bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential Regulation of Trichome Formation on the Adaxial and Abaxial Leaf Surfaces by Gibberellins and Photoperiod in Arabidopsis thaliana (L.) Heynh
Authors: Chien J. C. , Sussex I. M. 
Published: July 2002

Abstract
In wild-type (WT) Columbia and Landsberg erecta ecotypes of Arabidopsis thaliana (L.) Heynh., trichomes are present on the adaxial surfaces of all rosette leaves but are absent from the abaxial surfaces of the first-formed leaves. We have determined that both long-day (LD) photoperiod and gibberellin (GA) stimulate trichome formation. WT plants grown in LD conditions produce the first abaxial trichome on earlier leaves than plants grown in short-day (SD) conditions. Photoperiod sensitivity of abaxial trichome formation on WT plants develops gradually over time, reaching the maximum sensitivity about 24 d after germination. Application of gibberellic acid to WT plants growing in SD conditions accelerates the onset of abaxial trichomes. Conversely, application of 20 to 80 mg L-1 paclobutrazol, a GA biosynthesis inhibitor, to wild-type plants suppresses trichome initiation on the abaxial epidermis. The GA-deficient mutants ga1–5 and ga4–1 and the GA-insensitive mutant gai-1 exhibit delayed onset of abaxial trichomes when grown in LD conditions. The null mutant ga1–3 produces completely glabrous leaves when grown in SD conditions. Application of gibberellic acid to glabrous ga1–3 plants consistently induces earlier formation of trichomes on the adaxial epidermis than on the abaxial epidermis, demonstrating a difference between the adaxial and abaxial surfaces in their response to GA with regard to trichome formation.
Al Toxicity in Yeast (A Role for Mg?)
Authors: MacDiarmid C. W. , Gardner R. C. 
Published: July 2002

Abstract
We have established conditions in which soluble Al is toxic to the yeast Saccharomyces cerevisiae. The major modifications to a standard synthetic medium were lowering the pH and the concentration of Mg ions. Alterations to the PO4, Ca, or K concentration had little effect on toxicity. Organic acids known to chelate Al reduced its toxicity, suggesting that Al3+ is the toxic Al species. The unique ability of Mg ions to ameliorate Al toxicity led us to investigate the hypothesis that Al inhibits Mg uptake by yeast. Yeast cells accumulate Mg, Co, Zn, Ni, and Mn ions via the same transport system (G.F. Fuhrmann, A. Rothstein [1968] Biochim Biophys Acta 163: 325–330). Al3+ inhibited the accumulation of 57Co2+ by yeast cells more effectively than Ga, La, or Mg. In addition, a mutant yeast strain with a defect in divalent cation uptake proved to be more sensitive to Al than a wild-type strain. Taken together, these results suggest that Al may cause Mg deficiency in yeast by blocking Mg transport. We discuss the relevance of yeast as a model for the study of Al toxicity in plant systems.
Functional Analysis of a Brassica oleracea SLR1 Gene Promoter
Authors: Hackett R. M. , Cadwallader G. , Franklin FCH. 
Published: July 2002

Abstract
The Brassica oleracea S-locus-related gene 1 (SLR1) is expressed in the papillar cells of Brassica stigmas from a few days before anthesis. We have previously shown that a 1500-bp fragment of the SLR1 gene promoter is sufficient to direct high-level, temporally regulated expression of the β-glucuronidase reporter gene in the pistils of transgenic tobacco. We have carried out a deletion analysis of the SLR1 promoter and found that elements required for pistil expression are located between -258 and -327 bp (relative to the translation start site). Furthermore, specific binding of pistil nuclear factors to sequences within this region was demonstrated by gel retardation analysis. Sequences between -1350 and -1500 were found to be required for high-level expression.
Identification of a Receptor-Like Protein Kinase Gene Rapidly Induced by Abscisic Acid, Dehydration, High Salt, and Cold Treatments in Arabidopsis thaliana
Authors: Hong S. W. , Jon J. H. , Kwak J. M. , Nam H. G. 
Published: July 2002

Abstract
A cDNA clone for a receptor-like protein kinase gene (RPK1) was isolated from Arabidopsis thaliana. The clone is 1952 bp long with 1623 bp of an open reading frame encoding a peptide of 540 amino acids. The deduced peptide (RPK1) contains four distinctive domains characteristic of receptor kinases: (a) a putative amino-terminal signal sequence domain; (b) a domain with five extracellular leucine-rich repeat sequences; (c) a membrane-spanning domain; and (d) a cytoplasmic protein kinase domain that contains all of the 11 subdomains conserved among protein kinases. The RPK1 gene is expressed in flowers, stems, leaves, and roots. Expression of the RPK1 gene is induced within 1 h after treatment with abscisic acid (ABA). The gene is also rapidly induced by several environmental stresses such as dehydration, high salt, and low temperature, suggesting that the gene is involved in a general stress response. The dehydration-induced expression is not impaired in aba-1, abi1–1, abi2–1, and abi3–1 mutants, suggesting that the dehydration-induced expression of the RPK1 gene is ABA-independent. A possible role of this gene in the signal transduction pathway of ABA and the environmental stresses is discussed.
Importin α- from Arabidopsis thaliana Is a Nuclear Import Receptor That Recognizes Three Classes of Import Signals
Authors: Smith HMS. , Hicks G. R. , Raikhel N. V. 
Published: July 2002

Abstract
Protein import into the nucleus is a two-step process. In vitro import systems from vertebrate cell extracts have shown that several soluble factors are required. One of these factors is the receptor importin α-, which binds to nuclear localization signals (NLS) in vitro. We previously cloned an importin α- homolog from Arabidopsis thaliana (At-IMPα-) and demonstrated that this protein was not depleted from tobacco (Nicotiana tabacum) protoplasts after permeabilization of the plasma membrane (Hicks et al., 1996). To determine if At-IMPα- is functional, we used an in vitro NLS-binding assay. We found that At-IMPα- binding is specific, and the receptor is able to recognize three classes of NLS identified in plants. Purified antibodies to At-IMPα- were used to determine the in vivo location of importin α- in tobacco protoplasts. Importin α- is found in the cytoplasm and nucleus, and it is most highly concentrated at the nuclear envelope. The biochemical properties of nuclear importin α- and localization studies using purified nuclei demonstrate that importin α- is tightly associated with the plant nucleus. Moreover, these results suggest that a fraction of nuclear importin α- interacts with the nuclear pore complex.
Overexpression of the FAD3 Desaturase Gene in a Mutant of Arabidopsis
Authors: Shah S. , Xin Z. , Browse J. 
Published: July 2002

Abstract
A mutant of Arabidopsis contained increased levels of 18:3 fatty acids and correspondingly decreased levels of 18:2. The fatty acid phenotype was strongly expressed in root and seed tissues and this observation, together with other data, suggested that the mutation leads to increased activity of the endoplasmic reticulum 18:2 desaturase encoded by the FAD3 gene. Gel-blot analysis of RNA from wild-type and mutant plants established that FAD3 transcript levels were increased 80% in the mutant relative to the wild type. Genetic analysis demonstrated a linkage between the new mutation and the fad3 locus. Linkage of the mutation to fad3 raises the possibility that the lesion is an alteration to the promoter or another regulatory region of the FAD3 gene, which results in increased transcription.
Two Homologous Low-Temperature-Inducible Genes from Arabidopsis Encode Highly Hydrophobic Proteins
Authors: Capel J. , Jarillo J. A. , Salinas J. , Martinez-Zapater J. M. 
Published: July 2002

Abstract
We have characterized two related cDNAs (RCI2A and RCI2B) corresponding to genes from Arabidopsis thaliana, the expression of which is transiently induced by low, nonfreezing temperatures. RCI2A and RCI2B encode small (54 amino acids), highly hydrophobic proteins that bear two potential transmembrane domains. They show similarity to proteins encoded by genes from barley (Hordeum vulgare L.) and wheatgrass (Lophophyrum elongatum) that are regulated by different stress conditions. Their high level of sequence homology (78%) and their genomic location in a single restriction fragment suggest that both genes originated as a result of a tandem duplication. However, their regulatory sequences have diverged enough to confer on them different expression patterns. Like most of the cold-inducible plant genes characterized, the expression of RCI2A and RCI2B is also promoted by abscisic acid (ABA) and dehydration but is not a general response to stress conditions, since it is not induced by salt stress or by anaerobiosis. Furthermore, low temperatures are able to induce RCI2A and RCI2B expression in ABA-deficient and -insensitive genetic backgrounds, indicating that both ABA-dependent and -independent pathways regulate the low-temperature responsiveness of these two genes.
bor1-1, an Arabidopsis thaliana Mutant That Requires a High Level of Boron
Authors: Noguchi K. , Yasumori M. , Imai T. , Naito S. , Matsunaga T. , Oda H. , Hayashi H. , Chino M. , Fujiwara T. 
Published: July 2002

Abstract
bor1–1 (high boron requiring), an Arabidopsis thaliana mutant that requires a high level of B, was isolated. When the B concentration in the medium was reduced to 3 [mu]M, the expansion of rosette leaves was severely affected in bor1–1 but not in wild-type plants. In a medium containing 30 [mu]M B the mutant grew normally but showed female sterility, whereas the wild type was able to set seeds. These defects of the bor1–1 mutant were not detected with supplementation of 100 [mu]M B. In vivo concentrations of B in bor1–1 mutants were lower than those of the wild type, especially in the inflorescence stems. Tracer experiments using 10B suggested that the mutant has defects in uptake and/or translocation of B. The mutation was mapped on the lower arm of chromosome 2.
Developmental and Hormonal Regulation of the Arabidopsis CER2 Gene That Codes for a Nuclear-Localized Protein Required for the Normal Accumulation of Cuticular Waxes
Authors: Xia Y. , Nikolau B. J. , Schnable P. S. 
Published: July 2002

Abstract
The previously cloned CER2 gene is required for the normal accumulation of cuticular waxes and encodes a novel protein. Earlier reports suggested that the CER2 protein is either a membrane-bound component of the fatty acid elongase complex or a regulatory protein. Cell fractionation and immunoblot analyses using polyclonal antibodies raised against a chemically synthesized peptide with a sequence based on the predicted CER2 protein sequence have demonstrated that the 47-kD CER2 protein is soluble and nuclear localized. These results are consistent with CER2 being a regulatory protein. Detailed studies of plants harboring a CER2 promoter/GUS transgene (CER2-GUS), in combination with immunoblot analyses, revealed that CER2 is expressed and the CER2 protein accumulates in a variety of organs and cell types. Expression is highest early in the development of these organs and is epidermis specific in most tissues. In agreement with the activity of the CER2 promoter in hypocotyls, cuticular wax accumulates on this organ in a CER2-dependent fashion. In leaves CER2 expression is confined to the guard cells, trichomes, and petioles. However, application of the cytokinin 6-benzylaminopurine induces ectopic expression of CER2-GUS in all cell types of leaves that emerge following treatment.
Sequencing, Genomic Organization, and Preliminary Promoter Analysis of a Black Cherry (R)-(+)-Mandelonitrile Lyase Gene
Authors: Hu Z. , Poulton J. E. 
Published: July 2002

Abstract
The flavoprotein (R)-(+)-mandelonitrile lyase (MDL; EC 4.1.2.10) plays a key role in cyanogenesis in rosaceous stone fruits. An MDL gene (mdl3) and its corresponding cDNA (MDL3) were isolated from black cherry (Prunus serotina) and characterized. The mdl3 gene contains 2292 bp of the 5[prime] flanking region, the entire coding region, and 300 bp of the 3[prime] flanking region. The coding region is interrupted by three short introns, of which one possesses the unusual GC-AG splice junction dinucleotides. This gene encodes a polypeptide of 573 amino acids that includes a putative signal sequence, 13 potential N-glycosylation sites, and a presumptive flavin adenine dinucleotide-binding site. To determine whether the 5[prime] flanking region of the mdl3 gene is capable of driving MDL expression, it was fused to the β-glucuronidase reporter gene for Agrobacterium-mediated transformation into tobacco. Matching endogenous MDL expression patterns, β-glucuronidase staining was observed in maturing embryos and seeds; it also occurred in postembryonic tissues, especially in association with vascular tissues. After developing a homologous transient transformation system to facilitate identification of putative regulatory sequences, we demonstrated that 125 bp (-107 to +18) of the 5[prime] flanking sequence of the mdl3 gene is sufficient for MDL expression in protoplasts derived from immature black cherry embryos.
Molecular and Enzymatic Characterization of Three Phosphoinositide-Specific Phospholipase C Isoforms from Potato1
Authors: Kopka Joachim , Pical Christophe , Gray Julie E. , Müller-Röber Bernd 
Published: July 2002

Abstract
Many cellular responses to stimulation of cell-surface receptors by extracellular signals are transmitted across the plasma membrane by hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2), which is cleaved into diacylglycerol and inositol-1,4,5-tris-phosphate by phosphoinositide-specific phospholipase C (PI-PLC). We present structural, biochemical, and RNA expression data for three distinct PI-PLC isoforms, StPLC1, StPLC2, and StPLC3, which were cloned from a guard cell-enriched tissue preparation of potato (Solanum tuberosum) leaves. All three enzymes contain the catalytic X and Y domains, as well as C2-like domains also present in all PI-PLCs. Analysis of the reaction products obtained from PIP2 hydrolysis unequivocally identified these enzymes as genuine PI-PLC isoforms. Recombinant StPLCs showed an optimal PIP2-hydrolyzing activity at 10 μm Ca2+ and were inhibited by Al3+ in equimolar amounts. In contrast to PI-PLC activity in plant plasma membranes, however, recombinant enzymes could not be activated by Mg2+. All three stplc genes are expressed in various tissues of potato, including leaves, flowers, tubers, and roots, and are affected by drought stress in a gene-specific manner.
Synthesis and Phosphorylation of Maize Acidic Ribosomal Proteins1
Authors: Aguilar Raúl , Montoya Leonel , Sánchez de Jiménez Estela 
Published: July 2002

Abstract
The objective of this research was to determine the role of acidic ribosomal protein (ARP) phosphorylation in translation. Ribosomes (Rbs) from germinated maize (Zea mays L.) axes had four ARP bands within 4.2 to 4.5 isoelectric points when analyzed by isoelectric focusing. Two of these bands disappeared after alkaline phosphatase hydrolysis. During germination a progressive change from nonphosphorylated (0 h) to phosphorylated ARP (24 h) forms was observed in the Rbs; a free cytoplasmic pool of nonphosphorylated ARPs was also identified by immunoblot and isoelectric focusing experiments. De novo ARP synthesis initiated very slowly early in germination, whereas ARP phosphorylation occurred rapidly within this period. ARP-phosphorylated versus ARP-nonphosphorylated Rbs were tested in an in vitro reticulocyte lysate translation system. Greater in vitro mRNA translation rates were demonstrated for the ARP-phosphorylated Rbs than for the non-ARP-phosphorylated ones. Rapamycin application to maize axes strongly inhibited S6 ribosomal protein phosphorylation, but did not interfere with the ARP phosphorylation reaction. We conclude that ARP phosphorylation does not depend on ARP synthesis or on ARP assembly into Rbs. Rather, this process seems to be part of a translational regulation mechanism.
Structural Analysis and Molecular Model of a Self-Incompatibility RNase from Wild Tomato1
Authors: Parry Simon , Newbigin Ed , Craik David , Nakamura Kazuo T. , Bacic Antony , Oxley David 
Published: July 2002

Abstract
Self-incompatibility RNases (S-RNases) are an allelic series of style glycoproteins associated with rejection of self-pollen in solanaceous plants. The nucleotide sequences of S-RNase alleles from several genera have been determined, but the structure of the gene products has only been described for those from Nicotiana alata. We report on the N-glycan structures and the disulfide bonding of the S3-RNase from wild tomato (Lycopersicon peruvianum) and use this and other information to construct a model of this molecule. The S3-RNase has a singleN-glycosylation site (Asn-28) to which one of threeN-glycans is attached. S3-RNase has seven Cys residues; six are involved in disulfide linkages (Cys-16-Cys-21, Cys-46-Cys-91, and Cys-166-Cys-177), and one has a free thiol group (Cys-150). The disulfide-bonding pattern is consistent with that observed in RNase Rh, a related RNase for which radiographic-crystallographic information is available. A molecular model of the S3-RNase shows that four of the most variable regions of the S-RNases are clustered on one surface of the molecule. This is discussed in the context of recent experiments that set out to determine the regions of the S-RNase important for recognition during the self-incompatibility response.
Cloning of Sucrose:Sucrose 1-Fructosyltransferase from Onion and Synthesis of Structurally Defined Fructan Molecules from Sucrose1
Authors: Vijn Irma , van Dijken Anja , Lüscher Marcel , Bos Antoine , Smeets Edward , Weisbeek Peter , Wiemken Andres , Smeekens Sjef 
Published: July 2002

Abstract
Sucrose (Suc):Suc 1-fructosyltransferase (1-SST) is the key enzyme in plant fructan biosynthesis, since it catalyzes de novo fructan synthesis from Suc. We have cloned 1-SST from onion (Allium cepa) by screening a cDNA library using acid invertase from tulip (Tulipa gesneriana) as a probe. Expression assays in tobacco (Nicotiana plumbaginifolia) protoplasts showed the formation of 1-kestose from Suc. In addition, an onion acid invertase clone was isolated from the same cDNA library. Protein extracts of tobacco protoplasts transformed with this clone showed extensive Suc-hydrolyzing activity. Conditions that induced fructan accumulation in onion leaves also induced 1-SST mRNA accumulation, whereas the acid invertase mRNA level decreased. Structurally different fructan molecules could be produced from Suc by a combined incubation of protein extract of protoplasts transformed with 1-SST and protein extract of protoplasts transformed with either the onion fructan:fructan 6G-fructosyltransferase or the barley Suc:fructan 6-fructosyltransferase.
Piperonylic Acid, a Selective, Mechanism-Based Inactivator of the trans-Cinnamate 4-Hydroxylase: A New Tool to Control the Flux of Metabolites in the Phenylpropanoid Pathway1
Authors: Schalk Michel , Cabello-Hurtado Francisco , Pierrel Marie-Agnès , Atanassova Rossitza , Saindrenan Patrick , Werck-Reichhart Danièle 
Published: July 2002

Abstract
Piperonylic acid (PA) is a natural molecule bearing a methylenedioxy function that closely mimics the structure of trans-cinnamic acid. The CYP73A subfamily of plant P450s catalyzes trans-cinnamic acid 4-hydroxylation, the second step of the general phenylpropanoid pathway. We show that when incubated in vitro with yeast-expressed CYP73A1, PA behaves as a potent mechanism-based and quasi-irreversible inactivator of trans-cinnamate 4-hydroxylase. Inactivation requires NADPH, is time dependent and saturable (KI = 17 μm,kinact = 0.064 min−1), and results from the formation of a stable metabolite-P450 complex absorbing at 427 nm. The formation of this complex is reversible with substrate or other strong ligands of the enzyme. In plant microsomes PA seems to selectively inactivate the CYP73A P450 subpopulation. It does not form detectable complexes with other recombinant plant P450 enzymes. In vivo PA induces a sharp decrease in 4-coumaric acid concomitant to cinnamic acid accumulation in an elicited tobacco (Nicotiana tabacum) cell suspension. It also strongly decreases the formation of scopoletin in tobacco leaves infected with tobacco mosaic virus.
Intermediates of Salicylic Acid Biosynthesis in Tobacco
Authors: Ribnicky David M. , Shulaev Vladimir , Raskin Ilya 
Published: July 2002

Abstract
Salicylic acid (SA) is an important component of systemic-acquired resistance in plants. It is synthesized from benzoic acid (BA) as part of the phenylpropanoid pathway. Benzaldehyde (BD), a potential intermediate of this pathway, was found in healthy and tobacco mosaic virus (TMV)-inoculated tobacco (Nicotiana tabacum L. cv Xanthi-nc) leaf tissue at 100 ng/g fresh weight concentrations as measured by gas chromatography-mass spectrometry. BD was also emitted as a volatile organic compound from tobacco tissues. Application of gaseous BD to plants enclosed in jars caused a 13-fold increase in SA concentration, induced the accumulation of the pathogenesis-related transcript PR-1, and increased the resistance of tobacco to TMV inoculation. [13C6]BD and [2H5]benzyl alcohol were converted to BA and SA. Labeling experiments using [13C1]Phe in temperature-shifted plants inoculated with the TMV showed high enrichment of cinnamic acids (72%), BA (34%), and SA (55%). The endogenous BD, however, contained nondetectable enrichment, suggesting that BD was not the intermediate between cinnamic acid and BA. These results show that BD and benzyl alcohol promote SA accumulation and expression of defense responses in tobacco, and provide insight into the early steps of SA biosynthesis.
The Role of the Alternative Oxidase in Stabilizing the in Vivo Reduction State of the Ubiquinone Pool and the Activation State of the Alternative Oxidase
Authors: Millenaar Frank F. , Benschop Joris J. , Wagner Anneke M. , Lambers Hans 
Published: July 2002

Abstract
A possible function for the alternative (nonphosphorylating) pathway is to stabilize the reduction state of the ubiquinone pool (Qr/Qt), thereby avoiding an increase in free radical production. If the Qr/Qt were stabilized by the alternative pathway, then Qr/Qt should be less stable when the alternative pathway is blocked. Qr/Qtincreased when we exposed roots of Poa annua (L.) to increasing concentrations of KCN (an inhibitor of the cytochrome pathway). However, when salicylhydroxamic acid, an inhibitor of the alternative pathway, was added at the same time, Qr/Qt increased significantly more. Therefore, we conclude that the alternative pathway stabilizes Qr/Qt. Salicylhydroxamic acid increasingly inhibited respiration with increasing concentrations of KCN. In the experiments described here the alternative oxidase protein was invariably in its reduced (high-activity) state. Therefore, changes in the reduction state of the alternative oxidase cannot account for an increase in activity of the alternative pathway upon titration with KCN. The pyruvate concentration in intact roots increased only after the alternative pathway was blocked or the cytochrome pathway was severely inhibited. The significance of the pyruvate concentration and Qr/Qt on the activity of the alternative pathway in intact roots is discussed.