bluuebunny/crossref_metadata_2025 huggingface dataset:
Land‐use and meteorological aspects of the urban heat island
Authors: Unger J , Sümeghy Z , Gulyás Á , Bottyán Z , Mucsi L
Published: July 2002

This study examines the influence of urban and meteorological factors on the surface air temperature field of the medium‐sized city of Szeged, Hungary, using mobile and stationary measurements under different weather conditions between March and August 1999. This city, with a population of about 160 000, is situated on a low, flat flood plain. Efforts have been concentrated on investigating the maximum development of the urban heat island (UHI). Tasks include the determination of the spatial distribution of seasonal mean maximum UHI intensity and modelling of existing conditions in the period being studied. Multiple correlation and regression analyses are used to examine the effects of urban parameters (land‐use characteristics and distance from the city centre determined in a grid network) and of meteorological parameters (wind speed, temperature) on thermal conditions in the study area. The results indicate isotherms increasing in regular concentric shapes from the suburbs towards the inner urban areas where the mean maximum UHI intensity reaches more than 3°C in the studied periods. A strong relationship exists between urban thermal excess and distance, as well as built‐up ratio. In contrast, meteorological conditions do not have any significant effect on the UHI intensity at the time of its maximum development. Copyright © 2001 Royal Meteorological Society
THE CUT-OFF POINT IN SUB-CLINICAL OBSESSIVE-COMPULSIVE RESEARCH
Authors: Mataix-Cols David , Vallejo Julio , Sànchez-Turet Miquel
Published: July 2002

The question of which cut-off point would be more appropriate in the selection of sub-clinical obsessive-compulsive (OC) samples is an important methodological issue that has not been formally addressed, hence prompting the current study. Three groups of sub-clinical OC subjects, scoring 1, 1.5, and 2 standard deviations (SD) above the mean on the Padua Inventory, and a matched non-OC control group, were compared on various clinical and personality measures. As expected, the three sub-clinical groups had higher scores than the non-OC group on measures of OC symptoms (including obsessional slowness), depression, anxiety, and on personality measures of neuroticism, psychoticism, and obsessional traits. However, no significant differences were observed between the three sub-clinical groups on most measures, although the 2 SD group had higher scores on neuroticism and obsessional personality traits. It is concluded that a wide range of selection criteria can yield similar results that are interpretable within the current theoretical models of Obsessive-Compulsive Disorder (OCD). It is suggested that subjects with a diagnosis of OCD should be carefully excluded from sub-clinical studies. [A Spanish abstract follows the references.]
Speed and memory in WAIS–R–NI Digit Symbol performance
among healthy older adults
Authors: JOY STEPHEN , FEIN DEBORAH , KAPLAN EDITH , FREEDMAN MORRIS
Published: July 2002

Although roles have been proposed for both graphomotor
speed and learning in the execution of Digit Symbol, few
data have been available concerning performance across
the adult lifespan on the Symbol Copy, paired associates,
or free recall measures derived from Digit Symbol and recommended
in the WAIS–R–NI. We report findings on 177
healthy older adults (ages 50–90), providing normative
data by age group, education level, and gender. As previously
reported, Digit Symbol scores decline steeply with age
(r = −.64). Symbol Copy speed declines almost
as steeply (r = −.58). Incidental learning,
however, declines only modestly (r = −.26
on both measures). Symbol Copy is a far stronger correlate
of Digit Symbol (r = .72) than are paired associates
or free recall (r = .26 and r = .28,
respectively). The 2 incidental learning measures do, however,
offer valuable supplementary information as part of a comprehensive
individual assessment. When low Digit Symbol scores are
produced by slowing on Symbol Copy, further evaluation
of perceptual and motor speed and dexterity are indicated.
When low incidental learning scores are obtained, further
evaluation of memory is warranted. Qualitative analysis
of errors (e.g., rotations) made on the incidental learning
procedures may also be valuable. (JINS, 2000,
6, 770–780.)
Striatal contributions to category learning: Quantitative
modeling of simple linear and complex nonlinear rule learning
in patients with Parkinson's disease
Authors: MADDOX W. TODD , FILOTEO J. VINCENT
Published: July 2002

The contribution of the striatum to category learning was examined
by having patients with Parkinson's disease (PD) and matched
controls solve categorization problems in which the optimal
rule was linear or nonlinear using the perceptual categorization
task. Traditional accuracy-based analyses, as well as quantitative
model-based analyses were performed. Unlike accuracy-based
analyses, the model-based analyses allow one to quantify and
separate the effects of categorization rule learning from
variability in the trial-by-trial application of the
participant's rule. When the categorization rule was linear,
PD patients showed no accuracy, categorization rule learning,
or rule application variability deficits. Categorization accuracy
for the PD patients was associated with their performance on
a test believed to be sensitive to frontal lobe functioning.
In contrast, when the categorization rule was nonlinear, the
PD patients showed accuracy, categorization rule learning, and
rule application variability deficits. Furthermore, categorization
accuracy was not associated with performance on the test of
frontal lobe functioning. Implications for neuropsychological
theories of categorization learning are discussed. (JINS,
2001, 7, 710–727.)
Introduction to the environmental Kuznets curve special issue
Authors: BARBIER EDWARD B.
Published: July 2002

This special issue is concerned with environmental Kuznets curves (EKC) - the hypothesis that there is an ‘inverted-U’ relationship between various indicators of environmental degradation and levels of per capita income. Explanations as to why environmental degradation should first increase then decline with income have focused on a number of underlying relationships, including:

the effects of structural economic change on the use of the environment for resource inputs and to assimilate waste;

the link between the demand for environmental quality and income;

types of environmental degradation and ecological processes.
‘Charm of Sound’: something new in the Finnish contemporary music scene?
Authors: KULJUNTAUSTA PETRI
Published: July 2002

This article introduces the ‘Charm of Sound’ (COS) association, its purposes and activities, and gives a view of what the electroacoustic community at large means for this particular sub-community.
Locally free self-forms, logophoricity, and intensification in English
Authors: König Ekkehard , Siemund Peter
Published: July 2002

The article discusses the distribution and meaning of ‘locally free reflexives’ (‘untriggered reflexives’, ‘viewpoint reflexives’, ‘perspective logophors’) in English. After a thorough assessment of the contextual constraints on the use of such locally free self-forms, three analyses are discussed and compared: (a) the view that such self-forms are bound by a minimal subject of consciousness within their discourse (Zribi-Hertz, 1989); (b) the view that the relevant forms exhibit essentially the same distribution as pronouns and that the choice between the two is motivated by discourse considerations (Reinhart & Reuland, 1993); and (c) the view that locally free self-forms are intensifiers without pronominal heads (Baker, 1995). It is shown that the third analysis is by far the most adequate one, and that both the distribution and the meaning of such expressions can be explained on the basis of this analysis if it is combined with a suitable semantic analysis of intensifiers.
ON RANDOM MATCHING, MONETARY EQUILIBRIA, AND SUNSPOTS
Authors: Ennis Huberto M.
Published: July 2002

We study comparative statics results for the steady-state monetary equilibria of a simple random matching model of money with endogenous prices and no extrinsic uncertainty. Some of the results appear counterintuitive (both when take-it-or-leave-it offer or when Nash–Rubinstein bargaining is used in the model). Consistency of the equilibrium expectations causes the partial equilibrium intuitions to be reversed. We then proceed to apply the new insights to the analysis of sunspot equilibria in these type of models of bilateral trade with money.
Characterization and Repeat Analysis of the Compact Genome of the Freshwater Pufferfish Tetraodon nigroviridis
Authors: Crollius H. Roest , Jaillon O. , Dasilva C. , Ozouf-Costaz C. , Fizames C. , Fischer C. , Bouneau L. , Billault A. , Quetier F. , Saurin W. , Bernot A. , Weissenbach J.
Published: July 2002

Tetraodon nigroviridis is a freshwater pufferfish 20–30 million years distant from Fugu rubripes. The genome of both tetraodontiforms is compact, mostly because intergenic and intronic sequences are reduced in size compared to other vertebrate genomes. The previously uncharacterized Tetraodon genome is described here together with a detailed analysis of its repeat content and organization. We report the sequencing of 46 megabases of bacterial artificial chromosome (BAC) end sequences, which represents a random DNA sample equivalent to 13% of the genome. The sequence and location of rRNA gene clusters, centromeric and subtelocentric satellite sequences have been determined. Minisatellites and microsatellites have been cataloged and notable differences were observed in comparison with microsatellites from Fugu. The genome contains homologies to all known families of transposable elements, including Ty3-gypsy, Ty1-copia, Line retrotransposons, DNA transposons, and retroviruses, although their overall abundance is <1%. This structural analysis is an important prerequisite to sequencing the Tetraodongenome.

[The sequence data described in this paper have been submitted to the EMBL data library under accession nos.AJ245809, AJ270048, AJ245808, AJ270029–AJ270047, DS42722 andAL305790–AL352938.]
A Large Population of Small Chloroplasts in Tobacco Leaf Cells Allows More Effective Chloroplast Movement Than a Few Enlarged Chloroplasts
Authors: Jeong Won Joong , Park Youn-Il , Suh KyeHong , Raven John A. , Yoo Ook Joon , Liu Jang Ryol
Published: July 2002

We generated transgenic tobacco (Nicotiana tabacumcv Xanthi) plants that contained only one to three enlarged chloroplasts per leaf mesophyll cell by introducingNtFtsZ1-2, a cDNA for plastid division. These plants were used to investigate the advantages of having a large population of small chloroplasts rather than a few enlarged chloroplasts in a leaf mesophyll cell. Despite the similarities in photosynthetic components and ultrastructure of photosynthetic machinery between wild-type and transgenic plants, the overall growth of transgenic plants under low- and high-light conditions was retarded. In wild-type plants, the chloroplasts moved toward the face position under low light and toward the profile position under high-light conditions. However, chloroplast rearrangement in transgenic plants in response to light conditions was not evident. In addition, transgenic plant leaves showed greatly diminished changes in leaf transmittance values under both light conditions, indicating that chloroplast rearrangement was severely retarded. Therefore, under low-light conditions the incomplete face position of the enlarged chloroplasts results in decreased absorbance of light energy. This, in turn, reduces plant growth. Under high-light conditions, the amount of absorbed light exceeds the photosynthetic utilization capacity due to the incomplete profile position of the enlarged chloroplasts, resulting in photodamage to the photosynthetic machinery, and decreased growth. The presence of a large number of small and/or rapidly moving chloroplasts in the cells of higher land plants permits more effective chloroplast phototaxis and, hence, allows more efficient utilization of low-incident photon flux densities. The photosynthetic apparatus is, consequently, protected from damage under high-incident photon flux densities.
Agrobacterium tumefaciens-Mediated Transformation of Maize Embryos Using a Standard Binary Vector System
Authors: Frame Bronwyn R. , Shou Huixia , Chikwamba Rachel K. , Zhang Zhanyuan , Xiang Chengbin , Fonger Tina M. , Pegg Sue Ellen K. , Li Baochun , Nettleton Dan S. , Pei Deqing , Wang Kan
Published: July 2002

We have achieved routine transformation of maize (Zea mays) using an Agrobacterium tumefaciensstandard binary (non-super binary) vector system. Immature zygotic embryos of the hybrid line Hi II were infected with A. tumefaciens strain EHA101 harboring a standard binary vector and cocultivated in the presence of 400 mg L−1  l-cysteine. Inclusion of l-cysteine in cocultivation medium lead to an improvement in transient β-glucuronidase expression observed in targeted cells and a significant increase in stable transformation efficiency, but was associated with a decrease in embryo response after cocultivation. The average stable transformation efficiency (no. of bialaphos-resistant events recovered per 100 embryos infected) of the present protocol was 5.5%. Southern-blot and progeny analyses confirmed the integration, expression, and inheritance of the bar andgus transgenes in R0, R1, and R2 generations of transgenic events. To our knowledge, this represents the first report in which fertile, stable transgenic maize has been routinely produced using an A. tumefaciensstandard binary vector system.
The Negatively Acting Factors EID1 and SPA1 Have Distinct Functions in Phytochrome A-Specific Light Signaling
Authors: Zhou Yong-Chun , Dieterle Monika , Büche Claudia , Kretsch Thomas
Published: July 2002

EID1 (empfindlicher im dunkelroten Licht) and SPA1 (suppressor of phytochrome A[phyA]-105) function as negatively acting components in phyA-specific light signaling. Mutants in the respective genes led to very similar phenotypes under weak-light conditions. To examine whether both genes are functionally redundant, detailed physiological and genetic analyses were performed witheid1 and spa1 mutants isolated from the same wild-type background. Measurements of hypocotyl elongation, anthocyanin accumulation, and Lhcb1-transcript accumulation under different light treatments demonstrated that SPA1 has a strong influence on the regulation of very low fluence responses and a weaker influence on high-irradiance responses. In contrast, EID1 severely altered high-irradiance responses and caused almost no change on very low fluence responses. Analyses on eid1 phyA-105double mutants demonstrated that EID1 could not suppress the phenotype of the weak phyA allele under continuous far-red light. Measurements on eid1 spa1 double mutants exhibited a strong interference of both genes in the regulation of hypocotyl elongation. These results indicate that EID1 and SPA1 are involved in different but interacting phyA-dependent signal transduction chains.
Altering the Expression of the Chlorophyllase GeneATHCOR1 in Transgenic Arabidopsis Caused Changes in the Chlorophyll-to-Chlorophyllide Ratio
Authors: Benedetti Celso Eduardo , Arruda Paulo
Published: July 2002

The Arabidopsis gene ATHCOR1, which encodes the CORI1 (coronatine-induced) protein, was expressed in bacterial cells. Soluble recombinant CORI1 was purified and shown to possess chlorophyllase (Chlase) activity in vitro. To determine its activity in vivo, wild-type Arabidopsis and coi1 mutant, which lacksATHCOR1 transcripts, were transformed with sense and antisense forms of the gene. Wild-type and coi1 plants overexpressing ATHCOR1 showed increased contents of chlorophyllide (Chlide) without a substantial change in the total amount of the extractable chlorophyll (Chl). These plants presented high Chlide to Chl ratios in leaves, whereas antisense plants and nontransformed coi1 mutant showed undetectableATHCOR1 mRNA and significantly lower Chlide to Chl ratios, relative to wild-type control. Overexpression ofATHCOR1 caused an increased breakdown of Chla, as revealed by the Chlide a tob ratio, which was significantly higher in sense than wild-type, coi1 mutant, and antisense plants. This preferential activity of CORI1 toward Chl a was further supported by in vitro analyses using the purified protein. Increased Chlase activity was detected in developing flowers, which correlated to the constitutive expression of ATHCOR1 in this organ. Flowers of the antisense plant showed reduced Chlide to Chl ratio, suggesting a role of CORI1 in Chl breakdown during flower senescence. The results show that ATHCOR1 has Chlase activity in vivo, however, because coi1 flowers have no detectableATHCOR1 mRNA and present Chlide to Chl ratios comparable with the wild type, an additional Chlase is likely to be active in Arabidopsis. In accordance, transcripts of a second Arabidopsis Chlase gene, AtCLH2, were detected in both normal and mutant flowers.
Characterization of FRO1, a Pea Ferric-Chelate Reductase Involved in Root Iron Acquisition
Authors: Waters Brian M. , Blevins Dale G. , Eide David J.
Published: July 2002

To acquire iron, many plant species reduce soil Fe(III) to Fe(II) by Fe(III)-chelate reductases embedded in the plasma membrane of root epidermal cells. The reduced product is then taken up by Fe(II) transporter proteins. These activities are induced under Fe deficiency. We describe here the FRO1 gene from pea (Pisum sativum), which encodes an Fe(III)-chelate reductase. Consistent with this proposed role, FRO1 shows similarity to other oxidoreductase proteins, and expression of FRO1 in yeast conferred increased Fe(III)-chelate reductase activity. Furthermore,FRO1 mRNA levels in plants correlated with Fe(III)-chelate reductase activity. Sites of FRO1expression in roots, leaves, and nodules were determined.FRO1 mRNA was detected throughout the root, but was most abundant in the outer epidermal cells. Expression was detected in mesophyll cells in leaves. In root nodules, mRNA was detected in the infection zone and nitrogen-fixing region. These results indicate that FRO1 acts in root Fe uptake and they suggest a role in Fe distribution throughout the plant. Characterization of FRO1 has also provided new insights into the regulation of Fe uptake. FRO1expression and reductase activity was detected only in Fe-deficient roots of Sparkle, whereas both were constitutive in brzand dgl, two mutants with incorrectly regulated Fe accumulation. In contrast, FRO1 expression was responsive to Fe status in shoots of all three plant lines. These results indicate differential regulation of FRO1 in roots and shoots, and improper FRO1 regulation in response to a shoot-derived signal of iron status in the roots of thebrz and dgl mutants.
Overexpression of Polygalacturonase in Transgenic Apple Trees Leads to a Range of Novel Phenotypes Involving Changes in Cell Adhesion
Authors: Atkinson Ross G. , Schröder Roswitha , Hallett Ian C. , Cohen Daniel , MacRae Elspeth A.
Published: July 2002

Polygalacturonases (PGs) cleave runs of unesterified GalUA that form homogalacturonan regions along the backbone of pectin. Homogalacturonan-rich pectin is commonly found in the middle lamella region of the wall where two adjacent cells abut and its integrity is important for cell adhesion. Transgenic apple (Malus domestica Borkh. cv Royal Gala) trees were produced that contained additional copies of a fruit-specific apple PG gene under a constitutive promoter. In contrast to previous studies in transgenic tobacco (Nicotiana tabacum) where PG overexpression had no effect on the plant (K.W. Osteryoung, K. Toenjes, B. Hall, V. Winkler, A.B. Bennett [1990] Plant Cell 2: 1239–1248), PG overexpression in transgenic apple led to a range of novel phenotypes. These phenotypes included silvery colored leaves and premature leaf shedding due to reduced cell adhesion in leaf abscission zones. Mature leaves had malformed and malfunctioning stomata that perturbed water relations and contributed to a brittle leaf phenotype. Chemical and ultrastructural analyses were used to relate the phenotypic changes to pectin changes in the leaf cell walls. The modification of apple trees by a single PG gene has offered a new and unexpected perspective on the role of pectin and cell wall adhesion in leaf morphology and stomatal development.
A Flooding-Induced Xyloglucan Endo-Transglycosylase Homolog in Maize Is Responsive to Ethylene and Associated with Aerenchyma
Authors: Saab I. N. , Sachs M. M.
Published: July 2002

Development of aerenchyma (soft cortical tissue with large intercellular air spaces) in flooded plants results from cell-wall hydrolysis and eventual cell lysis and is promoted by endogenous ethylene. Despite its adaptive significance, the molecular mechanisms behind aerenchyma development remain unknown. We recently isolated a flooding-induced maize (Zea mays L.) gene (wusl1005[gfu]; abbreviated as 1005) encoding a homolog of xyloglucan endo-transglycosylase (XET), a putative cell-wall-loosening enzyme active during germination, expansion, and fruit softening. XET and related enzymes may also be involved in cell-wall metabolism during flooding-induced aerenchyma development. Under flooding, 1005 mRNA accumulated in root and mesocotyl locations that subsequently exhibited aerenchyma development and reached maximum levels within 12 h of treatment. Aerenchyma development was observed in the same locations by 48 h of treatment. Treatment with the ethylene synthesis inhibitor (aminooxy)acetic acid (AOA), which prevented cortical air space formation under flooding, almost completely inhibited 1005 mRNA accumulation in both organs. AOA treatment had little effect on the accumulation of mRNA encoded by adh1, indicating that it did not cause general suppression of flooding-responsive genes. Additionally, ethylene treatment under aerobic conditions resulted in aerenchyma development as well as induction of 1005 in both organs. These results indicate that 1005 is responsive to ethylene. Treatment with anoxia, which suppresses ethylene accumulation and aerenchyma development, also resulted in 1005 induction. However, in contrast to flooding, AOA treatment under anoxia did not affect 1005 mRNA accumulation, indicating that 1005 is induced via different mechanisms under flooding (hypoxia) and anoxia.
Molecular Characterization of Berberine Bridge Enzyme Genes from Opium Poppy
Authors: Facchini P. J. , Penzes C. , Johnson A. G. , Bull D.
Published: July 2002

In Papaver somniferum (opium poppy) and related species, (S)-reticuline serves as a branch-point intermediate in the biosynthesis of numerous isoquinoline alkaloids. The berberine bridge enzyme (BBE) ([S]-reticuline:oxygen oxidoreductase [methylene bridge forming], EC 1.5.3.9) catalyzes the stereospecific conversion of the N-methyl moiety of (S)-reticuline into the berberine bridge carbon of (S)-scoulerine and represents the first committed step in the pathway leading to the antimicrobial alkaloid sanguinarine. Three unique genomic clones (bbe1, bbe2, and bbe3) similar to a BBE cDNA from Eschscholtzia californica (California poppy) were isolated from opium poppy. Two clones (bbe2 and bbe3) contained frame-shift mutations of which bbe2 was identified as a putative, nonexpressed pseudogene by RNA blot hybridization using a gene-specific probe and by the lack of transient expression of a chimeric gene fusion between the bbe2 5[prime] flanking region and a β-glucuronidase reporter gene. Similarly, bbe1 was shown to be expressed in opium poppy plants and cultured cells. Genomic DNA blot-hybridization data were consistent with a limited number of bbe homologs. RNA blot hybridization showed that bbe genes are expressed in roots and stems of mature plants and in seedlings within 3 d after germination. Rapid and transient BBE mRNA accumulation also occurred after treatment with a fungal elicitor or with methyl jasmonate. However, sanguinarine was found only in roots, seedlings, and fungal elicitor-treated cell cultures.
Characterization of Maize Elongation Factor 1A and Its Relationship to Protein Quality in the Endosperm
Authors: Sun Y. , Carneiro N. , Clore A. M. , Moro G. L. , Habben J. E. , Larkins B. A.
Published: July 2002

The protein synthesis elongation factor 1A (eEF1A) is a multifunctional protein in eukaryotic cells. In maize (Zea mays L.) endosperm eEF1A co-localizes with actin around protein bodies, and its accumulation is highly correlated with the protein-bound lysine (Lys) content. We purified eEF1A from maize kernels by ammonium sulfate precipitation, ion-exchange, and chromatofocusing. The identity of the purified protein was confirmed by microsequencing of an endoproteinase glutamic acid-C fragment and by its ability to bundle actin. Using purified eEF1A as a standard, we found that this protein contributes 0.4% of the total protein in W64A+ endosperm and approximately 1% of the protein in W64Ao2. Because eEF1A contains 10% Lys, it accounts for 2.2% of the total Lys in W64A+ and 2.3% of the Lys in W64Ao2. However, its concentration predicts 90% of the Lys found in endosperm proteins of both genotypes, indicating that eEF1A is a key component of the group of proteins that determines the nutritional quality of the grain. This notion is further supported by the fact that in floury2, another high-Lys mutant, the content of eEF1A increases with the dosage of the floury2 gene. These data provide the biochemical basis for further investigation of the relationship between eEF1A content and the nutritional quality of cereals.
ADP-Glucose Pyrophosphorylase Is Localized to Both the Cytoplasm and Plastids in Developing Pericarp of Tomato Fruit1
Authors: Chen Bing-Yuan , Wang Yi , Janes Harry W.
Published: July 2002

The intracellular location of ADP-glucose pyrophosphorylase (AGP) in developing pericarp of tomato (Lycopersicon esculentum Mill) has been investigated by immunolocalization. With the use of a highly specific anti-tomato fruit AGP antibody, the enzyme was localized in cytoplasm as well as plastids at both the light and electron microscope levels. The immunogold particles in plastids were localized in the stroma and at the surface of the starch granule, whereas those in the cytoplasm occurred in cluster-like patterns. Contrary to the fruit, the labeling in tomato leaf cells occurred exclusively in the chloroplasts. These data demonstrate that AGP is localized to both the cytoplasm and plastids in developing pericarp cells of tomato.
Altered Growth of Transgenic Tobacco Lacking Leaf Cytosolic Pyruvate Kinase1
Authors: Knowles Vicki L. , McHugh Sylvia G. , Hu Zhiyuan , Dennis David T. , Miki Brian L. , Plaxton William C.
Published: July 2002

Previously, we reported that transformation of tobacco (Nicotiana tabacum L.) with a vector containing a potato cytosolic pyruvate kinase (PKc) cDNA generated two plant lines specifically lacking leaf PKc (PKc−) as a result of co-suppression. PKc deficiency in these primary transformants did not appear to alter plant development, although root growth was not examined. Here we report a striking reduction in root growth of homozygous progeny of both PKc− lines throughout development under moderate (600 μE m−2 s−1) or low (100 μE m−2 s−1) light intensities. When both PKc− lines were cultivated under low light, shoot and flower development were also delayed and leaf indentations were apparent. Leaf PK activity in the transformants was significantly decreased at all time points examined, whereas root activities were unaffected. Polypeptides corresponding to PKc were undetectable on immunoblots of PKc− leaf extracts, except in 6-week-old low-light-grown PKc− plants, in which leaf PKc expression appeared to be greatly reduced. The metabolic implications of the kinetic characteristics of partially purified PKc from wild-type tobacco leaves are discussed. Overall, the results suggest that leaf PKc deficiency leads to a perturbation in source-sink relationships.
Fruit Development in Trillium1
Authors: Lapointe Line
Published: July 2002

Leaves are the main source of carbon for fruit maturation in most species. However, in plants seeing contrasting light conditions such as some spring plants, carbon fixed during the spring could be used to support fruit development in the summer, when photosynthetic rates are low. We monitored carbohydrate content in the rhizome (a perennating organ) and the aboveground stem of trillium (Trillium erectum) over the entire growing season (May–November). At the beginning of the fruiting stage, stems carrying a developing fruit were harvested, their leaves were removed, and the leafless stems were maintained in aqueous solution under controlled conditions up to full fruit maturation. These experiments showed that stem carbohydrate content was sufficient to support fruit development in the absence of leaves and rhizome. This is the first reported case, to our knowledge, of complete fruit development sustained only by a temporary carbohydrate reservoir. This carbohydrate accumulation in the stem during the spring enables the plant to make better use of the high irradiances occurring at that time. Many other species might establish short-term carbohydrate reservoirs in response to seasonal changes in growing conditions.
Aluminum Resistance in the Arabidopsis Mutantalr-104 Is Caused by an Aluminum-Induced Increase in Rhizosphere pH1
Authors: Degenhardt Jörg , Larsen Paul B. , Howell Stephen H. , Kochian Leon V.
Published: July 2002

A mechanism that confers increased Al resistance in the Arabidopsis thaliana mutantalr-104 was investigated. A modified vibrating microelectrode system was used to measure H+ fluxes generated along the surface of small Arabidopsis roots. In the absence of Al, no differences in root H+ fluxes between wild type and alr-104 were detected. However, Al exposure induced a 2-fold increase in net H+ influx inalr-104 localized to the root tip. The increased flux raised the root surface pH of alr-104 by 0.15 unit. A root growth assay was used to assess the Al resistance ofalr-104 and wild type in a strongly pH-buffered nutrient solution. Increasing the nutrient solution pH from 4.4 to 4.5 significantly increased Al resistance in wild type, which is consistent with the idea that the increased net H+ influx can account for greater Al resistance in alr-104. Differences in Al resistance between wild type and alr-104 disappeared when roots were grown in pH-buffered medium, suggesting that Al resistance in alr-104 is mediated only by pH changes in the rhizosphere. This mutant provides the first evidence, to our knowledge, for an Al-resistance mechanism based on an Al-induced increase in root surface pH.
Three Mechanisms for the Calcium Alleviation of Mineral Toxicities
Authors: Kinraide Thomas B.
Published: July 2002

Ca2+ in rooting medium is essential for root elongation, even in the absence of added toxicants. In the presence of rhizotoxic levels of Al3+, H+, or Na+ (or other cationic toxicants), supplementation of the medium with higher levels of Ca2+alleviates growth inhibition. Experiments to determine the mechanisms of alleviation entailed measurements of root elongation in wheat (Triticum aestivum L. cv Scout 66) seedlings in controlled medium. A Gouy-Chapman-Stern model was used to compute the electrical potentials and the activities of ions at the root-cell plasma membrane surfaces. Analysis of root elongation relative to the computed surface activities of ions revealed three separate mechanisms of Ca2+ alleviation. Mechanism I is the displacement of cell-surface toxicant by the Ca2+-induced reduction in cell-surface negativity. Mechanism II is the restoration of Ca2+ at the cell surface if the surface Ca2+has been reduced by the toxicant to growth-limiting levels. Mechanism III is the collective ameliorative effect of Ca2+ beyond mechanisms I and II, and may involve Ca2+-toxicant interactions at the cell surface other than the displacement interactions of mechanisms I and II. Mechanism I operated in the alleviation of all of the tested toxicities; mechanism II was generally a minor component of alleviation; and mechanism III was toxicant specific and operated strongly in the alleviation of Na+toxicity, moderately in the alleviation of H+ toxicity, and not at all in the alleviation of Al3+ toxicity.
Mitochondrial Contribution to the Anoxic Ca2+ Signal in Maize Suspension-Cultured Cells
Authors: Subbaiah Chalivendra C. , Bush Douglas S. , Sachs Martin M.
Published: July 2002

Anoxia induces a rapid elevation of the cytosolic Ca2+concentration ([Ca2+]cyt) in maize (Zea mays L.) cells, which is caused by the release of the ion from intracellular stores. This anoxic Ca2+ release is important for gene activation and survival in O2-deprived maize seedlings and cells. In this study we examined the contribution of mitochondrial Ca2+ to the anoxic [Ca2+]cyt elevation in maize cells. Imaging of intramitochondrial Ca2+ levels showed that a majority of mitochondria released their Ca2+ in response to anoxia and took up Ca2+ upon reoxygenation. We also investigated whether the mitochondrial Ca2+ release contributed to the increase in [Ca2+]cyt under anoxia. Analysis of the spatial association between anoxic [Ca2+]cytchanges and the distribution of mitochondrial and other intracellular Ca2+ stores revealed that the largest [Ca2+]cyt increases occurred close to mitochondria and away from the tonoplast. In addition, carbonylcyanide p-trifluoromethoxyphenyl hydrazone treatment depolarized mitochondria and caused a mild elevation of [Ca2+]cyt under aerobic conditions but prevented a [Ca2+]cyt increase in response to a subsequent anoxic pulse. These results suggest that mitochondria play an important role in the anoxic elevation of [Ca2+]cyt and participate in the signaling of O2 deprivation.
Changes in Cell Wall Composition during Ripening of Grape Berries
Authors: Nunan Kylie J. , Sims Ian M. , Bacic Antony , Robinson Simon P. , Fincher Geoffrey B.
Published: July 2002

Cell walls were isolated from the mesocarp of grape (Vitis vinifera L.) berries at developmental stages from before veraison through to the final ripe berry. Fluorescence and light microscopy of intact berries revealed no measurable change in cell wall thickness as the mesocarp cells expanded in the ripening fruit. Isolated walls were analyzed for their protein contents and amino acid compositions, and for changes in the composition and solubility of constituent polysaccharides during development. Increases in protein content after veraison were accompanied by an approximate 3-fold increase in hydroxyproline content. The type I arabinogalactan content of the pectic polysaccharides decreased from approximately 20 mol % of total wall polysaccharides to about 4 mol % of wall polysaccharides during berry development. Galacturonan content increased from 26 to 41 mol % of wall polysaccharides, and the galacturonan appeared to become more soluble as ripening progressed. After an initial decrease in the degree of esterification of pectic polysaccharides, no further changes were observed nor were there large variations in cellulose (30–35 mol % of wall polysaccharides) or xyloglucan (approximately 10 mol % of wall polysaccharides) contents. Overall, the results indicate that no major changes in cell wall polysaccharide composition occurred during softening of ripening grape berries, but that significant modification of specific polysaccharide components were observed, together with large changes in protein composition.
Arginase Is Inoperative in Developing Soybean Embryos1
Authors: Goldraij Ariel , Polacco Joe C.
Published: July 2002

Arginase (EC 3.5.3.1) transcript level and activity were measured in soybean (Glycine maxL.) embryos from the reserve deposition stage to postgermination. Using a cDNA probe for a small soybean arginase gene family, no transcript was detected in developing embryos. However, arginase transcripts increased sharply on germination, reaching a maximum at 3 to 5 d after germination. There was low but measurable in vitro arginase specific activity in developing embryos (less than 6% of seedling maximum). During germination arginase specific activity increased in parallel with the sharply increasing arginase transcript level. Seedling arginase activity was largely localized in cotyledons. Arginase activity was assayed in vivo by measuring urea accumulation in a urease-deficient mutant. No urea was detected in developing embryos, whereas accumulated urea paralleled arginase specific activity and transcript level in germinating seedlings. As in planta embryos, cultured cotyledons did not accumulate urea when arginine (Arg) was provided with other amino acids in a “mock” seed-coat exudate. Arg as the sole nitrogen source was converted to urea but did not support cotyledon growth. There appeared to be a lack of recruitment of the low-level arginase activity to hydrolyze free Arg in developing embryos, thus avoiding a futile urea cycle.
Thermotolerance of Leaf Discs from Four Isoprene-Emitting Species Is Not Enhanced by Exposure to Exogenous Isoprene1
Authors: Logan Barry A. , Monson Russell K.
Published: July 2002

The effects of exogenously supplied isoprene on chlorophyll fluorescence characteristics were examined in leaf discs of four isoprene-emitting plant species, kudzu (Pueraria lobata[Willd.] Ohwi.), velvet bean (Mucunasp.), quaking aspen (Populus tremuloidesMichx.), and pussy willow (Salix discolor Muhl). Isoprene, supplied to the leaves at either 18 μL L−1 in compressed air or 21 μL L−1 in N2, had no effect on the temperature at which minimal fluorescence exhibited an upward inflection during controlled increases in leaf-disc temperature. During exposure to 1008 μmol photons m−2s−1 in an N2 atmosphere, 21 μL L−1 isoprene had no effect on the thermally induced inflection of steady-state fluorescence. The maximum quantum efficiency of photosystem II photochemistry decreased sharply as leaf-disc temperature was increased; however, this decrease was unaffected by exposure of leaf discs to 21 μL L−1 isoprene. Therefore, there were no discernible effects of isoprene on the occurrence of symptoms of high-temperature damage to thylakoid membranes. Our data do not support the hypothesis that isoprene enhances leaf thermotolerance.
The SLENDER Gene of Pea Encodes a Gibberellin 2-Oxidase
Authors: Martin David N. , Proebsting William M. , Hedden Peter
Published: July 2002

The amount of active gibberellin (GA) in plant tissues is determined in part by its rate of catabolism through oxidation at C-2. In pea (Pisum sativumL.) seeds, GA 2-oxidation is controlled by the SLN(SLENDER) gene, a mutation of which produces seedlings characterized by a slender or hyper-elongated phenotype. We cloned a GA 2-oxidase cDNA from immature pea seeds by screening an expression library for enzyme activity. The clone contained a full-length open reading frame encoding a protein of 327 amino acids. Lysate of bacterial cultures expressing the protein converted the C19-GAs, GA1, GA4, GA9, and GA20 to the corresponding 2β-hydroxy products. GA9 and GA20 were also converted to GA51 and GA29 catabolites, respectively. The gene appeared to be one member of a small family of GA 2-oxidases in pea. Transcript was found predominantly in roots, flowers, young fruits, and testae of seeds. The corresponding transcript fromsln pea contained a point mutation and did not produce active enzyme when expressed heterologously. RFLP analysis of a seedling population segregating for SLN andsln alleles showed the homozygous mutant allele co-segregating with the characteristic slender phenotype. We conclude that SLN encodes GA 2-oxidase.
Characterization and Expression of Four Proline-Rich Cell Wall Protein Genes in Arabidopsis Encoding Two Distinct Subsets of Multiple Domain Proteins
Authors: Fowler Thomas J. , Bernhardt Christine , Tierney Mary L.
Published: July 2002

We have characterized the molecular organization and expression of four proline-rich protein genes from Arabidopsis (AtPRPs). These genes predict two classes of cell wall proteins based on DNA sequence identity, repetitive motifs, and domain organization. AtPRP1 and AtPRP3encode proteins containing an N-terminal PRP-like domain followed by a C-terminal domain that is biased toward P, T, Y, and K.AtPRP2 and AtPRP4 represent a second, novel group of PRP genes that encode two-domain proteins containing a non-repetitive N-terminal domain followed by a PRP-like region rich in P, V, K, and C. Northern hybridization analysis indicated that AtPRP1 and AtPRP3 are exclusively expressed in roots, while transcripts encoding AtPRP2 and AtPRP4 were most abundant in aerial organs of the plant. Histochemical analyses of promoter/β-glucuronidase fusions localized AtPRP3 expression to regions of the root containing root hairs. AtPRP2 and AtPRP4expression was detected in expanding leaves, stems, flowers, and siliques. In addition, AtPRP4 expression was detected in stipules and during the early stages of lateral root formation. These studies support a model for involvement of PRPs in specifying cell-type-specific wall structures, and provide the basis for a genetic approach to dissect the function of PRPs during growth and development.
The Role of Chloroplast Electron Transport and Metabolites in Modulating Rubisco Activity in Tobacco. Insights from Transgenic Plants with Reduced Amounts of Cytochrome b/fComplex or Glyceraldehyde 3-Phosphate Dehydrogenase
Authors: Ruuska Sari A. , Andrews T. John , Badger Murray R. , Price G. Dean , von Caemmerer Susanne
Published: July 2002

Leaf metabolites, adenylates, and Rubisco activation were studied in two transgenic tobacco (Nicotiana tabacum L. cv W38) types. Plants with reduced amounts of cytochrome b/f complex (anti-b/f) have impaired electron transport and a low transthylakoid pH gradient that restrict ATP and NADPH synthesis. Plants with reduced glyceraldehyde 3-phosphate dehydrogenase (anti-GAPDH) have a decreased capacity to use ATP and NADPH in carbon assimilation. The activation of the chloroplast NADP-malate dehydrogenase decreased in anti-b/f plants, indicating a low NADPH/NADP+ ratio. The whole-leaf ATP/ADP in anti-b/f plants was similar to wild type, while it increased in anti-GAPDH plants. In both plant types, the CO2 assimilation rates decreased with decreasing ribulose 1,5-bisphosphate concentrations. In anti-b/f plants, CO2 assimilation was further compromised by reduced carbamylation of Rubisco, whereas in anti-GAPDH plants the carbamylation remained high even at subsaturating ribulose 1,5-bisphosphate concentrations. We propose that the low carbamylation in anti-b/f plants is due to reduced activity of Rubisco activase. The results suggest that light modulation of activase is not directly mediated via the electron transport rate or stromal ATP/ADP, but some other manifestation of the balance between electron transport and the consumption of its products. Possibilities include the transthylakoid pH gradient and the reduction state of the acceptor side of photosystem I and/or the degree of reduction of the thioredoxin pathway.
Removal of Feedback Inhibition of Δ1-Pyrroline-5-Carboxylate Synthetase Results in Increased Proline Accumulation and Protection of Plants from Osmotic Stress
Authors: Hong Zonglie , Lakkineni Karuna , Zhang Zhongming , Verma Desh Pal S.
Published: July 2002

The Δ1-pyrroline-5-carboxylate synthetase (P5CS; EC not assigned) is the rate-limiting enzyme in proline (Pro) biosynthesis in plants and is subject to feedback inhibition by Pro. It has been suggested that the feedback regulation of P5CS is lost in plants under stress conditions. We compared Pro levels in transgenic tobacco (Nicotiana tabacum) plants expressing a wild-type form of Vigna aconitifolia P5CS and a mutated form of the enzyme (P5CSF129A) whose feedback inhibition by Pro was removed by site-directed mutagenesis. Transgenic plants expressing P5CSF129A accumulated about 2-fold more Pro than the plants expressing V. aconitifolia wild-type P5CS. This difference was further increased in plants treated with 200 mm NaCl. These results demonstrated that the feedback regulation of P5CS plays a role in controlling the level of Pro in plants under both normal and stress conditions. The elevated Pro also reduced free radical levels in response to osmotic stress, as measured by malondialdehyde production, and significantly improved the ability of the transgenic seedlings to grow in medium containing up to 200 mm NaCl. These findings shed new light on the regulation of Pro biosynthesis in plants and the role of Pro in reducing oxidative stress induced by osmotic stress, in addition to its accepted role as an osmolyte.
The Expression of D-Cyclin Genes Defines Distinct Developmental Zones in Snapdragon Apical Meristems and Is Locally Regulated by the Cycloidea Gene
Authors: Gaudin Valérie , Lunness Patricia A. , Fobert Pierre R. , Towers Matthew , Riou-Khamlichi Catherine , Murray James A.H. , Coen Enrico , Doonan John H.
Published: July 2002

Three D-cyclin genes are expressed in the apical meristems of snapdragon (Antirrhinum majus). The cyclin D1 andD3b genes are expressed throughout meristems, whereascyclin D3a is restricted to the peripheral region of the meristem, especially the organ primordia. During floral development,cyclin D3b expression is: (a) locally modulated in the cells immediately surrounding the base of organ primordia, defining a zone between lateral organs that may act as a developmental boundary; (b) locally modulated in the ventral petals during petal folding; and (c) is specifically repressed in the dorsal stamen by thecycloidea gene. Expression of both cyclin D3 genes is reduced prior to the cessation of cell cycle activity, as judged by histone H4 expression. Expression of all three D-cyclin genes is modulated by factors that regulate plant growth, particularly sucrose and cytokinin. These observations may provide a molecular basis for understanding the local regulation of cell proliferation during plant growth and development.
The Plastidic Phosphoglucomutase from Arabidopsis. A Reversible Enzyme Reaction with an Important Role in Metabolic Control
Authors: Periappuram Cyril , Steinhauer Lee , Barton Dennis L. , Taylor David C. , Chatson Brock , Zou Jitao
Published: July 2002

An Arabidopsis cDNA (AtPGMp) encoding the plastidic phosphoglucomutase (PGM) predicted a 623-amino acid protein with an N-terminal sequence typical of a plastid signal peptide. Expression of a recombinant protein inEscherichia coli confirmed its enzyme activity. The recombinant enzyme had an apparent K  m value of 98.5 μm and a V  max of 4.48 μmol min−1 (mg protein)−1. The Calvin cycle intermediates fructose-1,6-bisphosphate and ribulose-1,5-bisphosphate exerted an inhibitory effect on PGM activity, supporting its proposed involvement in controlling photosynthetic carbon flow. A point mutation was identified in the AtPGMp gene of the Arabidopsis pgm-1 mutant. The mutation in the mutant transcript generated a stop codon at about one third of the wild-type open reading frame, and thus rendered the polypeptide nonfunctional. Storage lipid analysis of the pgm-1 mutant seeds showed a 40% reduction in oil content compared with that of wild type. Our results indicate that plastidic PGM is an important factor affecting carbon flux in triacylglycerol accumulation in oilseed plants, most likely through its essential role in starch synthesis.