bluuebunny/crossref_metadata_2025 huggingface dataset:
NPAT links cyclin E–Cdk2 to the regulation of replication-dependent histone gene transcription
Authors: Zhao Jiyong , Kennedy Brian K. , Lawrence Brandon D. , Barbie David A. , Matera A. Gregory , Fletcher Jonathan A. , Harlow Ed
Published: July 2002

In eukaryotic cells, histone gene expression is one of the major events that mark entry into S phase. While this process is tightly linked to cell cycle position, how it is regulated by the cell cycle machinery is not known. Here we show that NPAT, a substrate of the cyclin E–Cdk2 complex, is associated with human replication-dependent histone gene clusters on both chromosomes 1 and 6 in S phase. We demonstrate that NPAT activates histone gene transcription and that this activation is dependent on the promoter elements (SSCSs) previously proposed to mediate cell cycle–dependent transcription. Cyclin E is also associated with the histone gene loci, and cyclin E–Cdk2 stimulates the NPAT-mediated activation of histone gene transcription. Thus, our results both show that NPAT is involved in a key S phase event and provide a link between the cell cycle machinery and activation of histone gene transcription.
Coordination of chondrogenesis and osteogenesis by fibroblast growth factor 18
Authors: Liu Zhonghao , Xu Jingsong , Colvin Jennifer S. , Ornitz David M.
Published: July 2002

Gain of function mutations in fibroblast growth factor (FGF) receptors cause chondrodysplasia and craniosynostosis syndromes. The ligands interacting with FGF receptors (FGFRs) in developing bone have remained elusive, and the mechanisms by which FGF signaling regulates endochondral, periosteal, and intramembranous bone growth are not known. Here we show thatFgf18is expressed in the perichondrium and that mice homozygous for a targeted disruption ofFgf18exhibit a growth plate phenotype similar to that observed in mice lackingFgfr3and an ossification defect at sites that expressFgfr2. Mice lacking eitherFgf18orFgfr3exhibited expanded zones of proliferating and hypertrophic chondrocytes and increased chondrocyte proliferation, differentiation, and Indian hedgehog signaling. These data suggest that FGF18 acts as a physiological ligand for FGFR3. In addition, mice lackingFgf18display delayed ossification and decreased expression of osteogenic markers, phenotypes not seen in mice lackingFgfr3. These data demonstrate that FGF18 signals through another FGFR to regulate osteoblast growth. Signaling to multiple FGFRs positions FGF18 to coordinate chondrogenesis in the growth plate with osteogenesis in cortical and trabecular bone.
High-Throughput SNP Genotyping by Allele-Specific PCR with Universal Energy-Transfer-Labeled Primers
Authors: Myakishev Maxim V. , Khripin Yuri , Hu Stella , Hamer Dean H.
Published: July 2002

We have developed a new method for high-throughput genotyping of single nucleotide polymorphisms (SNPs). The technique involves PCR amplification of genomic DNA with two tailed allele-specific primers that introduce priming sites for universal energy-transfer-labeled primers. The output of red and green light is conveniently scored using a fluorescence plate reader. The new method, which was validated on nine model SNPs, is well suited for high-throughput, automated genotyping because it requires only one reaction per SNP, it is performed in a single tube with no post-PCR handling, the same energy-transfer-labeled primers are used for all analyses, and the instrumentation is inexpensive. Possible applications include multiple-candidate gene analysis, genomewide scans, and medical diagnostics.
Flexible Use of High-Density Oligonucleotide Arrays for Single-Nucleotide Polymorphism Discovery and Validation
Authors: Dong Shoulian , Wang Eugene , Hsie Linda , Cao Yanxiang , Chen Xiaogiong , Gingeras Thomas R.
Published: July 2002

A method for identifying and validating single nucleotide polymorphisms (SNPs) with high-density oligonucleotide arrays without the need for locus-specific polymerase chain reactions (PCR) is described in this report. Genomic DNAs were divided into subsets with complexity of ∼10 Mb by restriction enzyme digestion and gel-based fragment size resolution, ligated to a common adaptor, and amplified with one primer in a single PCR reaction. As a demonstration of this approach, a total of 124 SNPs were located in 190 kb of genomic sequences distributed across the entire human genome by hybridizing to high-density variant detection arrays (VDA). A set of independent validation experiments was conducted for these SNPs employing bead-based affinity selection followed by hybridization of the affinity-selected SNP-containing fragments to the same VDA that was used to identify the SNPs. A total of 98.7% (74/75) of these SNPs were confirmed using both DNA dideoxynucleotide sequencing and the VDA methodologies. With flexible sample preparation, high-density oligonucleotide arrays can be tailored for even larger scale genome-wide SNP discovery as well as validation.
A Genetic Strategy to Eliminate Self-Activator Baits Prior to High-Throughput Yeast Two-Hybrid Screens
Authors: Walhout Albertha J.M. , Vidal Marc
Published: July 2002

Large-scale sequencing projects have predicted high numbers of gene products for which no functional information is yet available. Hence, large-scale projects, such as gene knockouts, gene expression profiles, and protein-interaction mapping, are currently under way to initiate the understanding of the function of these gene products. The high-throughput strategies that are currently being developed to generate protein-interaction maps include automated versions of the yeast two-hybrid system. These strategies rely on the large-scale construction of DNA-binding domain/protein-of-interest hybrid constructs (DB-X baits). An inherent problem of large-scale two-hybrid systems is that a high percentage of cloned sequences encode polypeptides that, when fused to DB, can activate transcription in the absence of any two-hybrid-interacting partner protein. Here, we describe and validate a genetic strategy that efficiently eliminates such self-activator baits prior to screening procedures. The strategy is based on a negative-growth selection and is compatible with high-throughput settings.
Optical Recording of Odor-Evoked Responses in the Olfactory Brain of the Naı̈ve and Aversively Trained Terrestrial Snails
Authors: Nikitin Eugeny S. , Balaban Pavel M.
Published: July 2002

Regular spontaneous oscillations were recorded both electro- and optophysiologically using a voltage-sensitive absorption dye in the olfactory part of the brain (procerebral lobe of the cerebral ganglia) of the gastropod mollusk Helix lucorum. Odor application caused transient changes in procerebral oscillations, and an odor-evoked potential was recorded in the procerebrum (PC). The wave of evoked potential originated near the place of olfactory nerve entrance into the PC and propagated via the procerebral neuropile toward the cell body layer. The spread of the odor-evoked potential corresponded roughly to the neuropile area, whereas the spontaneous oscillations were recorded in the cell body layer of the PC and were not observed in the neuropile. Evoked potential did not produce additional events intercalated into the ongoing spontaneous oscillations. Changes in parameters of spontaneous oscillations to the repeated presentations of the same odor were variable. To estimate the role of spontaneous oscillations in odor encoding, we trained the snail to avoid cineole, using paired presentations of cineole and electric shock. Elaboration of conditioned aversion to cineole applications resulted in distinct pairing-specific changes in behavior of the snails and procerebral activity. Responses to odor (cineole) applications were not different in amplitude or frequency of spontaneous oscillations in control and trained snails, whereas ratio of amplitudes of the same oscillation wave in proximal and distal regions of the procerebrum was significantly different in control and aversively trained snails, reflecting changes in neural firing in certain areas of the olfactory lobe.
Contextual and Auditory Fear Conditioning are Mediated by the Lateral, Basal, and Central Amygdaloid Nuclei in Rats
Authors: Goosens Ki A. , Maren Stephen
Published: July 2002

A large body of literature implicates the amygdala in Pavlovian fear conditioning. In this study, we examined the contribution of individual amygdaloid nuclei to contextual and auditory fear conditioning in rats. Prior to fear conditioning, rats received a large electrolytic lesion of the amygdala in one hemisphere, and a nucleus-specific neurotoxic lesion in the contralateral hemisphere. Neurotoxic lesions targeted either the lateral nucleus (LA), basolateral and basomedial nuclei (basal nuclei), or central nucleus (CE) of the amygdala. LA and CE lesions attenuated freezing to both contextual and auditory conditional stimuli (CSs). Lesions of the basal nuclei produced deficits in contextual and auditory fear conditioning only when the damage extended into the anterior divisions of the basal nuclei; damage limited to the posterior divisions of the basal nuclei did not significantly impair conditioning to either auditory or contextual CS. These effects were typically not lateralized, although neurotoxic lesions of the posterior divisions of the basal nuclei had greater effects on contextual fear conditioning when the contralateral electrolytic lesion was placed in the right hemisphere. These results indicate that there is significant overlap within the amygdala in the neural pathways mediating fear conditioning to contextual and acoustic CS, and that these forms of learning are not anatomically dissociable at the level of amygdaloid nuclei.
Sequence Relationships, Conserved Domains, and Expression Patterns for Maize Homologs of the Polycomb Group GenesE(z), esc, andE(Pc)
Authors: Springer Nathan M. , Danilevskaya Olga N. , Hermon Pedro , Helentjaris Tim G. , Phillips Ronald L. , Kaeppler Heidi F. , Kaeppler Shawn M.
Published: July 2002

Polycomb group (PcG) proteins play an important role in developmental and epigenetic regulation of gene expression in fruit fly (Drosophila  melanogaster) and mammals. Recent evidence has shown that Arabidopsis homologs of PcG proteins are also important for the regulation of plant development. The objective of this study was to characterize the PcG homologs in maize (Zea mays). The 11 cloned PcG proteins from fruit fly and the Enhancer of zeste[E(z)], extra sex combs(esc), and Enhancer of Polycomb[E(Pc)] homologs from Arabidopsis were used as queries to perform TBLASTN searches against the public maize expressed sequence tag database and the Pioneer Hi-Bred database. Maize homologs were found for E(z), esc, and E(Pc), but not for Polycomb, pleiohomeotic,Posterior sex combs, Polycomblike,Additional sex combs, Sex combs on midleg, polyhometoic, or multi sex combs. Transcripts of the three maize Enhancer of zeste-like genes, Mez1, Mez2, andMez3, were detected in all tissues tested, and theMez2 transcript is alternatively spliced in a tissue-dependent pattern. Zea mays fertilization independent endosperm1 (ZmFie1) expression was limited to developing embryos and endosperms, whereas ZmFie2expression was found throughout plant development. The conservation ofE(z) and esc homologs across kingdoms indicates that these genes likely play a conserved role in repressing gene expression.
Effects of COR6.6 and COR15am Polypeptides Encoded by COR (Cold-Regulated) Genes of Arabidopsis thaliana on the Freeze-Induced Fusion and Leakage of Liposomes
Authors: Uemura M. , Gilmour S. J. , Thomashow M. F. , Steponkus P. L.
Published: July 2002

Several cold-regulated (COR) polypeptides, which have little or no amino acid sequence identity with known proteins, are synthesized during cold acclimation of Arabidopsis thaliana. However, the function of the polypeptides has yet to be elucidated. The objective of this study was to determine if COR6.6 and COR15am influence the incidence of either freeze-induced fusion or freeze-induced leakage of small unilamellar vesicles (SUVs) composed of either a single species of phosphatidylcholine (either 1-palmitoyl-2-oleoyl-, dioleoyl-, or dilinoleoylphosphatidylcholine), a mixture of dioleoylphosphatidylcholine, dioleoylphosphatidylethanolamine, and free sterols (1:1:1, mol:mol), or the total lipid extract of the plasma membrane of either nonacclimated or cold-acclimated rye leaves. When the SUVs were suspended in a dilute tris(hydroxymethyl)-aminomethane/2-(N-morpholino)ethanesulfonic acid buffer, both COR6.6 and COR15am invariably decreased the incidence of freeze-induced fusion regardless of the lipid composition. However, if the SUVs were suspended in a dilute solution of either sucrose or NaCl, the COR polypeptides had little or no effect on the incidence of freeze-induced fusion. Moreover, the COR polypeptides did not decrease the incidence of freeze-induced leakage[mdash]regardless of whether the SUVs were suspended in either the dilute buffer alone or with added sucrose or NaCl. In fact, with SUVs composed of a single species of phosphatidylcholine suspended in the dilute buffer, the COR polypeptides resulted in an anomalous increase in freeze-induced leakage. When considered collectively, these results suggest that neither COR6.6 nor COR15am has a direct cryoprotective effect on SUVs frozen in vitro.
Secretion of Active Recombinant Phytase from Soybean Cell-Suspension Cultures
Authors: Li J. , Hegeman C. E. , Hanlon R. W. , Lacy G. H. , Denbow D. M. , Grabau E. A.
Published: July 2002

Phytase, an enzyme that degrades the phosphorus storage compound phytate, has the potential to enhance phosphorus availability in animal diets when engineered into soybean (Glycine max) seeds. The phytase gene from Aspergillus niger was inserted into soybean transformation plasmids under control of constitutive and seed-specific promoters, with and without a plant signal sequence. Suspension cultures were used to confirm phytase expression in soybean cells. Phytase mRNA was observed in cultures containing constitutively expressed constructs. Phytase activity was detected in the culture medium from transformants that received constructs containing the plant signal sequence, confirming expectations that the protein would follow the default secretory pathway. Secretion also facilitated characterization of the biochemical properties of recombinant phytase. Soybean-synthesized phytase had a lower molecular mass than did the fungal enzyme. However, deglycosylation of the recombinant and fungal phytase yielded polypeptides of identical molecular mass (49 kD). Temperature and pH optima of the recombinant phytase were indistinguishable from the commercially available fungal phytase. Thermal inactivation studies of the recombinant phytase suggested that the additional protein stability would be required to withstand the elevated temperatures involved in soybean processing.
Desensitization of the Perception System for Chitin Fragments in Tomato Cells
Authors: Felix Georg , Baureithel Karl , Boller Thomas
Published: July 2002

Suspension-cultured tomato (Lycopersicon esculentum) cells react to stimulation by chitin fragments with a rapid, transient alkalinization of the growth medium, but behave refractory to a second treatment with the same stimulus (G. Felix, M. Regenass, T. Boller [1993] Plant J 4: 307–316). We analyzed this phenomenon and found that chitin fragments caused desensitization in a time- and concentration-dependent manner. Partially desensitized cells exhibited a clear shift toward lower sensitivity of the perception system. The ability of chitin oligomers to induce desensitization depended on the degree of polymerization (DP), with DP5 ≈ DP4 ≫ DP3 ≫ DP2 > DP1. This correlates with the ability of these oligomers to induce the alkalinization response and to compete for the high-affinity binding site on tomato cells and microsomal membranes, indicating that the alkalinization response and the desensitization process are mediated by the same receptor. The dose required for half-maximal desensitization was about 20 times lower than the dose required for half-maximal alkalinization; desensitization could therefore be used as a highly sensitive bioassay for chitin fragments and chitin-related stimuli such as lipochitooligosaccharides (nodulation factors) from Rhizobium leguminosarum. Desensitization was not associated with increased inactivation of the stimulus or with a disappearance of high-affinity binding sites from the cell surface, and thus appears to be caused by an intermediate step in signal transduction.
Characterization of a Red Beet Protein Homologous to the Essential 36-Kilodalton Subunit of the Yeast V-Type ATPase1
Authors: Bauerle Cynthia , Magembe Catherine , Briskin Donald P.
Published: July 2002

V-type proton-translocating ATPases (V-ATPases) (EC 3.6.1.3) are electrogenic proton pumps involved in acidification of endomembrane compartments in all eukaryotic cells. V-ATPases from various species consist of 8 to 12 polypeptide subunits arranged into an integral membrane proton pore sector (V0) and a peripherally associated catalytic sector (V1). Several V-ATPase subunits are functionally and structurally conserved among all species examined. In yeast, a 36-kD peripheral subunit encoded by the yeast (Saccharomyces cerevisiae) VMA6 gene (Vma6p) is required for stable assembly of the V0 sector as well as for V1 attachment. Vma6p has been characterized as a nonintegrally associated V0 subunit. A high degree of sequence similarity among Vma6p homologs from animal and fungal species suggests that this subunit has a conserved role in V-ATPase function. We have characterized a novel Vma6p homolog from red beet (Beta vulgaris) tonoplast membranes. A 44-kD polypeptide cofractionated with V-ATPase upon gel-filtration chromatography of detergent-solubilized tonoplast membranes and was specifically cross-reactive with anti-Vma6p polyclonal antibodies. The 44-kD polypeptide was dissociated from isolated tonoplast preparations by mild chaotropic agents and thus appeared to be nonintegrally associated with the membrane. The putative 44-kD homolog appears to be structurally similar to yeast Vma6p and occupies a similar position within the holoenzyme complex.
A High-Affinity Ca2+ Pump, ECA1, from the Endoplasmic Reticulum Is Inhibited by Cyclopiazonic Acid but Not by Thapsigargin
Authors: Liang Feng , Sze Heven
Published: July 2002

To identify and characterize individual Ca2+ pumps, we have expressed an Arabidopsis ECA1 gene encoding anendoplasmic reticulum-typeCa2+-ATPase homolog in the yeast (Saccharomyces cerevisiae) mutant K616. The mutant (pmc1pmr1cnb1) lacks a Golgi and a vacuolar membrane Ca2+ pump and grows very poorly on Ca2+-depleted medium. Membranes isolated from the mutant showed high H+/Ca2+-antiport but no Ca2+-pump activity. Expression of ECA1 in endomembranes increased mutant growth by 10- to 20-fold in Ca2+-depleted medium. 45Ca2+ pumping into vesicles fromECA1 transformants was detected after the H+/Ca2+-antiport activity was eliminated with bafilomycin A1 and gramicidin D. The pump had a high affinity for Ca2+ (K  m = 30 nm) and displayed two affinities for ATP (K  m of 20 and 235 μm). Cyclopiazonic acid, a specific blocker of animal sarcoplasmic/endoplasmic reticulum Ca2+-ATPase, inhibited Ca2+ transport (50% inhibition dose = 3 nmol/mg protein), but thapsigargin (3 μm) did not. Transport was insensitive to calmodulin. These results suggest that this endoplasmic reticulum-type Ca2+-ATPase could support cell growth in plants as in yeast by maintaining submicromolar levels of cytosolic Ca2+ and replenishing Ca2+ in endomembrane compartments. This study demonstrates that the yeast K616 mutant provides a powerful expression system to study the structure/function relationships of Ca2+ pumps from eukaryotes.
Differential Regulation of Enolase during Anaerobiosis in Maize
Authors: Lal Shailesh K. , Lee Chwenfang , Sachs Martin M.
Published: July 2002

It was reported previously that enolase enzyme activity and ENO1 transcript levels are induced by anaerobic stress in maize (Zea mays). Here we show that not all isoforms of maize enolase are anaerobically induced. We cloned and sequenced a second enolase cDNA clone (pENO2) from maize. Sequence analysis showed that pENO2 shares 75.6% nucleotide and 89.5% deduced amino acid sequence identity with pENO1 and is encoded by a distinct gene. Expression of ENO2 is constitutive under aerobic conditions, whereas ENO1 levels are induced 10-fold in maize roots after 24 h of anaerobic treatment. Western-blot analysis and N-terminal sequencing of in vivo-labeled maize roots identified two major proteins selectively synthesized upon anaerobic stress as isozymes of enolase. We describe the expression of enolase in maize roots under anaerobic stress.
The Interaction between Cold and Light Controls the Expression of the Cold-Regulated Barley Gene cor14b and the Accumulation of the Corresponding Protein1
Authors: Crosatti Cristina , Polverino de Laureto Patrizia , Bassi Roberto , Cattivelli Luigi
Published: July 2002

We report the expression of the barley (Hordeum vulgare L.) COR (cold-regulated) genecor14b (formerly pt59) and the accumulation of its chloroplast-localized protein product. A polyclonal antibody raised against the cor14b-encoded protein detected two chloroplast COR proteins: COR14a and COR14b. N-terminal sequencing of COR14a and expression of cor14b in Arabidopsis plants showed that COR14a is not encoded by thecor14b sequence, but it shared homology with the wheat (Triticum aestivum L.) WCS19 COR protein. The expression of cor14b was strongly impaired in the barley albino mutant an, suggesting the involvement of a plastidial factor in the control of gene expression. Low-level accumulation of COR14b was induced by cold treatment in etiolated plants, although cor14b expression and protein accumulation were enhanced after a short light pulse. Light quality was a determining factor in regulating gene expression: red or blue but not far-red or green light pulses were able to promote COR14b accumulation in etiolated plants, suggesting that phytochrome and blue light photoreceptors may be involved in the control of cor14bgene expression. Maximum accumulation of COR14b was reached only when plants were grown and/or hardened under the standard photoperiod. The effect of light on the COR14b stability was demonstrated by using transgenic Arabidopsis. These plants constitutively expressedcor14b mRNAs regardless of temperature and light conditions; nevertheless, green plants accumulated about twice as much COR14b protein as etiolated plants.
The Effect of Growth and Measurement Temperature on the Activity of the Alternative Respiratory Pathway1
Authors: Gonzàlez-Meler Miquel A. , Ribas-Carbo Miquel , Giles Larry , Siedow James N.
Published: July 2002

A postulated role of the CN-resistant alternative respiratory pathway in plants is the maintenance of mitochondrial electron transport at low temperatures that would otherwise inhibit the main phosphorylating pathway and prevent the formation of toxic reactive oxygen species. This role is supported by the observation that alternative oxidase protein levels often increase when plants are subjected to growth at low temperatures. We used oxygen isotope fractionation to measure the distribution of electrons between the main and alternative pathways in mung bean (Vigna radiata) and soybean (Glycine max) following growth at low temperature. The amount of alternative oxidase protein in mung bean grown at 19°C increased over 2-fold in both hypocotyls and leaves compared with plants grown at 28°C but was unchanged in soybean cotyledons grown at 14°C compared with plants grown at 28°C. When the short-term response of tissue respiration was measured over the temperature range of 35°C to 9°C, decreases in the activities of both main and alternative pathway respiration were observed regardless of the growth temperature, and the relative partitioning of electrons to the alternative pathway generally decreased as the temperature was lowered. However, cold-grown mung bean plants that up-regulated the level of alternative oxidase protein maintained a greater electron partitioning to the alternative oxidase when measured at temperatures below 19°C supporting a role for the alternative pathway in response to low temperatures in mung bean. This response was not observed in soybean cotyledons, in which high levels of alternative pathway activity were seen at both high and low temperatures.
The Endogenous Sulfated Pentapeptide Phytosulfokine-α Stimulates Tracheary Element Differentiation of Isolated Mesophyll Cells of Zinnia1
Authors: Matsubayashi Yoshikatsu , Takagi Leiko , Omura Naomi , Morita Akiko , Sakagami Youji
Published: July 2002

Dispersed zinnia (Zinnia elegans) mesophyll cells cannot differentiate into tracheary elements (TEs) at low cell density conditions even if auxin and cytokinin are present in the medium, indicating the involvement of intercellular interactions during the initiation and/or subsequent progresses in TE differentiation. When zinnia cells were incubated at a low density (2.5 × 104 cells mL−1) in TE-inductive medium in the presence of various concentrations of phytosulfokine (PSK)-α, which was originally identified as an intercellular signal peptide involved in cell proliferation, TE differentiation was strongly stimulated in a dose-dependent fashion; more than 35% of the living cells differentiated into TEs by 5 d of culture in the presence of 10 nm PSK-α. Enzyme-linked immunosorbent assay and mass spectroscopy confirmed that cultured zinnia cells produce nanomolar levels of PSKs under inductive conditions. These results suggest that PSK-α is a factor responsible for TE differentiation of zinnia mesophyll cells.
Elevation of the Cytosolic Free [Ca2+] Is Indispensable for the Transduction of the Nod Factor Signal in Alfalfa
Authors: Felle Hubert H. , Kondorosi Éva , Kondorosi Ádám , Schultze Michael
Published: July 2002

In root hairs of alfalfa (Medicago sativa), the requirement of Ca2+for Nod factor signaling has been investigated by means of ion-selective microelectrodes. Measured 50 to 100 μm behind the growing tip, 0.1 μm NodRm-IV(C16:2,S) increased the cytosolic free [Ca2+] by about 0.2 pCa, while the same concentration of chitotetraose, the nonactive glucosamine backbone, had no effect. We demonstrate that NodRm-IV(C16:2,S) still depolarized the plasma membrane at external Ca2+ concentrations below cytosolic values if the free EGTA concentration remained low (≤0.01 mm). Externally added Sr2+ was able to replace Ca2+, and to some extent even enhanced the Nod-factor-induced depolarization, whereas with Mg2+ it was decreased. This suggests that the Nod factor response is triggered by Ca2+ from external stores. The addition of the endomembrane Ca2+-ATPase inhibitor 2,5-di(t-butyl)-1,4-benzohydroquinone, which presumably mobilizes Ca2+ from Ins(1,4,5)P3-sensitive stores, mimicked the Nod factor response, i.e. increased the cytosolic free [Ca2+], triggered Cl−-efflux, depolarized the plasma membrane, and alkalized the root hair space. In all cases a refractory state toward Nod factor perception was produced, indicating a shortcut of Nod factor signal transduction by releasing Ca2+ from internal stores. These latter results strongly support the idea that an elevation of cytosolic free [Ca2+] is indispensable for the transduction of the Nod factor signal, which is consistent with the role of Ca2+ as a second messenger.
Loss of Tonoplast Integrity Programmed in Tracheary Element Differentiation
Authors: Kuriyama Hideo
Published: July 2002

A tracheary element (TE) is a typical example of a cell type that undergoes programmed cell death in the developmental processes of vascular plants. The loss of the selective permeability of the tonoplast, which corresponds to tonoplast disintegration, occurred after the cells commenced secondary wall thickening and played a pivotal role in the programmed cell death of TEs in a zinnia (Zinnia elegans L.) cell culture. A search for events specifically associated with the TE vacuole provided an important clue to the understanding of the cell death mechanism. The transport of fluorescein, a fluorescent organic anion, across the tonoplast declined drastically in differentiating TEs. The capacity of the vacuole to accumulate the probe was also impaired. Treatment with probenecid, an inhibitor of organic anion transport, caused rapid cell death of TEs and led to the ultimate disruption of the vacuole even in other types of cultured cells. These changes in vacuolar properties during TE development were suppressed by cycloheximide. Specific mRNA accumulation in cells cultured in a TE differentiation-inductive condition was abolished by probenecid. These results suggest that a change in vacuolar membrane permeability promotes programmed cell death in TEs.
High Throughput Cellular Localization of Specific Plant mRNAs by Liquid-Phase in Situ Reverse Transcription-Polymerase Chain Reaction of Tissue Sections
Authors: Koltai Hinanit , Bird David McKenzie
Published: July 2002

Advances in high throughput DNA sequencing and bioinformatic gene discovery far outpace our ability to analyze gene function, necessitating development of more efficient means to examine expression at the cellular level. Here we present a polymerase chain reaction-based method to detect mRNA species in situ in which essentially all of the steps are carried out in liquid phase in a 96-well microtiter tray and only the final signal detection is performed on a microscope slide. We demonstrate the sensitivity of the method by the cellular localization of mRNA for the Tkn2transcription factor in a wide variety of plant tissues, and its selectivity in discriminating a single gene family member by the in situ localization of rbcs3 transcripts. Furthermore, we demonstrate the utility of the in-well in situ method in detectingFDL and IFL1 transcripts in Arabidopsis sections, thus establishing the method as a tool to determine spatial expression pattern of sequences obtained from genomic sequencing projects. Being amenable to robotic processing, in-well in situ reverse transcription-polymerase chain reaction permits a great enhancement in the number of tissue samples that can be processed. Consequently, this method may become a powerful tool for functional genomics studies, permitting the cellular site of transcription of large numbers of sequences obtained from databases to be rapidly established.
LEFPS1, a Tomato Farnesyl Pyrophosphate Gene Highly Expressed during Early Fruit Development
Authors: Gaffe Joel , Bru Jean-Philippe , Causse Mathilde , Vidal Alain , Stamitti-Bert Linda , Carde Jean-Pierre , Gallusci Philippe
Published: July 2002

Farnesyl pyrophosphate synthase (FPS) catalyzes the synthesis of farnesyl pyrophosphate, a key intermediate in sterol and sesquiterpene biosynthesis. Using a polymerase chain reaction-based approach, we have characterized LeFPS1, a tomato (Lycoperscion esculentum cv Wva 106) fruit cDNA, which encodes a functional FPS. We demonstrate that tomato FPSs are encoded by a small multigenic family with genes located on chromosomes 10 and 12. Consistent with farnesyl pyrophosphate requirement in sterol biosynthesis,FPS genes are ubiquitously expressed in tomato plants. Using an LeFPS1 specific probe, we show that the corresponding gene can account for most of FPS mRNA in most plant organs, but not during young seedling development, indicating a differential regulation of FPS genes in tomato. FPS gene expression is also under strict developmental control: FPS mRNA was mainly abundant in young organs and decreased as organs matured with the exception of fruits that presented a biphasic accumulation pattern. In this latter case in situ hybridization studies have shown that FPSmRNA is similarly abundant in all tissues of young fruit. Taken together our results suggest that several FPS isoforms are involved in tomato farnesyl pyrophosphate metabolism and that FPSgenes are mostly expressed in relation to cell division and enlargement.
Oligandrin. A Proteinaceous Molecule Produced by the MycoparasitePythium oligandrum Induces Resistance to Phytophthora parasitica Infection in Tomato Plants
Authors: Picard Karine , Ponchet Michel , Blein Jean-Pierre , Rey Patrice , Tirilly Yves , Benhamou Nicole
Published: July 2002

A low-molecular weight protein, termed oligandrin, was purified to homogeneity from the culture filtrate of the mycoparasitic fungusPythium oligandrum. When applied to decapitated tomato (Lycopersicon esculentum Mill. var. Prisca) plants, this protein displayed the ability to induce plant defense reactions that contributed to restrict stem cell invasion by the pathogenic fungus Phytophthora parasitica. According to its N-terminal sequence, low-molecular weight, acidic isoelectric point, ultraviolet spectrum, and migration profile, the P. oligandrum-produced oligandrin was found to share some similarities with several elicitins from otherPhytophthora spp. and Pythium spp. However, oligandrin did not induce hypersensitive reactions. A significant decrease in disease incidence was monitored in oligandrin-treated plants as compared with water-treated plants. Ultrastructural investigations of the infected tomato stem tissues from non-treated plants showed a rapid colonization of all tissues associated with a marked host cell disorganization. In stems from oligandrin-treated plants, restriction of fungal growth to the outermost tissues and decrease in pathogen viability were the main features of the host-pathogen interaction. Invading fungal cells were markedly damaged at a time when the cellulose component of their cell walls was quite well preserved. Host reactions included the plugging of intercellular spaces as well as the occasional formation of wall appositions at sites of potential pathogen entry. In addition, pathogen ingress in the epidermis was associated with the deposition of an electron-opaque material in most invaded intercellular spaces. This material, lining the primary walls, usually extended toward the inside to form deposits that frequently interacted with the wall of invading hyphae. In the absence of fungal challenge, host reactions were not detected.
Effects of Iron Deficiency on the Composition of the Leaf Apoplastic Fluid and Xylem Sap in Sugar Beet. Implications for Iron and Carbon Transport
Authors: López-Millán Ana Flor , Morales Fermı́n , Abadı́a Anunciación , Abadı́a Javier
Published: July 2002

The effects of iron deficiency on the composition of the xylem sap and leaf apoplastic fluid have been characterized in sugar beet (Beta vulgaris Monohil hybrid). pH was estimated from direct measurements in apoplastic fluid and xylem sap obtained by centrifugation and by fluorescence of leaves incubated with 5-carboxyfluorescein and fluorescein isothiocyanate-dextran. Iron deficiency caused a slight decrease in the pH of the leaf apoplast (from 6.3 down to 5.9) and xylem sap (from 6.0 down to 5.7) of sugar beet. Major organic acids found in leaf apoplastic fluid and xylem sap were malate and citrate. Total organic acid concentration in control plants was 4.3 mm in apoplastic fluid and 9.4 mm in xylem sap and increased to 12.2 and 50.4 mm, respectively, in iron-deficient plants. Inorganic cation and anion concentrations also changed with iron deficiency both in apoplastic fluid and xylem sap. Iron decreased with iron deficiency from 5.5 to 2.5 μm in apoplastic fluid and xylem sap. Major predicted iron species in both compartments were [FeCitOH]−1 in the controls and [FeCit2]−3 in the iron-deficient plants. Data suggest the existence of an influx of organic acids from the roots to the leaves via xylem, probably associated to an anaplerotic carbon dioxide fixation by roots.
A Simple Procedure for the Analysis of Single Nucleotide Polymorphisms Facilitates Map-Based Cloning in Arabidopsis
Authors: Drenkard Eliana , Richter Brent G. , Rozen Steve , Stutius Lisa M. , Angell Nathaniel A. , Mindrinos Michael , Cho Raymond J. , Oefner Peter J. , Davis Ronald W. , Ausubel Frederick M.
Published: July 2002

We developed a modified allele-specific PCR procedure for assaying single nucleotide polymorphisms (SNPs) and used the procedure (called SNAP for single-nucleotide amplified polymorphisms) to generate 62 Arabidopsis mapping markers. SNAP primers contain a single base pair mismatch within three nucleotides from the 3′ end of one allele (the specific allele) and in addition have a 3′ mismatch with the nonspecific allele. A computer program called SNAPER was used to facilitate the design of primers that generate at least a 1,000-fold difference in the quantity of the amplification products from the specific and nonspecific SNP alleles. Because SNAP markers can be readily assayed by electrophoresis on standard agarose gels and because a public database of over 25,000 SNPs is available between the Arabidopsis Columbia and Landsberg erecta ecotypes, the SNAP method greatly facilitates the map-based cloning of Arabidopsis genes defined by a mutant phenotype.
Characterization of Maize Cytochrome P450 Monooxygenases Induced in Response to Safeners and Bacterial Pathogens
Authors: Persans Michael W. , Wang Jian , Schuler Mary A.
Published: July 2002

Plants use a diverse array of cytochrome P450 monooxygenases in their biosynthetic and detoxification pathways. To determine the extent to which various maize P450s are induced in response to chemical inducers, such as naphthalic anhydride (NA), triasulfuron (T), phenobarbital, and bacterial pathogens (Erwinia stuartii, Acidovorax avenae), we have analyzed the response patterns of seven P450 transcripts after treatment of seedlings with these inducers. Each of these P450 transcripts has distinct developmental, tissue-specific, and chemical cues regulating their expression even when they encode P450s within the same biosynthetic pathway. Most notably, the CYP71C1 andCYP71C3 transcripts, encoding P450s in the DIMBOA biosynthetic pathway, are induced to the same level in response to wounding and NA treatment of younger seedlings and differentially in response to NA/T treatment of younger seedlings and NA and NA/T treatment of older seedlings. NA and T induce expression of bothCYP92A1 and CYP72A5 transcripts in older seedling shoots, whereas phenobarbital induces CYP92A1expression in older seedling shoots and highly inducesCYP72A5 expression in young and older seedling roots. Expressed sequence tag (EST) 6c06b11 transcripts, encoding an undefined P450 activity, are highly induced in seedling shoots infected with bacterial pathogens.
Genetic Analysis of Amino Acid Accumulation inopaque-2 Maize Endosperm
Authors: Wang Xuelu , Larkins Brian A.
Published: July 2002

The opaque-2 mutation in maize (Zea mays) is associated with an increased level of free amino acids (FAA) in the mature endosperm. In particular, there is a high concentration of lysine, the most limiting essential amino acid. To investigate the basis for the high-FAA phenotype ofopaque-2 maize, we characterized amino acid accumulation during endosperm development of several wild-type andopaque-2 inbreds. Oh545o2 was found to have an exceptionally high level of FAA, in particular those derived from aspartate (Asp) and intermediates of glycolysis. The FAA content in Oh545o2 is 12 times greater than its wild-type counterpart, and three and 10 times greater than in Oh51Ao2 and W64Ao2, respectively. We crossed Oh545o2 to Oh51Ao2 and analyzed the F2:3 progeny to identify genetic loci linked with the high FAA level in these mutants. Quantitative trait locus mapping identified four significant loci that account for about 46% of the phenotypic variance. One locus on the long arm of chromosome 2 is coincident with genes encoding a monofunctional Asp kinase 2 and a bifunctional Asp kinase-homo-Ser dehydrogenase-2, whereas another locus on the short arm of chromosome 3 is linked with a cytosolic triose phosphate isomerase 4. The results suggest an alternation of amino acid and carbon metabolism leads to overproduction and accumulation of FAA in opaque-2 mutants.
Isolation of a CONSTANS Ortholog from Pharbitis nil and Its Role in Flowering
Authors: Liu Jiayou , Yu Jianping , McIntosh Lee , Kende Hans , Zeevaart Jan A.D.
Published: July 2002

The short-day plant Pharbitis nil is a model plant for the study of photoperiodic control of floral initiation. Flower formation can be induced at the cotyledon stage by a single long night of at least 14 h in duration. Using differential display of mRNA we identified a P. nil ortholog of the ArabidopsisCONSTANS (CO) gene, which will be referred to as PnCO. Expression of PnCOwas high after a 14-h night, but low when the dark period was 12 h or less. Our results indicate that the level of the PnCOtranscript is photoperiodically regulated. After transfer from continuous light to darkness, PnCO showed a circadian pattern of expression. Expression of the CAB gene, which is a molecular marker for the circadian clock, exhibited a different pattern of expression than did PnCO and was not subject to the same photoperiodic control. A major portion of thePnCO transcripts contained an unspliced intron. Only the intron-free PnCO was able to complement theco mutant of Arabidopsis by shortening the time to flower.
Signaling Events in the Hypoxic Induction of Alcohol Dehydrogenase Gene in Arabidopsis
Authors: Peng Hsiao-Ping , Chan Chui-Sien , Shih Ming-Che , Yang Shang Fa
Published: July 2002

Expression of the alcohol dehydrogenase gene (ADH) of Arabidopsis is induced during hypoxia. Because many plants increase their ethylene production in response to hypoxic stress, we examined in this report whether ethylene is involved in the hypoxic induction ofADH in Arabidopsis. We found that the hypoxic induction of ADH can be partially inhibited by aminooxy acetic acid, an inhibitor of ethylene biosynthesis. This partial inhibition can be reversed by the addition of 1-aminocyclopropane-1-carboxylic acid, a direct precursor of ethylene. In addition, the hypoxic induction of the ADH gene is also reduced inetr1-1 and ein2-1, two ethylene insensitive mutants in ethylene-signaling pathways, whereas the addition of exogenous ethylene or an increase in cellular ethylene alone does not induce ADH under normoxic conditions. Kinetic analyses of ADH mRNA accumulation indicated that an ethylene signal is required for the induction of ADHduring later stages of hypoxia. Therefore, we conclude that ethylene is needed, but not sufficient for, the induction of ADH in Arabidopsis during hypoxia.
The TASTY Locus on Chromosome 1 of Arabidopsis Affects Feeding of the Insect Herbivore Trichoplusia ni
Authors: Jander Georg , Cui Jianping , Nhan Betty , Pierce Naomi E. , Ausubel Frederick M.
Published: July 2002

The generalist insect herbivore Trichoplusia ni(cabbage looper) readily consumes Arabidopsis and can complete its entire life cycle on this plant. Natural isolates (ecotypes) of Arabidopsis are not equally susceptible to T. ni feeding. While some are hardly touched by T. ni, others are eaten completely to the ground. Comparison of two commonly studied Arabidopsis ecotypes in choice experiments showed that Columbia is considerably more resistant than Landsberg erecta. In no-choice experiments, where larvae were confined on one or the other ecotype, weight gain was more rapid on Landsberg erectathan on Columbia. Genetic mapping of this difference in insect susceptibility using recombinant inbred lines resulted in the discovery of the TASTY locus near 85 cM on chromosome 1 of Arabidopsis. The resistant allele of this locus is in the Columbia ecotype, and an F1 hybrid has a sensitive phenotype that is similar to that of Landsberg erecta. TheTASTY locus is distinct from known genetic differences between Columbia and Landsberg erecta that affect glucosinolate content, trichome density, disease resistance, and flowering time.
A study of lead silicate glass degradation behaviour with reference to glass‐to‐metal seal applications
Authors: Kothiyal G.P. , Phadnis S.V. , Shrikhande V.K. , Mirza T. , Totlani M.K. , Sahni V.C.
Published: July 2002

Investigates the chemical resistance properties of lead silicate glasses suitable for compression‐type glass‐to‐metal (GM) seals, to aggressive solvents, containing different amounts of Na, K, and Ba as modifier ions, in acidic and alkaline media. In general attack rate was observed to be higher in alkaline medium, with maximum dissolution of 53.35 mg/cm2 compared to the maximum of 10.6mg/cm2 in acidic medium after 50 hour exposure. An increase in the concentration of BaO was found to decrease the degradation rate, while samples with higher molar amounts of either Na2O or K2O showed more though similar damage rates. The degradation rate was observed to be linear for higher BaO concentration in alkali solution, whereas in other cases accelerated rates were observed with longer exposure time. GM seals prepared with glass, having higher BaO content, were less susceptible to damage and had higher insulation resistances.
Effect of some organic surfactants on corrosion inhibition of steel in sea water
Authors: Shalaby M.N. , Osman M.M. , El Feky A.A.
Published: July 2002

Corrosion inhibition of carbon steel by nonionic polyoxy ethylene (80) monopalmitate (Pa (EO)80), cationic hexadecyltrimethylammonium bromide (HTABr) and anionic sodium dodecyl sulfate (SDS) in sea water has been evaluated by weight loss method, correlated with adsorption measurements and X‐ray analysis. The inhibition efficiency of these compounds increases with their concentration and reaches a maximum value around their critical micelle concentrations (CMCs). The adsorption isotherms of the tested samples exhibit an L‐shape and the experimental data fit the Langmuir adsorption isotherm. The maximum amount adsorbed at the pseudo‐plateau region (Gmax) calculated from the Langmuir equation increases in the order SDS < HTABr < Pa (EO)80. The X‐ray spectra showed that the steel surfaces inhibited with these compounds were covered with lepidocrocite (FeOOH). The crystallite size is influenced by the type of the surfactant following their inhibition efficiency in the same order.
Academic libraries
Authors: Morgan Steve , Atkinson Jeremy
Published: July 2002

Reviews current trends in academic, mainly university, libraries. Issues selected for discussion as demonstrating most significant and longer lasting change include lifelong learning, frontline services and their quality, electronic libraries, and coping with continuous change.
Competences for future library professionals of academic libraries in Malaysia
Authors: ur Rehman Sajjad , Majid Shaheen , Bakeri Abu Baker Ahamd
Published: July 2002

Defines and validates competences for entry‐level professionals of academic libraries in Malaysia keeping in view the needs of the next five years. Top and middle managers of all the university libraries and two other academic libraries participated in the study. A scale of perceived importance of each competence was used for validation of competences organized in the six areas of foundation, cataloguing, circulation, information services, collection development, and serial control. A distinct emphasis is noted for contextual, managerial, technological and service competences. The validated competences can be used for the evaluation and revision of the curricula of formal education programmes.
Access to the world’s literature: the global strategy
Authors: Law Derek
Published: July 2002

Progress towards achieving the concepts of Universal Bibliographic Control and Universal Access to Publications is outlined in relation to printed publications and discussed in the context of electronic information. The unique problems relating to consistent identification of electronic materials are indicated and various metadata projects for recording and searching electronic files are outlined. The problems of access to electronic materials are discussed and various relevant international projects considered.