bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Cloning of Vacuolar H+-Pyrophosphatase and Its Developmental Expression in Growing Hypocotyl of Mung Bean1
Authors: Nakanishi Yoichi , Maeshima Masayoshi 
Published: July 2002

Abstract
Vacuolar proton-translocating inorganic pyrophosphatase and H+-ATPase acidify the vacuoles and power the vacuolar secondary active transport systems in plants. Developmental changes in the transcription of the pyrophosphatase in growing hypocotyls of mung bean (Vigna radiata) were investigated. The cDNA clone for the mung bean enzyme contains an uninterrupted open reading frame of 2298 bp, coding for a polypeptide of 766 amino acids. Hypocotyls were divided into elongating and mature regions. RNA analysis revealed that the transcript level of the pyrophosphatase was high in the elongating region of the 3-d-old hypocotyl but was extremely low in the mature region of the 5-d-old hypocotyl. The level of transcript of the 68-kD subunit of H+-ATPase also decreased after cell maturation. In the elongating region, the proton-pumping activity of pyrophosphatase on the basis of membrane protein was 3 times higher than that of H+-ATPase. After cell maturation, the pyrophosphatase activity decreased to 30% of that in the elongating region. The decline in the pyrophosphatase activity was in parallel with a decrease in the enzyme protein content. These findings indicate that the level of the pyrophosphatase, a main vacuolar proton pump in growing cells, is negatively regulated after cell maturation at the transcriptional level.
Tomato Flower Abnormalities Induced by Low Temperatures Are Associated with Changes of Expression of MADS-Box Genes1
Authors: Lozano Rafael , Angosto Trinidad , Gómez Pedro , Payán Carmen , Capel Juan , Huijser Peter , Salinas Julio , Martı́nez-Zapater José M. 
Published: July 2002

Abstract
Flower and fruit development in tomato (Lycopersicon esculentum Mill.) were severely affected when plants were grown at low temperatures, displaying homeotic and meristic transformations and alterations in the fusion pattern of the organs. Most of these homeotic transformations modified the identity of stamens and carpels, giving rise to intermediate organs. Complete homeotic transformations were rarely found and always affected organs of the reproductive whorls. Meristic transformations were also commonly observed in the reproductive whorls, which developed with an excessive number of organs. Scanning electron microscopy revealed that meristic transformations take place very early in the development of the flower and are related to a significant increase in the floral meristem size. However, homeotic transformations should occur later during the development of the organ primordia. Steady-state levels of transcripts corresponding to tomato MADS-box genesTM4, TM5, TM6, and TAG1 were greatly increased by low temperatures and could be related to these flower abnormalities. Moreover, in situ hybridization analyses showed that low temperatures also altered the stage-specific expression ofTM4.
Biochemical Analysis of Plant Protection Afforded by a Nonpathogenic Endophytic Mutant of Colletotrichum magna1
Authors: Redman Regina S. , Freeman Stanley , Clifton David R. , Morrel Jed , Brown Gayle , Rodriguez Rusty J. 
Published: July 2002

Abstract
A nonpathogenic mutant ofColletotrichum magna (path-1) was previously shown to protect watermelon (Citrullus lanatus) and cucumber (Cucumis sativus) seedlings from anthracnose disease elicited by wild-type C. magna. Disease protection was observed in stems of path-1-colonized cucurbits but not in cotyledons, indicating that path-1 conferred tissue-specific and/or localized protection. Plant biochemical indicators of a localized and systemic (peroxidase, phenylalanine ammonia-lyase, lignin, and salicylic acid) “plant-defense” response were investigated in anthracnose-resistant and -susceptible cultivars of cucurbit seedlings exposed to four treatments: (1) water (control), (2) path-1 conidia, (3) wild-type conidia, and (4) challenge conditions (inoculation into path-1 conidia for 48 h and then exposure to wild-type conidia). Collectively, these analyses indicated that disease protection in path-1-colonized plants was correlated with the ability of these plants to mount a defense response more rapidly and to equal or greater levels than plants exposed to wild-type C. magna alone. Watermelon plants colonized with path-1 were also protected against disease caused by Colletotrichumorbiculare and Fusarium oxysporum. A model based on the kinetics of plant-defense activation is presented to explain the mechanism of path-1-conferred disease protection.
Arabidopsis Sec21p and Sec23p Homologs. Probable Coat Proteins of Plant COP-Coated Vesicles1
Authors: Movafeghi Ali , Happel Nicole , Pimpl Peter , Tai Gui-Hua , Robinson David G. 
Published: July 2002

Abstract
Intracellular protein transport between the endoplasmic reticulum (ER) and the Golgi apparatus and within the Golgi apparatus is facilitated by COP (coatprotein)-coated vesicles. Their existence in plant cells has not yet been demonstrated, although the GTP-binding proteins required for coat formation have been identified. We have generated antisera against glutathione-S-transferase-fusion proteins prepared with cDNAs encoding the Arabidopsis Sec21p and Sec23p homologs (AtSec21p and AtSec23p, respectively). The former is a constituent of the COPI vesicle coatomer, and the latter is part of the Sec23/24p dimeric complex of the COPII vesicle coat. Cauliflower (Brassica oleracea) inflorescence homogenates were probed with these antibodies and demonstrated the presence of AtSec21p and AtSec23p antigens in both the cytosol and membrane fractions of the cell. The membrane-associated forms of both antigens can be solubilized by treatments typical for extrinsic proteins. The amounts of the cytosolic antigens relative to the membrane-bound forms increase after cold treatment, and the two antigens belong to different protein complexes with molecular sizes comparable to the corresponding nonplant coat proteins. Sucrose-density-gradient centrifugation of microsomal cell membranes from cauliflower suggests that, although AtSec23p seems to be preferentially associated with ER membranes, AtSec21p appears to be bound to both the ER and the Golgi membranes. This could be in agreement with the notion that COPII vesicles are formed at the ER, whereas COPI vesicles can be made by both Golgi and ER membranes. Both AtSec21p and AtSec23p antigens were detected on membranes equilibrating at sucrose densities equivalent to those typical for in vitro-induced COP vesicles from animal and yeast systems. Therefore, a further purification of the putative plant COP vesicles was undertaken.
Purification and Partial Characterization of a Dehydrin Involved in Chilling Tolerance during Seedling Emergence of Cowpea1
Authors: Ismail Abdelbagi M. , Hall Anthony E. , Close Timothy J. 
Published: July 2002

Abstract
Dehydrins are a family of proteins (LEA [late-embryogenesisabundant] D11) commonly induced by environmental stresses associated with low temperature or dehydration and during seed maturation drying. Our previous genetic studies suggested an association of an approximately 35-kD protein (by immunological evidence a dehydrin) with chilling tolerance during emergence of seedlings of cowpea (Vigna unguiculata) line 1393-2-11. In the present study we found that the accumulation of this protein in developing cowpea seeds is coordinated with the start of the dehydration phase of embryo development. We purified this protein from dry seeds of cowpea line 1393-2-11 by using the characteristic high-temperature solubility of dehydrins as an initial enrichment step, which was followed by three chromatography steps involving cation exchange, hydrophobic interaction, and anion exchange. Various characteristics of this protein confirmed that indeed it is a dehydrin, including total amino acid composition, partial amino acid sequencing, and the adoption of α-helical structure in the presence of sodium dodecyl sulfate. The propensity of dehydrins to adopt α-helical structure in the presence of sodium dodecyl sulfate, together with the apparent polypeptide adhesion property of this cowpea dehydrin, suggests a role in stabilizing other proteins or membranes. Taken together, the genetic, physiological, and physicochemical data are at this stage consistent with a cause-and-effect relationship between the presence in mature seeds of the approximately 35-kD dehydrin, which is the product of a single member of a multigene family, and an increment of chilling tolerance during emergence of cowpea seedlings.
Does Free-Air Carbon Dioxide Enrichment Affect Photochemical Energy Use by Evergreen Trees in Different Seasons? A Chlorophyll Fluorescence Study of Mature Loblolly Pine1
Authors: Hymus Graham J. , Ellsworth David S. , Baker Neil R. , Long Stephen P. 
Published: July 2002

Abstract
Previous studies of the effects of growth at elevated CO2 on energy partitioning in the photosynthetic apparatus have produced conflicting results. The hypothesis was developed and tested that elevated CO2increases photochemical energy use when there is a high demand for assimilates and decreases usage when demand is low. Modulated chlorophyll a fluorescence and leaf gas exchange were measured on needles at the top of a mature, 12-m loblolly pine (Pinus taeda L.) forest. Trees were exposed to ambient CO2 or ambient plus 20 Pa CO2 using free-air CO2 enrichment. During April and August, periods of shoot growth, light-saturated photosynthesis and linear electron transport were increased by elevated CO2. In November, when growth had ceased but temperatures were still moderate, CO2treatment had no significant effect on linear electron transport. In February, when low temperatures were likely to inhibit translocation, CO2 treatment caused a significant decrease in linear electron transport. This coincided with a slower recovery of the maximum photosystem II efficiency on transfer of needles to the shade, indicating that growth in elevated CO2 induced a more persistent photoinhibition. Both the summer increase and the winter decrease in linear electron transport in elevated CO2resulted from a change in photochemical quenching, not in the efficiency of energy transfer within the photosystem II antenna. There was no evidence of any effect of CO2 on photochemical energy sinks other than carbon metabolism. Our results suggest that elevated CO2 may increase the effects of winter stress on evergreen foliage.
Changes in Cytosolic pH within Arabidopsis Root Columella Cells Play a Key Role in the Early Signaling Pathway for Root Gravitropism
Authors: Scott Amie Caroline , Allen Nina Strömgren 
Published: July 2002

Abstract
Ratiometric wide-field fluorescence microscopy with 1′,7′- bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF)-dextran demonstrated that gravistimulation leads to rapid changes in cytoplasmic pH (pHc) in columella cells of Arabidopsis roots. The pHc of unstimulated columella cells in tiers 2 and 3, known sites of graviperception (E.B. Blancaflor, J.B. Fasano, S. Gilroy [1998] Plant Physiol 116: 213–222), was 7.22 ± 0.02 pH units. Following gravistimulation, the magnitude and direction of pHc changes in these cells depended on their location in the columella. Cells in the lower side of tier 2 became more alkaline by 0.4 unit within 55 s of gravistimulation, whereas alkalinization of the cells on the upper side was slower (100 s). In contrast, all cells in tier 3 acidified by 0.4 pH unit within 480 s after gravistimulation. Disrupting these pHc changes in the columella cells using pHc modifiers at concentrations that do not affect root growth altered the gravitropic response. Acidifying agents, including bafilomycin A1, enhanced curvature, whereas alkalinizing agents disrupted gravitropic bending. These results imply that pHc changes in the gravisensing cells and the resultant pH gradients across the root cap are important at an early stage in the signal cascade leading to the gravitropic response.
Abscisic Acid Inhibition of Radicle Emergence But Not Seedling Growth Is Suppressed by Sugars
Authors: Finkelstein Ruth R. , Lynch Tim J. 
Published: July 2002

Abstract
Low concentrations of sugars altered the sensitivity of seed germination to inhibition by exogenous abscisic acid (ABA). Germination of wild-type and ABA-insensitive (abi) Arabidopsis seeds was assayed on media containing ABA and a variety of sugars and sugar alcohols. The inhibitory effects of ABA were strongly repressed in the presence of 15 to 90 mm glucose (Glc), sucrose, or fructose, but not by comparable concentrations of sorbitol or mannitol. Several features of the response to Glc are inconsistent with a purely nutritional effect: The optimal sugar concentration is low and differs between the wild type and the abi mutants. Furthermore, Glc suppression of ABA inhibition is light dependent and limited to the process of radicle emergence.
A Stress-Inducible Gene for 9-cis-Epoxycarotenoid Dioxygenase Involved in Abscisic Acid Biosynthesis under Water Stress in Drought-Tolerant Cowpea
Authors: Iuchi Satoshi , Kobayashi Masatomo , Yamaguchi-Shinozaki Kazuko , Shinozaki Kazuo 
Published: July 2002

Abstract
Four cDNA clones named CPRD (cowpea responsive to dehydration) corresponding to genes that are responsive to dehydration were isolated using differential screening of a cDNA library prepared from 10-h dehydrated drought-tolerant cowpea (Vigna unguiculata) plants. One of the cDNA clones has a homology to 9-cis-epoxycarotenoid dioxygenase (named VuNCED1), which is supposed to be involved in abscisic acid (ABA) biosynthesis. The GST (glutathioneS-transferase)-fused protein indicates a 9-cis-epoxycarotenoid dioxygenase activity, which catalyzes the cleavage of 9-cis-epoxycarotenoid. The N-terminal region of the VuNCED1 protein directed the fused sGFP (synthetic green-fluorescent protein) into the plastids of the protoplasts, indicating that the N-terminal sequence acts as a transit peptide. Both the accumulation of ABA and expression of VuNCED1 were strongly induced by drought stress in the 8-d-old cowpea plant, whereas drought stress did not trigger the expression of VuABA1 (accession no.AB030295) gene that encodes zeaxanthin epoxidase. These results indicate that the VuNCED1 cDNA encodes a 9-cis-epoxycarotenoid dioxygenase and that its product has a key role in the synthesis of ABA under drought stress.
Alteration of the Adenine Nucleotide Response and Increased Rubisco Activation Activity of Arabidopsis Rubisco Activase by Site-Directed Mutagenesis
Authors: Kallis Russell P. , Ewy Robert G. , Portis Archie R. 
Published: July 2002

Abstract
Arabidopsis Rubisco was activated in vitro at rates 2- to 3-fold greater by recombinant Arabidopsis 43-kD Rubisco activase with the amino acid replacements Q111E and Q111D in a phosphate-binding loop, G-G-K-G-Q-G-K-S. However, these two mutant enzymes had only slightly greater rates of ATP hydrolysis. Activities of the Q111D enzyme were much less sensitive and those of Q111E were somewhat less sensitive to inhibition by ADP. Both mutant enzymes exhibited higher Rubisco activation activities over the physiological range of ADP to ATP ratios. Enzymes with non-polar, polar, and basic residues substituted at position Gln-111 exhibited rates of Rubisco activation less than the wild-type enzyme. Estimates of the relative affinity of the wild type and the Q111D, Q111E, and Q111S enzymes for adenosine nucleotides by a variety of methods revealed that the nucleotide affinities were the most diminished in the Q111D enzyme. The temperature stability of the Q111D and Q111E enzymes did not differ markedly from that of the 43-kD recombinant wild-type enzyme, which is somewhat thermolabile. The Q111D and Q111E enzymes, expressed in planta, may provide a means to better define the role of the ADP to ATP ratio in the regulation of Rubisco activation and photosynthesis rate.
Post-Transcriptional Maturation of the S Receptor Kinase ofBrassicaCorrelates with Co-Expression of theS-Locus Glycoprotein in the Stigmas of TwoBrassicaStrains and in Transgenic Tobacco Plants
Authors: Dixit Ram , Nasrallah Mikhail E. , Nasrallah June B. 
Published: July 2002

AbstractThe S-locus-encoded S receptor kinase (SRK) is an intrinsic plasma membrane protein that is viewed as the primary stigma determinant of specificity in the self-incompatibility response ofBrassica spp. We analyzed two self-compatible mutant strains that express low levels of the S-locus glycoprotein (SLG), a cell wall-localized protein also encoded at theS locus that is coordinately expressed with SRK. We found that mutant stigmas synthesized wild-type levels ofSRK transcripts but failed to produce SRK protein at any of the developmental stages analyzed. Furthermore, SRK was shown to form aberrant high-molecular mass aggregates when expressed alone in transgenic tobacco (Nicotiana tabacum) plants. This aggregation was prevented in tobacco plants that co-expressed SRK and SLG, but not in tobacco plants that co-expressed SRK and SLR1, an SLG-related secreted protein not encoded at the S locus. In analyses of protein extracts under reducing and non-reducing conditions, evidence of intermolecular association was obtained only for SLG, a fraction of which formed disulfide-linked oligomers and was membrane associated. The data indicate that, at least in plants carrying the S haplotypes we analyzed, SRK is an inherently unstable protein and that SLG facilitates its accumulation to physiologically relevant levels in Brassicastigmas.
Arabidopsis Species Hybrids in the Study of Species Differences and Evolution of Amphiploidy in Plants
Authors: Nasrallah Mikhail E. , Yogeeswaran Krithika , Snyder Stephen , Nasrallah June B. 
Published: July 2002

AbstractIt is estimated that 5 million years of evolution separateArabidopsis thaliana from its close relativeArabidopsis lyrata. The two taxa differ by many characteristics, and together they exemplify the differentiation of angiosperms into self-fertilizing and cross-fertilizing species as well as annual and perennial species. Despite their disparate life histories, the two species can be crossed to produce viable and vigorous hybrids exhibiting heterotic effects. Although pollen sterile, the hybrids produce viable ovules and were used as female parent in backcrosses to both parental species. The resulting backcross plants exhibited transgressive variation for a number of interesting developmental and growth traits as well as negative nuclear/cytoplasmic interactions. Moreover, the genesis of a fertile amphidiploid neospecies, apparently by spontaneous somatic doubling in an interspecific hybrid, was observed in the laboratory. The mechanisms responsible for the generation of amphiploids and the subsequent evolution of amphiploid genomes can now be studied through direct observation using the large arsenal of molecular tools available for Arabidopsis.
Regulation of Two Carotenoid Biosynthesis Genes Coding for Phytoene Synthase and Carotenoid Hydroxylase during Stress-Induced Astaxanthin Formation in the Green Alga Haematococcus pluvialis
Authors: Steinbrenner Jens , Linden Hartmut 
Published: July 2002

Abstract
Astaxanthin is a high-value carotenoid used as a pigmentation source in fish aquaculture. In addition, a beneficial role of astaxanthin as a food supplement for humans is becoming evident. The unicellular green alga Haematococcus pluvialis seems to be a suitable source for natural astaxanthin. Astaxanthin accumulation in H. pluvialis occurs in response to environmental stress such as high light and salt stress. Here, the isolation of the H. pluvialis carotenoid biosynthesis gene phytoene synthase is reported. Furthermore, the expression of phytoene synthase and carotenoid hydroxylase, two key enzymes in astaxanthin biosynthesis, was investigated at the transcriptional level. The application of environmental stress resulted in increased steady-state mRNA levels of both genes. High-light intensity led to a transient increase in carotenoid hydroxylase mRNA followed by moderate astaxanthin accumulation. In contrast, salt stress in combination with high light resulted in a sustained increase in both transcripts. The addition of compounds inducing reactive oxygen species did not influence transcript levels of phytoene synthase and carotenoid hydroxylase. The application of an inhibitor of photosynthesis, 3-(3, 4-dichlorophenyl)-1,1-dimethylurea, indicated that the light-induced expression of these carotenoid biosynthesis genes may be under photosynthetic control.
Structures and phase transitions of the A
7PSe6 (A = Ag, Cu) argyrodite-type ionic conductors. III. α-Cu7PSe6
Authors: Gaudin E. , Petricek V. , Boucher F. , Taulelle F. , Evain M. 
Published: July 2002

The crystal structure of the third polymorph of the Cu7PSe6 argyrodite compound, α-Cu7PSe6, heptacopper phosphorus hexaselenide, is determined by means of single-crystal diffraction from twinned crystals and X-ray powder diffraction, with the help of extensive NMR measurements. In the low-temperature form, i.e. below the last phase transition, α-Cu7PSe6 crystallizes in orthorhombic symmetry, space group Pna21, with a = 14.3179 (4), b = 7.1112 (2), c = 10.1023 (3) Å, V = 1028.590 (9) Å3 (deduced from powder data, T = 173 K) and Z = 4. Taking into account a twinning by reticular merohedry, the refinement of the α-Cu7PSe6 structure leads to the residual factors R = 0.0466 and wR = 0.0486 for 127 parameters and 3714 observed, independent reflections (single-crystal data, T = 173 K). A full localization of the Cu+
d
10 element is reached with one twofold-, one threefold- and five fourfold-coordinated Cu atoms. The observation of two phase transitions for Cu7PSe6, to be compared with only one for Ag7PSe6, is attributed to the d
10 element stability in a low coordination environment, copper being less prone to lower coordination sites than silver, especially at low temperature.
Structural similarity to link sequence space: New potential superfamilies and implications for structural genomics
Authors: Aloy Patrick , Oliva Baldomero , Querol Enrique , Aviles Francesc X. , Russell Robert B. 
Published: July 2002

AbstractThe current pace of structural biology now means that protein three‐dimensional structure can be known before protein function, making methods for assigning homology via structure comparison of growing importance. Previous research has suggested that sequence similarity after structure‐based alignment is one of the best discriminators of homology and often functional similarity. Here, we exploit this observation, together with a merger of protein structure and sequence databases, to predict distant homologous relationships. We use the Structural Classification of Proteins (SCOP) database to link sequence alignments from the SMART and Pfam databases. We thus provide new alignments that could not be constructed easily in the absence of known three‐dimensional structures. We then extend the method of Murzin (1993b) to assign statistical significance to sequence identities found after structural alignment and thus suggest the best link between diverse sequence families. We find that several distantly related protein sequence families can be linked with confidence, showing the approach to be a means for inferring homologous relationships and thus possible functions when proteins are of known structure but of unknown function. The analysis also finds several new potential superfamilies, where inspection of the associated alignments and superimpositions reveals conservation of unusual structural features or co‐location of conserved amino acids and bound substrates. We discuss implications for Structural Genomics initiatives and for improvements to sequence comparison methods.