bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pathogen‐derived resistance targeted against the negative‐strand RNA of tobacco mosaic virus: RNA strand‐specific gene silencing?
Authors: Marano María Rosa , Baulcombe David 
Published: March 2003

SummaryTobacco plants transformed with the open‐reading frame (ORF) of tobacco mosaic virus strain U1 (TMV‐U1) encoding a 54 kDa (54K) region of the viral replicase are resistant against TMV strain U1. These plants are not resistant against the crucifer strain of TMV or the heterologous virus, potato virus X (PVX). However, they are resistant against derivatives of PVX containing fragments of the 54K ORF inserted either in the sense or anti‐sense orientation. The smallest fragment that was a target of the resistance mechanism was a 383 nucleotide region from the central part of the 54K ORF. A transient gene expression assay revealed that this central region was also the target of a post‐transcriptional gene silencing mechanism. However, unlike other examples of gene silencing associated with virus resistance, the silencing was specific for the anti‐sense rather than the coding strand of the target RNA. Based on these data the authors propose that the TMV resistance is due, at least in part, to a type of transgene silencing.
Accumulation of small heat shock proteins, including mitochondrial HSP22, induced by oxidative stress and adaptive response in tomato cells
Authors: Banzet Nathalie , Richaud Christiane , Deveaux Yves , Kazmaier Michaël , Gagnon Jean , Triantaphylidès Christian 
Published: March 2003

SummaryChanges in gene expression, by application of H2O2, O2°–generating agents (methyl viologen, digitonin) and gamma irradiation to tomato suspension cultures, were investigated and compared to the well‐described heat shock response. Two‐dimensional gel protein mapping analyses gave the first indication that at least small heat shock proteins (smHSP) accumulated in response to application of H2O2 and gamma irradiation, but not to O2°– generating agents. While some proteins seemed to be induced specifically by each treatment, only part of the heat shock response was observed. On the basis of Northern hybridization experiments performed with four heterologous cDNA, corresponding to classes I–IV of pea smHSP, it could be concluded that significant amounts of class I and II smHSP mRNA are induced by H2O2 and by irradiation. Taken together, these results demonstrate that in plants some HSP genes are inducible by oxidative stresses, as in micro‐organisms and other eukaryotic cells. HSP22, the main stress protein that accumulates following H2O2 action or gamma irradiation, was also purified. Sequence homology of amino terminal and internal sequences, and immunoreactivity with Chenopodium rubrum mitochondrial smHSP antibody, indicated that the protein belongs to the recently discovered class of plant mitochondrial smHSP. Heat shock or a mild H2O2 pretreatment was also shown to lead to plant cell protection against oxidative injury. Therefore, the synthesis of these stress proteins can be considered as an adaptive mechanism in which mitochondrial protection could be essential.
Regulation of Rubisco activation in antisense plants of tobacco containing reduced levels of Rubisco activase
Authors: Hammond Edward T. , Andrews T. John , Mott Keith A. , Woodrow Ian E. 
Published: March 2003

SummaryFollowing an increase in photon flux density (PFD), ribulose bisphosphate carboxylase/oxygenase (Rubisco) undergoes a slow activation which substantially limits the rate of photosynthesis. This activation process is mediated in part by Rubisco activase. Antisense DNA plants of tobacco were used to quantify the degree to which activase limits Rubisco activation. Reductions in leaf activase content caused proportional reductions in the rate of Rubisco activation following a PFD increase from 110 to 1200 μmol m–2 sec–1. This was the case for activase levels up to and slightly beyond normal wild‐type activase levels. Activase therefore has a flux control coefficient of unity with respect to the Rubisco activation flux. Such a high control coefficient has rarely been measured for any metabolic system, and this is the highest control coefficient measured for an important photosynthetic flux. In contrast, the rate of Rubisco inactivation in leaves following a drop in PFD of 1200 to 110 μmol m–2 sec–1 was unchanged by a 60% reduction in activase levels. Despite the high degree of control that activase exerts over the rate of activation, and thus non‐steady‐state photosynthesis, it was shown that steady‐state photosynthesis was largely unaffected by activase concentration until it was reduced below approximately 15% of the wild‐type level. The significance of these results and their implications for published models of Rubisco activation are discussed.
Genetic evidence that the endodermis is essential for shoot gravitropism in Arabidopsis thaliana
Authors: Fukaki Hidehiro , Wysocka‐Diller Joanna , Kato Takehide , Fujisawa Hisao , Benfey Philip N. , Tasaka Masao 
Published: March 2003

Summary Shoots of higher plants exhibit negative gravitropism. However, little is known about the mechanism or site of gravity perception in shoots. We have identified two loci that are essential for normal shoot gravitropism in

Arabidopsis thaliana. Genetic analysis demonstrated that the shoot gravitropism mutants

sgr1and

sgr7are allelic to the radial pattern mutants,

scrand

shr, respectively. Characterization of the aerial phenotype of these mutants revealed that the primary defect is the absence of a normal endodermis in hypocotyls and inflorescence stems. This indicates that the endodermis is essential for shoot gravitropism and strongly suggests that this cell layer functions as the gravity‐sensing cell layer in dicotyledonous plant shoots. These results also demonstrate that, in addition to their previously characterized role in root radial patterning,

SCRand

SHRregulate the radial organization of the shoot axial organs in

Arabidopsis.
Molecular cloning of starch synthase I from maize (W64) endosperm and expression in Escherichia coli
Authors: Knight Mary E. , Harn Chee , Lilley Caroline E. R. , Guan Hanping , Singletary George W. , Mu‐Forster Chen , Wasserman Bruce P. , Keeling Peter L. 
Published: March 2003

SummaryA full length cDNA clone encoding a starch synthase (zSS) from maize endosperm (inbred line W64) was isolated and characterized. The cDNA clone (Ss1) is 2907 bp in length and contains an open reading frame of 1866 bp corresponding to a polypeptide of 622 amino acid residues including a transit peptide of 39 amino acids. The Ss1 cDNA clone was identified as zSSI by its direct alignment with sequences to: (i) the N‐terminus obtained from the granule‐associated form of the zSSI polypeptide, (ii) four internal peptide fragments obtained from the granule‐associated form of the zSSI protein, and (iii) one internal fragment from the soluble form of the zSSI protein. The deduced amino acid sequence of Ss1 shares 75.7 % sequence identity with rice soluble Ss and contains the highly conserved KSGGLGDV putative ADP–Glc binding site. Moreover, Ss1 exhibited significant activity when expressed in E. coli and the expressed protein is recognized by the antibody raised against the granule associated zSSI protein. Ss1 transcripts were detected in endosperm beginning at 15 days after pollination, but were not found in embryo, leaf or root. Maize contains a single copy of the Ss1 gene, which maps close to the Waxy locus of chromosome 9.
Phytepsin, a barley vacuolar aspartic proteinase, is highly expressed during autolysis of developing tracheary elements and sieve cells
Authors: Runeberg‐Roos Pia , Saarma Mart 
Published: March 2003

SummaryVacuolarisation, formation of autophagocytotic vacuoles and tonoplast disruption have been reported in plant cells undergoing developmentally regulated programmed cell death (PCD), but little is known about the vacuolar proteins involved. In HeLa cells, cathepsin D, a lysosomal aspartic proteinase has been shown to mediate PCD. Based on immunohistochemical staining of barley roots, we show here that the previously well characterised barley vacuolar aspartic proteinase (phytepsin), a plant homologue to cathepsin D, is highly expressed both during formation of tracheary elements and during partial autolysis of sieve cells. In serial transverse sections of the vascular cylinder, starting from the root tip, phytepsin is expressed in root cap cells, in the tracheary elements of early and late metaxylem, and in the sieve cells of the protophloem and metaphloem. Aleurain, a barley vacuolar cysteine proteinase, is expressed similarly in root cap cells but differently in the tracheary elements of protoxylem and early metaxylem. This is the first evidence that a vacuolar aspartic proteinase, in analogy to cathepsin D in animals, may play a role in the active autolysis of plant cells.
A gene encoding phosphatidylinositol‐4‐phosphate 5‐kinase is induced by water stress and abscisic acid inArabidopsis thaliana
Authors: Mikami Koji , Katagiri Takeshi , Iuchi Satoshi , Yamaguchi‐Shinozaki Kazuko , Shinozaki Kazuo 
Published: March 2003

Summary Phosphatidylinositol‐4‐phosphate 5‐kinase (PIP5K) phosphorylates phosphatidylinositol‐4‐phosphate to produce phosphatidylinositol‐4,5‐bisphosphate as a precursor of two second messengers, inositol‐1,4,5‐triphosphate and diacylglycerol, and as a regulator of many cellular proteins involved in signal transduction and cytoskeletal organization. Despite PIP5K playing such an essential role in a number of physiological processes, much still remains to be made clear about its association with plants. Searching the

Arabidopsis

expression sequence tag database against already known yeast and mammalian PIP5K cDNAs, we identified two clones which partly encode the same

Arabidopsis

PIP5K and isolated a corresponding full‐length cDNA encoding a protein that we designated AtPIP5K1. Recombinant AtPIP5K1 expressed in

Escherichia coli

possessed a PIP5K activity

in vitro

. Due to some structural and biochemical differences, AtPIP5K1 was not categorized as either a type I or type II PIP5K. The expression of the AtPIP5K1 mRNA was induced rapidly by treating

Arabidopsis

plants with drought, salt and abscisic acid, which suggests that AtPIP5K1 is involved in water‐stress signal transduction. These data give evidence for a close link between phosphoinositide signaling cascades and water‐stress responses in plants.
Endomycorrhizae and rhizobial Nod factors both require SYM8 to induce the expression of the early nodulin genesPsENOD5 and PsENOD12A
Authors: Albrecht Catherine , Geurts René , Lapeyrie Frederic , Bisseling Ton 
Published: March 2003

SummaryWe report here that the pea early nodulin genesPsENOD5andPsENOD12Aare induced during the interaction of pea roots and the endomycorrhizal fungusGigaspora margarita. Using the pea nodulation mutant Sparkle‐R25, which is mutated inSYM8, it is shown that SYM8 is essential for the induction ofPsENOD5andPsENOD12Ain pea roots interacting either withRhizobiumor the endomycorrhizal fungusGigaspora margarita. Our results suggest that mycorrhizal signals activate a signal transduction cascade sharing at least one common step with the Nod factor‐activated signal transduction cascade.
Developmental abnormalities associated with deoxyadenosine methylation in transgenic tobacco
Authors: Van Blokland Rik , Ross Simon , Corrado Giandomenico , Scollan Claire , Meyer Peter 
Published: March 2003

Summary As in other higher eukaryotes, DNA methylation in plants is predominantly found at deoxycytosine residues, while deoxyadenosine residues are not methylated at significant levels. 6mdA methylation has been successfully introduced into yeast and

Drosophila

via expression of a heterologous methyltransferase, but similar attempts in tobacco had, up until now, proved unsuccessful despite the correct expression of a methyltransferase construct. It was unclear whether this result reflected the failure of heterologous methyltransferases to enter the nucleus, or whether 6mdA methylation, which has been shown to interfere with promoter activity, was toxic for plants. Here we show that 6mdA methylation can be successfully introduced into transgenic tobacco plants via expression of the bacterial

dam

enzyme. The efficiency of 6mdA methylation was directly proportional to expression levels of the

dam

construct, and methylation of all GATC sites was observed in a highly expressing line. Increasing expression levels of the enzyme in different plants correlated with increasingly abnormal phenotypes affecting leaf pigmentation, apical dominance, and leaf and floral structure. Whilst introduction of

dam

‐specific methylation does not cause any developmental abnormalities in yeast or

Drosophila

, our data suggest that methylation of deoxyadenine residues in plants interferes with the expression of genes involved in leaf and floral development.
Ozone‐induced oxidative burst in the ozone biomonitor plant, tobacco Bel W3
Authors: Schraudner Martina , Moeder Wolfgang , Wiese Cosima , Camp Wim Van , Inzé Dirk , Langebartels Christian , Sandermann Heinrich 
Published: March 2003

Summary Localized cell death is a common feature of ozone phytotoxicity and is generally thought to be initiated by the strong oxidant ozone itself as well as by ozone‐derived reactive oxygen intermediates (ROIs). Here we report that ozone (150 nl l–1, 5 h) elicits cellular ROI production in the ozone‐sensitive tobacco cv. Bel W3, but not in the tolerant cv. Bel B. Both cultivars exhibited a transient first maximum of apoplastic ROI accumulation followed by a comparable induction of glutathione peroxidase transcript levels. During postcultivation in pollutant‐free air, a second and sustained peak of apoplastic ROI accumulation was detected only in cv. Bel W3. Histochemical staining revealed a spot‐like accumulation of H2O2 and, to a lesser extent, of superoxide anion radicals in this cultivar. The H2O2 spots (‘burst initiation sites’) occurred mainly in the vicinity of leaf veins and correlated in number and distribution with discrete sites of local cell death and with visible symptoms that evolved between 15 and 72 h. The results indicate that ozone effects are amplified in the sensitive tobacco cv. Bel W3 by an oxidative burst which participates in the generation of hypersensitive cell death‐like lesions.
A GFP‐mouse talin fusion protein labels plant actin filamentsin vivoand visualizes the actin cytoskeleton in growing pollen tubes
Authors: Kost Benedikt , Spielhofer Pius , Chua Nam‐Hai 
Published: March 2003

Summary The C‐terminus of mouse talin (amino acids 2345–2541) is responsible for all of the protein’s f‐actin binding capacity. Unlike full‐length talin, the C‐terminal f‐actin binding domain is unable to nucleate actin polymerization. We have found that transient and stable expression of the talin actin‐binding domain fused to the C‐terminus of the green fluorescent protein (GFP‐mTn) can visualize the actin cytoskeleton in different types of living plant cells without affecting cell morphology or function. Transiently expressed GFP‐mTn co‐localized with rhodamine‐phalloidin in permeabilized tobacco BY‐2 suspension cells, showing that the fusion protein can specifically label the plant actin cytoskeleton. Constitutive expression of GFP‐mTn in transgenic

Arabidopsis thaliana

plants visualized actin filaments in all examined tissues with no apparent effects on plant morphology or development at any stage during the life cycle. This demonstrates that in a number of different cell types GFP‐mTn can serve as a non‐invasive marker for the actin cytoskeleton. Confocal imaging of GFP‐mTn labeled actin filaments was employed to reveal novel information on the

in vivo

organization of the actin cytoskeleton in transiently transformed, normally elongating tobacco pollen tubes.
An oligo selection procedure for identification of sequence‐specific DNA‐binding activities associated with the plant defence response
Authors: Wang Zeping , Yang Peizhen , Fan Baofang , Chen Zhixiang 
Published: March 2003

Summary Sequence‐specific DNA‐binding (SSDB) factors play central roles in transcription, DNA replication, recombination and repair. This report describes a simple procedure for high‐throughput identification of SSDB activities without prior knowledge of their target genes or binding sequences. The procedure starts with a population of completely random oligo(nucleotide) sequences and selects for those oligo molecules that specifically bind to cellular SSDB factors by use of common gel‐retardation assays and PCR. Amplification and subsequent cloning of these selected oligo molecules result in the establishment of oligo DNA libraries enriched in DNA molecules containing specific sequences recognized by SSDB factors. These oligo libraries can be rapidly screened to identify a large number of SSDB activities, including those that are differentially regulated by developmental and environmental signals. With identified oligo DNA as probes, the corresponding SSDB factors can be isolated and analysed with respect to their structures, regulation and functions. Using this procedure, we have identified approximately 100 SSDB activities from tobacco leaves, including seven that are differentially regulated during the tobacco mosaic virus‐induced hypersensitive response in resistant tobacco plants.
Intimate association of microsatellite repeats with retrotransposons and other dispersed repetitive elements in barley
Authors: Ramsay Luke , Macaulay Malcolm , Cardle Linda , Morgante Michele , Ivanissevich Stephania degli , Maestri Elena , Powell Wayne , Waugh Robbie 
Published: March 2003

Summary Simple sequence repeat (SSR)‐based genetic markers are being actively developed for the majority of crop plant species. In barley, characterization of 290 dinucleotide repeat‐containing clones from SSR‐enriched libraries has revealed that a high percentage are associated with cereal retrotransposon‐like and other dispersed repetitive elements. Associations found were with BARE‐1, WIS2‐1A, PREM1 and the dispersed repetitive element R173. Additional similarities between different SSR clones, which have no matches in DNA sequence databases, indicate that this phenomenon is probably widespread in the barley genome. Sequence homologies to the non‐coding regions of several cereal genes were also explained by homology to mobile genetic elements. The SSRs found can therefore be classified into two types: (1) those with unique sequences on either flank, and (2) those which are intimately associated with retro‐transposons and other dispersed repetitive elements. As the cereal genome is thought to consist largely of this type of DNA, some random association would be expected. However, the conserved positions of the SSRs, relative to repetitive elements, indicate that they have arisen non‐randomly. Furthermore, this class of SSRs can be classified into three subtypes: (1) those which are positioned 3′ of a transposable element with unique sequence on the other flank, (2) those positioned 5′ of a transposable element, and (3) those which have arisen from an internal sequence and so have transposable element sequence on both flanks. The first appear to be analogous to the class of SSRs in mammalian systems which are associated with Alu elements and SINEs (short interspersed elements) and which have been postulated to arise following integration of an extended and polyadenylated retro‐transcript into the host genome, followed by mutation of the poly(A) tract and expansion into an SSR. For the second, we postulate that a proto‐SSR (A‐rich sequence) has acted as a ‘landing pad' for transposable element insertion (rather than being the result of insertion), while the third includes those which have evolved as a component of an active transposable element which has spread throughout the genome during bursts of transposition activity. The implications of these associations for genome and SSR evolution in barley are discussed.
Re‐evaluation of phytohormone‐independent division of tobacco protoplast‐derived cells
Authors: Schell Jeff , Bisseling Ton , Dülz Marion , Franssen Henk , Fritze Klaus , John Michael , Kleinow Tatjana , Leßnick Angela , Miklashevichs Edvins , Pawlowski Katharina , Röhrig Horst , De Sande Karin van , Schmidt Jürgen , Steinbiß Hans‐Henning , Stoll Marion 
Published: March 2003

Summary We have used a [3H] thymidine incorporation assay and microscopic observation in order to reassess recently published data dealing with the response of tobacco protoplasts to phytohormones, lipochitooligosaccharides and peptides (

Harling
et al
. 1997

;

Hayashi
et al
. 1992

;

Miklashevichs
et al
. 1996

;

Miklashevichs
et al
. 1997

;

Röhrig
et al
. 1995

;

Röhrig
et al
. 1996

;

van de Sande
et al
. 1996

;

Walden
et al
. 1994

). These proliferation assays reveal that, in contrast to published data, isolated cells of the investigated mutant plant lines axi159 (

Hayashi
et al
. 1992

;

Walden
et al
. 1994

), axi4/1 (

Harling
et al
. 1997

) and cyi1 (

Miklashevichs
et al
. 1997

), which were generated by activation T‐DNA tagging, were unable to grow in the absence of auxin or cytokinin. Furthermore, lipochitooligosaccharides which play a key role in the induction of nodules on roots of legumes were unable to promote auxin‐ or cytokinin‐independent cell division in tobacco protoplasts as claimed by

Röhrig
et al
. (1995

,

1996

). The finding of

van de Sande
et al
. (1996

) that
ENOD40
confers tolerance of high auxin concentration to wild‐type tobacco protoplasts was also reinvestigated. The results of our investigations show that we were unable to reproduce the proliferation data presented in this study, which were obtained by counting tobacco protoplast‐derived cells undergoing division. In total, none of the published data on phytohormone‐independent division of tobacco cells could be reproduced.
Biological functions of proline in morphogenesis and osmotolerance revealed in antisense transgenic Arabidopsis thaliana
Authors: Nanjo Tokihiko , Kobayashi Masatomo , Yoshiba Yoshu , Sanada Yukika , Wada Keishiro , Tsukaya Hirokazu , Kakubari Yoshitaka , Yamaguchi‐Shinozaki Kazuko , Shinozaki Kazuo 
Published: March 2003

SummaryMany organisms, including higher plants, accumulate free proline (Pro) in response to osmotic stress. Although various studies have focused on the ability of Pro as a compatible osmolyte involved in osmotolerance, its specific role throughout plant growth is still unclear. It has been reported that Pro is synthesized from Glu catalyzed by a key enzyme, Δ1‐pyrroline‐5‐carboxylate synthetase (P5CS), in plants. To elucidate essential roles of Pro, we generated antisense transgenic Arabidopsis plants with a P5CS cDNA. Several transgenics accumulated Pro at a significantly lower level than wild‐type plants, providing direct evidence for a key role of P5CS in Pro production in Arabidopsis. These antisense transgenics showed morphological alterations in leaves and a defect in elongation of inflorescences. Furthermore, transgenic leaves were hypersensitive to osmotic stress. Microscopic analysis of transgenic leaves, in which the mutated phenotype clearly occurred, showed morphological abnormalities of epidermal and parenchymatous cells and retardation of differentiation of vascular systems. These phenotypes were suppressed by exogenous L‐Pro but not by D‐Pro or other Pro analogues. In addition, Pro deficiency did not broadly affect all proteins but specifically affected structural proteins of cell walls in the antisense transgenic plants. These results indicate that Pro is not just an osmoregulator in stressed plants but has a unique function involved in osmotolerance as well as in morphogenesis as a major constituent of cell wall structural proteins in plants.