bluuebunny/crossref_metadata_2025 huggingface dataset:
Income and environmental R&D: empirical evidence from OECD countries
Authors: KOMEN MARINUS H.C. , GERKING SHELBY , FOLMER HENK
Published: July 2002

This paper extends previous empirical studies of the environmental Kuznets curve by examining the role of rising incomes in promoting development of new technologies directed toward environmental improvements. The main result, based on an analysis of data from 19 OECD countries for the period 1980–94, shows that the income elasticity of public research and development funding for environmental protection is positive, and may be close to unity. This finding suggests that emissions of at least some pollutants may decline with income after a threshold level of income is reached. However, this should be interpreted cautiously in light of: (1) the small size of public research and development funding relative to overall spending on environmental protection, (2) the ability of a country to substitute between public and private research and development expenditures, as well as among alternative policy instruments, and (3) the possibility that public research and development funding may be a form of industrial subsidy in some countries.
Special Topic I: Structural Adjustment Policies and the Environment
Authors: MUNASINGHE MOHAN
Published: July 2002

Background to structural adjustment
The oil price increases of the 1970s, the worldwide recession, and developing country debt crisis of the 1980s, led to the adoption of so-called structural adjustment policies (SAPs). These economic reform packages which included stringent monetary and fiscal measures, sought to restore conditions for growth and development by a combination of short-term ‘stabilization’ and more medium-term ‘adjustment’ policies for the macro-economy. SAPs have not always achieved their economic goals, for a variety of reasons. Of greater relevance is the fact that even where economic gains have been realized through structural adjustment, both
environmental and social problems have persisted in several countries. The growing sustainable development literature is seeking to identify and remedy development strategies that lead to the unsustainable use of natural resources and the environment. One key question is whether the very economic policies being prescribed to alleviate economic problems are perhaps undermining the environmental resources and social fabric on which the long-term development of nations will ultimately depend.
Developing an Autism
Assessment Service I:
Procedures, Priorities, and
Pitfalls over the First 5 Years
Authors: Moore Vanessa , Titcomb Josie , Cronk Elaine , Goodson Sally , Rolles Chris
Published: July 2002

This paper describes the development of a new assessment service
in
Southampton for children with autism and related disorders. The evolution

of the service is described and the multidisciplinary assessment process
is
outlined. The response of families to the service is evaluated and the

current status of the service is examined critically. The importance of

forging good working links with other local services for children is
emphasised.
MONEY, SEARCH, AND COSTLY MATCHMAKING
Authors: Camera Gabriele
Published: July 2002

I examine the robustness of monetary equilibria
in a random-matching model, where a more efficient mechanism
for trade is available. Agents choose between two trading
sectors: the search and the intermediated sector. In the
former, trade partners arrive randomly and there is a
trading externality. In the latter, a costly matching
technology provides deterministic double-coincidence
matches. Multiple equilibria exist with the extent of costly
matching endogenously determined. Money and “mediated” trade
may coexist. This depends on the size of the probability of
a trade, relative to the cost of deterministic matching.
This outcome is inferior for an increasing-returns
externality. Under certain conditions, regimes with only
costly matching are welfare superior to monetary regimes
with random matching.
INTRODUCTION TO THE SPECIAL ISSUE: NEW APPROACHES TO LEARNING IN MACROECONOMIC MODELS
Authors: Arifovic Jasmina , Bullard James
Published: July 2002

The research questions addressed by the literature on learning in macroeconomics can be classified into four categories: First, there are issues related to the convergence and stability under learning in models with unique rational expectations equilibria. Authors here are concerned mainly with the learnability of a rational expectations equilibrium, as a measure of that equilibrium's plausibility as an observed outcome in an actual economy. Second, there are issues related to convergence and stability under learning in models with multiple rational expectations equilibria. In this case, learnability serves as an equilibrium selection device, helping economists decide which equilibria are the more likely to be actually observed among the many that exist under rational expectations. A third set of issues involves the examination of transitional dynamics that accompanies the equilibrium selection process. Following some type of unexpected strcutural change or change in policy regime, for instance, economies necessarily must follow temporary transitional paths to a rational expectations equilibrium associated with the new reality. Learning is sometimes used to help model such transitional dynamics. Finally, there are issues related to the examination of learning dynamics that are intrinsically different, even asymptotically, from the dynamics of the rational expectations versions of the models. In these cases, the learning dynamics do not converge to the rational expectations fixed points, and (unexploitable) expectational errors persist indefinitely. Some authors have tried to make use of this possibility in order to build explanations of otherwise puzzling macroeconomic phenomena based on constantly changing expectations.
High-level networking with mobile code and first order AND-continuations
Authors: TARAU PAUL , DAHL VERONICA
Published: July 2002

We describe a scheme for moving living code between a set of distributed processes coordinated
with unification based Linda operations, and its application to building a comprehensive Logic
programming based Internet programming framework. Mobile threads are implemented by
capturing first order continuations in a compact data structure sent over the network. Code
is fetched lazily from its original base turned into a server as the continuation executes at the
remote site. Our code migration techniques, in combination with a dynamic recompilation
scheme, ensure that heavily used code moves up smoothly on a speed hierarchy while volatile
dynamic code is kept in a quickly updatable form. Among the examples, we describe how
to build programmable client and server components (Web servers, in particular) and mobile
agents.
The World Trade Organization's legitimacy crisis
Authors: ESTY DANIEL C.
Published: July 2002

Despite the successful launch of a new round of multilateral trade
negotiations at Doha, the World Trade Organization faces a legitimacy crisis.
Protests continue to rock major international economic meetings, and the WTO's
role in globalization is being questioned by many observers. This paper examines
the contours of this crisis and explores the possibility that the WTO's indirect ties to
popular sovereignty – through national governments – provide an insufficient
foundation for the trade regime's authority and central role in the emerging
structure of global governance. Arguing that the WTO needs to re-establish its
legitimacy based on wider links to the public around the world in whose name freer
trade is pursued, the paper suggests that the WTO must also re-build its reputation
for efficacy in a context where success is no longer measured exclusively in narrow
economic terms. To be seen as serving the interests of the world community
broadly, the trade regime needs to pursue its economic goals in a fashion that shows
sensitivity to other important goals and values, such as poverty alleviation,
environmental protection, and the promotion of public health. Long-term success
further depends on the trade regime becoming embedded within a broader structure
of global governance that provides ‘checks and balances’ and reinforces the
legitimacy of international trade policy making.
Two enhancers and one silencer located in the introns of regA control somatic cell differentiation in Volvox carteri
Authors: Stark Klaus , Kirk David L. , Schmitt Rüdiger
Published: July 2002

The regA gene plays a central role in germ-soma differentiation of Volvox carteri by suppressing all reproductive functions in somatic cells. Here we show that the minimal promoter of regA consists of only 42 bp immediately upstream of the transcription start site, and that it contains no discernible regulatory elements. However, introns 3 and 5 are both required forregA expression in somatic cells, and intron 7 is essential for silencing regA in gonidia (asexual reproductive cells). AregA gene lacking intron 7 rescues the normal phenotype of mutant somatic cells, but also results in gonidia that reproduce only weakly and soon die out. The same phenotype is observed when aregA gene containing intron 7 is placed under control of a constitutive promoter, suggesting that the silencing activity of intron 7 is promoter specific. Intron 7 is unusual in that it contains a potential ORF that is in frame with exons 7 and 8, and some transcripts are produced in which intron 7 is retained. However, a regulatory role for the intron 7 translation product can be ruled out, because a construct in which intron 7 must be translated, and one in which it cannot be translated, both result in wild-type development of both cell types. Furthermore, intron 7 is unable to act in trans to silence regA, but is able to exert its normal effect when placed in a different location within the gene. Therefore, it appears that intron 7 functions in gonidia as a classical cell-type-specific and promoter-specific enhancer, of the inhibitory type that is often referred to as a silencer.
Differentiation of embryonic stem cells is induced by GATA factors
Authors: Fujikura Junji , Yamato Eiji , Yonemura Shigenobu , Hosoda Kiminori , Masui Shinji , Nakao Kazuwa , Miyazaki Jun-ichi , Niwa Hitoshi
Published: July 2002

Extraembryonic endoderm (ExE) is differentiated from the inner cell mass of the late blastocyst-stage embryo to form visceral and parietal endoderm, both of which have an important role in early embryogenesis. The essential roles of Gata-6 and Gata-4 on differentiation of visceral endoderm have been identified by analyses of knockout mice. Here we report that forced expression of either Gata-6 or Gata-4 in embryonic stem (ES) cells is sufficient to induce the proper differentiation program towards ExE. We believe that this is the first report of a physiological differentiation event induced by the ectopic expression of a transcription factor in ES cells.
Genomic Sequence Analysis of Fugu rubripes CFTR and Flanking Genes in a 60 kb Region Conserving Synteny with 800 kb of Human Chromosome 7
Authors: Davidson Heather , Taylor Martin S. , Doherty Ann , Boyd A. Christopher , Porteous David J.
Published: July 2002

To define control elements that regulate tissue-specific expression of the cystic fibrosis transmembrane regulator (CFTR), we have sequenced 60 kb of genomic DNA from the puffer fish Fugu rubripes (Fugu) that includes the CFTR gene. This region of the Fugu genome shows conservation of synteny with 800-kb sequence of the human genome encompassing the WNT2, CFTR, Z43555, and CBP90 genes. Additionally, the genomic structure of each gene is conserved. In a multiple sequence alignment of human, mouse, andFugu, the putative WNT2 promoter sequence is shown to contain highly conserved elements that may be transcription factor or other regulatory binding sites. We have found two putative ankyrin repeat-containing genes that flank the CFTR gene. Overall sequence analysis suggests conservation of intron/exon boundaries betweenFugu and human CFTR and revealed extensive homology between functional protein domains. However, the immediate 5′ regions of human and Fugu CFTR are highly divergent with few conserved sequences apart from those resembling diminished cAMP response elements (CRE) and CAAT box elements. Interestingly, the polymorphic polyT tract located upstream of exon 9 is present in human and Fugu but absent in mouse. Similarly, an intron 1 and intron 9 element common to human and Fugu is absent in mouse. The euryhaline killifish CFTR coding sequence is highly homologous to the Fugusequence, suggesting that upregulation of CFTR in that species in response to salinity may be regulated transcriptionally.

[The sequence data described in this paper have been submitted to the GenBank data library under accession no. AJ271361, for the combined cosmids 159C9, 146H13, 6M15, and 145M20.]
Extended Intermarker Linkage Disequilibrium in the Afrikaners
Authors: Hall Diana , Wijsman Ellen M. , Roos J. Louw , Gogos Joseph A. , Karayiorgou Maria
Published: July 2002

In this study we conducted an investigation of the background level of linkage disequilibrium (LD) in the Afrikaner population to evaluate the appropriateness of this genetic isolate for mapping complex traits. We analyzed intermarker LD in 62 nuclear families using microsatellite markers covering extended chromosomal regions. The markers were selected to allow the first direct comparison of long-range LD in the Afrikaners to LD in other demographic groups. Using several statistical measures, we find significant evidence for LD in the Afrikaners extending remarkably over a 6-cM range. In contrast, LD decays significantly beyond 3-cM distances in the other founder and outbred populations examined. This study strongly supports the appropriateness of the Afrikaner population for genome-wide scans that exploit LD to map common, multigenic disorders.
RePS: A Sequence Assembler That Masks Exact Repeats Identified from the Shotgun Data
Authors: Wang Jun , Wong Gane Ka-Shu , Ni Peixiang , Han Yujun , Huang Xiangang , Zhang Jianguo , Ye Chen , Zhang Yong , Hu Jianfei , Zhang Kunlin , Xu Xin , Cong Lijuan , Lu Hong , Ren Xide , Ren Xiaoyu , He Jun , Tao Lin , Passey Douglas A. , Wang Jian , Yang Huanming , Yu Jun , Li Songgang
Published: July 2002

We describe a sequence assembler, RePS(repeat-masked Phrap with scaffolding), that explicitly identifies exact 20mer repeats from the shotgun data and removes them prior to the assembly. The established software Phrap is used to compute meaningful error probabilities for each base. Clone-end-pairing information is used to construct scaffolds that order and orient the contigs. We show with real data for human and rice that reasonable assemblies are possible even at coverages of only 4× to 6×, despite having up to 42.2% in exact repeats.

[The following individuals kindly provided reagents, samples, or unpublished information as indicated in the paper: P. Green and A.F. Smit.]
Linkage Disequilibrium Between Microsatellite Markers Extends Beyond 1 cM on Chromosome 20 in Finns
Authors: Mohlke Karen L. , Lange Ethan M. , Valle Timo T. , Ghosh Soumitra , Magnuson Victoria L. , Silander Kaisa , Watanabe Richard M. , Chines Peter S. , Bergman Richard N. , Tuomilehto Jaakko , Collins Francis S. , Boehnke Michael
Published: July 2002

Linkage disequilibrium (LD) is a proven tool for evaluating population structure and localizing genes for monogenic disorders. LD-based methods may also help localize genes for complex traits. We evaluated marker–marker LD using 43 microsatellite markers spanning chromosome 20 with an average density of 2.3 cM. We studied 837 individuals affected with type 2 diabetes and 386 mostly unaffected spouse controls. A test of homogeneity between the affected individuals and their spouses showed no difference, allowing the 1223 individuals to be analyzed together. Significant (P < 0.01) LD was observed using a likelihood ratio test in all (11/11) marker pairs within 1 cM, 78% (25/32) of pairs 1–3 cM apart, and 39% (7/18) of pairs 3–4 cM apart, but for only 12 of 842 pairs more than 4 cM apart. We used the human genome project working draft sequence to estimate kilobase (kb) intermarker distances, and observed highly significant LD (P < 10−10) for all six marker pairs up to 350 kb apart, although the correlation of LD with cM is slightly better than the correlation with megabases. These data suggest that microsatellites present at 1-cM density are sufficient to observe marker–marker LD in the Finnish population.
Genetic Plasticity ofVGenes Under Somatic Hypermutation: Statistical Analyses Using a New Resampling-Based Methodology
Authors: Oprea Mihaela , Kepler Thomas B.
Published: July 2002

Evidence for somatic hypermutation of immunoglobulin genes has been observed in all of the species in which immunoglobulins have been found. Previous studies have suggested that codon usage in immunoglobulin variable (V) region genes is such that the sequence-specificity of somatic hypermutation results in greater mutability in complementarity-determining regions of the gene than in the framework regions. We have developed a new resampling-based methodology to explore genetic plasticity in individualVgenes and inVgene families in a statistically meaningful way. We determine what factors contribute to this mutability difference and characterize the strength of selection for this effect. We find that although the codon usage in immunoglobulinVgenes renders them distinct among translationally equivalent sequences with random codon usage, they are nevertheless not optimal in this regard. We find that the mutability patterns in a number of species are similar to those we find for human sequences. Interestingly, sheep sequences show extremely strong mutability differences, consistent with the role of somatic hypermutation in the diversification of primary antibody repertoire in these animals. Human TCRVβsequences resemble immunoglobulin in mutability pattern, suggesting one of several alternatives, that hypermutation is functionally operating in TCR, that it was once operating in TCR or in the common precursor of TCR and immunoglobulin, or that the hypermutation mechanism has evolved to exploit the codon usage in immunoglobulin (and fortuitously, TCR) rather than vice-versa. Our findings provide support to the hypothesis that somatic hypermutation appeared very early in the phylogeny of immune systems, that it is, to a large extent, shared between species, and that it makes an essential contribution to the generation of the antibody repertoire.
Xenobiotic Biotransformation in Unicellular Green Algae (Involvement of Cytochrome P450 in the Activation and Selectivity of the Pyridazinone Pro-Herbicide Metflurazon)
Authors: Thies F. , Backhaus T. , Bossmann B. , Grimme L. H.
Published: July 2002

The N-demethylation of the pyridazinone pro-herbicide metflurazon into norflurazon implies a toxification in photosynthetic organisms. This is confirmed by quantitative structure activity relationships determined for two unicellular green algae, Chlorella sorokiniana and Chlorella fusca; however, the latter is 25 to 80 times more sensitive to metflurazon. This sensitivity is linked to differences in the N-demethylase activity of both algae, as determined by an optimized in vivo biotransformation assay. Apparent Km values of the metflurazon-N-demethylase indicate a 10-fold higher affinity for this xenobiotic substrate for Chlorella fusca. Furthermore, algal metflurazon-N-demethylation is characterized by distinct variations in activity, depending on the stage of cell development within the cell cycle. Several well-established inhibitors of cytochrome P450-mediated reactions, including piperonyl-butoxide, 1-aminobenzotriazole, 1-phenoxy-3-(1H-1,2,4-triol-1yI)-4-hydroxy-5,5-dimethylhexane, and tetcyclacis, as well as cinnamic acid, a potential endogenous substrate, inhibited the N-demethylation of metflurazon. The results suggest that the N-demethylation of metflurazon by both algae is mediated by a cytochrome P450 monooxygenase. The determination of antigenic cross-reactivity of algal proteins with heterologous polyclonal antibodies originally raised against plant P450s, anti-cinnamic acid 4-hydroxylase (CYP73A1), anti-ethoxycoumarin-O-dealkylase, anti-tulip allene oxidase (CYP74), and an avocado P450 (CYP71A1) or those of bacterial origin, CYP105A1 and CYP105B1, suggests the presence of distinct P450 isoforms in both algae.
Purification and Immunological Identification of Metallothioneins 1 and 2 from Arabidopsis thaliana
Authors: Murphy A. , Zhou J. , Goldsbrough P. B. , Taiz L.
Published: July 2002

Gene families encoding two types of metallothioneins (MTs), MT1 and MT2, have been identified in Arabidopsis thaliana, and their respective mRNAs have been shown to be regulated by copper in a tissue-specific manner (J. Zhou and P.B. Goldsbrough [1994] Plant Cell 6: 875–884; J. Zhou and P.B. Goldsbrough [1995] Mol Gen Genet 248: 318–328; A.S. Murphy and L. Taiz [1995] Plant Physiol 109:1–10). However, to date the protein products have not been identified. To purify MT proteins from Arabidopsis, we isolated low-molecular-mass, copper-binding, thiol-rich proteins using selective precipitation followed by size-exclusion, copper-affinity, and thiol-affinity chromatographies. Polyclonal antibodies raised against Arabidopsis MT-glutathione-S-transferase fusion proteins cross-reacted with the 4.5- and 8-kD bands in immunoblots of low-molecular-mass, copper-binding proteins purified from seedling, mature leaf, and mature root tissues. The identity of the proteins was subsequently confirmed by amino acid sequencing. MT1 expression was constitutive in roots and inducible by copper in mature leaves; the reverse pattern was observed for MT2. MT2 expression was also concentrated in the growing tip of the root. The accumulation of the MT1- and MT2-encoded proteins thus parallels the regulation of their respective mRNAs with regard to tissue specificity and induction by copper. In addition, a new type of MT, designated MT3, was derived from the database, detected by reverse transcription-polymerase chain reaction, and tentatively identified at the protein level by amino acid sequencing of a 7-kD cysteine-rich polypeptide.
Calmodulin-stimulated Ca2+-ATPases in the Vacuolar and Plasma Membranes in Cauliflower
Authors: Askerlund P.
Published: July 2002

The subcellular locations of Ca2+-ATPases in the membranes of cauliflower (Brassica oleracea L.) inflorescences were investigated. After continuous sucrose gradient centrifugation a 111-kD calmodulin (CaM)-stimulated and CaM-binding Ca2+-ATPase (BCA1; P. Askerlund [1996] Plant Physiol 110: 913–922; S. Malmstrom, P. Askerlund, M.G. Palmgren [1997] FEBS Lett 400: 324–328) comigrated with vacuolar membrane markers, whereas a 116-kD CaM-binding Ca2+-ATPase co-migrated with a marker for the plasma membrane. The 116-kD Ca2+-ATPase was enriched in plasma membranes obtained by aqueous two-phase partitioning, which is in agreement with a plasma membrane location of this Ca2+-ATPase. Countercurrent distribution of a low-density intracellular membrane fraction in an aqueous two-phase system resulted in the separation of the endoplasmic reticulum and vacuolar membranes. The 111-kD Ca2+-ATPase co-migrated with a vacuolar membrane marker after countercurrent distribution but not with markers for the endoplasmic reticulum. A vacuolar membrane location of the 111-kD Ca2+-ATPase was further supported by experiments with isolated vacuoles from cauliflower: (a) Immunoblotting with an antibody against the 111-kD Ca2+-ATPase showed that it was associated with the vacuoles, and (b) ATP-dependent Ca2+ uptake by the intact vacuoles was found to be CaM stimulated and partly protonophore insensitive.
Activation of Pollen Tube Callose Synthase by Detergents (Evidence for Different Mechanisms of Action)
Authors: Li H. , Bacic A. , Read S. M.
Published: July 2002

In pollen tubes of Nicotiana alata, a membrane-bound, Ca2+-independent callose synthase (CalS) is responsible for the biosynthesis of the (1,3)-β-glucan backbone of callose, the main cell wall component. Digitonin increases CalS activity 3- to 4-fold over a wide range of concentrations, increasing the maximum initial velocity without altering the Michaelis constant for UDP-glucose. The CalS activity that requires digitonin for assay (the latent CalS activity) is not inhibited bythe membrane-impermeant, active-site-directed reagent UDP-pyridoxal when the reaction is conducted in the absence of digitonin. This is consistent with digitonin increasing CalS activity bythe permeabilization of membrane vesicles. A second group of detergents, including 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate (CHAPS), Zwittergent 3–16, and 1-α--lysolecithin, activate pollen tube CalS 10- to 15-fold, but only over a narrow range of concentrations just below their respective critical micellar concentrations. This activation could not be attributed to any particular chemical feature of these detergents. CHAPS increases maximum initial velocity and decreases the Michaelis constant for UDP-glucose and activates CalS even in the presence of permeabilizing concentrations of digitonin. Inhibition studies with UDP-pyridoxal indicate that activation by CHAPS occurs by recruitment of previously inactive CalS molecules to the pool of active enzyme. The activation of pollen tube CalS by these detergents therefore resembles activation of the enzyme by trypsin.
Convergence of the Abscisic Acid, CO2, and Extracellular Calcium Signal Transduction Pathways in Stomatal Guard Cells
Authors: Webb AAR. , Hetherington A. M.
Published: July 2002

We show that guard cells from Arabidopsis thaliana plants carrying the abscisic acid-insensitive mutations abi1 and abi2 fail to respond to CO2 and extracellular calcium. This demonstrates that the signal transduction pathways for all three stimuli converge on, or close to, the ABI1 and ABI2 gene products.
Analysis of cDNA Clones Encoding Sucrose-Phosphate Synthase in Relation to Sugar Interconversions Associated with Dehydration in the Resurrection Plant Craterostigma plantagineum Hochst
Authors: Ingram J. , Chandler J. W. , Gallagher L. , Salamini F. , Bartels D.
Published: July 2002

Sucrose-phosphate synthase (SPS) is a key enzyme in the regulation of sucrose metabolism, being responsible for the synthesis of sucrose 6-phosphate from fructose 6-phosphate and uridine 5[prime]-diphosphate-glucose. We report on the isolation and characterization of cDNA clones encoding SPS from Craterostigma plantagineum Hochst., a resurrection plant in which the accumulation of sucrose is considered to play an important role in tolerance to severe protoplastic dehydration. Two distinct classes of cDNAs encoding SPS were isolated from C. plantagineum, and are represented by the clones Cpsps1 and Cpsps2. The transcripts corresponding to both cDNAs decrease to very low levels in dehydrating leaves of C. plantagineum. Only the Cpsps1 transcript occurs in the roots, where it is present at a higher level than in leaves and increases upon dehydration of the plant. Higher enzymatic activities have been determined in protein extracts of dehydrated tissues compared with untreated tissues, which correlates with an increase in protein levels. It is suggested that the overall regulation of SPS is strongly influenced by the changing composition of the cytoplasm in C. plantagineum leaves during the dehydration-rehydration cycle.
Manipulation of Catalase Levels Produces Altered Photosynthesis in Transgenic Tobacco Plants1
Authors: Brisson Louise F. , Zelitch Israel , Havir Evelyn A.
Published: July 2002

Constructs containing the cDNAs encoding the primary leaf catalase inNicotiana or subunit 1 of cottonseed (Gossypium hirsutum) catalase were introduced in the sense and antisense orientation into the Nicotiana tabacum genome. TheN. tabacum leaf cDNA specifically overexpressed CAT-1, the high catalytic form, activity. Antisense constructs reduced leaf catalase specific activities from 0.20 to 0.75 times those of wild type (WT), and overexpression constructs increased catalase specific activities from 1.25 to more than 2.0 times those of WT. The NADH-hydroxypyruvate reductase specific activity in transgenic plants was similar to that in WT. The effect of antisense constructs on photorespiration was studied in transgenic plants by measuring the CO2 compensation point (Γ) at a leaf temperature of 38°C. A significant linear increase was observed in Γ with decreasing catalase (at 50% lower catalase activity Γ increased 39%). There was a significant temperature-dependent linear decrease in Γ in transgenic leaves with elevated catalase compared with WT leaves (at 50% higher catalase Γ decreased 17%). At 29°C, Γ also decreased with increasing catalase in transgenic leaves compared with WT leaves, but the trend was not statistically significant. Rates of dark respiration were the same in WT and transgenic leaves. Thus, photorespiratory losses of CO2 were significantly reduced with increasing catalase activities at 38°C, indicating that the stoichiometry of photorespiratory CO2 formation per glycolate oxidized normally increases at higher temperatures because of enhanced peroxidation.
The Chloroplast Small Heat-Shock Protein Oligomer Is Not Phosphorylated and Does Not Dissociate during Heat Stress in Vivo1
Authors: Suzuki Teri Chizue , Krawitz Denise C. , Vierling Elizabeth
Published: July 2002

Plants synthesize several classes of small (15- to 30-kD monomer) heat-shock proteins (sHSPs) in response to heat stress, including a nuclear-encoded, chloroplast-localized sHSP (HSP21). Cytosolic sHSPs exist as large oligomers (approximately 200–800 kD) composed solely or primarily of sHSPs. Phosphorylation of mammalian sHSPs causes oligomer dissociation, which appears to be important for regulation of sHSP function. We examined the native structure and phosphorylation of chloroplast HSP21 to understand this protein's basic properties and to compare it with cytosolic sHSPs. The apparent size of native HSP21 complexes was > 200 kD and they did not dissociate during heat stress. We found no evidence that HSP21 or the plant cytosolic sHSPs are phosphorylated in vivo. A partial HSP21 complex purified from heat-stressed pea (Pisum sativum L.) leaves contained no proteins other than HSP21. Mature recombinant pea andArabidopsis thaliana HSP21 were expressed inEscherichia coli, and purified recombinant Arabidopsis HSP21 assembled into homo-oligomeric complexes with the same apparent molecular mass as HSP21 complexes observed in heat-stressed leaf tissue. We propose that the native, functional form of chloroplast HSP21 is a large, oligomeric complex containing nine or more HSP21 subunits, and that plant sHSPs are not regulated by phosphorylation-induced dissociation.
Wound Signaling in Tomato Plants1
Authors: Birkenmeier Guy F. , Ryan Clarence A.
Published: July 2002

The effects of abscisic acid (ABA) on the accumulation of proteinase inhibitors I (Inh I) and II (Inh II) in young, excised tomato (Lycopersicon esculentum L.) plants were investigated. When supplied to excised plants through the cut stems, 100 μm ABA induced the activation of the ABA-responsive le4 gene. However, under the same conditions of assay, ABA at concentrations of up to 100 μm induced only low levels of proteinase-inhibitor proteins or mRNAs, compared with levels induced by systemin or jasmonic acid over the 24 h following treatment. In addition, ABA only weakly induced the accumulation of mRNAs of several other wound-response proteins. Assays of the ABA concentrations in leaves following wounding indicated that the ABA levels increased preferentially near the wound site, suggesting that ABA may have accumulated because of desiccation. The evidence suggests that ABA is not a component of the wound-inducible signal transduction pathway leading to defense gene activation but is likely involved in the general maintenance of a healthy plant physiology that facilitates a normal wound response.
Control of Meristem Development by CLAVATA1 Receptor Kinase and Kinase-Associated Protein Phosphatase Interactions1
Authors: Stone Julie M. , Trotochaud Amy E. , Walker John C. , Clark Steven E.
Published: July 2002

TheCLAVATA1 (CLV1) gene encodes a putative receptor kinase required for the proper balance between cell proliferation and differentiation in Arabidopsis shoot and flower meristems. Impaired CLV1 signaling results in masses of undifferentiated cells at the shoot and floral meristems. Although many putative receptor kinases have been identified in plants, the mechanism of signal transduction mediated by plant receptor-like kinases is largely unknown. One potential effector of receptor kinase signaling is kinase-associated protein phosphatase (KAPP), a protein that binds to multiple plant receptor-like kinases in a phosphorylation-dependent manner. To examine a possible role for KAPP in CLV1-dependent plant development, the interaction of CLV1 and KAPP was investigated in vitro and in vivo. KAPP binds directly to autophosphorylated CLV1 in vitro and co-immunoprecipitates with CLV1 in plant extracts derived from meristematic tissue. Reduction ofKAPP transcript accumulation in an intermediateclv1 mutant suppresses the mutant phenotype, and the degree of suppression is inversely correlated with KAPPmRNA levels. These data suggest that KAPP functions as a negative regulator of CLV1 signaling in plant development. This may represent a general model for the interaction of KAPP with receptor kinases.
A Model for Signal Transduction during Gamete Release in the Fucoid Alga Pelvetia compressa1
Authors: Pearson Gareth Anthony , Howard Brawley Susan
Published: July 2002

Fucoid algae release gametes into seawater following an inductive light period (potentiation), and gamete expulsion from potentiated receptacles ofPelvetia compressa began about 2 min after a light-to-dark transition. Agitation of the medium reversed potentiation, with an exponential time course completed in about 3 h. Light regulated two signaling pathways during potentiation and gamete expulsion: a photosynthetic pathway and a photosynthesis-independent pathway in which red light was active but blue light was not. Uptake of K+ appears to have an important role in potentiation, because a 50% inhibition of potentiation occurred in the presence of the tetraethylammonium ion, a K+-channel blocker. A central role of anion channels in the maintenance of potentiation is suggested by the premature release of gametes in the light when receptacles were incubated with inhibitors of slow-type anion channels. An inhibitor of tyrosine kinases, tyrphostin A63, also inhibited potentiation. A model for gamete release fromP. compressa is presented that proposes that illumination results in the accumulation of ions (e.g. K+) throughout the cells of the receptacle during potentiation, which then move into the extracellular matrix during gamete expulsion to generate osmomechanical force, resulting in gamete release.
New ArabidopsiscueMutants Suggest a Close Connection between Plastid- and Phytochrome Regulation of Nuclear Gene Expression
Authors: López-Juez Enrique , Paul Jarvis R. , Takeuchi Atsuko , Page Anton M. , Chory Joanne
Published: July 2002

We searched for new components that are involved in the positive regulation of nuclear gene expression by light by extending a screen for Arabidopsis cue(chlorophyll a/b-binding [CAB] protein-underexpressed) mutants (H.-M. Li, K. Culligan, R.A. Dixon, J. Chory [1995] Plant Cell 7: 1599–1610). cue mutants display reduced expression of the CAB3 gene, which encodes light-harvesting chlorophyll protein, the main chloroplast antenna. The new mutants can be divided into (a) phytochrome-deficient mutants (hy1and phyB), (b) virescent or delayed-greening mutants (cue3, cue6, and cue8), and (c) uniformly pale mutants (cue4 andcue9). For each of the mutants, the reduction inCAB expression correlates with the visible phenotype, defective chloroplast development, and reduced abundance of the light-harvesting chlorophyll protein. Levels of protochlorophyllide oxidoreductase (POR) were reduced to varying degrees in etiolated mutant seedlings. In the dark, whereas the virescent mutants displayed reduced CAB expression and the lowest levels of POR protein, the other mutants expressed CAB and accumulated POR at near wild-type levels. All of the mutants, with the exception ofcue6, were compromised in their ability to derepressCAB expression in response to phytochrome activation. Based on these results, we propose that the previously postulated plastid-derived signal is closely involved in the pathway through which phytochrome regulates the expression of nuclear genes encoding plastid proteins.
Extragenic Suppressors of the Arabidopsis gaiMutation Alter the Dose-Response Relationship of Diverse Gibberellin Responses1
Authors: Peng Jinrong , Richards Donald E. , Moritz Thomas , Caño-Delgado Ana , Harberd Nicholas P.
Published: July 2002

Active gibberellins (GAs) are endogenous factors that regulate plant growth and development in a dose-dependent fashion. Mutant plants that are GA deficient, or exhibit reduced GA responses, display a characteristic dwarf phenotype. Extragenic suppressor analysis has resulted in the isolation of Arabidopsis mutations, which partially suppress the dwarf phenotype conferred by GA deficiency and reduced GA-response mutations. Here we describe detailed studies of the effects of two of these suppressors,spy-7 and gar2–1, on several different GA-responsive growth processes (seed germination, vegetative growth, stem elongation, chlorophyll accumulation, and flowering) and on the in planta amounts of active and inactive GA species. The results of these experiments show that spy-7 and gar2–1affect the GA dose-response relationship for a wide range of GA responses and suggest that all GA-regulated processes are controlled through a negatively acting GA-signaling pathway.
A Cross-Polarization, Magic-Angle-Spinning,13C-Nuclear-Magnetic-Resonance Study of Polysaccharides in Sugar Beet Cell Walls1
Authors: Renard Catherine M.G.C. , Jarvis Michael C.
Published: July 2002

Solid-state nuclear magnetic resonance relaxation experiments were used to study the rigidity and spatial proximity of polymers in sugar beet (Beta vulgaris) cell walls. ProtonT1ρ decay and cross-polarization patterns were consistent with the presence of rigid, crystalline cellulose microfibrils with a diameter of approximately 3 nm, mobile pectic galacturonans, and highly mobile arabinans. A direct-polarization, magic-angle-spinning spectrum recorded under conditions adapted to mobile polymers showed only the arabinans, which had a conformation similar to that of beet arabinans in solution. These cell walls contained very small amounts of hemicellulosic polymers such as xyloglucan, xylan, and mannan, and no arabinan or galacturonan fraction closely associated with cellulose microfibrils, as would be expected of hemicelluloses. Cellulose microfibrils in the beet cell walls were stable in the absence of any polysaccharide coating.
Transformation of the Collateral Vascular Bundles into Amphivasal Vascular Bundles in an Arabidopsis Mutant1
Authors: Zhong Ruiqin , Taylor Jennifer J. , Ye Zheng-Hua
Published: July 2002

Arabidopsis inflorescence stems develop a vascular pattern similar to that found in most dicots. The arrangement of vascular tissues within the bundle is collateral, and vascular bundles in the stele are arranged in a ring. Although auxin has been shown to be an inducer of vascular differentiation, little is known about the molecular mechanisms controlling vascular pattern formation. By screening ethyl methanesufonate-mutagenized populations of Arabidopsis, we have isolated an avb1(amphivasal vascular bundle) mutant with a novel vascular pattern. Unlike the collateral vascular bundles seen in the wild-type stems, the vascular bundles in theavb1 stems were similar to amphivasal bundles, i.e. the xylem completely surrounded the phloem. Furthermore, branching vascular bundles in the avb1 stems abnormally penetrated into the pith, which resulted in a disruption in the ring-like arrangement of vascular bundles in the stele. The avb1 mutation did not affect leaf venation pattern and root vascular organization. Auxin polar transport assay indicated that the avb1 mutation did not disrupt the auxin polar transport activity in inflorescence stems. The avb1 mutation also exhibited pleiotropic phenotypes, including curled stems and extra cauline branches. Genetic analysis indicated that the avb1 mutation was monogenic and partially dominant. The avb1 locus was mapped to a region between markers mi69 and ASB2, which is covered by a yeast artificial chromosome clone, CIC9E2, on chromosome 5. Isolation of theavb1 mutant provides a novel means to study the evolutionary mechanisms controlling the arrangement of vascular tissues within the bundle, as well as the mechanisms controlling the arrangement of vascular bundles in the stele.
Nodule-Inducing Activity of Synthetic Sinorhizobium meliloti Nodulation Factors and Related Lipo-Chitooligosaccharides on Alfalfa.Importance of the Acyl Chain Structure1
Authors: Demont-Caulet Nathalie , Maillet Fabienne , Tailler Denis , Jacquinet Jean-Claude , Promé Jean-Claude , Nicolaou Kyriacos C. , Truchet Georges , Beau Jean-Marie , Dénarié Jean
Published: July 2002

Sinorhizobium meliloti nodulation factors (NFs) elicit a number of symbiotic responses in alfalfa (Medicago sativa) roots. Using a semiquantitative nodulation assay, we have shown that chemically synthesized NFs trigger nodule formation in the same range of concentrations (down to 10−10m) as natural NFs. The absence of O-sulfate orO-acetate substitutions resulted in a decrease in morphogenic activity of more than 100-fold and approximately 10-fold, respectively. To address the question of the influence of the structure of the N-acyl chain, we synthesized a series of sulfated tetrameric lipo-chitooligosaccharides (LCOs) having fatty acids of different lengths and with unsaturations either conjugated to the carbonyl group (2E) or located in the middle of the chain (9Z). A nonacylated, sulfated chitin tetramer was unable to elicit nodule formation. Acylation with short (C8) chains rendered the LCO active at 10−7m. The optimal chain length was C16, with the C16-LCO being more than 10-fold more active than the C12- and C18-LCOs. Unsaturations were important, and the diunsaturated 2E,9Z LCO was more active than the monounsaturated LCOs. We discuss different hypotheses for the role of the acyl chain in NF perception.
Cloning and Expression of a Hexose Transporter Gene Expressed during the Ripening of Grape Berry1
Authors: Fillion Laurent , Ageorges Agnès , Picaud Sarah , Coutos-Thévenot Pierre , Lemoine Rémi , Romieu Charles , Delrot Serge
Published: July 2002

The ripening of grape (Vitis vinifera L.) is characterized by massive sugar import into the berries. The events triggering this process and the pathways of assimilate transport are still poorly known. A genomic cloneVvht1 (Vitisvinifera hexose transporter1) and the corresponding cDNA encoding a hexose transporter whose expression is induced during berry ripening have been isolated. Vvht1is expressed mainly in the berries, with a first peak of expression at anthesis, and a second peak about 5 weeks after véraison (a viniculture term for the inception of ripening). Vvht is strictly conserved between two grape cultivars (Pinot Noir and Ugni-Blanc). The organization of the Vvht1 genomic sequence is homologous to that of the Arabidopsis hexose transporter, but differs strongly from that of the Chlorella kessleri hexose transporter genes. The Vvht1 promoter sequence contains several potential regulating cis elements, including ethylene-, abscisic acid-, and sugar-responsive boxes. Comparison of the Vvht1 promoter with the promoter of grape alcohol dehydrogenase, which is expressed at the same time during ripening, also allowed the identification of a 15-bp consensus sequence, which suggests a possible co-regulation of the expression of these genes. The expression of Vvht1 during ripening indicates that sucrose is at least partially cleaved before uptake into the flesh cells.
Cloning and First Functional Characterization of a Plant Cyclic Nucleotide-Gated Cation Channel
Authors: Leng Qiang , Mercier Richard W. , Yao Weizhe , Berkowitz Gerald A.
Published: July 2002

Cyclic nucleotide-gated (cng) non-selective cation channels have been cloned from a number of animal systems. These channels are characterized by direct gating upon cAMP or cGMP binding to the intracellular portion of the channel protein, which leads to an increase in channel conductance. Animal cng channels are involved in signal transduction systems; they translate stimulus-induced changes in cytosolic cyclic nucleotide into altered cell membrane potential and/or cation flux as part of a signal cascade pathway. Putative plant homologs of animal cng channels have been identified. However, functional characterization (i.e. demonstration of cyclic-nucleotide-dependent ion currents) of a plant cng channel has not yet been accomplished. We report the cloning and first functional characterization of a plant member of this family of ion channels. The Arabidopsis cDNA AtCNGC2 encodes a polypeptide with deduced homology to the α-subunit of animal channels, and facilitates cyclic nucleotide-dependent cation currents upon expression in a number of heterologous systems. AtCNGC2 expression in a yeast mutant lacking a low-affinity K+ uptake system complements growth inhibition only when lipophilic cyclic nucleotides are present in the culture medium. Voltage clamp analysis indicates that Xenopus laevis oocytes injected with AtCNGC2 cRNA demonstrate cyclic-nucleotide-dependent, inward-rectifying K+ currents. Human embryonic kidney cells (HEK293) transfected with AtCNGC2 cDNA demonstrate increased permeability to Ca2+ only in the presence of lipophilic cyclic nucleotides. The evidence presented here supports the functional classification of AtCNGC2 as a cyclic-nucleotide-gated cation channel, and presents the first direct evidence (to our knowledge) identifying a plant member of this ion channel family.
Apoplastic pH and Fe3+ Reduction in Intact Sunflower Leaves
Authors: Kosegarten Harald U. , Hoffmann Bernd , Mengel Konrad
Published: July 2002

It has been hypothesized that under NO3  − nutrition a high apoplastic pH in leaves depresses Fe3+ reductase activity and thus the subsequent Fe2+ transport across the plasmalemma, inducing Fe chlorosis. The apoplastic pH in young green leaves of sunflower (Helianthus annuus L.) was measured by fluorescence ratio after xylem sap infiltration. It was shown that NO3  − nutrition significantly increased apoplastic pH at distinct interveinal sites (pH ≥ 6.3) and was confined to about 10% of the whole interveinal leaf apoplast. These apoplastic pH increases presumably derive from NO3  −/proton cotransport and are supposed to be related to growing cells of a young leaf; they were not found in the case of sole NH4  + or NH4NO3 nutrition. Complementary to pH measurements, the formation of Fe2+-ferrozine from Fe3+-citrate was monitored in the xylem apoplast of intact leaves in the presence of buffers at different xylem apoplastic pH by means of image analysis. This analysis revealed that Fe3+reduction increased with decreasing apoplastic pH, with the highest rates at around pH 5.0. In analogy to the monitoring of Fe3+ reduction in the leaf xylem, we suggest that under alkaline nutritional conditions at interveinal microsites of increased apoplastic pH, Fe3+ reduction is depressed, inducing leaf chlorosis. The apoplastic pH in the xylem vessels remained low in the still-green veins of leaves with intercostal chlorosis.