bluuebunny/crossref_metadata_2025_split huggingface dataset:
At‐HSP17.6A, encoding a small heat‐shock protein in Arabidopsis, can enhance osmotolerance upon overexpression
Authors: Sun Weining , Bernard Catherine , Van De Cotte Brigitte , Van Montagu Marc , Verbruggen Nathalie 
Published: March 2003

SummaryOwing to their sessile lifestyle, it is crucial for plants to acquire stress tolerance. The function of heat‐shock proteins, including small heat‐shock proteins (smHSPs), in stress tolerance is not fully explored. To gain further knowledge about the smHSPs, the gene that encoded the cytosolic class II smHSP in Arabidopsis thaliana (At‐HSP17.6A) was characterized. The At‐HSP17.6A expression was induced by heat and osmotic stress, as well as during seed development. Accumulation of At‐HSP17.6A proteins could be detected with heat and at a late stage of seed development, but not with osmotic stress, suggesting stress‐induced post‐transcriptional regulation of At‐HSP17.6A expression. Overproduction of At‐HSP17.6A could increase salt and drought tolerance in Arabidopsis. The chaperone activity of At‐HSP17.6A was demonstrated in vitro.
Mutagenesis and computer modelling approach to study determinants for recognition of signal peptides by the mitochondrial processing peptidase
Authors: Zhang Xiao‐Ping , Sjöling Sara , Tanudji Marcel , Somogyi László , Andreu David , Eriksson L. E. Göran , Gräslund Astrid , Whelan James , Glaser Elzbieta 
Published: March 2003

SummaryDeterminants for the recognition of a mitochondrial presequence by the mitochondrial processing peptidase (MPP) have been investigated using mutagenesis and bioinformatics approaches. All plant mitochondrial presequences with a cleavage site that was confirmed by experimental studies can be grouped into three classes. Two major classes contain an arginine residue at position −2 or −3, and the third class does not have any conserved arginines. Sequence logos revealed loosely conserved cleavage motifs for the first two classes but no significant amino acid conservation for the third class. Investigation of processing determinants for a class III precursor, Nicotiana plumbaginifolia F1β precursor of ATP synthase (pF1β), was performed using a series of pF1β presequence mutants and mutant presequence peptides derived from the C‐terminal portion of the presequence. Replacement of −2 Gln by Arg inhibited processing, whereas replacement of either the most proximally located −5 Arg or −15 Arg by Leu had only a low inhibitory effect. The C‐terminal portion of the pF1β presequence forms a helix–turn–helix structure. Mutations disturbing or prolonging the helical element upstream of the cleavage site inhibited processing significantly. Structural models of potato MPP and the C‐terminal pF1β presequence peptide were built by homology modelling and empirical conformational energy search methods, respectively. Molecular docking of the pF1β presequence peptide to the MPP model suggested binding of the peptide to the negatively charged binding cleft formed by the α‐MPP and β‐MPP subunits in close proximity to the H111XXE114H115X(116−190)E191 proteolytic active site on β‐MPP. Our results show for the first time that the amino acid at the −2 position, even if not an arginine, as well as structural properties of the C‐terminal portion of the presequence are important determinants for the processing of a class III precursor by MPP.
Tissue‐specific patterns of a maize Myb transcription factor are epigenetically regulated
Authors: Cocciolone Suzy M. , Chopra Surinder , Flint‐Garcia Sherry A. , McMullen Michael D. , Peterson Thomas 
Published: March 2003

SummaryThe maize p1 gene encodes a Myb‐homologous regulator of red pigment biosynthesis. To investigate the tissue‐specific regulation of the p1 gene, maize plants were transformed with constructs combining promoter and cDNA sequences of two alleles which differ in pigmentation patterns: P1‐wr (white pericarp/red cob) and P1‐rr (red pericarp/red cob). Surprisingly, all promoter/cDNA combinations produced transgenic plants with red pericarp and red cob (RR pattern), indicating that the P1‐wr promoter and encoded protein can function in pericarp. Some of the RR patterned transgenic plants produced progeny plants with white pericarp and red cob (WR pattern), and this switch in tissue‐specificity correlated with increased transgene methylation. A similar inverse correlation between pericarp pigmentation and DNA methylation was observed for certain natural p1 alleles, which have a gene structure characteristic of standard P1‐wr alleles, but which confer red pericarp pigmentation and are consistently less methylated than standard P1‐wr alleles. Although we cannot rule out the possible existence of tissue‐specific regulatory elements within the p1 non‐coding sequences or flanking regions, the data from transgenic and natural alleles suggest that the tissue‐specific pigmentation pattern characteristic of the P1‐wr phenotype is epigenetically controlled.
Strong decrease in lignin content without significant alteration of plant development is induced by simultaneous down‐regulation of cinnamoyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) in tobacco plants
Authors: Chabannes Matthieu , Barakate Abdellah , Lapierre Catherine , Marita Jane M. , Ralph John , Pean Michel , Danoun Saïda , Halpin Claire , Grima‐Pettenati Jacqueline , Boudet Alain Michel 
Published: March 2003

SummaryDifferent transgenic tobacco lines down‐regulated for either one or two enzymes of the monolignol pathway were compared for their lignin content and composition, and developmental patterns. The comparison concerned CCR and CAD down‐regulated lines (homozygous or heterozygous for the transgene) and the hybrids resulting from the crossing of transgenic lines individually altered for CCR or CAD activities. Surprisingly, the crosses containing only one allele of each antisense transgene, exhibit a dramatic reduction of lignin content similar to the CCR down‐regulated parent but, in contrast to this transgenic line, display a normal phenotype and only slight alterations of the shape of the vessels. Qualitatively the lignin of the double transformant displays characteristics more like the wild type control than either of the other transgenics. In the transgenics with a low lignin content, the transformations induced other biochemical changes involving polysaccharides, phenolic components of the cell wall and also soluble phenolics. These results show that the ectopic expression of a specific transgene may have a different impact depending on the genetic background and suggest that the two transgenes present in the crosses may operate synergistically to reduce the lignin content. In addition, these data confirm that plants with a severe reduction in lignin content may undergo normal development at least in controlled conditions.
Maize VP1 complements Arabidopsisabi3 and confers a novel ABA/auxin interaction in roots
Authors: Suzuki Masaharu , Kao Chien‐Yuan , Cocciolone Suzy , McCarty Donald R. 
Published: March 2003

SummaryThe maize Vp1 gene and abi3 gene of Arabidopsis are believed to be orthologs based on similarities of the mutant phenotypes and amino acid sequence conservation. Here we show that expression of VP1 driven by the 35S promoter can partially complement abi3–6, a deletion mutant allele of abi3. The visible phenotype of seed produced from VP1 expression in the abi3 mutant background is nearly indistinguishable from wild type. VP1 fully restores abscisic acid (ABA) sensitivity of abi3 during seed germination and suppresses the early flowering phenotype of abi3. The temporal regulation of C1‐β‐glucronidase (GUS) and chlorophyl a/b binding protein (cab3)‐GUS reporter genes in developing seeds of 35S‐VP1 lines were similar to wild type. On the other hand, two qualitative differences are observed between the 35S‐VP1 line and wild type. The levels of CRC and C1‐GUS expression are markedly lower in the seeds of 35S‐VP1 lines than in wild type suggesting incomplete complementation of gene activation functions. Similar to ectopic expression of ABI3 (Parcy et al., 1994), ectopic expression of VP1 in vegetative tissue enhances ABA inhibition of root growth. In addition, 35S‐VP1 confers strong ABA inducible expression of the normally seed‐specific cruciferin C (CRC) gene in leaves. In contrast, ectopic ABA induction of C1‐GUS is restricted to a localized region of the root elongation zone. The ABA‐dependent C1‐GUS expression expanded to a broader area in the root tissues treated with exogenous application of auxin. Interestingly, auxin‐induced lateral root formation is completely suppressed by ABA in 35S‐VP1 plants but not in wild type. These results indicate VP1 mediates a novel interaction between ABA and auxin signaling that results in developmental arrest and altered patterns of gene expression.
Novel ABA‐ and dehydration‐inducible aldehyde dehydrogenase genes isolated from the resurrection plant Craterostigma plantagineum and Arabidopsis thaliana
Authors: Kirch Hans‐Hubert , Nair Ambili , Bartels Dorothea 
Published: March 2003

SummaryIn order to identify genes that are critical for the ABA‐dependent stress response in the resurrection plant Craterostigma plantagineum, a gene was isolated with homology to class 3 variable substrate aldehyde dehydrogenases (ALDH). The C. plantagineum gene Cp‐ALDH constitutes a novel class of plant ALDHs. In a search for corresponding genes from Arabidopsis thaliana, Ath‐ALDH3 and Ath‐ALDH4 were isolated, showing 70% and 80% similarity to Cp‐ALDH. Phylogenetically, the Cp‐ and Ath‐ALDH3 and ‐ALDH4 proteins are closely related to aldehyde dehydrogenases from bacteria and mammalian species and are separated from known plant ALDHs and betaine‐aldehyde dehydrogenases (BADH). Cp‐ALDH transcript and polypeptide are up‐regulated in vegetative tissues and callus in response to dehydration or ABA‐treatment. Ath‐ALDH3 expression was induced in response to dehydration and ABA treatment, while Ath‐ALDH4 is constitutively expressed at a low level. Recombinant Cp‐ALDH protein oxidizes nonanal, propionaldehyde and acetaldehyde, with Km values of 2.2 µm, 0.27 mm and 3.23 mm, respectively, in an NAD‐dependent manner. Immunogold electron microscopy shows that Cp‐ALDH is localized in plastids.
Sub‐cellular localisation of GFP‐tagged tobacco mitotic cyclins during the cell cycle and after spindle checkpoint activation
Authors: Criqui Marie Claire , Weingartner Magdalena , Capron Arnaud , Parmentier Yves , Shen Wen‐Hui , Heberle‐Bors Erwin , Bögre Laszlo , Genschik Pascal 
Published: March 2003

SummaryWe have previously shown that the tobacco cyclin B1;1 protein accumulates during the G2 phase of the cell cycle and is subsequently destroyed during mitosis. Here, we investigated the sub‐cellular localisation of two different B1‐types and one A3‐type cyclin during the cell cycle by using confocal imaging and differential interference contrast (DIC) microscopy. The cyclins were visualised as GFP‐tagged fusion proteins in living tobacco cells. Both B1‐type cyclins were found in the cytoplasm and in the nucleus during G2 but when cells entered into prophase, both cyclins became associated with condensing chromatin and remained on chromosomes until metaphase. As cells exited metaphase, the B1‐type cyclins became degraded, as shown by time‐lapse images. A stable variant of cyclin B1;1‐GFP fusion protein, in which the destruction box had been mutated, maintained its association with the nuclear material at later phases of mitosis such as anaphase and telophase. Furthermore, we demonstrated that cyclin B1;1 protein is stabilised in metaphase‐arrested cells after microtubule destabilising drug treatments. In contrast to the B1‐type cyclins, the cyclin A3;1 was found exclusively in the nucleus in interphase cells and disappeared earlier than the cyclin B1 proteins during mitosis.
Sensitive and high throughput metabolite assays for inorganic pyrophosphate, ADPGlc, nucleotide phosphates, and glycolytic intermediates based on a novel enzymic cycling system
Authors: Gibon Yves , Vigeolas Helene , Tiessen Axel , Geigenberger Peter , Stitt Mark 
Published: March 2003

SummaryMetabolite assays are required to characterise how metabolism changes between genotypes during development and in response to environmental perturbations. They provide a springboard to identify important regulatory sites and investigate the underlying mechanisms. Due to their small size, Arabidopsis seeds pose a technical challenge for such measurements. A set of assays based on a novel enzymic cycling system between glycerol‐3‐phosphate dehydrogenase and glycerol‐3‐phosphate oxidase have been developed and optimised for use with growing Arabidopsis seeds. In combination with existing assays they provide a suite of high throughput, sensitive assays for the immediate precursors for starch (adenine diphosphate glucose) and lipid (acetyl coenzyme A, glycerol‐3‐phosphate) synthesis, as well as pyrophosphate, ATP, ADP and most of the glycolytic intermediates. A method is also presented to rapidly quench intact siliques, lyophilise them and then manually separate seeds for metabolite analysis. These techniques are used to investigate changes in overall seed metabolite levels during development and maturation, and in response to a stepwise decrease of the external oxygen concentration.
Constitutive expression of ETHYLENE‐RESPONSE‐FACTOR1 in Arabidopsis confers resistance to several necrotrophic fungi
Authors: Berrocal‐Lobo Marta , Molina Antonio , Solano Roberto 
Published: March 2003

SummaryInfection of a plant by a pathogen induces a variety of defense responses that imply the action of several signaling molecules, including salicylic acid (SA), jasmonic acid (JA) and ethylene (E). Here we describe the role of ETHYLENE‐RESPONSE‐FACTOR1 (ERF1) as a regulator of ethylene responses after pathogen attack in Arabidopsis. The ERF1 transcript is induced on infection by Botrytis cinerea, and overexpression of ERF1 in Arabidopsis is sufficient to confer resistance to necrotrophic fungi such as B. cinerea and Plectosphaerella cucumerina. A positive co‐operation between E and SA pathways was observed in the plant response to P. cucumerina. Infection by Pseudomonas syringae tomato DC3000, however, does not affect ERF1 expression, and activation of ethylene responses by ERF1 overexpression in Arabidopsis plants reduces tolerance against this pathogen, suggesting negative crosstalk between E and SA signaling pathways, and demonstrating that positive and negative interactions between both pathways can be established depending on the type of pathogen.
Herbivore‐induced volatiles induce the emission of ethylene in neighboring lima bean plants
Authors: Arimura Gen‐ichiro , Ozawa Rika , Nishioka Takaaki , Boland Wilhelm , Koch Thomas , Kühnemann Frank , Takabayashi Junji 
Published: March 2003

SummaryHerbivore attacks induce leaves to emit a specific blend of volatiles. Here we show that exposure to Tetranychus urticae‐induced volatiles, as well as T. urticae infestation and artificial wounding, activates the transcription of the genes involved in the biosynthesis of ethylene [S‐adenosylmethionine (SAM) synthetase and 1‐aminocyclopropane‐1‐carboxylic acid oxidase] and a gene involved in the biosynthesis of polyamines from SAM (SAM decarboxylase) in lima bean leaves. Moreover, exposure of leaves to any one of the seven major chemical components of T. urticae‐induced volatiles also induces expression of these genes. Furthermore, we found that, when lima bean plants were exposed to T. urticae‐induced volatiles, they emitted ethylene. Lima bean plants infested by T. urticae and artificially wounded plants also emitted ethylene. Endogenous polyamine levels were not increased in the exposed leaves or the infested leaves, suggesting that polyamine production from SAM was only slightly promoted at the metabolic levels present in the leaves. We found that jasmonate (JA) accumulated in leaves exposed to T. urticae‐induced volatiles, and that both JA and salicylate (SA) accumulated in leaves infested by T. urticae. These findings, as well as results of pharmacological analyses, suggest that, in leaves exposed to T. urticae‐induced volatiles, ethylene biosynthesis might be regulated by pathways involving JA and the ethylene positive feedback loop. They also suggest that ethylene biosynthesis might be regulated by signaling pathways involving JA, SA and ethylene in T. urticae‐infested leaves.
Light signalling mediated by phytochrome plays an important role in cold‐induced gene expression through the C‐repeat/dehydration responsive element (C/DRE) in Arabidopsis thaliana
Authors: Kim Hyoun‐Joung , Kim Yun‐Kyoung , Park Jin‐Young , Kim Jungmook 
Published: March 2003

SummaryLow temperature induces a number of genes that encode the proteins promoting tolerance to freezing, mediated by ABA‐dependent and ABA–independent pathways in plants. The cis‐acting element called C/DRE is known to respond to low temperature independently of ABA action. To investigate the signalling and network of ABA‐independent pathways, the transgenic Arabidopsis plants were generated containing several copies of the C/DRE derived from cor15a gene with a minimal promoter fused to a GUS reporter gene. The transgenic plants containing four copies of the C/DRE (4C/DRE‐GUS) showed responsiveness to cold and drought treatments and were used for characterization of cold signalling and cross‐talk. Cold‐induced GUS expression was inhibited by okadaic acid at 1 nm, indicating that protein phosphatase 2A might act as a positive regulator. Light was shown to activate cold‐ and drought‐induced GUS expression. Photo‐reversibility of the GUS mRNA by red and far‐red light with concomitant cold treatment suggests a role of phytochrome as a photoreceptor in mediating light signalling to activate the cold‐induced gene expression through the C/DRE. Furthermore, GUS expression analysis in phyA or phyB or phyAphyB mutant backgrounds showed that phytochrome B is a primary photoreceptor responsible for the activation of cold‐stress signalling in response to light. Light enhanced the induction kinetics of CBF1, 2, and 3 encoding the cognate transcription factors, and cor15a, in a consecutive manner compared to the dark condition in the cold, suggesting that the connection point between cold and light signalling mediated by phytochrome is at a higher step than the expression of CBF genes.
Identification of a hard surface contact‐induced gene in Colletotrichum gloeosporioides conidia as a sterol glycosyl transferase, a novel fungal virulence factor
Authors: Kim Yeon‐Ki , Wang Yuhuan , Liu Zhi‐mei , Kolattukudy Pappachan E. 
Published: March 2003

SummaryHard surface contact has been known to be necessary to induce infection structure (appressorium) formation in many phytopathogenic fungi. However, the molecular basis of this requirement is unknown. We have used a differential display approach to clone some of the genes induced in the conidia by hard surface contact. We report that one of the genes induced by hard‐surface contact of the conidia of Colletotrichum gloeosporioides, chip6, encodes a protein with homology to sterol glycosyl transferases. chip6 expressed in E. coli catalyses glucosyl transfer from UDP‐glucose to cholesterol. Disruption of chip6 causes a marked decrease in the transferase activity and a drastic reduction in virulence on its natural host, avocado fruits, although the mutant is capable of normal growth and appressorium formation. The requirement for sterol glycosyl transferase for pathogenicity suggests a novel biological function for this transferase.
Fertilization in Arabidopsis thaliana wild type: Developmental stages and time course
Authors: Faure Jean‐Emmanuel , Rotman Nicolas , Fortuné Philippe , Dumas Christian 
Published: March 2003

SummaryWe describe some previously uncharacterised stages of fertilization in Arabidopsis thaliana and provide for the first time a precise time course of the fertilization process. We hand‐pollinated wild type pistils with wild type pollen (Columbia ecotype), fixed them at various times after pollination, and analysed 600 embryo sacs using Confocal Laser Scanning Microscopy. Degeneration of one of the synergid cells starts at 5 Hours After Pollination (HAP). Polarity of the egg changes rapidly after this synergid degeneration. Karyogamy is then detected by the presence of two nucleoli of different diameters in both the egg and central cell nuclei, 7–8 HAP. Within the next hour, first nuclear division takes place in the fertilized central cell and two nucleoli can then be seen transiently in each nucleus produced. In a second set of experiments, we hand‐pollinated wild type pistils with pollen from a transgenic promLAT52::EGFP line that expresses EGFP in its pollen vegetative cell. Release of the pollen tube contents into the synergid cell could be detected in living material. We show that the timing of synergid degeneration and pollen tube release correlate well, suggesting that either the synergid cell degenerates at the time of pollen tube discharge or very shortly before it. These observations and protocols constitute an important basis for the further phenotypic analysis of mutants affected in fertilization.
A role for nuclear localised proteasomes in mediating auxin action
Authors: R. Bahrami Ahmad ,   Ruth Bastow, Rolfe Stephen , Price Clive , Gray Julie E. 
Published: March 2003

SummaryA number of important cellular events in animals and yeast are regulated by protein degradation, and it is becoming apparent that such regulated proteolysis is involved in many facets of plant physiology and development. We have investigated the role of protein degradation by proteasomes in plants using NtPSA1, a tobacco gene that is predominantly expressed in young developing tobacco tissues and has extensive homology to yeast and human α‐type proteasome subunit genes. The NtPSA1 cDNA was used to complement a lethal mutation of the yeast PRC1α subunit gene indicating that NtPSA1 encodes a functional proteasome subunit, and transient expression of an NtPSA1::GUS protein fusion in onion cells confirmed that the nuclear localisation signal that is present in the NtPSA1 peptide sequence is active in plant cells. Plants transformed with an antisense NtPSA1 gene had reduced levels of NtPSA1 mRNA and exhibited reduced apical dominance. In addition, these low NtPSA1 plants displayed several morphological defects associated with auxin resistance such as reduced stamen length, and showed increased tolerance to high concentrations of auxin. These results support a role for nuclear localised proteasomes in floral development and auxin responses.
Expression analysis suggests novel roles for members of the Pht1 family of phosphate transporters in Arabidopsis
Authors: Mudge Stephen R. , Rae Anne L. , Diatloff Eugene , Smith Frank W. 
Published: March 2003

SummaryThe completion of the Arabidopsis thaliana genome has revealed that there are nine members of the Pht1 family of phosphate transporters in this species. As a step towards identifying the role of this gene family in phosphorus nutrition, we have isolated the promoter regions from each of these genes, and fused them to the reporter genes β‐glucuronidase and/or green fluorescent protein. These chimeric genes have been introduced into A. thaliana, and reporter gene expression has been assayed in plants grown in soil containing high and low concentrations of inorganic phosphate (Pi). Four of these promoters were found to direct reporter gene expression in the root epidermis, and were induced under conditions of phosphate deprivation in a manner similar to previously characterised Pht1 genes. Other members of this family, however, showed expression in a range of shoot tissues and in pollen grains, which was confirmed by RT‐PCR. We also provide evidence that the root epidermally expressed genes are expressed most strongly in trichoblasts, the primary sites for uptake of Pi. These results suggest that this gene family plays a wider role in phosphate uptake and remobilisation throughout the plant than was previously believed.