bluuebunny/crossref_metadata_2025 huggingface dataset:
THE OCCURRENCE OF INTRUSIVE THOUGHTS TRANSFORMS MEANING IN AMBIGUOUS SITUATIONS: THE OCCURRENCE OF INTRUSIVE THOUGHTS TRANSFORMS MEANING IN AMBIGUOUS SITUATIONS:

AN EXPERIMENTAL STUDY AN EXPERIMENTAL STUDY
Authors: Forrester Elizabeth , Wilson Charlotte , Salkovskis Paul M.
Published: July 2002

It has been noted that obsessional patients appear to be equally sensitive to ideas regarding the possibility

that they may cause harm by both their actions and by their failure to act (i.e., omission). This observation is

discrepant with findings in non-clinical populations. The cognitive theory of obsessive-compulsive disorder

suggests that it is the very occurrence of intrusive thoughts about potential harm that mediates this effect. In this

study, 22 obsessional patients and 30 non-clinical participants were provided with details of ambiguous situations

and either a negative or neutral intrusive thought pertaining to this situation. Behavioural and emotional responses

to these situations were rated using self-reported measures. It was found that situations including an intrusive

thought about harm were associated with higher intensity behavioural and emotional responses compared with the

same situation when the intrusion was neutral. Obsessional participants scored higher overall; only on the rating of

perceived responsibility was there an interaction between group and item type. These results are consistent with

the idea that the occurrence of an intrusion about harm modifies both obsessional and non-clinical participants'

reactions in ways that suggest obsessionality, and support cognitive theories that emphasize that obsessional

experiences arise from normal processes.
Stroke and Its Emotional Aftermath
Authors: Nelson L.D.
Published: July 2002

This book, based on over two decades of research
conducted by Robinson and colleagues, is primarily about
poststroke emotional sequelae. Major topics include depression,
mania, and anxiety, each organized by chapter headings
and similar chapter subheadings. Robinson defines each
emotional problem, explains how it is diagnosed, compares
it to brain–behavior relationships, and recommends
treatment, all the while weaving an empirical foundation
that matches interpretations and ideas with results. The
fabric of this foundation consists mainly of Robinson's
collective research. Case histories sprinkled throughout
capture the essence of his remarks, bringing them to life
for the reader. Contributions of his predecessors are reported
as an historical base. As a result, Robinson brings under
one cover the wealth of knowledge and information we currently
have on the subject of emotional disorders following vascular
brain injury.
Neuropsychological performance of right- and left-frontotemporal
dementia compared to Alzheimer's disease
Authors: RAZANI JILL , BOONE KYLE BRAUER , MILLER BRUCE L. , LEE ALISON , SHERMAN DALE
Published: July 2002

The performance of 16 patients with Alzheimer's
disease (AD) was compared to 11 patients with right-frontotemporal
dementia (FTD) and 11 patients with left-FTD on a comprehensive
neuropsychological battery. Standardized scores (i.e.,
z scores based on normal control data) were analyzed
for 5 cognitive domains. The results revealed that the
AD group displayed significant impairment in visual–constructional
ability relative to the two FTD groups; however, no significant
difference was found between the groups on memory scores
(verbal and nonverbal). Patients with left-FTD scored significantly
below patients with AD on the language measures (e.g.,
word retrieval, verbal semantic memory), and verbal executive
ability (phonemic fluency); AD patients did not differ
from patients with right-FTD on these measures. Patients
with right-FTD exhibited significantly more perseverative
behavior than AD patients; AD patients did not differ from
left-FTD patients on this parameter. These results indicate
that the pattern of neuropsychological performance of AD
patients is distinguishable from patients with left and
right frontal frontotemporal dementia. (JINS,
2001, 7, 468–480)
MRI extrahippocampal volumes and visual memory: Correlations
independent of MRI hippocampal volumes in temporal lobe
epilepsy patients
Authors: MARTIN ROY C. , HUGG JAMES W. , ROTH DAVID L. , BILIR ERHAN , GILLIAM FRANK G. , FAUGHT EDWARD , KUZNIECKY RUBEN I.
Published: July 2002

Limbic system atrophy and memory dysfunction are
common in patients with temporal lobe epilepsy (TLE). However,
the relationship between extrahippocampal limbic structures
and memory functioning within TLE has received little attention.
The present study examined associations of MRI volumetric
measurements of the mammillary body, fornix, amygdala,
and hippocampus to measures of episodic verbal and visual
memory. The Logical Memory and Visual Reproduction subtests
from the Wechsler Memory Scale were administered to 47
unilateral TLE patients (25 right, 22 left). Normalized
right and left MRI volumes were determined for each patient
by cursor tracing 1.5 mm slices from 3D-MRI. Significant
associations were found between left hippocampal volume
and the immediate, delayed, and percent retention scores
of the Logical Memory Test; between the left mammillary
body volume and the Logical Memory Test delayed and percent
retention scores; immediate Visual Reproduction performance
was significantly related to the right and left amygdala
volumes, and right mammillary body volume; only the right
amygdala and right mammillary body volume were associated
with the delayed Visual Reproduction trial. However, neither
right nor left hippocampal volumes were related to visual
memory performance. Multiple limbic system structural volumes
were independently associated with verbal and nonverbal
memory performance. Results suggest that visual memory,
as measured by the Visual Reproduction Test, may be uniquely
associated with extrahippocampal volumes in patients with
TLE. (JINS, 1999, 5, 540–548.)
Caveats from a dyed-in-the-wool futurist
Authors: Mountain Rosemary
Published: July 2002

It is recommended that we collaborate with science and industry in the search for technological innovation in media-related fields, in order to help design a future environment that will benefit a healthy musical culture. Since those of us who are already immersed in the technology are accustomed to its less attractive attributes as well as its potentials, we can consult with colleagues about essential characteristics of the old-fashioned world which we and they do not want to lose. With our collective imaginations, it should be possible to preserve many of these aspects by transforming them, with sensitivity, to fit new contexts. A few diverse examples are given of features that might be considered both attractive and endangered. Suggestions ranging from the practical to the whimsical illustrate some possibilities for injecting the essence of these experiences into a more technological world, thereby enriching it.
Computer music animations
Authors: Rudi Jøran
Published: July 2002

Electroacoustic music, since its inception, has been situated in a cross-disciplinary

no-man's-land, with areas of interest spread in many directions; from

ideas of musical structures ordered through traditional pitch-classes to research

on physical modelling and analysis of sound and compositional structures through the

use of neural networks. Much of the material found in computer music has been developed

through processes of appropriation, both from sound recordings of physical events

and from the application of various principles found in the natural sciences.
Overview
Authors: White Richard , Adcock Margaret
Published: July 2002

This issue of Child Psychology and Psychiatry Review is
devoted to consideration of the new Needs Assessment
Framework for children and families who are the concern
of Social Services Departments, the new Youth Justice
Assessment for children and young people who break the
law, and the processes for the assessment of special
educational needs. The new frameworks provide different
professional approaches to children and should have a
significant impact on the work of all professionals involved
with children and families. In many cases the processes of
all three areas should overlap and be integrated.
Child Mental Health Services in the New South Africa
Authors: Milne Mary , Robertson Brian
Published: July 2002

Health departments in the new South Africa are undergoing major

restructuring and, in some cases, severe financial cutbacks as new policies

attempt to redress the inequities of the past. A district system is being

phased in, with a shift in funding from academic hospitals to secondary

and primary level care. The process is being undermined by the current

recession, which also affects Welfare and Education facilities, and by

widespread poverty, violence, and other adverse conditions. Child mental

health services are discussed in the light of current human resources,

epidemiological data, the effects of violence and cultural issues, together

with some reflections on their future.
Agenda Power in the Japanese House of Representatives
Authors: Cox Gary W. , Masuyama Mikitaka , McCubbins Mathew D.
Published: July 2002

In this paper we provide evidence from Japan that bears on a general theory of agenda power in legislatures. By agenda power we mean the power to determine: (a) which bills are considered in the plenary session of the legislature and (b) restrictions on debate and amendment to these bills, when they are considered. While a substantial amount of work has focused on the second category of agenda power, including studies of special rules in the US House (e.g., Sinclair forthcoming), closure in the UK House of Commons (e.g., Cox, 1987; Dion, 1997), and the guillotine in the French National Assembly (e.g., Huber, 1996), there is very little on the first and arguably more fundamental sort of agenda power. This agenda power – the power to decide which bills will actually be considered on the floor of the legislature – is our focus here, and henceforth when we refer to ‘agenda power’ we shall mean this narrower conception.
Host-based genotype variation in insects revisited
Authors: Lushai G. , Markovitch O. , Loxdale H.D.
Published: July 2002

Elucidation of the genetic variability of a model insect species, the grain aphid, Sitobion avenae (Fabricius), a predominantly asexual herbivore within the temperate agro-ecosystem tested, was initiated using molecular DNA markers (RAPDs). This revealed genetic profiles that appeared related to host adaptation at the specific level amongst the natural populations colonizing different grasses and cereals (Poaceae) within the same geographic location. These profiles were recorded either as ‘specialist’genotypes found on specific grasses, or as ‘generalist’ genotypes colonizing several host types including cultivated cereals or native grasses. These findings are compared with analogous systems found amongst insect species, including at a higher trophic level, i.e. interactions between hymenopterous aphid parasitoids. As the aphids and their respective plant hosts occur in the same geographical region at the same time, this appears to be a rare example of the evolutionary transition leading to sympatric speciation in insects. Hence, this study highlights the importance of understanding not only the demographic parameters to genetic diversity, but also the more intricate correlation of genetic diversity to host types in agricultural environments.
A homeotic mutation in the trithorax SET domain impedes histone binding
Authors: Katsani Katerina R. , Arredondo Juan J. , Kal Arnoud J. , Verrijzer C. Peter
Published: July 2002

Trithorax (TRX) is a Drosophila SET domain protein that is required for the correct expression of homeotic genes. Here, we show that the TRX SET domain efficiently binds to core histones and nucleosomes. The primary target for the SET domain is histone H3 and binding requires the N-terminal histone tails. The previously describedtrxZ11 mutation changes a strictly conserved glycine in the SET domain to serine and causes homeotic transformations in the fly. We found that this mutation selectively interferes with histone binding, suggesting that histones represent a critical target during developmental gene regulation by TRX.
E2F3 contributes both to the inappropriate proliferation and to the apoptosis arising in Rb mutant embryos
Authors: Ziebold Ulrike , Reza Tammi , Caron Alicia , Lees Jacqueline A.
Published: July 2002

The E2F transcription factors are thought to be key downstream targets of the retinoblastoma protein (pRB) tumor suppressor. It is widely believed that E2F1, E2F2, and E2F3 can all activate cellular proliferation but that E2F1 is the specific inducer of apoptosis. Here we show that the E2f3 mutation completely suppresses both the inappropriate proliferation and the p53-dependent apoptosis arising in the Rb mutant embryos. Through the analysis ofRb−/−;E2f3+/− embryos, we have been able to separate E2F3's role in the induction of apoptosis from its ability to induce proliferation. Thus, contrary to the prevailing view of E2F action, E2F3 makes a major contribution to the apoptosis resulting from pRB loss.
Tumor formation and inactivation of RIZ1, an Rb-binding member of a nuclear protein–methyltransferase superfamily
Authors: Steele-Perkins George , Fang Wei , Yang Xiao-Hong , Van Gele Mireille , Carling Tobias , Gu Jian , Buyse Inge M. , Fletcher Jonathon A. , Liu Jinsong , Bronson Roderick , Chadwick Robert B. , de la Chapelle Albert , Zhang Xiao-kun , Speleman Frank , Huang Shi
Published: July 2002

The retinoblastoma protein-interacting zinc finger gene RIZ(PRDM2) is a member, by sequence homology, of a nuclear protein–methyltransferase (MTase) superfamily involved in chromatin-mediated gene expression. The gene produces two protein products, RIZ1 that contains a conserved MTase domain and RIZ2 that lacks the domain. RIZ1 gene expression is frequently silenced in human cancers, and the gene is also a common target of frameshift mutation in microsatellite-unstable cancers. We now report studies of mice with a targeted mutation in the RIZ1 locus. The mutation inactivatesRIZ1 but not RIZ2. These RIZ1 mutant mice were viable and fertile but showed a high incidence of diffuse large B-cell lymphomas (DLBL) and a broad spectrum of unusual tumors. RIZ1deficiency also accelerated tumorigenesis in p53 heterozygous mutant mice. Finally, several missense mutations of RIZ1 were found in human tumor tissues and cell lines; one of these was particularly common in human DLBL tumors. These missense mutations, as well as the previously described frameshift mutation, all mapped to the MTase functional domains. All abolished the capacity of RIZ1 to enhance estrogen receptor activation of transcription. These data suggest a direct link between tumor formation and the MTase domain of RIZ1 and describe for the first time a tumor susceptibility gene among methyltransferases.
The Drosophila Su(var)2-10 locus regulates chromosome structure and function and encodes a member of the PIAS protein family
Authors: Hari Kumar L. , Cook Kevin R. , Karpen Gary H.
Published: July 2002

The conserved heterochromatic location of centromeres in higher eukaryotes suggests that intrinsic properties of heterochromatin are important for chromosome inheritance. Based on this hypothesis, mutations in Drosophila melanogaster that alter heterochromatin-induced gene silencing were tested for effects on chromosome inheritance. Here we describe the characterization of theSu(var)2-10 locus, initially identified as aSuppressor of Position-Effect Variegation.Su(var)2-10 is required for viability, and mutations cause both minichromosome and endogenous chromosome inheritance defects. Mitotic chromosomes are improperly condensed in mutants, and polytene chromosomes are structurally abnormal and disorganized in the nucleus.Su(var)2-10 encodes a member of the PIAS protein family, a group of highly conserved proteins that control diverse functions. SU(VAR)2-10 proteins colocalize with nuclear lamin in interphase, and little to no SU(VAR)2-10 is found on condensed mitotic chromosomes. SU(VAR)2-10 is present at some polytene chromosome telomeres, and FISH analyses in mutant polytene nuclei revealed defects in telomere clustering and telomere–nuclear-lamina associations. We propose thatSu(var2-10 controls multiple aspects of chromosome structure and function by establishing/maintaining chromosome organization in interphase nuclei.
Tissue-specific deletion of Foxa2 in pancreatic β cells results in hyperinsulinemic hypoglycemia
Authors: Sund Newman J. , Vatamaniuk Marko Z. , Casey Melissa , Ang Siew-Lan , Magnuson Mark A. , Stoffers Doris A. , Matschinsky Franz M. , Kaestner Klaus H.
Published: July 2002

We have used conditional gene ablation to uncover a dramatic and unpredicted role for the winged-helix transcription factor Foxa2 (formerly HNF-3β) in pancreatic β-cell differentiation and metabolism. Mice that lack Foxa2 specifically in β cells (Foxa2loxP/loxP; Ins.Cre mice) are severely hypoglycemic and show dysregulated insulin secretion in response to both glucose and amino acids. This inappropriate hypersecretion of insulin in the face of profound hypoglycemia mimics pathophysiological and molecular aspects of familial hyperinsulinism. We have identified the two subunits of the β-cell ATP-sensitive K+ channel (KATP), the most frequently mutated genes linked to familial hyperinsulinism, as novel Foxa2 targets in islets. TheFoxa2loxP/loxP; Ins.Cre mice will serve as a unique model to investigate the regulation of insulin secretion by the β cell and suggest the human FOXA2 as a candidate gene for familial hyperinsulinism.
Genomic Approaches to Understanding Asthma
Authors: Palmer Lyle J. , Cookson William O.C.M.
Published: July 2002

Asthma is the most common chronic childhood disease in developed nations, and it is a complex disease that has high social and economic costs. Asthma and its associated intermediate phenotypes are under a substantial degree of genetic control. The genetic aetiology of asthma offers a means of better understanding its pathogenesis and, thus, improving preventive strategies, diagnostic tools, and therapies. Considerable effort and expense have been expended in attempts to detect genetic loci contributing to asthma susceptibility, and extensive candidate gene studies and a number of whole-genome screens have been undertaken. This article reviews the current state of knowledge of the genetics of asthma, with a focus on genomic approaches to understanding allergic diseases.
Compositional Gradients inGramineaeGenes
Authors: Wong Gane Ka-Shu , Wang Jun , Tao Lin , Tan Jun , Zhang JianGuo , Passey Douglas A. , Yu Jun
Published: July 2002

In this study, we describe a property ofGramineaegenes, and perhaps all monocot genes, that is not observed in eudicot genes. Along the direction of transcription, beginning at the junction of the 5′-UTR and the coding region, there are gradients in GC content, codon usage, and amino-acid usage. The magnitudes of these gradients are large enough to hinder the annotation of the rice genome and to confound the detection of protein homologies across the monocot–eudicot divide.
Transgenic Expression in Arabidopsis of a Polyprotein Construct Leading to Production of Two Different Antimicrobial Proteins
Authors: François Isabelle E.J.A. , De Bolle Miguel F.C. , Dwyer Geoff , Goderis Inge J.W.M. , Woutors Piet F.J. , Verhaert Peter D. , Proost Paul , Schaaper Wim M.M. , Cammue Bruno P.A. , Broekaert Willem F.
Published: July 2002

We developed a method for expression in Arabidopsis of a transgene encoding a cleavable chimeric polyprotein. The polyprotein precursor consists of a leader peptide and two different antimicrobial proteins (AMPs), DmAMP1 originating from Dahlia merckiiseeds and RsAFP2 originating from Raphanus sativusseeds, which are linked by an intervening sequence (“linker peptide”) originating from a natural polyprotein occurring in seed ofImpatiens balsamina. The chimeric polyprotein was found to be cleaved in transgenic Arabidopsis plants and the individual AMPs were secreted into the extracellular space. Both AMPs were found to exert antifungal activity in vitro. It is surprising that the amount of AMPs produced in plants transformed with some of the polyprotein transgene constructs was significantly higher compared with the amount in plants transformed with a transgene encoding a single AMP, indicating that the polyprotein expression strategy may be a way to boost expression levels of small proteins.
Gibberellin Signaling in Barley Aleurone Cells. Control of SLN1 and GAMYB Expression
Authors: Gubler Frank , Chandler Peter Michael , White Rosemary G. , Llewellyn Danny J. , Jacobsen John V.
Published: July 2002

We have previously identified GAMYB, a gibberellin (GA)-regulated transcriptional activator of α-amylase gene expression, in aleurone cells of barley (Hordeum vulgare). To examine the regulation of GAMYB expression, we describe the use of nuclear run-on experiments to show that GA causes a 2-fold increase in the rate of GAMYB transcription and that the effect of GA can be blocked by abscisic acid (ABA). To identify GA-signaling components that regulate GAMYB expression, we examined the role of SLN1, a negative regulator of GA signaling in barley. SLN1, which is the product of the Sln1(Slender1) locus, is necessary for repression of GAMYB in barley aleurone cells. The activity of SLN1 in aleurone cells is regulated posttranslationally. SLN1 protein levels decline rapidly in response to GA before any increase in GAMYB levels. Green fluorescent protein-SLN1 fusion protein was targeted to the nucleus of aleurone protoplasts and disappeared in response to GA. Evidence from a dominant dwarf mutant at Sln1, and from thegse1 mutant (that affects GA “sensitivity”), indicates that GA acts by regulating SLN1 degradation and not translation. Mutation of the DELLA region of SLN1 results in increased protein stability in GA-treated layers, indicating that the DELLA region plays an important role in GA-induced degradation of SLN1. Unlike GA, ABA had no effect on SLN1 stability, confirming that ABA acts downstream of SLN1 to block GA signaling.
Regulated Copper Uptake in Chlamydomonas reinhardtii in Response to Copper Availability
Authors: Hill K. L. , Hassett R. , Kosman D. , Merchant S.
Published: July 2002

A saturable and temperature-dependent copper uptake pathway has been identified in Chlamydomonas reinhardtii. The uptake system has a high affinity for copper ions (Km approximately 0.2 [mu]M) and is more active in cells that are adapted to copper deficiency than to cells grown in a medium containing physiological (submicromolar to micromolar) copper ion concentrations. The maximum velocity of copper uptake by copper-deficient cells (169 pmol h-1 106 cells-1 or 62 ng min-1 mg-1 chlorophyll) is up to 20-fold greater than that of fully copper-supplemented cells, and the Km (approximately 2 x 102 nM) is unaffected. Thus, the same uptake system appears to operate in both copper-replete and copper-deficient cells, but its expression or activity must be induced under copper-deficient conditions. A cupric reductase activity is also increased in copper-deficient compared with copper-sufficient cells. The physiological characteristics of the regulation of this cupric reductase are compatible with its involvement in the uptake path-way. Despite the operation of the uptake pathway under both copper-replete and copper-deficient conditions, C. reinhardtii cells maintained in fully copper-supplemented cells do not accumulate copper in excess of their metabolic need. These results provide evidence for a homeostatic mechanism for copper metabolism in C. reinhardtii.
An Intracellular Signal Transduction Pathway between the Chloroplast and Nucleus Is Involved in De-Etiolation
Authors: Mochizuki N. , Susek R. , Chory J.
Published: July 2002

Chloroplast development requires the coordinated expression of nuclear and chloroplastic genes. A hypothesized signal from the chloroplast couples the transcription of certain nuclear genes encoding photosynthetic proteins with chloroplast function. We have previously described an Arabidopsis thaliana mutant, gun1, which has a defect in the signal transduction pathway coupling such nuclear and plastidic gene expression. Here we show that gun1 seedlings are also defective in establishing photoautotrophic growth. gun1 seedlings develop normally in the dark, but, based on morphological criteria and the kinetics of chlorophyll accumulation, photosynthetic mRNA accumulation, and the differentiation of etioplasts to chloroplasts, are retarded in their ability to de-etiolate. Therefore, we propose that the GUN1 gene plays an important role in the transition from heterotrophic to photoautotrophic growth, suggesting an important physiological role for the plastid-nucleus signaling pathway during chloroplast biogenesis.
The Sorghum Photoperiod Sensitivity Gene, Ma3, Encodes a Phytochrome B
Authors: Childs K. L. , Miller F. R. , Cordonnier-Pratt M. M. , Pratt L. H. , Morgan P. W. , Mullet J. E.
Published: July 2002

The Ma3 gene is one of six genes that regulate the photoperiodic sensitivity of flowering in sorghum (Sorghum bicolor [L.] Moench). The ma3R mutation of this gene causes a phenotype that is similar to plants that are known to lack phytochrome B, and ma3R sorghum lacks a 123-kD phytochrome that predominates in light-grown plants and that is present in non-ma3R plants. A population segregating for Ma3 and ma3R was created and used to identify two randomly amplified polymorphic DNA markers linked to Ma3. These two markers were cloned and mapped in a recombinant inbred population as restriction fragment length polymorphisms. cDNA clones of PHYA and PHYC were cloned and sequenced from a cDNA library prepared from green sorghum leaves. Using a genome-walking technique, a 7941-bp partial sequence of PHYB was determined from genomic DNA from ma3R sorghum. PHYA, PHYB, and PHYC all mapped to the same linkage group. The Ma3- linked markers mapped with PHYB more than 121 centimorgans from PHYA and PHYC. A frameshift mutation resulting in a premature stop codon was found in the PHYB sequence from ma3R sorghum. Therefore, we conclude that the Ma3 locus in sorghum is a PHYB gene that encodes a 123-kD phytochrome.
Mutations in the Small Subunit of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Increase the Formation of the Misfire Product Xylulose-1,5-Bisphosphate
Authors: Flachmann R. , Zhu G. , Jensen R. G. , Bohnert H. J.
Published: July 2002

The small subunit (S) increases the catalytic efficiency of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) by stabilizing the active sites generated by four large subunit (L) dimers. This stabilization appears to be due to an influence of S on the reaction intermediate 2,3-enediol, which is formed after the abstraction of a proton from the substrate ribulose-1,5-bisphosphate. We tested the functional significance of residues that are conserved among most species in the carboxy-terminal part of S and analyzed their influence on the kinetic parameters of Synecho-coccus holoenzymes. The replacements in S (F92S, Q99G, and P108L) resulted in catalytic activities ranging from 95 to 43% of wild type. The specificity factors for the three mutant enzymes were little affected (90–96% of wild type), but Km(CO2) values increased 0.5- to 2-fold. Mutant enzymes with replacements Q99G and P108L showed increased mis-protonation, relative to carboxylation, of the 2,3-enediol intermediate, forming 2 to 3 times more xylulose-1,5-bisphosphate per ribulose-1,5-bisphosphate utilized than wild-type or F92S enzymes. The results suggest that specific alterations of the L/S interfaces and of the hydrophobic core of S are transmitted to the active site by long-range interactions. S interactions with L may restrict the flexibility of active-site residues in L.
Molecular Cloning and Further Characterization of a Probable Plant Vacuolar Sorting Receptor
Authors: Paris N. , Rogers S. W. , Jiang L. , Kirsch T. , Beevers L. , Phillips T. E. , Rogers J. C.
Published: July 2002

BP-80 is a type I integral membrane protein abundant in pea (Pisum sativum) clathrin-coated vesicles (CCVs) that binds with high affinity to vacuole-targeting determinants containing asparagine-proline-isoleucine-arginine. Here we present results from cDNA cloning and studies of its intracellular localization. Its sequence and sequences of homologs from Arabidopsis, rice (Oryza sativa), and maize (Zea mays) define a novel family of proteins unique to plants that is highly conserved in both monocotyledons and dicotyledons. The BP-80 protein is present in dilated ends of Golgi cisternae and in “prevacuoles,” which are small vacuoles separate from but capable of fusing with lytic vacuoles. Its cytoplasmic tail contains a Tyr-X-X-hydrophobic residue motif associated with transmembrane proteins incorporated into CCVs. When transiently expressed in tobacco (Nicotiana tabacum) suspension-culture protoplasts, a truncated form lacking transmembrane and cytoplasmic domains was secreted. These results, coupled with previous studies of ligand-binding specificity and pH dependence, strongly support our hypothesis that BP-80 is a vacuolar sorting receptor that trafficks in CCVs between Golgi and a newly described prevacuolar compartment.
Expression and Characterization of Pea Chloroplastic Glyceraldehyde-3-Phosphate Dehydrogenase Composed of Only the B-Subunit
Authors: Li A. D. , Anderson L. E.
Published: July 2002

A cDNA fragment coding for the pea (Pisum sativum L.) chloroplastic glyceraldehyde-3-P dehydrogenase (EC 1.2.1.13) B-subunit and a truncated form corresponding in length to the A-subunit have been cloned into an expression vector, expressed in the absence of the A-subunit in a gap- Escherichia coli strain, purified, and studied. Like the isolated enzyme from higher plant chloroplasts, the recombinant enzymes have dual specificity for NADPH and NADH. The recombinant glyceraldehyde-3-P dehydrogenases have the same optimal pH as the enzyme isolated from pea chloroplasts. Like the native chloroplast enzyme, the recombinant B-subunit has a marked tendency to form large aggregates, whereas the truncated B-subunit exists as the tetramer. The recombinant B-subunit glyceraldehyde 3-P dehydrogenase is more sensitive to dithiothreitol than its truncated form. It seems likely that a different pair of cysteines is responsible for the redox sensitivity of the activity of the enzyme composed of B-subunits than the cysteine residues implicated in the modulation of the activity of the enzyme composed of A-subunits by previous work in this laboratory.
Gene Fusions of Signal Sequences with a Modified β-Glucuronidase Gene Results in Retention of the β-Glucuronidase Protein in the Secretory Pathway/Plasma Membrane
Authors: Yan X. , Gonzales R. A. , Wagner G. J.
Published: July 2002

Signal sequences and endoplasmic reticulum (ER) retention signals are known to play central roles in targeting and translocation in the secretory pathway, but molecular aspects about their involvement are poorly understood. We tested the effectiveness of deduced signal sequences from various genes (hydroxyproline-rich glycoprotein [HRGP] from Phaseolus vulgaris; Serpin from Manduca sexta) to direct a modified β-glucuronidase (GUS) protein into the secretory pathway in transgenic tobacco (Nicotiana tabacum L.). The reporter protein was not secreted to the cell wall/extracellular space as monitored using extracellular fluid analysis (low- or high-ionic-strength conditions) but occurred in membranes with a density of 1.16 to 1.20 g/mL. Membrane-bound GUS equilibrated with the plasma membrane (PM) and the ER on linear sucrose gradients with or without ethylenediaminetetraacetic acid, suggesting that GUS associates with the ER and the PM. Confocal microscopy of fixed cultured cells prepared from GUS control and HRGP signal peptide (SP)-GUS-expressing plants suggested only cytosolic localization in GUS-expressing plants but substantial peripheral localization in HRGP SP-GUS plants, which is consistent with GUS being associated with the PM. Aqueous two-phase partitioning of microsomal membranes from HRGP SP-GUS and Serpin SP-GUS transgenic leaves also indicated that GUS activity was enriched in the ER and the PM. These observations, together with hydrophobic moment plot analysis, suggest that properties of the SP-GUS protein result in its retention in the secretory pathway and PM.
Endogenous Methyl Salicylate in Pathogen-Inoculated Tobacco Plants1
Authors: Seskar Mirjana , Shulaev Vladimir , Raskin Ilya
Published: July 2002

The tobacco (Nicotiana tabacum) cultivar Xanthi-nc (genotype NN) produces high levels of salicylic acid (SA) after inoculation with the tobacco mosaic virus (TMV). Gaseous methyl salicylate (MeSA), a major volatile produced in TMV-inoculated tobacco plants, was recently shown to be an airborne defense signal. Using an assay developed to measure the MeSA present in tissue, we have shown that in TMV-inoculated tobacco plants the level of MeSA increases dramatically, paralleling increases in SA. MeSA accumulation was also observed in upper, noninoculated leaves. In TMV-inoculated tobacco shifted from 32 to 24°C, the MeSA concentration increased from nondetectable levels to 2318 ng/g fresh weight 12 h after the temperature shift, but subsequently decreased with the onset of the hypersensitive response. Similar results were observed in plants inoculated withPseudomonas syringae pathovarphaseolicola, in which MeSA levels were highest just before the hypersensitive response-induced tissue desiccation. Transgenic NahG plants unable to accumulate SA also did not accumulate MeSA after TMV inoculation, and did not show increased resistance to TMV following MeSA treatment. Based on the spatial and temporal kinetics of its accumulation, we conclude that tissue MeSA may play a role similar to that of volatile MeSA in the pathogen-induced defense response.
Stress Induction of Mitochondrial Formate Dehydrogenase in Potato Leaves1
Authors: Hourton-Cabassa Cécile , Ambard-Bretteville Françoise , Moreau François , de Virville Jacques Davy , Rémy René , Colas des Francs-Small Catherine
Published: July 2002

In higher plants formate dehydrogenase (FDH, EC 1.2.1.2.) is a mitochondrial, NAD-dependent enzyme. We previously reported that in potato (Solanum tuberosum L.) FDH expression is high in tubers but low in green leaves. Here we show that in isolated tuber mitochondria FDH is involved in formate-dependent O2 uptake coupled to ATP synthesis. The effects of various environmental and chemical factors on FDH expression in leaves were tested using the mitochondrial serine hydroxymethyltransferase as a control. The abundance of FDH transcripts is strongly increased under various stresses, whereas serine hydroxymethyltransferase transcripts decline. The application of formate to leaves strongly enhances FDH expression, suggesting that it might be the signal for FDH induction. Our experiments using glycolytic products suggest that glycolysis may play an important role in formate synthesis in leaves in the dark and during hypoxia, and in tubers. Of particular interest is the dramatic accumulation of FDH transcripts after spraying methanol on leaves, as this compound is known to increase the yields of C3 plants. In addition, although the steady-state levels of FDH transcript increase very quickly in response to stress, protein accumulation is much slower, but can eventually reach the same levels in leaves as in tubers.
Role of the Ascorbate-Glutathione Cycle of Mitochondria and Peroxisomes in the Senescence of Pea Leaves
Authors: Jiménez Ana , Hernández José A. , Pastori Gabriela , del Rı́o Luis A. , Sevilla Francisca
Published: July 2002

We investigated the relationship between H2O2 metabolism and the senescence process using soluble fractions, mitochondria, and peroxisomes from senescent pea (Pisum sativum L.) leaves. After 11 d of senescence the activities of Mn-superoxide dismutase, dehydroascorbate reductase (DHAR), and glutathione reductase (GR) present in the matrix, and ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) activities localized in the mitochondrial membrane, were all substantially decreased in mitochondria. The mitochondrial ascorbate and dehydroascorbate pools were reduced, whereas the oxidized glutathione levels were maintained. In senescent leaves the H2O2 content in isolated mitochondria and the NADH- and succinate-dependent production of superoxide (O2  ·−) radicals by submitochondrial particles increased significantly. However, in peroxisomes from senescent leaves both membrane-bound APX and MDHAR activities were reduced. In the matrix the DHAR activity was enhanced and the GR activity remained unchanged. As a result of senescence, the reduced and the oxidized glutathione pools were considerably increased in peroxisomes. A large increase in the glutathione pool and DHAR activity were also found in soluble fractions of senescent pea leaves, together with a decrease in GR, APX, and MDHAR activities. The differential response to senescence of the mitochondrial and peroxisomal ascorbate-glutathione cycle suggests that mitochondria could be affected by oxidative damage earlier than peroxisomes, which may participate in the cellular oxidative mechanism of leaf senescence longer than mitochondria.
Arabidopsis Roots and Shoots Have Different Mechanisms for Hypoxic Stress Tolerance
Authors: Ellis Marc H. , Dennis Elizabeth S. , James Peacock W.
Published: July 2002

Arabidopsis has inducible responses for tolerance of O2 deficiency. Plants previously exposed to 5% O2 were more tolerant than the controls to hypoxic stress (0.1% O2 for 48 h) in both roots and shoots, but hypoxic acclimation did not improve tolerance to anoxia (0% O2). The acclimation of shoots was not dependent on the roots: increased shoot tolerance was observed when the roots of the plants were removed. An adh(alcohol dehydrogenase) null mutant did not show acclimation of the roots but retained the shoot survival response. Abscisic acid treatment also differentiated the root and shoot responses; pretreatment induced root survival in hypoxic stress conditions (0.1% O2) but did not induce any increase in the survival of shoots. Cycloheximide blocked both root and shoot acclimation, indicating that both acclimation mechanisms are dependent on protein synthesis.
Proline Accumulation in Developing Grapevine Fruit Occurs Independently of Changes in the Levels of Δ1-Pyrroline-5-Carboxylate Synthetase mRNA or Protein1
Authors: Stines Anna P. , Naylor Dean J. , Høj Peter B. , van Heeswijck Robyn
Published: July 2002

Mature fruit of grapevine (Vitis vinifera) contains unusually high levels of free proline (Pro; up to 24 μmol or 2.8 mg/g fresh weight). Pro accumulation does not occur uniformly throughout berry development but only during the last 4 to 6 weeks of ripening when both berry growth and net protein accumulation have ceased. In contrast, the steady-state levels of both the mRNA encoding V. viniferaΔ1-pyrroline-5-carboxylate synthetase (VVP5CS), a key regulatory enzyme in Pro biosynthesis, and its protein product remain relatively uniform throughout fruit development. In addition, the steady-state protein levels of Pro dehydrogenase, the first enzyme in Pro degradation, increased throughout early fruit development but thereafter remained relatively constant. The developmental accumulation of free Pro late in grape berry ripening is thus clearly distinct from the osmotic stress-induced accumulation of Pro in plants. It is not associated with either sustained increases in steady-state levels of P5CS mRNA or protein or a decrease in steady-state levels of Pro dehydrogenase protein, suggesting that other physiological factors are important for its regulation.
Carbon and Amino Acids Reciprocally Modulate the Expression of Glutamine Synthetase in Arabidopsis
Authors: Oliveira Igor C. , Coruzzi Gloria M.
Published: July 2002

In bacteria and yeast, glutamine synthetase (GS) expression is tightly regulated by the metabolic status of the cell, both at the transcriptional and posttranscriptional levels. We discuss the relative contributions of light and metabolic cues on the regulation of members of the GS gene family (chloroplastic GS2 and cytosolic GS1) in Arabidopsis. These studies reveal that the dramatic induction of mRNA for chloroplastic GS2 by light is mediated in part by phytochrome and in part by light-induced changes in sucrose (Suc) levels. In contrast, the modest induction of mRNA for cytosolic GS1 by light is primarily mediated by changes in the levels of carbon metabolites. Suc induction of mRNA for GS2 and GS1 occurs in a time- and dose-dependent manner. Suc-induced changes in GS mRNA levels were also observed at the level of GS enzyme activity. In contrast, amino acids were shown to antagonize the Suc induction of GS, both at the level of mRNA accumulation and that of enzyme activity. For GS2, the gene whose expression was the most dramatically regulated by metabolites, we used a GS2 promoter-β-glucuronidase fusion to demonstrate that transcriptional control is involved in this metabolic regulation. Our results suggest that the metabolic regulation of GS expression in plants is controlled by the relative abundance of carbon skeletons versus amino acids. This would allow nitrogen assimilation into glutamine to proceed (or not) according to the metabolic status and biosynthetic needs of the plant. This type of GS gene regulation is reminiscent of the nitrogen regulatory system in bacteria, and suggests an evolutionary link between metabolic sensing and signaling in bacteria and plants.
A Proline-, Threonine-, and Glycine-Rich Protein Down-Regulated by Drought Is Localized in the Cell Wall of Xylem Elements
Authors: Harrak Hassan , Chamberland Hélène , Plante Michèle , Bellemare Guy , Lafontaine Jean G. , Tabaeizadeh Zohreh
Published: July 2002

A cDNA clone encoding a proline-, threonine-, and glycine-rich protein (PTGRP) was isolated from a wild tomato species (Lycopersicon chilense) (L.X. Yu, H. Chamberland, J.G. Lafontain, Z. Tabaeizadeh [1996] Genome 39: 1185–1193). Northern-blot analysis and in situ hybridization studies revealed that PTGRP is down-regulated by drought stress. The level of the mRNA in leaves and stems of 8-d drought-stressed plants decreased 5- to 10-fold compared with that in regularly watered plants. The mRNA re-accumulated when drought-stressed plants were rewatered. Antibodies raised against a glutathione S-transferase/PTGRP fusion protein were used to elucidate the subcellular localization of the protein by immunogold labeling. In regularly watered L. chilense plants, PTGRP protein was found to be localized in xylem pit membranes and disintegrated primary walls. Examination of sections from drought-stressed plants revealed a significant decrease in the levels of labeling. In these samples, only a few scattered gold particles were detected in the same areas. In the leaf tissues of plants that had been rewatered for 3 d following an 8-d drought stress, the labeling pattern was similar to that of the regularly watered plants. To our knowledge, PTGRP is the first drought-regulated protein that has been precisely localized in the cell wall.
Snow-Mold-Induced Apoplastic Proteins in Winter Rye Leaves Lack Antifreeze Activity
Authors: Hiilovaara-Teijo Mervi , Hannukkala Asko , Griffith Marilyn , Yu Xiao-Ming , Pihakaski-Maunsbach Kaarina
Published: July 2002

During cold acclimation, winter rye (Secale cereale L.) plants secrete antifreeze proteins that are similar to pathogenesis-related (PR) proteins. In this experiment, the secretion of PR proteins was induced at warm temperatures by infection with pink snow mold (Microdochium nivale), a pathogen of overwintering cereals. A comparison of cold-induced and pathogen-induced proteins showed that PR proteins accumulated in the leaf apoplast to a greater level in response to cold. The PR proteins induced by cold and by snow mold were similar when separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and examined by immunoblotting. Both groups of PR proteins contained glucanase-like, chitinase-like, and thaumatin-like proteins, and both groups exhibited similar levels of glucanase and chitinase activities. However, only the PR proteins induced by cold exhibited antifreeze activity. Our findings suggest that the cold-induced PR proteins may be isoforms that function as antifreeze proteins to modify the growth of ice during freezing while also providing resistance to the growth of low-temperature pathogens in advance of infection. Both functions of the cold-induced PR proteins may improve the survival of overwintering cereals.
Mercuric Chloride Effects on Root Water Transport in Aspen Seedlings
Authors: Wan Xianchong , Zwiazek Janusz J.
Published: July 2002

HgCl2 (0.1 mm) reduced pressure-induced water flux and root hydraulic conductivity in the roots of 1-year-old aspen (Populus tremuloides Michx.) seedlings by about 50%. The inhibition was reversed with 50 mm mercaptoethanol. Mercurial treatment reduced the activation energy of water transport in the roots from 10.82 ± 0.700 kcal mol−1 to 6.67 ± 0.193 kcal mol−1 when measured over the 4°C to 25°C temperature range. An increase in rhodamine B concentration in the xylem sap of mercury-treated roots suggested a decrease in the symplastic transport of water. However, the apoplastic pathway in both control and mercury-treated roots constituted only a small fraction of the total root water transport. Electrical conductivity and osmotic potentials of the expressed xylem sap suggested that 0.1 mmHgCl2 and temperature changes over the 4°C to 25°C range did not induce cell membrane leakage. The 0.1 mmHgCl2 solution applied as a root drench severely reduced stomatal conductance in intact plants, and this reduction was partly reversed by 50 mm mercaptoethanol. In excised shoots, 0.1 mm HgCl2 did not affect stomatal conductance, suggesting that the signal that triggered stomatal closure originated in the roots. We suggest that mercury-sensitive processes in aspen roots play a significant role in regulating plant water balance by their effects on root hydraulic conductivity.
Interaction of a Plant 14-3-3 Protein with the Signal Peptide of a Thylakoid-Targeted Chloroplast Precursor Protein and the Presence of 14-3-3 Isoforms in the Chloroplast Stroma
Authors: Sehnke Paul C. , Henry Ralph , Cline Kenneth , Ferl Robert J.
Published: July 2002

The 14-3-3 proteins are acidic, dimeric proteins that have been implicated in many eukaryotic cellular processes because of direct protein association with enzymes and other metabolic and regulatory proteins. 14-3-3 proteins are largely considered to be cytoplasmic, but a search for proteins that specifically interact with a plant 14-3-3 resulted in the isolation of a nuclear-encoded, thylakoid-targeted chloroplast precursor, the full-length Arabidopsis photosystem I N-subunit At pPSI-N (P.C. Sehnke, R.J. Ferl [1995] Plant Physiol 109: 1126). Using precursor truncations in the two-hybrid system, it was determined that the leader sequence is the site of PSI-N that associates with 14-3-3. This suggested the novel possibility that 14-3-3 would be found within chloroplasts. Immuno-electron microscopy of leaf tissue and western analysis of chloroplast fractions with monoclonal anti-14-3-3 antibodies localized 14-3-3 proteins to the chloroplast stroma and the stromal side of thylakoid membranes. Using peptide-generated, isoform-specific antibodies, GF14ν, GF14ε, GF14μ, and GF14υ were shown to be present in the chloroplast stromal extract. These isoforms represent two distinct phylogenetic 14-3-3 groupings. These data suggest a novel interorganellar role for these phylogenetically distinct 14-3-3 proteins.