bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Biosynthesis of Salicylic Acid in Potato Plants1
Authors: Coquoz Jean-Luc , Buchala Antony , Métraux Jean-Pierre 
Published: July 2002

Abstract
Spraying potato (Solanum tuberosum L.) leaves with arachidonic acid (AA) at 1500 μg mL−1 led to a rapid local synthesis of salicylic acid (SA) and accumulation of a SA conjugate, which was shown to be 2-O-β-glucopyranosylsalicylic acid. Radiolabeling studies with untreated leaves showed that SA was synthesized from phenylalanine and that both cinnamic and benzoic acid were intermediates in the biosynthesis pathway. Using radiolabeled phenylalanine as a precursor, the specific activity of SA was found to be lower when leaves were treated with AA than in control leaves. Similar results were obtained when leaves were fed with the labeled putative intermediates cinnamic acid and benzoic acid. Application of 2-aminoindan-2-phosphonic acid at 40 μm, an inhibitor of phenylalanine ammonia-lyase, prior to treatment with AA inhibited the local accumulation of SA. When the putative intermediates were applied to leaves in the presence of 2-aminoindan-2-phosphonic acid, about 40% of the expected accumulation of free SA was recovered, but the amount of the conjugate remained constant.
Dehydration-Stress-Regulated Transgene Expression in Stably Transformed Rice Plants1
Authors: Su Jin , Shen Qingxi , David Ho Tuan-Hua , Wu Ray 
Published: July 2002

Abstract
To confer abscisic acid (ABA) and/or stress-inducible gene expression, an ABA-response complex (ABRC1) from the barley (Hordeum vulgare L.) HVA22gene was fused to four different lengths of the 5′ region from the rice (Oryza sativa L.) Act1 gene. Transient assay of β-glucuronidase (GUS) activity in barley aleurone cells shows that, coupled with ABRC1, the shortest minimal promoter (Act1–100P) gives both the greatest induction and the highest level of absolute activity following ABA treatment. Two plasmids with one or four copies of ABRC1 combined with the same Act1–100P and HVA22(I) of barley HVA22 were constructed and used for stable expression of uidA in transgenic rice plants. Three Southern blot-positive lines with the correct hybridization pattern for each construct were obtained. Northern analysis indicated thatuidA expression is induced by ABA, water-deficit, and NaCl treatments. GUS activity assays in the transgenic plants confirmed that the induction of GUS activity varies from 3- to 8-fold with different treatments or in different rice tissues, and that transgenic rice plants harboring four copies of ABRC1 show 50% to 200% higher absolute GUS activity both before and after treatments than those with one copy of ABRC1.
A Novel Gene, pmgA, Specifically Regulates Photosystem Stoichiometry in the CyanobacteriumSynechocystis Species PCC 6803 in Response to High Light1
Authors: Hihara Yukako , Sonoike Kintake , Ikeuchi Masahiko 
Published: July 2002

Abstract
Previously, we identified a novel gene, pmgA, as an essential factor to support photomixotrophic growth of Synechocystis species PCC 6803 and reported that a strain in which pmgA was deleted grew better than the wild type under photoautotrophic conditions. To gain insight into the role of pmgA, we investigated the mutant phenotype of pmgA in detail. When low-light-grown (20 μE m−2 s−1) cells were transferred to high light (HL [200μE m−2s−1]), pmgA mutants failed to respond in the manner typically associated with Synechocystis. Specifically, mutants lost their ability to suppress accumulation of chlorophyll and photosystem I and, consequently, could not modulate photosystem stoichiometry. These phenotypes seem to result in enhanced rates of photosynthesis and growth during short-term exposure to HL. Moreover, mixed-culture experiments clearly demonstrated that loss ofpmgA function was selected against during longer-term exposure to HL, suggesting that pmgA is involved in acquisition of resistance to HL stress. Finally, early induction ofpmgA expression detected by reverse transcriptase-PCR upon the shift to HL led us to conclude that pmgA is the first gene identified, to our knowledge, as a specific regulatory factor for HL acclimation.
Characterization of Two Glutamate Decarboxylase cDNA Clones from Arabidopsis
Authors: Turano Frank J. , Fang Tung K. 
Published: July 2002

Abstract
Two distinct cDNA clones encoding for the glutamate decarboxylase (GAD) isoenzymes GAD1 andGAD2 from Arabidopsis (L.) Heynh. were characterized. The open reading frames for GAD1 and GAD2 were expressed inEscherichia coli and the recombinant proteins were purified by affinity chromatography. Analysis of the recombinant proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis suggest that GAD1 andGAD2 encode for 58- and 56-kD peptides, respectively. The enzymatic activities of the pure recombinant GAD1 and GAD2 proteins were stimulated 35- and 13-fold, respectively, by Ca2+/calmodulin but not by Ca2+ or calmodulin alone. Southern-blot analysis of genomic DNA suggests that there is only one copy of each gene in Arabidopsis. The GAD1transcript and a corresponding 58-kD peptide were detected in roots only. Conversely, the GAD2 transcript and a corresponding 56-kD peptide were detected in all organs tested. The specific activity, GAD2 transcript, and 56-kD peptide increased in leaves of plants treated with 10 mmNH4Cl, 5 mm NH4NO3, 5 mm glutamic acid, or 5 mm glutamine as the sole nitrogen source compared with samples from plants treated with 10 mm KNO3. The results from these experiments suggest that in leaves GAD activity is partially controlled by gene expression or RNA stability. Results from preliminary analyses of different tissues imply that these tendencies were not the same in flower stalks and flowers, suggesting that other factors may control GAD activity in these organs. The results from this investigation demonstrate that GAD activity in leaves is altered by different nitrogen treatments, suggesting that GAD2 may play a unique role in nitrogen metabolism.
Oxalate Exudation by Taro in Response to Al
Authors: Ma Zhong , Miyasaka Susan C. 
Published: July 2002

Abstract
Roots of taro (Colocasia esculenta [L.] Schott cvs Bun-long and Lehua maoli) exuded increasing concentrations of oxalate with increasing Al stress. This exudation was a specific response to excess Al and not to P deficiency. Addition of oxalate to Al-containing solutions ameliorated the toxic effect of Al.
Phytochrome Regulates Gibberellin Biosynthesis during Germination of Photoblastic Lettuce Seeds
Authors: Toyomasu Tomonobu , Kawaide Hiroshi , Mitsuhashi Wataru , Inoue Yasunori , Kamiya Yuji 
Published: July 2002

Abstract
Germination of lettuce (Lactuca sativa L.) seed is regulated by phytochrome. The requirement for red light is circumvented by the application of gibberellin (GA). We have previously shown that the endogenous content of GA1, the main bioactive GA in lettuce seeds, increases after red-light treatment. To clarify which step of GA1synthesis is regulated by phytochrome, cDNAs encoding GA 20-oxidases (Ls20ox1 and Ls20ox2, for L. sativa GA20-oxidase) and 3β-hydroxylases (Ls3h1 and Ls3h2 for L. sativa GA3β-hydroxylase) were isolated from lettuce seeds by reverse-transcription polymerase chain reaction. Functional analysis of recombinant proteins expressed inEscherichia coli confirmed that the Ls20ox and Ls3h encode GA 20-oxidases and 3β-hydroxylases, respectively. Northern-blot analysis showed that Ls3h1 expression was dramatically induced by red-light treatment within 2 h, and that this effect was canceled by a subsequent far-red-light treatment. Ls3h2 mRNA was not detected in seeds that had been allowed to imbibe under any light conditions. Expression of the two Ls20ox genes was induced by initial imbibition alone in the dark. The level of Ls20ox2 mRNA decreased after the red-light treatment, whereas that of Ls20ox1 was unaffected by light. These results suggest that red light promotes GA1synthesis in lettuce seeds by inducing Ls3h1 expression via phytochrome action.
Root Xylem Embolisms and Refilling. Relation to Water Potentials of Soil, Roots, and Leaves, and Osmotic Potentials of Root Xylem Sap1
Authors: McCully Margaret E. 
Published: July 2002

Abstract
Embolism and refilling of vessels was monitored directly by cryomicroscopy of field-grown corn (Zea mays L.) roots. To test the reliability of an earlier study showing embolism refilling in roots at negative leaf water potentials, embolisms were counted, and root water potentials (Ψroot) and osmotic potentials of exuded xylem sap from the same roots were measured by isopiestic psychrometry. All vessels were full at dawn (Ψroot −0.1 MPa). Embolisms were first seen in late metaxylem vessels at 8 am. Embolized late metaxylem vessels peaked at 50% at 10 am (Ψroot −0.1 MPa), fell to 44% by 12 pm (Ψroot −0.23 MPa), then dropped steadily to zero by early evening (Ψroot−0.28 MPa). Transpiration was highest (8.5 μg cm−2s−1) between 12 and 2 pm when the percentage of vessels embolized was falling. Embolized vessels were refilled by liquid moving through their lateral walls. Xylem sap was very low in solutes. The mechanism of vessel refilling, when Ψroot is negative, requires further investigation. Daily embolism and refilling in roots of well-watered plants is a normal occurrence and may be a component of an important hydraulic signaling mechanism between roots and shoots.
Abscisic Acid Induction of Vacuolar H+-ATPase Activity in Mesembryanthemum crystallinum Is Developmentally Regulated1
Authors: Barkla Bronwyn J. , Vera-Estrella Rosario , Maldonado-Gama Minerva , Pantoja Omar 
Published: July 2002

Abstract
Abscisic acid (ABA) has been implicated as a key component in water-deficit-induced responses, including those triggered by drought, NaCl, and low- temperature stress. In this study a role for ABA in mediating the NaCl-stress-induced increases in tonoplast H+-translocating ATPase (V-ATPase) and Na+/H+ antiport activity in Mesembryanthemum crystallinum, leading to vacuolar Na+ sequestration, were investigated. NaCl or ABA treatment of adult M. crystallinum plants induced V-ATPase H+ transport activity, and when applied in combination, an additive effect on V-ATPase stimulation was observed. In contrast, treatment of juvenile plants with ABA did not induce V-ATPase activity, whereas NaCl treatment resulted in a similar response to that observed in adult plants. Na+/H+ antiport activity was induced in both juvenile and adult plants by NaCl, but ABA had no effect at either developmental stage. Results indicate that ABA-induced changes in V-ATPase activity are dependent on the plant reaching its adult phase, whereas NaCl-induced increases in V-ATPase and Na+/H+ antiport activity are independent of plant age. This suggests that ABA-induced V-ATPase activity may be linked to the stress-induced, developmentally programmed switch from C3 metabolism to Crassulacean acid metabolism in adult plants, whereas, vacuolar Na+ sequestration, mediated by the V-ATPase and Na+/H+ antiport, is regulated through ABA-independent pathways.
A Plastidial Lysophosphatidic Acid Acyltransferase from Oilseed Rape1
Authors: Bourgis Fabienne , Kader Jean-Claude , Barret Pierre , Renard Michel , Robinson David , Robinson Colin , Delseny Michel , Roscoe Thomas J. 
Published: July 2002

Abstract
The biosynthesis of phosphatidic acid, a key intermediate in the biosynthesis of lipids, is controlled by lysophosphatidic acid (LPA, or 1-acyl-glycerol-3-P) acyltransferase (LPAAT, EC 2.3.1.51). We have isolated a cDNA encoding a novel LPAAT by functional complementation of the Escherichia coli mutant plsC with an immature embryo cDNA library of oilseed rape (Brassica napus). Transformation of the acyltransferase-deficientE. coli strain JC201 with the cDNA sequence BAT2 alleviated the temperature-sensitive phenotype of theplsC mutant and conferred a palmitoyl-coenzyme A-preferring acyltransferase activity to membrane fractions. The BAT2 cDNA encoded a protein of 351 amino acids with a predicted molecular mass of 38 kD and an isoelectric point of 9.7. Chloroplast-import experiments showed processing of a BAT2 precursor protein to a mature protein of approximately 32 kD, which was localized in the membrane fraction. BAT2 is encoded by a minimum of two genes that may be expressed ubiquitously. These data are consistent with the identity of BAT2 as the plastidial enzyme of the prokaryotic glycerol-3-P pathway that uses a palmitoyl-ACP to produce phosphatidic acid with a prokaryotic-type acyl composition. The homologies between the deduced protein sequence of BAT2 with prokaryotic and eukaryotic microsomal LAP acytransferases suggest that seed microsomal forms may have evolved from the plastidial enzyme.
Observations of Hydrogen and Oxygen Isotopes in Leaf Water Confirm the Craig-Gordon Model under Wide-Ranging Environmental Conditions1
Authors: Roden John S. , Ehleringer James R. 
Published: July 2002

Abstract
The Craig-Gordon evaporative enrichment model of the hydrogen (δD) and oxygen (δ18O) isotopes of water was tested in a controlled-environment gas exchange cuvette over a wide range (400‰ δD and 40‰ δ18O) of leaf waters. (Throughout this paper we use the term “leaf water” to describe the site of evaporation, which should not be confused with “bulk leaf water” a term used exclusively for uncorrected measurements obtained from whole leaf water extractions.) Regardless of how the isotopic composition of leaf water was achieved (i.e. by changes in source water, atmospheric vapor δD or δ18O, vapor pressure gradients, or combinations of all three), a modified version of the Craig-Gordon model was shown to be sound in its ability to predict the δD and δ18O values of water at the site of evaporation. The isotopic composition of atmospheric vapor was shown to have profound effects on the δD and δ18O of leaf water and its influence was dependent on vapor pressure gradients. These results have implications for conditions in which the isotopic composition of atmospheric vapor is not in equilibrium with source water, such as experimental systems that grow plants under isotopically enriched water regimes. The assumptions of steady state were also tested and found not to be a major limitation for the utilization of the leaf water model under relatively stable environmental conditions. After a major perturbation in the δD and δ18O of atmospheric vapor, the leaf reached steady state in approximately 2 h, depending on vapor pressure gradients. Following a step change in source water, the leaf achieved steady state in 24 h, with the vast majority of changes occurring in the first 3 h. Therefore, the Craig-Gordon model is a useful tool for understanding the environmental factors that influence the hydrogen and oxygen isotopic composition of leaf water as well as the organic matter derived from leaf water.
Roles of Sugar Alcohols in Osmotic Stress Adaptation. Replacement of Glycerol by Mannitol and Sorbitol in Yeast
Authors: Shen Bo , Hohmann Stefan , Jensen Richard G. , Bohnert and Hans J. 
Published: July 2002

Abstract
For many organisms there is a correlation between increases of metabolites and osmotic stress tolerance, but the mechanisms that cause this protection are not clear. To understand the role of polyols, genes for bacterial mannitol-1-P dehydrogenase and apple sorbitol-6-P dehydrogenase were introduced into a Saccharomyces cerevisiae mutant deficient in glycerol synthesis. Sorbitol and mannitol provided some protection, but less than that generated by a similar concentration of glycerol generated by glycerol-3-P dehydrogenase (GPD1). Reduced protection by polyols suggested that glycerol had specific functions for which mannitol and sorbitol could not substitute, and that the absolute amount of the accumulating osmoticum might not be crucial. The retention of glycerol and mannitol/sorbitol, respectively, was a major difference. During salt stress, cells retained more of the six-carbon polyols than glycerol. We suggest that the loss of &gt;98% of the glycerol synthesized could provide a safety valve that dissipates reducing power, while a similar high intracellular concentration of retained polyols would be less protective. To understand the role of glycerol in salt tolerance, salt-tolerant suppressor mutants were isolated from the glycerol-deficient strain. One mutant, sr13, partially suppressed the salt-sensitive phenotype of the glycerol-deficient line, probably due to a doubling of [K+] accumulating during stress. We compare these results to the “osmotic adjustment” concept typically applied to accumulating metabolites in plants. The accumulation of polyols may have dual functions: facilitating osmotic adjustment and supporting redox control.
Stimulation of Border Cell Production in Response to Increased Carbon Dioxide Levels
Authors: Zhao Xiaowen , Misaghi Iraj J. , Hawes Martha C. 
Published: July 2002

AbstractField soil atmospheres have higher CO2 and lower O2 concentrations compared with ambient atmosphere, but little is known about the impact of such conditions on root exudation patterns. We used altered levels of CO2 and O2 relative to ambient conditions to examine the influence of the atmosphere on the production of root border cells by pea (Pisum sativum) root tips. During germination, atmospheres with high CO2 and low O2 inhibited root development and border cell separation in pea seedlings. Later in development, the same atmospheric composition stimulated border cell separation without significantly influencing root growth. Increased CO2, not low O2, was responsible for the observed stimulation of border cell number. High CO2 apparently can override endogenous signals that regulate the number of border cells released from pea roots into the rhizosphere. The same conditions that stimulated border cell production in pea had no such effect in alfalfa (Medicago sativa).
A Small Heat Shock Protein Cooperates with Heat Shock Protein 70 Systems to Reactivate a Heat-Denatured Protein
Authors: Lee Garrett J. , Vierling Elizabeth 
Published: July 2002

AbstractSmall heat shock proteins (sHsps) are a diverse group of heat-induced proteins that are conserved in prokaryotes and eukaryotes and are especially abundant in plants. Recent in vitro data indicate that sHsps act as molecular chaperones to prevent thermal aggregation of proteins by binding non-native intermediates, which can then be refolded in an ATP-dependent fashion by other chaperones. We used heat-denatured firefly luciferase (Luc) bound to pea (Pisum sativum) Hsp18.1 as a model to define the minimum chaperone system required for refolding of a sHsp-bound substrate. Heat-denatured Luc bound to Hsp18.1 was effectively refolded either with Hsc/Hsp70 from diverse eukaryotes plus the DnaJ homologs Hdj1 and Ydj1 (maximum = 97% Luc reactivation with k ob = 1.0 × 10−2/min), or with prokaryotic Escherichia coli DnaK plus DnaJ and GrpE (100% Luc reactivation,k ob = 11.3 × 10−2/min). Furthermore, we show that Hsp18.1 is more effective in preventing Luc thermal aggregation than the Hsc70 or DnaK systems, and that Hsp18.1 enhances the yields of refolded Luc even when other chaperones are present during heat inactivation. These findings integrate the aggregation-preventive activity of sHsps with the protein-folding activity of the Hsp70 system and define an in vitro system for further investigation of the mechanism of sHsp action.
Response to Xanthomonas campestris pv.vesicatoria in Tomato Involves Regulation of Ethylene Receptor Gene Expression
Authors: Ciardi Joseph A. , Tieman Denise M. , Lund Steven T. , Jones Jeffrey B. , Stall Robert E. , Klee Harry J. 
Published: July 2002

Abstract
Although ethylene regulates a wide range of defense-related genes, its role in plant defense varies greatly among different plant-microbe interactions. We compared ethylene's role in plant response to virulent and avirulent strains of Xanthomonas campestrispv. vesicatoria in tomato (Lycopersicon esculentum Mill.). The ethylene-insensitive Never ripe (Nr) mutant displays increased tolerance to the virulent strain, while maintaining resistance to the avirulent strain. Expression of the ethylene receptor genes NR andLeETR4 was induced by infection with both virulent and avirulent strains; however, the induction of LeETR4expression by the avirulent strain was blocked in the Nrmutant. To determine whether ethylene receptor levels affect symptom development, transgenic plants overexpressing a wild-typeNR cDNA were infected with virulent X. campestris pv. vesicatoria. Like theNr mutant, the NR overexpressors displayed greatly reduced necrosis in response to this pathogen.NR overexpression also reduced ethylene sensitivity in seedlings and mature plants, indicating that, like LeETR4, this receptor is a negative regulator of ethylene response. Therefore, pathogen-induced increases in ethylene receptors may limit the spread of necrosis by reducing ethylene sensitivity.
The Role of the Arabidopsis ELD1 Gene in Cell Development and Photomorphogenesis in Darkness
Authors: Cheng Jin-Chen , Lertpiriyapong Kvin , Wang Susanna , Sung Zinmay Renee 
Published: July 2002

Abstract
Because cell growth and differentiation are regulated by complex interactions among different signaling pathways, a growth defect affects subsequent differentiation. We report on a growth-defective mutant of Arabidopsis, called eld1 (elongation defective 1). Cell elongation was impaired in every organ examined. Later characteristics of the eld1 phenotype include defective vascular tissue differentiation, the inability to grow in soil, ectopic deposition of suberin around twisted vascular bundles, the de-etiolation phenotype, and continuation of shoot development and flowering in the dark. The dwarf phenotype of eld1 could not be rescued by treatment with exogenous growth regulators. Because defective cell elongation is the earliest and most universal feature detected in eld1 mutants, control of or activity in cell elongation may be the primary function of the ELD1 gene. The impaired cell growth results in pleiotropic effects on cell proliferation and differentiation, and the retardation in hypocotyl elongation enables growth and development in darkness.
Auxin Inhibition of Decapitation-Induced Branching Is Dependent on Graft-Transmissible Signals Regulated by GenesRms1andRms2
Authors: Beveridge Christine A. , Symons Gregory M. , Turnbull Colin G.N. 
Published: July 2002

AbstractDecapitation-induced axillary bud outgrowth is a vital mechanism whereby shoots are able to continue normal growth and development. In many plants, including wild-type garden pea (Pisum sativum L.), this process can be inhibited by exogenous auxin. Using the ramosus (rms) increased branching mutants of pea, we present evidence that this response to auxin is dependent on graft-transmissible substance(s) regulated by the genes Rms1 and Rms2. The response to exogenous auxin is massively diminished in decapitatedrms1 and rms2 mutant plants. However, basipetal auxin transport is not reduced in intact or decapitated mutants. Grafting rms1 or rms2 shoots onto wild-type rootstocks restored the auxin response, indicating thatRms1 and Rms2 gene action in the rootstock is sufficient to enable an auxin response in mutant shoots. We conclude that Rms1 and Rms2 act in the rootstock and shoot to control levels of mobile substance(s) that interact with exogenous auxin in the inhibition of bud outgrowth after decapitation. At least for rms1, the reduced auxin response is unlikely to be due to an inability of auxin to decrease xylem sap cytokinin content, as this is already low in intactrms1 plants. Consequently, we have genetic evidence that auxin action in decapitated plants depends on at least one novel long-distance signal.