bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of Sulfate Assimilation by Nitrogen in Arabidopsis
Authors: Koprivova Anna , Suter Marianne , den Camp Roel Op , Brunold Christian , Kopriva Stanislav 
Published: July 2002

Abstract
Using Arabidopsis, we analyzed the effect of omission of a nitrogen source and of the addition of different nitrogen-containing compounds on the extractable activity and the enzyme and mRNA accumulation of adenosine 5′-phosphosulfate reductase (APR). During 72 h without a nitrogen source, the APR activity decreased to 70% and 50% of controls in leaves and roots, respectively, while cysteine (Cys) and glutathione contents were not affected. Northern and western analysis revealed that the decrease of APR activity was correlated with decreased mRNA and enzyme levels. The reduced APR activity in roots could be fully restored within 24 h by the addition of 4 mm each of NO3 −, NH4 +, or glutamine (Gln), or 1 mm O-acetylserine (OAS). 35SO4 2− feeding showed that after addition of NH4 +, Gln, or OAS to nitrogen-starved plants, incorporation of 35S into proteins significantly increased in roots; however, glutathione and Cys labeling was higher only with Gln and OAS or with OAS alone, respectively. OAS strongly increased mRNA levels of all three APR isoforms in roots and also those of sulfite reductase, Cys synthase, and serine acetyltransferase. Our data demonstrate that sulfate reduction is regulated by nitrogen nutrition at the transcriptional level and that OAS plays a major role in this regulation.
Characterization of XET-Related Genes of Rice
Authors: Uozu Sakurako , Tanaka-Ueguchi Miyako , Kitano Hidemi , Hattori Kazumi , Matsuoka Makoto 
Published: July 2002

Abstract
To elucidate the mechanism of internodal elongation in rice (Oryza sativa L.), we analyzed genes encoding xyloglucan endotransglycosylase (XET), a cell wall-loosening enzyme essential for cell elongation. Four riceXET-related (XTR) genes,OsXTR1, OsXTR2,OsXTR3, and OsXTR4, were isolated and their expression patterns in rice plants determined. The expression of the four XTR genes showed different patterns of organ specificity and responses to several plant hormones.OsXTR1 and OsXTR3 were up-regulated by gibberellin and brassinosteroids, whereas OsXTR2 andOsXTR4 showed no clear response to these hormones. Expression of the four XTR genes was also investigated in elongating internodes at different developmental stages.OsXTR1 and OsXTR3 were preferentially expressed in the elongating zone of internodes, whileOsXTR2 and OsXTR4 were expressed in nodes and in the divisional and elongating zones of internodes. In three genetic mutants with abnormal heights, the expression ofOsXTR1 and OsXTR3 correlated with the height of the mutants, whereas no such correlation was observed forOsXTR2 and OsXTR4. Based on these observations, we discuss the roles that OsXTR1 andOsXTR3 may play in internodal elongation in rice.
Inactivation of Photosystems I and II in Response to Osmotic Stress in Synechococcus. Contribution of Water Channels
Authors: Allakhverdiev Suleyman I. , Sakamoto Atsushi , Nishiyama Yoshitaka , Murata Norio 
Published: July 2002

Abstract
The effects of osmotic stress due to sorbitol on the photosynthetic machinery were investigated in the cyanobacterium Synechococcus R-2. Incubation of cells in 1.0 m sorbitol inactivated photosystems I and II and decreased the intracellular solute space by 50%. These effects of sorbitol were reversible: Photosynthetic activity and cytoplasmic volume returned to the original values after removal of the osmotic stress. A blocker of water channels prevented the osmotic-stress-induced inactivation and shrinkage of the intracellular space. It also prevented the recovery of photosynthetic activity and cytoplasmic volume when applied just before release from osmotic stress. Inhibition of protein synthesis by lincomycin had no significant effects on the inactivation and recovery processes, an observation that suggests that protein synthesis was not involved in these processes. Our results suggest that osmotic stress decreased the amount of water in the cytoplasm via the efflux of water through water channels (aquaporins), with resultant increases in intracellular concentrations of ions and a decrease in photosynthetic activity.
Effects of Acetate on Facultative Autotrophy inChlamydomonas reinhardtii Assessed by Photosynthetic Measurements and Stable Isotope Analyses
Authors: Heifetz Peter B. , Förster Britta , Osmond C. Barry , Giles Lawrence J. , Boynton John E. 
Published: July 2002

Abstract
The green alga Chlamydomonas reinhardtii can grow photoautotrophically utilizing CO2, heterotrophically utilizing acetate, and mixotrophically utilizing both carbon sources. Growth of cells in increasing concentrations of acetate plus 5% CO2 in liquid culture progressively reduced photosynthetic CO2 fixation and net O2 evolution without effects on respiration, photosystem II efficiency (as measured by chlorophyll fluorescence), or growth. Using the technique of on-line oxygen isotope ratio mass spectrometry, we found that mixotrophic growth in acetate is not associated with activation of the cyanide-insensitive alternative oxidase pathway. The fraction of carbon biomass resulting from photosynthesis, determined by stable carbon isotope ratio mass spectrometry, declined dramatically (about 50%) in cells grown in acetate with saturating light and CO2. Under these conditions, photosynthetic CO2 fixation and O2 evolution were also reduced by about 50%. Some growth conditions (e.g. limiting light, high acetate, solid medium in air) virtually abolished photosynthetic carbon gain. These effects of acetate were exacerbated in mutants with slowed electron transfer through the D1 reaction center protein of photosystem II or impaired chloroplast protein synthesis. Therefore, in mixotrophically grown cells of C. reinhardtii, interpretations of the effects of environmental or genetic manipulations of photosynthesis are likely to be confounded by acetate in the medium.
Use of Recombinant Aequorin to Study Calcium Homeostasis and Monitor Calcium Transients in Response to Heat and Cold Shock in Cyanobacteria
Authors: Torrecilla Ignacio , Leganés Francisco , Bonilla Ildefonso , Fernández-Piñas Francisca 
Published: July 2002

Abstract
We investigated the possibility of Ca2+ signaling in cyanobacteria (blue-green algae) by measuring intracellular free Ca2+ levels ([Ca2+]i) in a recombinant strain of the nitrogen fixing cyanobacteriumAnabaena strain sp. PCC7120, which constitutively expresses the Ca2+-binding photoprotein apoaequorin. The homeostasis of intracellular Ca2+ in response to increasing external Ca2+ has been studied in this strain. The resting level of free Ca2+ in Anabaena was found to be between 100 and 200 nm. Additions of increasing concentrations of external Ca2+ gave a transient burst of [Ca2+]i followed by a very quick decline, reaching a plateau within seconds that brought the level of [Ca2+]i back to the resting value. These results indicate that Anabaena strain sp. PCC7120 is able to regulate its internal Ca2+ levels. We also monitored Ca2+ transients in our recombinant strain in response to heat and cold shock. The cell's response to both stresses was dependent on the way they were induced. The use of inhibitors suggests that heat shock mobilizes cytosolic Ca2+ from both intracellular and extracellular sources, while the Ca2+source for cold shock signaling is mostly extracellular.
The YeastHAL1Gene Improves Salt Tolerance of Transgenic Tomato
Authors: Gisbert Carmina , Rus Ana M. , Boları́n M. Carmen , López-Coronado J. Miguel , Arrillaga Isabel , Montesinos Consuelo , Caro Manuel , Serrano Ramon , Moreno Vicente 
Published: July 2002

AbstractOverexpression of the HAL1 gene in yeast has a positive effect on salt tolerance by maintaining a high internal K+ concentration and decreasing intracellular Na+ during salt stress. In the present work, the yeast geneHAL1 was introduced into tomato (Lycopersicon esculentum Mill.) by Agrobacterium tumefaciens-mediated transformation. A sample of primary transformants was self-pollinated, and progeny from both transformed and non-transformed plants (controls) were evaluated for salt tolerance in vitro and in vivo. Results from different tests indicated a higher level of salt tolerance in the progeny of two different transgenic plants bearing four copies or one copy of the HAL1 gene. In addition, measurement of the intracellular K+ to Na+ ratios showed that transgenic lines were able to retain more K+ than the control under salt stress. Although plants and yeast cannot be compared in an absolute sense, these results indicate that the mechanism controlling the positive effect of theHAL1 gene on salt tolerance may be similar in transgenic plants and yeast.
A DEFICIENS Homolog from the Dioecious Tree Black Cottonwood Is Expressed in Female and Male Floral Meristems of the Two-Whorled, Unisexual Flowers
Authors: Sheppard Lorraine A. , Brunner Amy M. , Krutovskii Konstantin V. , Rottmann William H. , Skinner Jeffrey S. , Vollmer Sheila S. , Strauss Steven H. 
Published: July 2002

Abstract
We isolated PTD, a member of theDEFICIENS (DEF) family of MADS box transcription factors, from the dioecious tree, black cottonwood (Populus trichocarpa). In females, in situ hybridization experiments showed that PTD mRNA was first detectable in cells on the flanks of the inflorescence meristem, before differentiation of individual flowers was visually detectable. In males, the onset of PTD expression was delayed until after individual flower differentiation had begun and floral meristems were developing. Although PTD was initially expressed throughout the inner whorl meristem in female and male flowers, its spatial expression pattern became sex-specific as reproductive primordia began to form. PTD expression was maintained in stamen primordia, but excluded from carpel primordia, as well as vegetative tissues. Although PTD is phylogenetically most closely related to the largely uncharacterized TM6subfamily of theDEF/APETELA3(AP3)/TM6group, its spatio-temporal expression patterns are more similar to that of DEF and AP3 than to other members of the TM6 subfamily.
A Leaf Lipoxygenase of Potato Induced Specifically by Pathogen Infection
Authors: Kolomiets Michael V. , Chen Hao , Gladon Richard J. , Braun E.J. , Hannapel David J. 
Published: July 2002

Abstract
Lipoxygenase (LOX) activity has been identified consistently during pathogen-induced defense responses. Here we report the involvement of a specific leaf LOX gene of potato (Solanum tuberosum), designated POTLX-3 (GenBank/EMBL accession no. U60202), in defense responses against pathogens. The sequence ofPOTLX-3 does not match any other LOX genes of potato and has the greatest match to a tobacco LOX gene that contributes to a resistance mechanism against Phytophthora parasitica varnicotianae. POTLX-3 transcript accumulation was not detected in untreated, healthy potato organs or in wounded mature leaves. POTLX-3 mRNA accumulation was induced in potato leaves treated with ethylene or methyl jasmonate or infected with either virulent or avirulent strains of Phytophthora infestans, the causal agent of late blight. During the resistance response, POTLX-3 was induced within 6 hours, increased steadily through 24 hours, and its mRNA continued to accumulate for a week after inoculation. In contrast, when a plant was susceptible to P. infestans, induction of mRNA accumulation in response to inoculation was inconsistent and delayed. LOX activity assayed during an incompatible interaction in leaves peaked 3 days earlier than during a compatible interaction.POTLX-3 mRNA accumulation also was induced during hypersensitive response development caused by the incompatible pathogenPseudomonas syringae pv phaseolicola. Our results show that POTLX-3 may be involved specifically in defense responses against pathogen infection.
Complex I Impairment, Respiratory Compensations, and Photosynthetic Decrease in Nuclear and Mitochondrial Male Sterile Mutants of Nicotiana sylvestris
Authors: Sabar Mohammed , De Paepe Rosine , de Kouchkovsky Yaroslav 
Published: July 2002

Abstract
We have previously shown that in Nicotiana sylvestris cytoplasmic male-sterile (CMS) mutants where the mtDNA lacks the nad7 gene coding for a subunit of respiratory Complex I (NADH:ubiquinone oxidoreductase, EC 1.6.5.3), glycine (Gly) oxidation was lower than in the wild type and insensitive to rotenone, suggesting Complex I dysfunction. In contrast, the oxidation rate of exogenous NADH and the capacity of the cyanide-resistant respiration (AOX) were enhanced. Here we report that, in contrast to Gly, the rate of malate oxidation was not affected, but proceeded totally in a rotenone-insensitive pathway, strongly suggesting that survival of CMS plants depends on the activation of internal and external alternative NAD(P) H dehydrogenases and that Gly decarboxylase activity depends on Complex I functioning. A similar defect in Complex I activity and Gly oxidation was found in the NMS1 nuclear mutant, defective in the processing of the nad4transcript, but alternative NAD(P) H dehydrogenases were less activated. In CMS and NMS1, the fraction of the AOX pathway was increased, as compared to wild type, associated with higher amounts ofaox transcripts, AOX protein, and plant resistance to cyanide. Non-phosphorylating respiratory enzymes maintained normal in vivo respiration levels in both mutants, but photosynthesis was decreased, in correlation with lower leaf conductance, emphasizing mitochondrial control on photosynthesis.
New Techniques Enable Comparative Analysis of Microtubule Orientation, Wall Texture, and Growth Rate in Intact Roots of Arabidopsis
Authors: Sugimoto Keiko , Williamson Richard E. , Wasteneys Geoffrey O. 
Published: July 2002

Abstract
This article explores root epidermal cell elongation and its dependence on two structural elements of cells, cortical microtubules and cellulose microfibrils. The recent identification of Arabidopsis morphology mutants with putative cell wall or cytoskeletal defects demands a procedure for examining and comparing wall architecture and microtubule organization patterns in this species. We developed methods to examine cellulose microfibrils by field emission scanning electron microscopy and microtubules by immunofluorescence in essentially intact roots. We were able to compare cellulose microfibril and microtubule alignment patterns at equivalent stages of cell expansion. Field emission scanning electron microscopy revealed that Arabidopsis root epidermal cells have typical dicot primary cell wall structure with prominent transverse cellulose microfibrils embedded in pectic substances. Our analysis showed that microtubules and microfibrils have similar orientation only during the initial phase of elongation growth. Microtubule patterns deviate from a predominantly transverse orientation while cells are still expanding, whereas cellulose microfibrils remain transverse until well after expansion finishes. We also observed microtubule-microfibril alignment discord before cells enter their elongation phase. This study and the new technology it presents provide a starting point for further investigations on the physical properties of cell walls and their mechanisms of assembly.
The Arabidopsis Genome. An Abundance of Soluble N-Ethylmaleimide-Sensitive Factor Adaptor Protein Receptors
Authors: Sanderfoot Anton A. , Assaad Farhah F. , Raikhel Natasha V. 
Published: July 2002

Abstract
Many factors have been characterized as essential for vesicle trafficking, including a number of proteins commonly referred to as soluble N-ethylmaleimide-sensitive factor adaptor protein receptor (SNARE) components. The Arabidopsis genome contains a remarkable number of SNAREs. In general, the vesicle fusion machinery appears highly conserved. However, whereas some classes of yeast and mammalian genes appear to be lacking in Arabidopsis, this small plant genome has gene families not found in other eukaryotes. Very little is known about the precise function of plant SNAREs. By contrast, the intracellular localization of and interactions between a large number of plant SNAREs have been determined, and these data are discussed in light of the phylogenetic analysis.
The Ubiquitin-Specific Protease Family from Arabidopsis.AtUBP1 and 2 Are Required for the Resistance to the Amino Acid Analog Canavanine
Authors: Yan Ning , Doelling Jed H. , Falbel Tanya G. , Durski Adam M. , Vierstra Richard D. 
Published: July 2002

Abstract
Ubiquitin-specific proteases (UBPs) are a family of unique hydrolases that specifically remove polypeptides covalently linked via peptide or isopeptide bonds to the C-terminal glycine of ubiquitin. UBPs help regulate the ubiquitin/26S proteolytic pathway by generating free ubiquitin monomers from their initial translational products, recycling ubiquitins during the breakdown of ubiquitin-protein conjugates, and/or by removing ubiquitin from specific targets and thus presumably preventing target degradation. Here, we describe a family of 27 UBP genes from Arabidopsis that contain both the conserved cysteine (Cys) and histidine boxes essential for catalysis. They can be clustered into 14 subfamilies based on sequence similarity, genomic organization, and alignments with their closest relatives from other organisms, with seven subfamilies having two or more members. Recombinant AtUBP2 functions as a bona fide UBP: It can release polypeptides attached to ubiquitins via either α- or ε-amino linkages by an activity that requires the predicted active-site Cys within the Cys box. From the analysis of T-DNA insertion mutants, we demonstrate that the AtUBP1 and2 subfamily helps confer resistance to the arginine analog canavanine. This phenotype suggests that theAtUBP1 and 2 enzymes are needed for abnormal protein turnover in Arabidopsis.
Gibberellin Biosynthesis Mutations and Root Development in Pea
Authors: Yaxley Julian R. , Ross John J. , Sherriff Leanne J. , Reid James B. 
Published: July 2002

Abstract
Dwarf mutants of pea (Pisum sativum), with impaired gibberellin (GA) biosynthesis in the shoot, were studied to determine whether the roots of these genotypes had altered elongation and GA levels. Mutations na, lh-2, andls-1 reduced GA levels in root tips and taproot elongation, although in lh-2 and ls-1roots the reduction in elongation was small (less than 15%). Thena mutation reduced taproot length by about 50%. The roots of na plants elongated in response to applied GA1 and recombining na with mutationsln (which blocks GA catabolism) increased GA1 levels in root tips and completely restored normal root development. In shoots, Mendel's le-1 mutation impairs the 3β-hydroxylation of GA20 to the bioactive GA1, resulting in dwarfism. However, GA1 and GA20 levels were normal in le-1 roots, as was root development. The null mutation le-2 also did not reduce root GA levels or elongation. The results support the theory that GAs are important for normal root elongation in pea, and indicate that a 3β-hydroxylase gene other than LE operates in pea roots.
Molecular Interactions between the Specialist HerbivoreManduca sexta (Lepidoptera, Sphingidae) and Its Natural Host Nicotiana attenuata. III. Fatty Acid-Amino Acid Conjugates in Herbivore Oral Secretions Are Necessary and Sufficient for Herbivore-Specific Plant Responses
Authors: Halitschke Rayko , Schittko Ursula , Pohnert Georg , Boland Wilhelm , Baldwin Ian T. 
Published: July 2002

Abstract
Feeding by the tobacco specialist Manduca sexta(Lepidoptera, Sphingidae) and application of larval oral secretions and regurgitant (R) to mechanical wounds are known to elicit: (a) a systemic release of mono- and sesquiterpenes, (b) a jasmonate burst, and (c) R-specific changes in transcript accumulation of putatively growth- and defense-related mRNAs in Nicotiana attenuata Torr. ex Wats. We identified several fatty acid-amino acid conjugates (FACs) in the R of M. sexta and the closely related species Manduca quinquemaculata which, when synthesized and applied to mechanical wounds at concentrations comparable with those found in R, elicited all three R-specific responses. Ion-exchange treatment of R, which removed all detectable FACs and free fatty acids (FAs), also removed all detectable activity. The biological activity of ion-exchanged R could be completely restored by the addition of synthetic FACs at R-equivalent concentrations, whereas the addition of FAs did not restore the biological activity of R. We conclude that the biological activity of R is not related to the supply of FAs to the octadecanoid cascade for endogenous jasmonate biosynthesis, but that FACs elicit the herbivore-specific responses by another mechanism and that the insect-produced modification of plant-derived FAs is necessary for the plant's recognition of this specialized herbivore.
A Complete Set of Maize Individual Chromosome Additions to the Oat Genome
Authors: Kynast Ralf G. , Riera-Lizarazu Oscar , Vales M. Isabel , Okagaki Ron J. , Maquieira Silvia B. , Chen Gang , Ananiev Evgueni V. , Odland Wade E. , Russell Charles D. , Stec Adrian O. , Livingston Suzanne M. , Zaia Herika A. , Rines Howard W. , Phillips Ronald L. 
Published: July 2002

Abstract
All 10 chromosomes of maize (Zea mays, 2n = 2x = 20) were recovered as single additions to the haploid complement of oat (Avena sativa, 2n = 6x = 42) among F1 plants generated from crosses involving three different lines of maize to eight different lines of oat. In vitro rescue culture of more than 4,300 immature F1 embryos resulted in a germination frequency of 11% with recovery of 379 F1plantlets (8.7%) of moderately vigorous growth. Some F1plants were sectored with distinct chromosome constitutions among tillers of the same plant and also between root and shoot cells. Meiotic restitution facilitated development of un-reduced gametes in the F1. Self-pollination of these partially fertile F1 plants resulted in disomic additions (2n = 6x + 2 = 44) for maize chromosomes 1, 2, 3, 4, 6, 7, and 9. Maize chromosome 8 was recovered as a monosomic addition (2n = 6x + 1 = 43). Monosomic additions for maize chromosomes 5 and 10 to a haploid complement of oat (n = 3x + 1 = 22) were recovered several times among the F1 plants. Although partially fertile, these chromosome 5 and 10 addition plants have not yet transmitted the added maize chromosome to F2 offspring. We discuss the development and general utility of this set of oat-maize addition lines as a novel tool for maize genomics and genetics.