bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered regulation of tomato and tobacco pigmentation genes caused by the delila gene of Antirrhinum
Authors: Mooney Mark , Desnos Thierry , Harrison Kate , Jones Jonathan , Carpenter Rosemary , Coen Enrico 
Published: March 2003

Summary Delila (del), a regulatory gene of Antirrhinum, alters anthocyanin pigmentation when introduced into two Solanaceous species. In tomato, pigmentation in vegetative tissues is strongly increased while in tobacco, intensification of pigment is restricted to flowers. Although del transcripts are ubiquitous in the transgenic plants, transcript levels of host anthocyanin biosynthetic genes are only increased in pigmented regions. Constructs carrying the maize transposon Ac, inserted at the 3′ end of the 35S promoter prior to the start of translation of the del gene, give variegated leaves in tomato, suggesting that del acts cell‐autonomously and that it may be used as a phenotypic marker. In Arabidopsis, del has no strong phenotypic effects, suggesting that del may not be able to function effectively in all plant hosts.
Saturating the genetic map of Arabidopsis thaliana with embryonic mutations
Authors: Franzmann Linda H. , Yoon Elizabeth S. , Meinke David W. 
Published: March 2003

SummaryOne goal of the Arabidopsis genome project is to identify every gene with an essential function in growth and development. Towards that end, the results are reported here of a mapping project designed to enhance the linkage map of Arabidopsis and establish a valuable resource of mutations in essential genes with known map locations. Embryo‐defective (emb) mutations were chosen because they represent the most common heritable defect identified following mutagenesis in Arabidopsis. Multiple marker lines with easily scored phenotypes were constructed to facilitate mapping efforts. Recombination data were obtained for 169 mutants defective in embryo‐genesis. The chromosomal locations of 110 emb genes are presented in this report. Twenty‐six of these genes are tagged with T‐DNA. Nine other mutants isolated following seed transformation appear to contain chromosomal translocations. Another 31 mutant genes in the collectiohave been assigned to a linkage group but not yet placed on the map. Nineteen examples of duplicate alleles have also been found. This is consistent with the estimate that approximately 500 genes readily mutate to give an embryo‐defective phenotype in Arabidopsis. With continued progress, it may therefore be possible to approach saturation for this important class of mutations. Molecular cloning of these genes should be facilitated by identifying cDNAs and genomic sequences that map to similar locations.
Targeted disruption of the TGA3 locus in Arabidopsis thaliana
Authors: Miao Zhong‐He , Lam Eric 
Published: March 2003

SummaryA major drawback to study gene functions in plant systems is the lack of an effective gene knockout strategy. With a large number of plant genes isolated and the accelerating pace by which this collection is growing, the need for their functional analyses at the whole plant level has become increasingly urgent. Here evidence is reported for the first successful disruption of a non‐selectable gene in Arabidopsis thaliana by creating a mutant of the TGA3 locus via targeted insertion of the bacterial neo gene conferring kanamycin (Km) resistance. A β‐glucuronidase (GUS) expression unit outside the region of homology was used as a screenable marker to distinguish homologous recombination events from those of ectopic insertions. PCR amplification coupled with Southern blot screening identified two putative homologous recombination events among 2580 Kmr calli. One callus line was subsequently isolated and the structure of the targeted TGA3 allele confirmed by Southern blot analyses. This study demonstrates the feasibility of targeting a non‐selectable locus in Arabidopsis. Combined with future improvements in negative selection strategies and efficient, transformation methodologies, gene replacement studies in plants could become a routine technique.
Systemin induces rapid ion fluxes and ethylene biosynthesis in Lycopersicon peruvianum cells
Authors: Felix Georg , Boller Thomas 
Published: March 2003

SummarySuspension‐cultured cells of Lycopersicon peruvianum L. reacted to the presence of mechanically damaged cells with a transient alkalinization of their culture medium. This response resembled the alkalinization observed after treatment with fungal signal molecules such as chitin fragments and ergosterol or after application of the protein phosphatase inhibitor calyculin A. When compounds implicated in wound signalling were tested, the 18 amino acid peptide systemin was found to be a potent inducer of the alkalinization response, with a half‐maximal activity at concentrations of ∼100 pM. The decrease in extracellular H+ was paralleled by an increase of K+, and induction of both ion fluxes was blocked by the protein kinase inhibitor K‐252a. Systemin also caused rapid increases in the activities of 1‐aminocyclopropane‐1‐carboxylate (ACC) synthase and phenylalanine ammonia‐lyase, two other responses commonly observed in cells treated with elicitors. The systemin analogue systemin‐Ala17, a reported systemin antagonist in the induction of proteinase inhibitors in tomato plants, provoked a much weaker alkalinization response and did not induce ACC synthase at all. When applied together with authentic systemin, this analogue antagonized induction of both responses, indicating that the perception system for systemin had very similar properties in the L. peruvianum cells as in tomato plants. In conclusion, suspension‐cultured L. peruvianum cells provide a convenient and highly sensitive system to study elements of wound response and, in particular, systemin perception.
Genetic dissection of the co‐expression of genes encoding the two isoforms of oleosins in the oil bodies of maize kernel
Authors: Lee Keunmyoung , Ratnayake Chandra , Huang Anthony H.C. 
Published: March 2003

SummaryOleosins are abundant structural proteins on the surface of intracellular oil bodies in seeds. In many maize (Zea mays L.) inbreds, there are three oleosins, OLE18, OLE17, and OLE16, termed according to their apparent molecular weight, which are present in the proportional amounts of about 1:1:2 in isolated oil bodies. In some inbreds, OLE18 and OLE17 occur as molecular weight variants with a molecular weight difference of 1000 or less. In inbreds CM555 and FR2, OLE18 and OLE17, respectively, are absent; the respective genes ole18 and ole17 in the inbreds are present, but are transcriptionally inactive. The F1 of CM555 x FR2 possesses both OLE18 and OLE17, as expected from the inheritance of ole18 and ole17 genes. In all inbreds examined, including CM555, FR2, and their F1 hybrids, and in both the diploidic embryos and triploidic aleurone layers, the quantity of OLE18 and/or OLE17 equals that of OLE16. Since OLE18 and OLE17 are close members of the high‐molecular weight (H) oleosin isoform whereas OLE16 belongs to the low‐molecular weight (L) oleosin isoform, the results indicate the presence of equal amounts of the H and L isoforms in the oil bodies. The equality suggests the occurrence of a hetero‐dimer, or ‐multimer, of the two isoforms. To probe the control mechanism for such a hetero‐mer formation, CM555, FR2, and their F1 hybrids, as well as Mo17 (a common inbred) have been used to analyze oleosin gene copy number, nuclear run‐off transcription activity, transcript amount, and oleosin protein content. It has been determined that equal levels of H and L oleosin isoforms accumulate in oil bodies irrespective of the dosage of functional H and L genes. Therefore, the control of equality is not the consequence of the competition among the active H isoform genes for transcriptional machineries, but occurs at the post‐transcriptional level, presumably at translation and/or through oleosin interaction (formation of hetero‐mer) and stability.
The promoter of a H2O2‐inducible, Arabidopsis glutathione S‐transferase gene contains closely linked OBF‐ and OBP1‐binding sites
Authors: Chen Wenqiong , Chao Gerald , Singh Karam B. 
Published: March 2003

SummaryGlutathione S‐transferases (GSTs) are a family of multi‐functional enzymes that play critical roles in the detoxification of xenobiotics and the protection of tissues against oxidative damage. GSTs are important enzymes in plant responses to a number of environmental stresses including herbicides and pathogen attack. Ocs elements are a group of related, 20 bp promoter elements which have been exploited by some plant pathogens to express genes in plants. Ocs elements have also been found to regulate the expression of a plant GST promoter. An Arabidopsis GST gene, called GST6 has been isolated. GST6 expression is under tissue‐specific control and is induced following treatment with auxin, salicylic acid and H2O2. The GST6 promoter contains a binding site for two Arabidopsis ocs element binding factors (OBF), that has some sequence homology to ocs element sequences. Interestingly, OBP1 (OBF binding protein), a DNA‐binding protein that was isolated by screening an Arabidopsis cDNA library with a labeled OBF protein as a probe, binds next to the OBF‐binding site on the GST6 promoter. OBP1 was able to significantly stimulate the binding of OBF proteins to the GST6 promoter, raising the possibility that interactions between the OBP1 and OBF proteins may be important for GST6 expression.
Li+‐regulated 1‐aminocyclopropane‐1‐carboxylate synthase gene expression in Arabidopsis thaliana
Authors: Liang Xiaowu , Shen Nancy F. , Theologis Athanasios 
Published: March 2003

SummaryIn Arabidopsis thaliana, 1‐aminocyclopropane‐1‐carboxylate synthase (ACS) is encoded by a multigene family consisting of at least five members whose expression is induced by hormones, developmental signals, and protein synthesis inhibition. Li+, known to interfere with the phosphoinositide (PI) second messenger system by inhibiting the activity of inositol‐phosphate phosphatases, is one of the strongest inducers of ACC synthase activity in plants. Treatment of etiolated Arabidopsis seedlings with LiCl results in a rapid induction of the ACS5 gene. Also, LiCl represses the cycloheximide (CHX)‐induced accumulation of the ACS2 mRNA. The effects of Li+ on the expression of ACS5 and ACS2 are specific, dose‐dependent, and can be reversed by Ca2+ and mimicked by the protein kinase inhibitor K‐252a. The results suggest that the regulation of some ACS genes by various inducers may involve protein kinase activity, which in turn may be controlled through an inositol 1,4,5‐triphosphate (IP3)‐mediated Ca2+ mobilization. Since plants contain no Li+, the cation appears to unmask pre‐existing biochemical capacity that may be utilized by various unknown transducers during plant growth and development.
The elongation of amylose and amylopectin chains in isolated starch granules
Authors: Denyer Kay , Clarke Belinda , Hylton Christopher , Tatge Helma , Smith Alison M. 
Published: March 2003

SummaryThe aim of this work was to investigate the conditions required for amylose synthesis in starch granules. Although the major granule‐bound isoform of starch synthase ‐ GBSSI ‐ catalyses the synthesis of amylose in vivo, 14C from ADP[14C]glucose was incorporated primarily into a specific subset of amylopectin chains when supplied to starch granules isolated from pea (Pisum sativum L.) embryos and potato (Solanum tuberosum L.) tubers. Incubation of granules with soluble extracts of these organs revealed that the extracts contained compounds that increased the incorporation of 14C into amylose. These compounds were rendered inactive by treatment of the extracts with α‐glucosidase, suggesting that they were malto‐oligosaccharides. Consistent with this idea, provision of pure malto‐oligosaccharides to isolated granules resulted in a dramatic shift in the pattern of incorporation of 14C, from amylopectin chains to amylose molecules. Comparison of the pattern of incorporation in granules from wild‐type peas and lam mutant peas which lack GBSSI showed that this effect of malto‐oligosaccharides was specifically on GBSSI. The significance of these results for understanding of the synthesis of amylose and amylopectin in storage organs is discussed.
Roscovitine, a novel cyclin‐dependent kinase inhibitor, characterizes restriction point and G2/M transition in tobacco BY‐2 cell suspension
Authors: Planchais Séverine , Glab Nathalie , Tréhin Christophe , Perennes Claudette , Bureau Jean‐Marc , Meijer Laurent , Bergounioux Catherine 
Published: March 2003

SummaryAlthough the developmental programs of plants and animals differ, key regulatory components of their cell cycle have been conserved. Particular attention has been paid to the role of the complexes between highly conserved cyclin and cyclin‐dependent kinases in regulating progression through the cell cycle. The recent demonstration that roscovitine is a potent and selective inhibitor of the animal cyclin‐dependent kinases cdc2 (CDK1), CDK2 and CDK5 prompted an investigation into its effects on progression through the plant cell cycle. Roscovitine induced arrests both in late G1 and late G2 phase in BY‐2 tobacco cell suspensions. Both blocks were fully reversible when roscovitine was used at concentrations similar to those used in the animal system. Stationary‐phase cells subcultured in the presence of roscovitine were arrested at a 2C DNA content. This arrest was more efficient without exogenous addition of plant growth regulator. Roscovitine induced a block in G1 earlier than that induced by aphidicolin. S‐phase synchronized cells treated with roscovitine were arrested at a 4C DNA content at the G2/ M transition. The expression analysis of a mitotic cyclin (NTCYC1) indicated that the roscovitine‐induced G2 block probably occurs in late G2. Finally, cells in metaphase were insensitive to roscovitine. The purified CDK/cyclin kinase activities of late G1 and early M arrested cells were inhibited in vitro by roscovitine. The implications of these experimental observations for the requirement for CDK activity during progression through the plant cell cycle are discussed.
Transgenic potato tubers accumulate high levels of 1‐kestose and nystose: functional identification of a sucrose sucrose 1‐fructosyltransferase of artichoke (Cynara scolymus) blossom discs
Authors: Hellwege Elke M. , Gritscher Dominique , Willmitzer Lothar , Heyer Arnd G. 
Published: March 2003

SummaryBy screening a cDNA library of artichoke (Cynara scolymus) blosssom discs for fructosyltransferases, we isolated a clone designated Cy21. The deduced amino acid sequence shows homology to acid β‐fructosyl hydrolases and to the sucrose‐fructan 6‐fructosyltransferase (6‐SFT) of barley. Transiently expressed in Nicotiana tabacum protoplasts, the Cy21 gene‐product synthesized 1‐kestose, indicating that Cy21 codes for a sucrose sucrose 1‐fructosyltransferase (1‐SST). The enzyme worked at physiologically relevant sucrose concentrations (25 mM sucrose). In the protoplast system, 1‐kestose seemed to be the only fructan product of the 1‐SST.The enzyme activity was not affected by pyridoxal‐HCl, an inhibitor of both the β‐fructosyl hydrolase and the fructosyltransferase activity of invertases. The fructosyltransferase activity of the Cy21 gene‐product, however, could be inhibited by Zn2+, Ag+ and Cu2+ ions. In artichoke plants the Cy21 transcript was highly abundant in primary roots and blossom discs. Transgenic potato tubers expressing Cy21 contain high levels of 1‐kestose along with nystose and traces of fructosyl‐nystose, supporting the conclusion that the Cy21 clone encodes a sucrose sucrose 1‐fructosyltransferase.
In vivo evidence for 5′→3′ exoribonuclease degradation of an unstable chloroplast mRNA
Authors: Drager Robert G. , Girard‐bascou Jacqueline , Choquet Yves , Kindle Karen L. , Stern David B. 
Published: March 2003

SummaryThe acetate‐requiring Chlamydomonas reinhardtii nuclear mutant F16 harbors the mutation mcd1–1 and fails to accumulate the cytochrome b6/f complex. The primary defect of mcd1–1 was determined to be the instability of petD mRNA, which encodes subunit IV of the complex. Chimeric reporter genes introduced by chloroplast transformation demonstrated that the determinant of petD mRNA instability in the mcd1–1 background is located in the 5′ untranslated region (UTR). However, when this 5′ UTR was present downstream of other sequences in dicistronic or chimeric transcripts, the RNAs were no longer destabilized in the mcd1–1 background. Together, these results suggest that the 5′ end of the petD 5′ UTR interacts with the MCD1 product. The insertion of a polyguanosine sequence into the petD 5′ UTR fused to a reporter gene allowed accumulation of the reporter gene transcript in the mutant background. Since polyguanosine forms a structure that is known to impede exonucleases, these data provide in vivo evidence that petD mRNA can be degraded by 5′→3′ exoribonuclease activity. Furthermore, the data support a model in which protein binding to the petD 5′ UTR protects the mRNA from 5′→3′ degradation in wild‐type cells.
The role of ion fluxes in Nod factor signalling in Medicago sativa
Authors: Felle Hubert H. , Kondorosi Éva , Kondorosi Ádám , Schultze Michael 
Published: March 2003

SummaryUsing ion‐selective microelectrodes, the basis of Nod factor‐induced changes in the plasma membrane potential was analysed by measuring the extracellular free concentrations of Ca2+, K+, H+ and Cl– in the root hair zone of alfalfa. After addition of the Rhizobium meliloti Nod factor NodRm‐IV(C16:2,S) at a concentration of 0.1 μM, a decrease in [Ca2+] was observed first, which was followed after a few seconds by an increase of [Cl–], by an alkalinization, and then by a delayed increase of [K+], all of which were transient changes. Simultaneously with the appearance of Cl– ions in the root hair zone, a decrease in cytosolic [Cl–] was measured. It was concluded that the depolarization was caused by temporary short‐circuiting of the proton pump through the rapid release of Cl– ions along their steep electrochemical gradient. Since under resting conditions the driving force for K+ ions was inwardly directed, their release was delayed until their driving force was inverted. This indicates that K+ serves as a charge balance that eventually stops depolarization and initiates repolarization. Since the decrease in [Ca2+] was observed seconds before the increase in [Cl–] and the depolarization, it is argued that Ca2+ entering into the cell does not cause the depolarization directly, but might initiate it by triggering the activation of an anion channel that then releases the chloride ions. The observations that the Ca2+ ionophore A23187 mimicks the Nod factor response, and that the Ca2+ channel antagonist nifedipine inhibits this response, support the idea that Ca2+ plays a primary role in the transduction of the Nod signal in alfalfa.
Solubilization and characterization of a galacturonosyltransferase that synthesizes the pectic polysaccharide homogalacturonan
Authors: Doong Ron Lou , Mohnen Debra 
Published: March 2003

SummaryPolygalacturonate 4‐α‐galacturonosyltransferase (PGA‐GalAT), the glycosyltransferase that synthesizes the plant cell wall pectic polysaccharide homogalacturonan, has previously been identified and partially characterized in tobacco membranes. Membrane bound PGA‐GalAT catalyzes the transfer of galacturonic acid from UDP‐galacturonic acid (UDP‐GalA) onto an endogenous acceptor to produce polymeric homogalacturonan ( Doong et al. (1995) Plant Physiol. 109, 141
–152). It is shown here that a galacturonosyltransferase is solubilized from tobacco membranes with a HEPES buffer, pH 6.8, containing 40 mM CHAPS and 2 mM EDTA. The solubilized galacturonosyltransferase was identified as putative PGA‐GalAT because it transfered [14C]GalA from UDP‐[14C]GalA onto exogenous homogalacturonan acceptors with degrees of polymerization (DP) of ≥ 10. Maximal solubilized PGA‐GalAT activity in the presence of 0.9 μM UDP‐[14C]GalA required approximately 125 μM exogenous homogalacturonan acceptor [e.g. oligogalacturonide (OGA) of DP 15]. Solubilized PGA‐GalAT was active over a broad pH range of 6.3–7.8, and had an apparent Km for UDP‐GalA of 37 μM and a Vmax of 290 pmol min–1 mg–1 protein. Approximately 44% of the PGA‐GalAT activity in detergent‐dispersed membranes, corresponding to 21% of the PGA‐GalAT activity in intact membranes, was solubilized. PGA‐GalAT solubilized with 40 mM CHAPS was shown, by exopolygalacturonase treatment in combination with size exclusion and high performance anion exchange chromatographies, to add a single α‐1,4‐linked galacturonic acid residue onto an OGA exogenous acceptor of DP 15 to yield an OGA product of DP 16. The significance of the apparent lack of processivity of the solubilized PGA‐GalAT is discussed.
Inhibition of plant viral systemic infection by non‐toxic concentrations of cadmium
Authors: Ghoshroy Soumitra , Freedman Karen , Lartey Robert , Citovsky Vitaly 
Published: March 2003

SummaryHeavy metals, such as cadmium, have a significant impact on plant physiology. However, their potential effect on plant–pathogen interaction, an important biological process, has not been examined. This study shows that exposure of tobacco plants to non‐toxic concentrations of cadmium completely blocked viral disease caused by turnip vein clearing virus. Cadmium‐mediated viral protection was due to inhibition of the systemic movement of the virus, i.e. its spread from the inoculated into uninoculated leaves. Exposure of plants to cadmium had no effect on viral replication, assembly and local movement within the inoculated leaf. Analysis of the viral presence in different tissues suggested that cadmium treatment inhibited virus exit from the vascular tissue into uninoculated leaves rather than its entry into the host plant vasculature. Higher, toxic levels of cadmium did not produce this inhibitory effect on viral movement, allowing the systemic spread of the virus and development of the viral disease. These observations suggest that cadmium‐induced viral protection requires a relatively healthy, unpoisoned plant in which non‐toxic levels of cadmium may trigger the production of cellular factors which interfere with the viral systemic movement.
Induction of systemic resistance to Pythium damping‐off in cucumber plants by benzothiadiazole: ultrastructure and cytochemistry of the host response
Authors: Benhamou Nicole , Bélanger Richard R. 
Published: March 2003

SummaryBenzo (1,2,3) thiadiazole‐7‐carbothioic acid S‐methyl ester (BTH, CGA 245704), a non‐toxic, synthetic chemical, was applied as a foliar spray to cucumber plants and evaluated for its potential to induce defense mechanisms in root tissues infected by the soilborne pathogen, Pythium ultimum Trow. In non‐treated cucumber plants, fungal colonization was intense and paralleled marked host tissue damage, whereas in BTH‐treated plants, pathogen ingress towards the vascular stele was apparently halted by the massive deposition of a phenolic‐enriched material which occluded a large number of cortical and vascular parenchyma cells. This considerable increase in the accumulation of phenolics was accompanied by cytological disorders of the invading pathogen at a time when the wall‐bound cellulose component was preserved. In addition to phenolic compounds, the occluding material contained large amounts of β‐glucoside residues. These residues gradually decreased in the areas neighboring fungal cells whereas phenolic deposition appeared to be more uniformly distributed throughout the occluded host cells. Pathogen penetration in non‐occluded cucumber root cells coincided with other changes, mainly characterized by both the deposition onto the inner surface of the cell walls of some heterogeneous wall appositions and the coating of some intercellular spaces with an electron‐opaque material. Evidence is provided in this study that BTH has the ability to induce SAR in cucumber. Exogenous, foliar applications of the chemical sensitize susceptible cucumber plants to react more rapidly and more efficiently to P. ultimum attack, mainly through the massive accumulation of phenolic compounds at sites of attempted pathogen penetration.