bluuebunny/crossref_metadata_2025 huggingface dataset:
Acrosomal status and motility of guinea pig spermatozoa during in vitro penetration of the cumulus oophorus
Authors: Schroer Sarah C. , Yudin Ashley I. , Myles Diana G. , Overstreet James W.
Published: July 2002

Previous studies have suggested that both acrosome-intact and acrosome-reacted guinea pig sperm are capable of binding to the zona pellucida of cumulus-free oocytes, but the acrosomal status of guinea pig sperm during penetration of the cumulus has not been reported. We made video recordings of the interaction between capacitated guinea pig sperm and cumulus-invested guinea pig oocytes. The videotapes were analysed to identify sperm with hyperactivated motility and to classify the acrosomal status of sperm during penetration of the cumulus and after binding to the zona pellucida. The resolution of the video recordings was not sufficient to recognise sperm with swollen acrosomes. However, sperm that had completed the acrosome reaction were easily identified. Acrosome-reacted sperm were found adherent to the outer boundary of the cumulus, but were never observed to penetrate the cumulus. The percentage of acrosome-intact, hyperactivated sperm was higher in the cumulus oophorus than in culture medium, suggesting that changes in motility were elicited in response to contact with the cumulus. Fully acrosome-reacted sperm were found adherent to the zona pellucida, and solubilised guinea pig zona pellucida was capable of inducing acrosome reactions in capacitated guinea pig sperm. Acrosome-intact sperm were also observed on the zona, but they were not tightly bound and did not have hyperactivated motility, suggesting that these sperm were not functionally capacitated. Our observations demonstrate that guinea pig sperm penetrate the cumulus matrix in an acrosome-intact state. Although we did not observe sperm undergoing the acrosome reaction, our observations and experimental data suggest that the acrosome reaction of guinea pig sperm is completed on or near the surface of the zona pellucida.
The omega equation: Q‐G interpretations of simple circulation features
Authors: Pedder Mike A
Published: July 2002

Quasi‐geostrophic (Q‐G) theory can be used to infer the vertical circulation associated with a synoptic distribution of pressure and temperature in much the same sense as geostrophic theory is used to infer a three‐dimensional distribution of the horizontal circulation. For the purposes of subjective analysis, a diagnosis of the vertical circulation and implied surface development can be based on identifying the sign and magnitude of a geostrophic forcing function associated with the particular distributions of geopotential and thickness shown on a conventional 500 hPa analysis chart. Examples of idealised circulation features are used to demonstrate both the strengths and the weaknesses of this approach, with reference to an analysis based on three different methods of evaluating the geostrophic forcing. Copyright © 1997 Royal Meteorological Society
Odor detection, learning, and memory in Huntington's disease
Authors: HAMILTON JOANNE M. , MURPHY CLAIRE , PAULSEN JANE S.
Published: July 2002

We compared 7 mildly affected Huntington's
disease (HD) patients to 7 age- and education-matched healthy
controls (NC) on an odor detection test, the California
Odor Learning Test, and the California Verbal Learning
Test. Results demonstrated that odor detection sensitivity,
but not group membership, accounted for significant variance
in total olfactory learning. Both groups learned fewer
items in the olfactory modality compared to the verbal
modality, but retained a similar amount following a delay.
No group differences were demonstrated for verbal recognition
discriminability, but the HD group demonstrated significantly
impaired odor recognition discriminability. Finally, odor
detection provided excellent classification sensitivity
and specificity between the patients and controls, suggesting
that olfactory testing may provide a sensitive measure
of the early disease process in HD. (JINS, 1999,
5, 609–615.)
Agroindustrialization, globalization, and international development: the environmental implications
Authors: Barrett Christopher B. , Barbier Edward B. , Reardon Thomas
Published: July 2002

‘Agroindustrialization’ comprises three related sets of changes: 1 growth of commercial, off-farm agro-processing, distribution, and input provision activities; 2 institutional and organizational change in the relations between farms and firms both upstream and downstream, such as a marked increased in vertical integration and contract-based procurement; and 3 related changes in product composition, technologies, and sectoral and market structure (Reardon and Barrett, 2000). The actual and potential environmental effect of these changes have been sparsely documented to date. There does not seem to have been any attempt at a reasonably general analysis of the pathways by which such effects might occur or of the instruments governments might have at their disposal to influence these pathways. This essay is meant to fill the latter gap while the articles and policy forum that follow provide more detailed findings and perspectives on constituent issues.
Simulating options for carbon sequestration through improved management of a lowland tropical rainforest
Authors: BOSCOLO MARCO , BUONGIORNO JOSEPH , PANAYOTOU THEODORE
Published: July 2002

The growing evidence that increased levels of carbon dioxide in the atmosphere are related to global warming has prompted several countries to consider options for reducing and offsetting current carbon dioxide emissions. Opportunities for carbon sequestration with forestry activities have been analysed in detail primarily in industrialized nations, mainly because of data availability. This article presents a model that simulates a tropical forest stand in its role as a source of income and as a carbon store, and quantifies the potential for and cost-effectiveness of carbon sequestration through modifications of management practices. Results suggest that financing modifications of forestry practices may achieve net carbon sequestration in a relatively cost-effective way. Tropical countries with extensive forest resources may be in a position to offer cost-effective net carbon sequestration options.
Environmental degradation, property rights and population movements: hypotheses and evidence from Rajasthan (India)
Authors: CHOPRA KANCHAN , GULATI S.C.
Published: July 2002

This study examines, in a developing-country context, the nature of the linkages between deforestation, land degradation and the movement of population from one region to another. While it is usually hypothesized that environmental degradation leads to stress migration from rural areas, changes in institutional arrangements and the subsequent regeneration of land and water may change the situation, decreasing the attractiveness of the option to migrate. Primary data from six villages in Rajasthan (a region in Western India) are used to set up alternative models using OLS, logit and 3SLS systems methods to test alternative forms of the hypotheses. It is found that the proper specification of group property rights, as a consequence of the existence of non-governmental organizations, does reduce migration. Further, a household's decisions to migrate and/or to participate in common property right creation are interrelated, being parts of its labour force allocation decisions. Other variables influencing household decisions to participate are levels of asset ownership, degree of dependence on common land and level of education.
Morphological productivity across speech and writing
Authors: Plag Ingo , Dalton-Puffer Christiane , Baayen Harald
Published: July 2002

Claims about the productivity of a given affix are generally made without differentiating productivity according to type of discourse, although it is commonly assumed that certain kinds of derivational suffixes are more pertinent in certain kinds of texts than in others. Conversely, studies in register variation have paid very little attention to the role derivational morphology may play in register variation.

This paper explores the relation between register variation and derivational morphology through a quantitative investigation of the productivity of a number of English derivational suffixes across three types of discourse in the British National Corpus (written language, context-governed spoken language, and everyday conversations). Three main points emerge from the analysis. First, within a single register, different suffixes may differ enormously in their productivity, even if structurally they are constrained to a similar extent. Second, across the three registers under investigation a given suffix may display vast differences in productivity. Third, the register variation of suffixes is not uniform, i.e. there are suffixes that show differences in productivity across registers while other suffixes do not, or do so to a lesser extent. We offer some tentative explanations for these findings and discuss the implications for morphological theory.
STOCHASTIC VERSION OF POLTEROVICH'S MODEL:
EXPONENTIAL TURNPIKE THEOREMS FOR EQUILIBRIUM PATHS
Authors: Amir Rabah , Evstigneev Igor
Published: July 2002

The paper examines a stochastic analogue of the Polterovich model of
economic dynamics. The study focuses on the asymptotic properties of
equilibrium paths. The main results are stochastic turnpike theorems with
exponential estimates of the convergence rate.
Social Capital in Japan
Authors: Inoguchi Takashi
Published: July 2002

Japanese society is often said to be one with a high premium on social capital. Two major theses have been put forward with regard to social capital in the last few years. One, advanced by Putnam (1993), is that social capital enables democracy to work. In other words, the historically acquired and accumulated social capital in terms of the propensity of individuals to engage with others in community and associational life facilitates the task of democratically working out the resolution of conflicts of interest and collectively producing good public policy. The other, advanced by Fukuyama (1995), postulates that social capital allows the creation of prosperity. In other words, a high level of social capital enables business firms to take risks and stretch networks fully in the creation of wealth on a large scale for a prolonged period of time.
Discoidin domain receptor 1 functions in axon extension of cerebellar granule neurons
Authors: Bhatt Rupal S. , Tomoda Toshifumi , Fang Yin , Hatten Mary E.
Published: July 2002

In the developing cerebellum, granule neuron axon outgrowth is a key step toward establishing proper connections with Purkinje neurons, the principal output neuron of the cerebellum. During a search for genes that function in this process, we identified a receptor tyrosine kinase discoidin domain receptor 1 (DDR1) expressed in granule cells throughout their development. Overexpression of a dominant-negative form of DDR1 in immature granule cells results in severe reduction of neurite outgrowth in vitro, in dissociated primary culture, and in vivo, in organotypic slices of neonatal cerebellum. Granule cells that fail to extend axons are positive for differentiation markers such as TAG-1 and the neuron-specific class III β-tubulin, suggesting that development is affected after granule cells commit to terminal differentiation. DDR1 activation appears to be mediated by its ligand, collagen, which is localized to the pial layer of the developing cerebellum, thereby leading to granule cell parallel fiber extension. Our results therefore indicate that collagen–DDR1 signaling is essential for granule neuron axon formation and further suggest a unique role of pia in cerebellar cortex histogenesis.
The forkhead domain gene unc-130 generates chemosensory neuron diversity in C. elegans
Authors: Sarafi-Reinach Trina R. , Sengupta Piali
Published: July 2002

Caenorhabditis elegans responds to its complex chemical environment using a small number of chemosensory neurons. Each of these neurons exhibits a unique sensory response repertoire. The developmental mechanisms that generate this diversity of function are largely unknown. Many C. elegans chemosensory neurons, including the AWA and ASG neurons, arise as lineal sisters of an asymmetric division. Here we describe the gene unc-130, which plays a role in the generation of the AWA and ASG neurons. Inunc-130 mutants, the ASG neurons adopt the fate of the AWA neurons. unc-130 encodes a member of the forkhead domain family of transcription factors, and is expressed in the precursors to AWA and ASG neurons. Misexpression of unc-130 in the AWA neurons is partly sufficient to repress the AWA fate, but not to promote ASG fate.unc-130 also plays a role in the development of additional chemosensory neurons. Our experiments show that the ASG neurons share a developmental default state in common with three types of olfactory neurons. We propose that distinct cell fates and hence diversity of function in the chemosensory neurons of C. elegans are generated in a hierarchical manner, utilizing both lineage-dependent and independent mechanisms.
Cdc13 both positively and negatively regulates telomere replication
Authors: Chandra Abha , Hughes Timothy R. , Nugent Constance I. , Lundblad Victoria
Published: July 2002

Cdc13 is a single-strand telomeric DNA-binding protein that positively regulates yeast telomere replication by recruiting telomerase to chromosome termini through a site on Cdc13 that is eliminated by the cdc13-2 mutation. Here we show that Cdc13 has a separate role in negative regulation of telomere replication, based on analysis of a new mutation, cdc13-5. Loss of this second regulatory activity results in extensive elongation of the G strand of the telomere by telomerase, accompanied by a reduced ability to coordinate synthesis of the C strand. Both the cdc13-5mutation and DNA polymerase α mutations (which also exhibit elongated telomeres) are suppressed by increased expression of the Cdc13-interacting protein Stn1, indicating that Stn1 coordinates action of the lagging strand replication complex with the regulatory activity of CDC13. However, the association between Cdc13 and Stn1 is abolished by cdc13-2, the same mutation that eliminates the interaction between Cdc13 and telomerase. We propose that Cdc13 participates in two regulatory steps—first positive, then negative—as a result of successive binding of telomerase and the negative regulator Stn1 to overlapping sites on Cdc13. Thus, Cdc13 coordinates synthesis of both strands of the telomere by first recruiting telomerase and subsequently limiting G-strand synthesis by telomerase in response to C-strand replication.
Transcriptional activation: risky business
Authors: Tansey William P.
Published: July 2002

Transcriptional regulation is all about getting RNA polymerase to the right place on the gene at the right time and making sure that it is competent to conduct transcription. Traditional views of this process place most of their emphasis on the events that precede initiation of transcription. We imagine a promoter-bound transcriptional activator (or collection of activators) recruiting components of the basal transcriptional machinery to the DNA, eventually leading to the recruitment of RNA polymerase II and the onset of gene transcription. Although these events play a crucial role in regulating gene expression, they are only half the story. Correct regulation of transcription requires that polymerase not only initiates when and where it should, but that it stops initiating when no longer appropriate. But how are the signals from transcriptional activators, telling RNA polymerase to fire, terminated? Is this process governed by chance, with activators simply falling off the promoter at a certain frequency? Or is there some more direct mechanism, whereby activators are aggressively limited from uncontrolled promoter activation? A new article by Chi et al. (2001) suggests the latter may be true, and provides a mechanism for how a component of the basal transcription machinery can mark the activators it has encountered, sentencing them to an early death or banishing them from the nucleus. The ability of the basal transcriptional apparatus to mark activators provides an efficient way to limit activator function and ensures that continuing transcription initiation at a promoter is coupled to the continuing synthesis and activation of transcriptional activators.
Recruitment of HU by piggyback: a special role of GalR in repressosome assembly
Authors: Kar Sudeshna , Adhya Sankar
Published: July 2002

In Gal repressosome assembly, a DNA loop is formed by the interaction of two GalR, bound to two distal operators, and the binding of the histone-like protein, HU, to an architecturally critical position on DNA to facilitate the GalR–GalR interaction. We show that GalR piggybacks HU to the critical position on the DNA through a specific GalR–HU interaction. This is the first example of HU making a specific contact with another protein. The GalR–HU contact that results in cooperative binding of the two proteins to DNA may be transient and absent in the final repressosome structure. A sequence-independent DNA-binding protein being recruited to an architectural site on DNA through a specific association with a regulatory protein may be a common mode for assembly of complex nucleoprotein structures.
Functional overlap between Sgs1–Top3 and the Mms4–Mus81 endonuclease
Authors: Kaliraman Vivek , Mullen Janet R. , Fricke William M. , Bastin-Shanower Suzanne A. , Brill Steven J.
Published: July 2002

The RecQ DNA helicases, human BLM and yeast Sgs1, form a complex with topoisomerase III (Top3) and are thought to act during DNA replication to restart forks that have paused due to DNA damage or topological stress. We have shown previously that yeast cells lackingSGS1 or TOP3 require MMS4 and MUS81 for viability. Here we show that Mms4 and Mus81 form a heterodimeric structure-specific endonuclease that cleaves branched DNA. Both subunits are required for optimal expression, substrate binding, and nuclease activity. Mms4 and Mus81 are conserved proteins related to the Rad1–Rad10 (XPF/ERCC1) endonuclease required for nucleotide excision repair (NER). However, the Mms4–Mus81 endonuclease is 25 times more active on branched duplex DNA and replication fork substrates than simple Y-forms, the preferred substrate for the NER complexes. We also present genetic data that indicate a novel role for Mms4–Mus81 in meiotic recombination. Our results suggest that stalled replication forks are substrates for Mms4–Mus81 cleavage—particularly in the absence of Sgs1 or BLM. Repair of this double-strand break (DSB) by homologous recombination may be responsible for the elevated levels of sister chromatid exchange (SCE) found in BLM−/− cells.
A System for Specific, High-throughput Genotyping by Allele-specific Primer Extension on Microarrays
Authors: Pastinen Tomi , Raitio Mirja , Lindroos Katarina , Tainola Päivi , Peltonen Leena , Syvänen Ann-Christine
Published: July 2002

This study describes a practical system that allows high-throughput genotyping of single nucleotide polymorphisms (SNPs) and detection of mutations by allele-specific extension on primer arrays. The method relies on the sequence-specific extension of two immobilized allele-specific primers that differ at their 3′-nucleotide defining the alleles, by a reverse transcriptase (RT) enzyme at optimized reaction conditions. We show the potential of this simple one-step procedure performed on spotted primer arrays of low redundancy by generating over 8000 genotypes for 40 mutations or SNPs. The genotypes formed three easily identifiable clusters and all known genotypes were assigned correctly. Higher degrees of multiplexing will be possible with this system as the power of discrimination between genotypes remained unaltered in the presence of over 100 amplicons in a single reaction. The enzyme-assisted reaction provides highly specific allele distinction, evidenced by its ability to detect minority sequence variants present in 5% of a sample at multiple sites. The assay format based on miniaturized reaction chambers at standard 384-well spacing on microscope slides carrying arrays with two primers per SNP for 80 samples results in low consumption of reagents and makes parallel analysis of a large number of samples convenient. In the assay one or two fluorescent nucleotide analogs are used as labels, and thus the genotyping results can be interpreted with presently available array scanners and software. The general accessibility, simple set-up, and the robust procedure of the array-based genotyping system described here will offer an easy way to increase the throughput of SNP typing in any molecular biology laboratory.
A Comparative Genomics Approach to Prediction of New Members of Regulons
Authors: Tan Kai , Moreno-Hagelsieb Gabriel , Collado-Vides Julio , Stormo Gary D.
Published: July 2002

Identifying the complete transcriptional regulatory network for an organism is a major challenge. For each regulatory protein, we want to know all the genes it regulates, that is, its regulon. Examples of known binding sites can be used to estimate the binding specificity of the protein and to predict other binding sites. However, binding site predictions can be unreliable because determining the true specificity of the protein is difficult because of the considerable variability of binding sites. Because regulatory systems tend to be conserved through evolution, we can use comparisons between species to increase the reliability of binding site predictions. In this article, an approach is presented to evaluate the computational predicitions of regulatory sites. We combine the prediction of transcription units having orthologous genes with the prediction of transcription factor binding sites based on probabilistic models. We augment the sets of genes inEscherichia coli that are expected to be regulated by two transcription factors, the cAMP receptor protein and the fumarate and nitrate reduction regulatory protein, through a comparison with theHaemophilus influenzae genome. At the same time, we learned more about the regulatory networks of H. influenzae, a species with much less experimental knowledge than E. coli. By studying orthologous genes subject to regulation by the same transcription factor, we also gained understanding of the evolution of the entire regulatory systems.
Gene Targeting of Desrt, a Novel ARID Class DNA-Binding Protein, Causes Growth Retardation and Abnormal Development of Reproductive Organs
Authors: Lahoud Mireille H. , Ristevski Sika , Venter Deon J. , Jermiin Lars S. , Bertoncello Ivan , Zavarsek Silva , Hasthorpe Sue , Drago John , de Kretser David , Hertzog Paul J. , Kola Ismail
Published: July 2002

We have cloned and characterized a novel murine DNA-binding protein Desrt, with a motif characteristic of the ARID (A-Trichinteractiondomain) family of transcription factors. TheDesrtgene encodes an 83-kD protein that is shown to bind DNA and is widely expressed in adult tissues. To examine the in vivo function ofDesrt, we have generated mice with a targeted mutation in the ARID domain ofDesrt. Homozygous mutants have reduced viability, pronounced growth retardation, and a high incidence of abnormalities of the female and male reproductive organs including cryptorchidism. This may thus serve as a model to dissect the mechanisms involved in the development of the reproductive tract including testicular descent. Gene-targeted mice also display a reduction in the thickness of the zona reticularis of the adrenal gland and transient aberrations of the T and B cell compartments of primary lymphoid organs. These data show that this novel DNA-binding protein, Desrt, has a nonredundant function during growth and in the development of the reproductive system.
Compound Microsatellite Repeats: Practical and Theoretical Features
Authors: Bull Laura N. , Pabón-Peña Carlos R. , Freimer Nelson B.
Published: July 2002

Most linkage and population genetic studies that use microsatellites assume that the polymorphism observed at these loci is due simply to variation in the number of units of a single repeat. Variation is far more complex, however, for the numerous microsatellites that contain interruptions within the repeat or contain more than one type of repeat. We observed that for D18S58, a compound microsatellite containing (CG)m, as well as (CA)n repeats, the apparent length of certain alleles varied between genotyping experiments. Similar results were obtained with other (CG)m–(CA)n repeats. Sequencing demonstrated that the D18S58 alleles demonstrating variable mobility contained longer (CG)m stretches than those alleles whose length did not appear to vary between experiments. These results suggest that (CG)m repeats, which are frequently present in compound human microsatellites, are prone to form an unusually stable secondary structure. We discuss the relative frequency of different classes of compound microsatellites identified through database searches, as well as their patterns of sequence and variation. Further characterization of such variation is important for elucidating the origin, mutational processes, and structure of these widely used, but incompletely understood, sequences.
The Endoplasmic Reticulum-Associated Maize GL8 Protein Is a Component of the Acyl-Coenzyme A Elongase Involved in the Production of Cuticular Waxes
Authors: Xu Xiaojie , Dietrich Charles R. , Lessire Rene , Nikolau Basil J. , Schnable Patrick S.
Published: July 2002

The gl8 gene is required for the normal accumulation of cuticular waxes on maize (Zea mays) seedling leaves. The predicted GL8 protein exhibits significant sequence similarity to a class of enzymes that catalyze the reduction of a ketone group to a hydroxyl group. Polyclonal antibodies raised against the recombinantEscherichia coli-expressed GL8 protein were used to investigate the function of this protein in planta. Subcellular fractionation experiments indicate that the GL8 protein is associated with the endoplasmic reticulum membranes. Furthermore, polyclonal antibodies raised against the partially purified leek (Allium porrum) microsomal acyl-coenzyme A (CoA) elongase can react with the E. coli-expressed GL8 protein. In addition, anti-GL8 immunoglobulin G inhibited the in vitro elongation of stearoyl-CoA by leek and maize microsomal acyl-CoA elongase. In combination, these findings indicate that the GL8 protein is a component of the acyl-CoA elongase. In addition, the finding that anti-GL8 immunoglobulin G did not significantly inhibit the 3-ketoacyl-CoA synthase, 3-ketoacyl-CoA dehydrase, and (E) 2,3-enoyl-CoA reductase partial reactions of leek or maize acyl-CoA elongase lends further support to our previous hypothesis that the GL8 protein functions as a β-ketoacyl reductase during the elongation of very long-chain fatty acids required for the production of cuticular waxes.
Influence of Iron Status on Cadmium and Zinc Uptake by Different Ecotypes of the Hyperaccumulator Thlaspi caerulescens
Authors: Lombi Enzo , Tearall Kathryn L. , Howarth Jonathan R. , Zhao Fang-Jie , Hawkesford Malcolm J. , McGrath Steve P.
Published: July 2002

We have previously identified an ecotype of the hyperaccumulator Thlaspi caerulescens (Ganges), which is far superior to other ecotypes (including Prayon) in Cd uptake. In this study, we investigated the effect of Fe status on the uptake of Cd and Zn in the Ganges and Prayon ecotypes, and the kinetics of Cd and Zn influx using radioisotopes. Furthermore, the T. caerulescens ZIP (Zn-regulated transporter/Fe-regulated transporter-like protein) genes TcZNT1-G andTcIRT1-G were cloned from the Ganges ecotype and their expression under Fe-sufficient and -deficient conditions was analyzed. Both short- and long-term studies revealed that Cd uptake was significantly enhanced by Fe deficiency only in the Ganges ecotype. The concentration-dependent kinetics of Cd influx showed that theV  max of Cd was 3 times greater in Fe-deficient Ganges plants compared with Fe-sufficient plants. In Prayon, Fe deficiency did not induce a significant increase inV  max for Cd. Zn uptake was not influenced by the Fe status of the plants in either of the ecotypes. These results are in agreement with the gene expression study. The abundance ofZNT1-G mRNA was similar between the Fe treatments and between the two ecotypes. In contrast, abundance of theTcIRT1-G mRNA was greatly increased only in Ganges root tissue under Fe-deficient conditions. The present results indicate that the stimulatory effect of Fe deficiency on Cd uptake in Ganges may be related to an up-regulation in the expression of genes encoding for Fe2+ uptake, possibly TcIRT1-G.
The Arabidopsis Phospholipase D Family. Characterization of a Calcium-Independent and Phosphatidylcholine-Selective PLDζ1 with Distinct Regulatory Domains
Authors: Qin Chunbo , Wang Xuemin
Published: July 2002

Four types of phospholipase D (PLD), PLDα, β, γ, and δ, have been characterized in Arabidopsis, and they display different requirements for Ca2+, phosphatidylinositol 4,5-bisphosphate (PIP2), substrate vesicle composition, and/or free fatty acids. However, all previously cloned plant PLDs contain a Ca2+-dependent phospholipid-binding C2 domain and require Ca2+ for activity. This study documents a new type of PLD, PLDζ1, which is distinctively different from previously characterized PLDs. It contains at the N terminus a Phox homology domain and a pleckstrin homology domain, but not the C2 domain. A full-length cDNA for Arabidopsis PLDζ1 has been identified and used to express catalytically active PLD in Escherichia coli. PLDζ1 does not require Ca2+ or any other divalent cation for activity. In addition, it selectively hydrolyzes phosphatidylcholine, whereas the other Arabidopsis PLDs use several phospholipids as substrates. PLDζ1 requires PIP2 for activity, but unlike the PIP2-requiring PLDβ or γ, phosphatidylethanolamine is not needed in substrate vesicles. These differences are described, together with a genomic analysis of 12 putative Arabidopsis PLD genes that are grouped into α, β, δ, γ, and ζ based on their gene architectures, sequence similarities, domain structures, and biochemical properties.
A Multiple-Stimuli-Responsive as-1-Related Element of parA Gene Confers Responsiveness to Cadmium but Not to Copper
Authors: Kusaba M. , Takahashi Y. , Nagata T.
Published: July 2002

The expression of parA, an auxin-regulated gene expressed during the culture of tobacco (Nicotiana tabacum L.) mesophyll protoplasts, is induced by cadmium. To identify the cadmium-responsive element, we examined the parA promoter using the GUS reporter gene. Cadmium responsiveness was retained in a 5[prime] deletion of the parA promoter to -78 bp, but it was nullified by further deletion to -49 bp, which implies that the region -49 to -78 bp contained a cadmium-responsive element. This region contains a sequence similar to as-1, an enhancer sequence from the cauliflower mosaic virus 35S RNA promoter that binds the nuclear factor ASF-1. We named the sequence in the parA promoter pas. Gel-shift assays revealed that pas and as-1 compete for the same DNA-binding nuclear protein(s). Since pentamers of either pas and as-1 were able to confer cadmium responsiveness on a minimal promoter but mutant as-1 was not, we propose that pas and as-1 are involved in cadmium-responsive gene expression. Neither pas nor as-1 conferred responsiveness to copper. The specificity of this response, involving the fuction of as-1- related elements including pas, is discussed.
O-Acetylated Oligosaccharides from Pectins of Potato Tuber Cell Walls
Authors: Ishii T.
Published: July 2002

Acetylated trigalacturonides and rhamnogalacturonan I (RG-I)-derived oligosaccharides were isolated from a Driselase digest of potato tuber cell walls by ion-exchange and size-exclusion chromatography. The oligosaccharides were structurally characterized by fast atom bombardment-mass spectroscopy, nuclear magnetic resonance spectroscopy, and glycosyl-linkage composition analysis. One trigalacturonide contained a single acetyl group at O–3 of the reducing galacturonic acid residue. A second trigalacturonide contained two acetyl substituents, which were located on O–3 or O–4 of the nonreducing galacturonic acid residue and O–3 of the reducing galacturonic acid residue. RG-I backbone-derived oligomers had acetyl groups at O–2 of the galacturonic acid residues. Some of these galacturonic acid residues were O-acetylated at both O–2 and O–3 positions. Rhamnosyl residues of RG-I oligomers were not acetylated.
Products of Proline Catabolism Can Induce Osmotically Regulated Genes in Rice1
Authors: Iyer Suresh , Caplan Allan
Published: July 2002

Many plants accumulate high levels of free proline (Pro) in response to osmotic stress. This imino acid is widely believed to function as a protector or stabilizer of enzymes or membrane structures that are sensitive to dehydration or ionically induced damage. The present study provides evidence that the synthesis of Pro may have an additional effect. We found that intermediates in Pro biosynthesis and catabolism such as glutamine and Δ1-pyrroline-5-carboxylic acid (P5C) can increase the expression of several osmotically regulated genes in rice (Oryza sativa L.), including salT anddhn4. One millimolar P5C or its analog, 3,4-dehydroproline, produced a greater effect on gene expression than 1 mm l-Pro or 75 mm NaCl. These chemicals did not induce hsp70,S-adenosylmethionine synthetase, or another osmotically induced gene, Em, to any significant extent. Unlike NaCl, gene induction by P5C did not depend on the normal levels of either de novo protein synthesis or respiration, and did not raise abscisic acid levels significantly. P5C- and 3,4-dehydroproline-treated plants consumed less O2, had reduced NADPH levels, had increased NADH levels, and accumulated many osmolytes associated with osmotically stressed rice. These experiments indicate that osmotically induced increases in the concentrations of one or more intermediates in Pro metabolism could be influencing some of the characteristic responses to osmotic stress.
Heat-Stress Response of Maize Mitochondria1
Authors: Lund Adrian A. , Blum Paul H. , Bhattramakki Dinakar , Elthon Thomas E.
Published: July 2002

We have identified maize (Zea mays L. inbred B73) mitochondrial homologs of the Escherichia coli molecular chaperones DnaK (HSP70) and GroEL (cpn60) using two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblots. During heat stress (42°C for 4 h), levels of HSP70 and cpn60 proteins did not change significantly. In contrast, levels of two 22-kD proteins increased dramatically (HSP22). Monoclonal antibodies were developed to maize HSP70, cpn60, and HSP22. The monoclonal antibodies were characterized with regard to their cross-reactivity to chloroplastic, cytosolic, and mitochondrial fractions, and to different plant species. Expression of mitochondrial HSP22 was evaluated with regard to induction temperature, time required for induction, and time required for degradation upon relief of stress. Maximal HSP22 expression occurred in etiolated seedling mitochondria after 5 h of a +13°C heat stress. Upon relief of heat stress, the HSP22 proteins disappeared with a half-life of about 4 h and were undetectable after 21 h of recovery. Under continuous heat-stress conditions, the level of HSP22 remained high. A cDNA for maize mitochondrial HSP22 was cloned and extended to full length with sequences from an expressed sequence tag database. Sequence analysis indicated that HSP22 is a member of the plant small heat-shock protein superfamily.
Indole-3-Acetic Acid Controls Cambial Growth in Scots Pine by Positional Signaling1
Authors: Uggla Claes , Mellerowicz Ewa J , Sundberg Björn
Published: July 2002

The vascular cambium produces secondary xylem and phloem in plants and is responsible for wood formation in forest trees. In this study we used a microscale mass-spectrometry technique coupled with cryosectioning to visualize the radial concentration gradient of endogenous indole-3-acetic acid (IAA) across the cambial meristem and the differentiating derivatives in Scots pine (Pinus sylvestris L.) trees that had different rates of cambial growth. This approach allowed us to investigate the relationship between growth rate and the concentration of endogenous IAA in the dividing cells. We also tested the hypothesis that IAA is a positional signal in xylem development (C. Uggla, T. Moritz, G. Sandberg, B. Sundberg [1996] Proc Natl Acad Sci USA 93: 9282–9286). This idea postulates that the width of the radial concentration gradient of IAA regulates the radial number of dividing cells in the cambial meristem, which is an important component for determining cambial growth rate. The relationship between IAA concentration in the dividing cells and growth rate was poor, although the highest IAA concentration was observed in the fastest-growing cambia. The radial width of the IAA concentration gradient showed a strong correlation with cambial growth rate. The results indicate that IAA gives positional information in plants.
Gibberellins Promote Trichome Formation by Up-RegulatingGLABROUS1in Arabidopsis1
Authors: Perazza Daniel , Vachon Gilles , Herzog Michel
Published: July 2002

Trichome development is dependent on gibberellin (GA) signaling inArabidopsis thaliana. Using the GA-deficient mutantga1–3, the GA-response mutant spy-5, and uniconazol (a GA-biosynthesis inhibitor), we show that the GA level response correlates positively with both trichome number and trichome branch number. Two genes, GL1 and TTG, are required for trichome initiation. In ga1–3, coexpression of GL1 and R, the maizeTTG functional homolog, under control of the constitutive 35S promoter, restored trichome development, whereas overexpression of neither GL1 nor R alone was sufficient to significantly suppress the glabrous phenotype. We next focused on GL1 regulation by GAs. In the double mutant the gl1–1 glabrous phenotype is epistatic to thespy-5 phenotype, suggesting that GL1 acts downstream of the GA signal transduction pathway. The activity of a β-glucuronidase reporter gene driven by the GL1promoter was decreased in the wild type grown on uniconazol and showed a clear GA-dependent activation in ga1–3. Finally, quantification of GL1 transcript levels by reverse transcriptase-polymerase chain reaction demonstrated that relative to wild type, ga1–3 plants contained less transcript. These data support the hypothesis that GAs induce trichome development through up-regulation of GL1 and possiblyTTG genes.
Electric Signaling and Pin2 Gene Expression on Different Abiotic Stimuli Depend on a Distinct Threshold Level of Endogenous Abscisic Acid in Several Abscisic Acid-Deficient Tomato Mutants1
Authors: Herde Oliver , Peña Cortés Hugo , Wasternack Claus , Willmitzer Lothar , Fisahn Joachim
Published: July 2002

Experiments were performed on three abscisic acid (ABA)-deficient tomato (Lycopersicon esculentum Mill.) mutants, notabilis,flacca, and sitiens, to investigate the role of ABA and jasmonic acid (JA) in the generation of electrical signals and Pin2 (proteinaseinhibitor II) gene expression. We selected these mutants because they contain different levels of endogenous ABA. ABA levels in the mutant sitiens were reduced to 8% of the wild type, in notabilis they were reduced to 47%, and in flacca they were reduced to 21%. In wild-type and notabilis tomato plants the induction ofPin2 gene expression could be elicited by heat treatment, current application, or mechanical wounding. Inflacca and sitiens only heat stimulation induced Pin2 gene expression. JA levels inflacca and sitiens plants also accumulated strongly upon heat stimulation but not upon mechanical wounding or current application. Characteristic electrical signals evolved in the wild type and in the notabilis andflacca mutants consisting of a fast action potential and a slow variation potential. However, in sitiens only heat evoked electrical signals; mechanical wounding and current application did not change the membrane potential. In addition, exogenous application of ABA to wild-type tomato plants induced transient changes in membrane potentials, indicating the involvement of ABA in the generation of electrical signals. Our data strongly suggest the presence of a minimum threshold value of ABA within the plant that is essential for the early events in electrical signaling and mediation of Pin2 gene expression upon wounding. In contrast, heat-induced Pin2 gene expression and membrane potential changes were not dependent on the ABA level but, rather, on the accumulation of JA.
Differential Expression of Genes for Cyclin-Dependent Protein Kinases in Rice Plants1
Authors: Umeda Masaaki , Umeda-Hara Chikage , Yamaguchi Masatoshi , Hashimoto Junji , Uchimiya Hirofumi
Published: July 2002

Cyclin-dependent protein kinases (CDKs) play key roles in regulating the eukaryotic cell cycle. We have analyzed the expression of four rice (Oryza sativa) CDK genes, cdc2Os1, cdc2Os2,cdc2Os3, and R2, by in situ hybridization of sections of root apices. Transcripts of cdc2Os1,cdc2Os2, and R2 were detected uniformly in the dividing region of the root apex. cdc2Os1 andcdc2Os2 were also expressed in differentiated cells such as those in the sclerenchyma, pericycle, and parenchyma of the central cylinder. By contrast, signals corresponding to transcripts ofcdc2Os3 were distributed only in patches in the dividing region. Counterstaining of sections with 4′,6-diamidino-2-phenylindole and double-target in situ hybridization with a probe for histone H4 transcripts revealed that cdc2Os3 transcripts were abundant from the G2 to the M phase, but were less abundant or absent during the S phase. The levels of the Cdc2Os3 protein and its associated histone H1-kinase activity were reduced by treatment of cultured cells with hydroxyurea, which blocks cycling cells at the onset of the S phase. Our results suggest that domains other than the conserved amino acid sequence (the PSTAIRE motif) have important roles in the function of non-PSTAIRE CDKs in distinct cell-cycle phases.
An Allele of the Ripening-Specific 1-Aminocyclopropane-1-Carboxylic Acid Synthase Gene (ACS1) in Apple Fruit with a Long Storage Life1
Authors: Sunako Tomomi , Sakuraba Wakako , Senda Mineo , Akada Shinji , Ishikawa Ryuji , Niizeki Minoru , Harada Takeo
Published: July 2002

An allele of the 1-aminocyclopropane-1-carboxylic acid (ACC) synthase gene (Md-ACS1), the transcript and translated product of which have been identified in ripening apples (Malus domestica), was isolated from a genomic library of the apple cultivar, Golden Delicious. The predicted coding region of this allele (ACS1-2) showed that seven nucleotide substitutions in the corresponding region ofACS1-1 resulted in just one amino acid transition. A 162-bp sequence characterized as a short interspersed repetitive element retrotransposon was inserted in the 5′-flanking region of ACS1-2 corresponding to position −781 in ACS1-1. TheXhoI site located near the 3′ end of the predicted coding region of ACS1-2 was absent from the reverse transcriptase-polymerase chain reaction product, revealing that exclusive transcription from ACS1-1occurs during ripening of cv Golden Delicious fruit. DNA gel-blot and polymerase chain reaction analyses of genomic DNAs showed clearly that apple cultivars were either heterozygous forACS1-1 andACS1-2 or homozygous for each type. RNA gel-blot analysis of the ACS1-2homozygous Fuji apple, which produces little ethylene and has a long storage life, demonstrated that the level of transcription fromACS1-2 during the ripening stage was very low.
Cucumber Hypocotyls Respond to Cutin Monomers via Both an Inducible and a Constitutive H2O2-Generating System1
Authors: Kauss Heinrich , Fauth Markus , Merten Axel , Jeblick Wolfgang
Published: July 2002

Hypocotyls from etiolated cucumber (Cucumis sativa L.) seedlings were gently abraded at their surface to allow permeation of elicitors. Segments from freshly abraded hypocotyls were only barely competent for H2O2 elicitation with fungal elicitor or hydroxy fatty acids (classical cutin monomers). However, elicitation competence developed subsequent to abrasion, reaching an optimum after about 4 h. This process was potentiated in seedlings displaying acquired resistance to Colletotrichum lagenarium due to root pretreatment with 2,6-dichloroisonicotinic acid or a benzothiadiazole. Induction of competence depended on protein synthesis and could be effected not only by surface abrasion, but also by fungal spore germination on the epidermal surface or by rotating the seedlings in buffer. Inhibitor studies indicated that the inducible mechanism for H2O2 production involves protein phosphorylation, Ca2+ influx, and NAD(P)H oxidase. In contrast, a novel cucumber cutin monomer, dodecan-1-ol, also elicited H2O2 in freshly abraded hypocotyls without previous competence induction. This finding suggests the presence of an additional H2O2-generating system that is constitutive. It is insensitive to inhibitors and has, in addition, a different specificity for alkanols. Thus, dodecan-1-ol might initiate defense before the inducible H2O2-generating system becomes effective.
Glutathione and Homoglutathione Synthesis in Legume Root Nodules
Authors: Matamoros Manuel A. , Moran Jose F. , Iturbe-Ormaetxe Iñaki , Rubio Maria C. , Becana Manuel
Published: July 2002

High-performance liquid chromatography (HPLC) with fluorescence detection was used to study thiol metabolism in legume nodules. Glutathione (GSH) was the major non-protein thiol in all indeterminate nodules examined, as well as in the determinate nodules of cowpea (Vigna unguiculata), whereas homoglutathione (hGSH) predominated in soybean (Glycine max), bean (Phaseolus vulgaris), and mungbean (Vigna radiata) nodules. All nodules had greater thiol concentrations than the leaves and roots of the same plants because of active thiol synthesis in nodule tissue. The correlation between thiol tripeptides and the activities of glutathione synthetase (GSHS) and homoglutathione synthetase (hGSHS) in the nodules of eight legumes, and the contrasting thiol contents and activities in alfalfa (Medicago sativa) leaves (98% hGSH, 100% hGSHS) and nodules (72% GSH, 80% GSHS) indicated that the distribution of GSH and hGSH is determined by specific synthetases. Thiol contents and synthesis decreased with both natural and induced nodule senescence, and were also reduced in the senescent zone of indeterminate nodules. Thiols and GSHS were especially abundant in the meristematic and infected zones of pea (Pisum sativum) nodules. Thiols and γ-glutamylcysteinyl synthetase were also more abundant in the infected zone of bean nodules, but hGSHS was predominant in the cortex. Isolation of full-length cDNA sequences coding for γ-glutamylcysteinyl synthetase from legume nodules revealed that they are highly homologous to those from other higher plants.
Nitric Oxide Modulates the Activity of Tobacco Aconitase
Authors: Navarre Duroy A. , Wendehenne David , Durner Jörg , Noad Robert , Klessig Daniel F.
Published: July 2002

Recent evidence suggests an important role for nitric oxide (NO) signaling in plant-pathogen interactions. Additional elucidation of the role of NO in plants will require identification of NO targets. Since aconitases are major NO targets in animals, we examined the effect of NO on tobacco (Nicotiana tabacum) aconitase. The tobacco aconitases, like their animal counterparts, were inhibited by NO donors. The cytosolic aconitase in animals, in addition to being a key redox and NO sensor, is converted by NO into an mRNA binding protein (IRP, or iron-regulatory protein) that regulates iron homeostasis. A tobacco cytosolic aconitase gene (NtACO1) whose deduced amino acid sequence shared 61% identity and 76% similarity with the human IRP-1 was cloned. Furthermore, residues involved in mRNA binding by IRP-1 were conserved in NtACO1. These results reveal additional similarities between the NO signaling mechanisms used by plants and animals.