bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of an alternative promoter in the Arabidopsis thaliana HMG1 gene generates an mRNA that encodes a novel 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase isoform with an extended N‐terminal region
Authors: Lumbreras Victoria , Campos Narciso , Boronat Albert 
Published: March 2003

SummaryThe enzyme 3‐hydroxy‐3‐methylglutaryl‐CoA reductase (HMGR, EC 1.1.1.34) catalyses the synthesis of mevalonate, the committed precursor of the great variety of isoprenoid compounds and derivatives synthesized in higher plants. It has previously been reported that Arabidopsis thaliana contains two differentially expressed genes, HMG1 and HMG2, that encode two HMGR isoforms (HMGR1 and HMGR2, respectively). This paper reports the characterization of a novel HMGR mRNA (HMGR1L mRNA) derived from the HMG1 gene. This mRNA is initiated 121 bp upstream from the transcription start site previously characterized. In contrast with the previously reported HMGR1 mRNA (HMGR1S mRNA), which is detected at high levels in all tissues of the plant, HMGR1L mRNA is present at relatively low levels and its expression is restricted mostly to seedlings, roots and inflorescences. HMGR1L and HMGR1S mRNAs are transcribed from alternative promoters. HMGR1L mRNA contains an in‐phase AUG start codon which allows the synthesis of a novel HMGR isoform (HMGR1L) having 50 additional amino acid residues at its N‐terminal end. Using an in vitro transcription‐translation system we have shown that HMGR1L is inserted into ER‐derived microsomes. It is thus unlikely that the extended N‐terminal region of HMGR1L might have a role in targeting the enzyme to plastids or mitochondria. These results support the previous proposal that the endoplasmic reticulum is the only cell compartment for the primary targeting of HMGR in Arabidopsis and reinforce the view that plant HMGR is under the control of complex mechanims operating at both transcriptional and post‐transcriptional levels.
A plant kinesin heavy chain‐like protein is a calmodulin‐binding protein
Authors: Reddy A.S.N. , Narasimhulu S.B. , Safadi F. , Golovkin M. 
Published: March 2003

SummaryCalmodulin, a calcium modulated protein, regulates the activity of several proteins that control cellular functions. A cDNA encoding a unique calmodulin‐binding protein, PKCBP, was isolated from a potato expression library using protein‐protein interaction based screening. The cDNA encoded protein bound to biotinylated calmodulin and 35S‐labeled calmodulin in the presence of calcium and failed to bind in the presence of EGTA, a calcium chelator. The deduced amino acid sequence of the PKCBP has a domain of about 340 amino acids in the C‐terminus that showed significant sequence similarity with the kinesin heavy chain motor domain and contained conserved ATP‐ and microtubule‐binding sites present in the motor domain of all known kinesin heavy chains. Outside the motor domain, the PKCBP showed no sequence similarity with any of the known kinesins, but contained a globular domain in the N‐terminus and a putative coiled‐coil region in the middle. The calmodulin‐binding region was mapped to a stretch of 64 amino acid residues in the C‐terminus region of the protein. The gene is differentially expressed with the highest expression in apical buds. A homolog of PKCBP from Arabidopsis (AKCBP) showed identical structural organization indicating that kinesin heavy chains that bind to calmodulin are likely to exist in other plants. This paper presents evidence that the motor domain has microtubule stimulated ATPase activity and binds to microtubules in a nucleotide‐dependent manner. The kinesin heavy chain‐like calmodulin‐binding protein is a new member of the kinesin superfamily as none of the known kinesin heavy chains contain a calmodulin‐binding domain. The presence of a calmodulin‐binding motif and a motor domain in a single polypeptide suggests regulation of kinesin heavy chain driven motor function(s) by calcium and calmodulin.
A benzothiadiazole derivative induces systemic acquired resistance in tobacco
Authors: Friedrich Leslie , Lawton Kay , Ruess Wilhelm , Masner Peter , Specker Nicole , Rella Manuela Gut , Meier Beatrice , Dincher Sandra , Staub Theodor , Uknes Scott , Métraux Jean‐Pierre , Kessmann Helmut , Ryals John 
Published: March 2003

SummarySystemic acquired resistance (SAR) is a pathogen‐induced disease resistance response in plants that is characterized by broad spectrum disease control and an associated coordinate expression of a set of SAR genes. Benzo(1,2,3)‐thiadiazole‐7‐carbothioic acid S‐methyl ester (BTH) is a novel synthetic chemical capable of inducing disease resistance in a number of dicotyledenous and monocotyledenous plant species. In this report, the response of tobacco plants to BTH treatment is characterized and the fact that it controls disease by activating SAR is demonstrated. BTH does not cause an accumulation of salicylic acid (SA), an intermediate in the SAR signal transduction pathway. As BTH also induces disease resistance and gene expression in transgenic plants expressing the nahG gene, it appears to activate the SAR signal transduction pathway at the site of or downstream of SA accumulation. BTH, SA and TMV induce the PR‐1a promoter using similar cis‐acting elements and gene expression is blocked by cycloheximide treatment. Thus, BTH induces SAR based on all of the physiological and biochemical criteria that define SAR in tobacco.
The developmentally regulated bZIP factor ROM1 modulates transcription from lectin and storage protein genes in bean embryos
Authors: Chern Maw‐Shenq , Eiben Hans Georg , Bustos Mauricio M. 
Published: March 2003

SummaryExpression of the MAT genes DLEC2 and PHSβ, coding for phytohemagglutinin L‐subunit and β‐phaseolin, respectively, is coordinately induced in bean embryos at the onset of seed maturation and regulated at the level of transcription. Previously, it was reported that expression of DLEC2 and PHSβ genes is positively regulated by the acidic transcription activator PvALF. This article describes the regulator of MAT1 (ROM1), a basic/leucine‐zipper protein that binds to hybrid G box/C box motifs found on the DLEC2 and PHSβ seed enhancers. ROM1 repressed DLEC2‐ and PHSβ‐driven expression and antagonized transactivation of either promoter by PvALF, in a dosage‐dependent manner. By contrast, a PvALF/ROM1 hybrid protein activated transcription. Both repression by ROM1 and activation by the hybrid protein required the presence of intact G‐box/C‐box motifs. The abundance of ROM1 mRNA in embryos was highest during the cotyledon stage and decreased rapidly at the beginning of maturation, as phytohemagglutinin and phaseolin mRNAs were induced. The results demonstrate that ROM1 is a DNA‐binding site‐dependent repressor and point to its possible role as a negative modulator of PvALF‐activated transcription of MAT genes.
A novel, soluble form of phytoene desaturase from Narcissus pseudonarcissus chromoplasts is Hsp70‐complexed and competent for flavinylation, membrane association and enzymatic activation
Authors: Al‐Babili Salim , Lintig Johannes v. , Haubruck Heinz , Beyer Peter 
Published: March 2003

SummaryA cDNA coding for the carotenoid biosynthetic enzyme phytoene desaturase from Narcissus pseudonarcissus was cloned and the corresponding protein expressed in insect cells using the baculovirus system. Polyclonal antibodies raised against the recombinant protein allowed the detection of soluble and tightly membrane‐bound populations of phytoene desaturase in the chromoplasts isolated from petals. The soluble form is enzymatically inactive and a constituent of a larger Hsp 70‐containing protein complex in the stroma, whereas the membrane‐bound form is functional. In vitro, the soluble form is able to associate on to/into protein‐free liposomal membranes made from chromoplast lipids, thereby gaining activity by binding added flavine adenine dinucleotide (FAD). Once bound to membranes, activated phytoene desaturase works independently of any added FAD, employing membrane‐bound electron acceptors. FAD, however, exerts no positive effect on the membrane‐association process. Its role is confined to enzymatic activation. Although carotenoid accumulation is strongly induced during flower development, only very low concentrations of phytoene desaturase transcripts are detectable, while the corresponding protein accumulates in low, but measurable amounts, appearing in soluble and membrane‐bound states. Post‐transcriptional mechanisms contribute significantly to carotenoid accumulation, as do factors determining the enzymatic activity of phytoene desaturase, for example by influencing the redox‐state of membrane‐bound electron acceptors.
Post‐transcriptional silencing of chalcone synthase in Petunia by inverted transgene repeats
Authors: Stam Maike , De Bruin Rob , Kenter Susan , Van Der Hoorn Renier A.L. , Van Blokland Rik , Mol Joseph N.M. , Kooter Jan M. 
Published: March 2003

SummaryTo induce post‐transcriptional silencing of flower pigmentation genes by homologous sense transgenes in transgenic petunias, it is not necessary for the transgenes to be highly transcribed. Even promoterless transgenes can induce silencing. Here it is shown that in these cases silencing is mediated by multimeric transgene/T‐DNA loci in which the T‐DNAs are arranged as inverted repeats (IRs). With the transgene constructs used, monomeric T‐DNA loci are unable to confer silencing even though they modulate IR‐induced silencing. IRsfs with the silencing sequences proximal to the centre (IRc) induce a more severe silencing than IRs with these sequences distal to the centre (IRn). Somatic reversion of silencing, as observed in a side branch of one of the chalcone synthase (Chs) transformants, was associated with a deletion of the IR locus from L1 cells, the meristematic cell layer that expresses the endogenous Chs genes in the flower corolla. Taken together, these data indicate that the post‐transcriptional silencing mechanism can be activated by inverted transgene repeats. It is also shown that a silent IR UidA—ChsA locus silences the expression of a monomeric 35S promoter‐driven UidA—ChsA transgene only in corollas where the endogenous Chs genes are highly transcribed. These results are consistent with a model in which an IR, by virtue of its palindromic sequence organization, is able to promote the production of aberrant RNAs from the endogenous homologs as a result of ectopic pairing.
Expression of heterologous phytochromes A, B or C in transgenic tobacco plants alters vegetative development and flowering time
Authors: Halliday Karen J. , Thomas Brian , Whitelam Garry C. 
Published: March 2003

SummaryIn this study, oat phytochrome A (phyA), Arabidopsis phytochrome B (phyB) or Arabidopsis phytochrome C (phyC) were expressed in both day‐neutral and photo‐period‐sensitive (short‐day) tobacco (Nicotiana tabacum cv. Hicks). Introgression of the Maryland Mammoth (MM) gene into cv Hicks was used to confer short‐day photo‐periodic sensitivity. Expression of oat phyA led to characteristic hypersensitivity of hypocotyls to red light (R) and far‐red light (FR) and an overall dwarfing of the mature plant. Expression of Arabidopsis phyB enhanced the sensitivity of hypocotyls to R and caused even more marked dwarfing of the mature plant. In contrast, the expression of Arabidopsis phyC had no detectable consequences for the photocontrol of hypocotyl elongation. However, phyC expression did lead to a R‐dependent increase in cotyledon expansion in de‐etiolating seedlings and to a significant increase in leaf area in mature plants. This provides the first experimental evidence that phyC is biologically active. The flowering time of cv Hicks plants grown under 8 h photoperiods was virtually unaffected by a 30 min white light (W) night break given 8 h into the dark period. In contrast, cv Hicks MM plants responded to a night break with a delay in flowering. Expression of phyA or phyB led to a night break‐dependent delay in flowering in cv Hicks plants. For cv Hicks MM plants, the expression of any of phyA, phyB or phyC caused a marked enhancement of the flower‐delaying effect of a night break. These observations indicate that transgenic phyA, phyB or phyC can interact with the endogenous mechanisms controlling flowering time in tobacco.
Ozone induction of ethylene emission in tomato plants: regulation by differential accumulation of transcripts for the biosynthetic enzymes
Authors: Tuomainen Jaana , Betz Christian , Kangasjärvi Jaakko , Ernst Dieter , Yin Zu‐Hua , Langebartels Christian , Sandermann Heinrich 
Published: March 2003

SummaryStress ethylene emission is positively correlated with ozone sensitivity in various plant species, indicating that ethylene may be involved in the control of ozone damage. This study shows that ozone exposure of tomato plants for 5 h at 85 nl l−1 and above leads to leaf injury within 24 h. 1‐aminocyclopropane‐1‐carboxylic acid (ACC) content and ACC synthase activity were accordingly elevated within 1–2 h. Pre‐treatment of leaves with inhibitors of ACC synthase and ACC oxidase significantly inhibited the evolution of ethylene and reduced ozone‐induced visible damage. Transcript levels for only one out of three S‐adenosyl‐l‐methionine (SAM) synthetase genes (SAM3), and one out of four ACC synthase genes (LE‐ACS2) were induced by ozone (maximum at 2 h). Treatment with protein kinase (K‐252a) and phosphatase inhibitors (calyculin A) revealed that ACC synthase activity was additionally regulated by protein phosphorylation/dephosphorylation. Transcripts of ACC oxidase (pTOM13 cDNA probe) displayed the fastest response of the parameters tested (maximum at 30 min), suggesting a regulatory role for ACC oxidase in ethylene formation of ozone‐exposed plants. The results demonstrate a highly selective ozone response by ethylene biosynthetic genes which resembles that of plant—pathogen interactions.
Isolation and molecular characterization of the Arabidopsis TPS1 gene, encoding trehalose‐6‐phosphate synthase
Authors: Blázquez Miguel A. , Santos Elisa , Flores Carmen‐lisset , Martínez‐Zapater José M. , Salinas Julio , Gancedo Carlos 
Published: March 2003

SummaryAn Arabidopsis thaliana cDNA clone, AtTPS1, that encodes a trehalose‐6‐phosphate synthase was isolated. The identity of this protein is supported by both structural and functional evidence. On one hand, the predicted sequence of the protein encoded by AtTPS1 showed a high degree of similarity with trehalose‐6‐phosphate synthases of different organisms. On the other hand, expression of the AtTPS1 cDNA in the yeast tps1 mutant restored its ability to synthesize trehalose and suppressed its growth defect related to the lack of trehalose‐6‐phosphate. Genomic organization and expression analyses suggest that AtTPS1 is a single‐copy gene and is expressed constitutively at very low levels.
Ectopic expression of a novel MYB gene modifies the architecture of the Arabidopsis inflorescence
Authors: Kirik Victor , Kölle Kerstin , Wohlfarth Thomas , Miséra Simon , Bäumlein Helmut 
Published: March 2003

SummaryThe Arabidopsis thaliana mutants fus3, lec1 and abi3 have pleiotropic defects during late embryogenesis. Mutant embryos fail to enter the maturation programme and initiate a vegetative germination pathway instead. Screening for genes which are differentially expressed in the fus3 mutant of Arabidopsis resulted in the isolation of several members of the MYB family. MYB domain proteins in plants represent an extended gene family of transcription factors, suggesting their participation in a variety of plant specific cellular functions. Here, the authors describe one of these genes, designated AtMYB13, representing a novel member of the MYB gene family. The structure of the gene as well as its genomic organisation and localisation are reported. The expression of the gene is regulated by dehydration, exogenous abscisic acid, light and wounding. A chimeric AtMYB13 promoter/GUS gene is tissue‐specifically expressed in transgenic Arabidopsis plants. The GUS staining was predominantly detected in the shoot apex zone and at the basis of developing flowers. In addition, the AtMYB13 gene promoter is active at branching points of the inflorescence. Furthermore, ectopic expression of the AtMYB13 gene has a characteristic impact on the architecture of the inflorescence leading to peculiar hook structures at pedicel branching points. In addition, some transgenic plants exhibit a reversed order of first flowers and axillary buds. These data suggest a function of the AtMYB13 gene product in linking shoot morphogenic activity with environmental as well as intrinsic signals.
Cloning and functional expression of AtCOQ3, the Arabidopsis homologue of the yeast COQ3 gene, encoding a methyltransferase from plant mitochondria involved in ubiquinone biosynthesis
Authors: Avelange‐Macherel Marie‐Hélène , Joyard Jacques 
Published: March 2003

SummaryA mutant of Saccharomyces cerevisiae deleted for the COQ3 gene was constructed. COQ3 encodes a 3,4‐dihydroxy‐5‐hexaprenylbenzoate (DHHB) methyltransferase that catalyses the fourth step in the biosynthesis of ubiquinone from p‐hydroxybenzoic acid. A full length cDNA encoding a homologue of DHHB‐methyltransferase was cloned from an Arabidopsis thaliana cDNA library by functional complementation of a yeast coq3 deletion mutant. The Arabidopsis thaliana cDNA (AtCOQ3) was able to restore the respiration ability and ubiquinone synthesis of the mutant. The product of the 1372 bp cDNA contained 322 amino acids and had a molecular mass of 35 360 Da. The predicted amino acid sequence contained all consensus regions for S‐adenosyl methionine methyltransferases and presented 26% identity with Saccharomyces cerevisiae DHHB‐methyltransferase and 38% identity with the rat protein, as well as with a bacterial (Escherichia coli and Salmonella typhimurium) methyltransferase encoded by the UBIG gene. Southern analysis showed that the Arabidopsis thaliana enzyme was encoded by a single nuclear gene. The NH2‐terminal part of the cDNA product contained features consistent with a putative mitochondrial transit sequence. The cDNA in Escherichia coli was overexpressed and antibodies were raised against the recombinant protein. Western blot analysis of Arabidopsis thaliana and pea protein extracts indicated that the AtCOQ3 gene product is localized within mitochondrial membranes. This result suggests that at least this step of ubiquinone synthesis takes place in mitochondria.
Significance of plasmalemma aquaporins for water‐transport in Arabidopsis thaliana
Authors: Kaldenhoff Ralf , Grote Karsten , Zhu Jian‐Jun , Zimmermann Ulrich 
Published: March 2003

SummaryThe plant plasma membrane intrinsic protein, PIP1b, facilitates water transport. These features were characterized in Xenopus oocytes and it has asked whether aquaporins are relevant for water transport in plants. In order to elucidate this uncertainty Arabidopsis thaliana was transformed with an anti‐sense construct targeted to the PIP1b gene. Molecular analysis revealed that the anti‐sense lines have reduced steady‐state levels of PIP1b and the highly homologous PIP1a mRNA. The cell membrane water permeability was analyzed by swelling of protoplasts, which had been transferred into hypotonic conditions. The results indicate that the reduced expression of the specific aquaporins decreases the cellular osmotic water permeability coefficient approximately three times. The morphology and development of the anti‐sense lines resembles that of control plants, with the exception of the root system, which is five times as abundant as that of control plants. Xylem pressure measurement suggests that the increase of root mass compensates the reduced cellular water permeability in order to ensure a sufficient water supply to the plant. The results obtained by this study, therefore, clearly demonstrate that aquaporins are important for plant water transport.
Rapid discrimination of sequences flanking and within T‐DNA insertions in the Arabidopsis genome
Authors: Ponce María Rosa , Quesada Víctor , Micol José Luis 
Published: March 2003

SummaryAn improvement to previous methods for recovering Arabidopsis thaliana genomic DNA flanking T‐DNA insertions is presented that allows for the avoidance of some of the cloning difficulties caused by the concatameric nature of T‐DNA inserts. The principle of the procedure is to categorize by size restriction fragments of mutant DNA, produced in separate digestions with NdeI and Bst1107I. Given that the sites for these two enzymes are contiguous within the pGV3850:1003 T‐DNA construct, the restriction fragments obtained fall into two categories: those showing identical size in both digestions, which correspond to sequences internal to T‐DNA concatamers; and those of different sizes, that contain the junctions between plant DNA and the T‐DNA insert. Such a criterion makes it possible to easily distinguish the digestion products corresponding to internal T‐DNA parts, which do not deserve further attention, and those which presumably include a segment of the locus of interest. Discrimination between restriction fragments of genomic mutant DNA can be made on rescued plasmids, inverse PCR amplification products or bands in a genomic blot.
Enzymatic oxidations in the biosynthesis of complex alkaloids
Authors: Chou Wing‐Ming , Kutchan Toni M. 
Published: March 2003

Summary The biosynthesis of complex alkaloids in plants involves enzymes that, due to high substrate specificity, appear to have evolved solely for a role in secondary metabolism. At least one class of these enzymes, the oxidoreductases, catalyze transformations that are in some cases difficult to chemically mimick with an equivalent stereo‐ or regiospecificity and yield. Oxidoreductases are frequently catalyzing reactions that result in the formation of parent ring systems, thereby determining the class of alkaloid that a plant will produce. The oxidoreductases of alkaloid formation are a potential target for the biotechnological exploitation of medicinal plants in that they could be used for biomimetic syntheses of alkaloids. Analyzing the molecular genetics of alkaloid biosynthetic oxidations is requisite to eventual commercial application of these enzymes. To this end, a wealth of knowledge has been gained on the biochemistry of select monoterpenoid indole and isoquinoline biosynthetic pathways, and in recent years this has been complemented by molecular genetic analyses. As the nucleotide sequences of the oxidases of alkaloid synthesis become known, consensus sequences specific to select classes of enzymes can be identified. These consensus sequences will potentially facilitate the direct cloning of alkaloid biosynthetic genes without the need to purify the native enzyme for partial amino acid sequence determination or for antibody production prior to cDNA isolation. The current state of our knowledge of the biochemistry and molecular genetics of oxidases involved in alkaloid biosynthesis is reviewed herein.