phenylpropanoid pathway into the SA biosynthetic branch. Under these conditions, in vivo labeling and radioisotope dilution experiments with [14C]trans-cinnamic acid as precursor clearly indicated that the free form of BA produced in elicited tobacco cells is not the major precursor of SA biosynthesis. The main conjugated form of BA accumulating after elicitation of tobacco cells was identified for the first time as benzoyl-glucose. Our data point to the likely role of conjugated forms of BA in SA biosynthesis.
The 5′ End of the Pea Ferredoxin-1 mRNA Mediates Rapid and Reversible Light-Directed Changes in Translation in Tobacco
Authors: Hansen Eric R. , Petracek Marie E. , Dickey Lynn F. , Thompson William F.
Published: July 2002

Ferredoxin-1 (Fed-1) mRNA contains an internal light response element (iLRE) that destabilizes mRNA when light-grown plants are placed in darkness. mRNAs containing this element dissociate from polyribosomes in the leaves of transgenic tobacco (Nicotiana tabacum) plants transferred to the dark for 2 d. Here, we report in vivo labeling experiments with a chloramphenicol acetyl transferase mRNA fused to theFed-1 iLRE. Our data indicate that theFed-1 iLRE mediates a rapid decline in translational efficiency and that iLRE-containing mRNAs dissociate from polyribosomes within 20 min after plants are transferred to darkness. Both events occur before the decline in mRNA abundance, and polyribosome association is rapidly reversible if plants are re-illuminated. These observations support a model in which Fed-1 mRNA in illuminated leaves is stabilized by its association with polyribosomes, and/or by translation. In darkness a large portion of the mRNA dissociates from polyribosomes and is subsequently degraded. We also show that a significant portion of total tobacco leaf mRNA is shifted from polyribosomal to non-polyribosomal fractions after 20 min in the dark, indicating that translation of other mRNAs is also rapidly down-regulated in response to darkness. This class includes some, but not all, cytoplasmic mRNAs encoding proteins involved in photosynthesis.
Asymmetric Subcellular mRNA Distribution Correlates with Carbonic Anhydrase Activity in Acetabularia acetabulum
Authors: Serikawa Kyle A. , Porterfield D. Marshall , Mandoli Dina F.
Published: July 2002

The unicellular green macroalga Acetabularia acetabulum L. Silva is an excellent system for studying regional differentiation within a single cell. In late adults, physiologically mediated extracellular alkalinity varies along the long axis of the alga with extracellular pH more alkaline along the apical and middle regions of the stalk than at and near the rhizoid. Respiration also varies with greater respiration at and near the rhizoid than along the stalk. We hypothesized that the apical and middle regions of the stalk require greater carbonic anhydrase (CA) activity to facilitate inorganic carbon uptake for photosynthesis. Treatment of algae with the CA inhibitors acetazolamide and ethoxyzolamide decreased photosynthetic oxygen evolution along the stalk but not at the rhizoid, indicating that CA facilitates inorganic carbon uptake in the apical portions of the alga. To examine the distribution of enzymatic activity within the alga, individuals were dissected into apical, middle, and basal tissue pools and assayed for both total and external CA activity. CA activity was greatest in the apical portions. We cloned two CA genes (AaCA1 andAaCA2). Northern analysis demonstrated that both genes are expressed throughout much of the life cycle of A. acetabulum. AaCA1 mRNA first appears in early adults.AaCA2 mRNA appears in juveniles. TheAaCA1 and AaCA2 mRNAs are distributed asymmetrically in late adults with highest levels of each in the apical portion of the alga. mRNA localization and enzyme activity patterns correlate for AaCA1 and AaCA2, indicating that mRNA localization is one mechanism underlying regional differentiation in A. acetabulum.