bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molybdenum Sequestration in BrassicaSpecies. A Role for Anthocyanins?
Authors: Hale Kerry L. , McGrath Steve P. , Lombi Enzo , Stack Stephen M. , Terry Norman , Pickering Ingrid J. , George Graham N. , Pilon-Smits Elizabeth A.H. 
Published: October 2002

Abstract
To elucidate plant mechanisms involved in molybdenum (Mo) sequestration and tolerance, Brassica spp. seedlings were supplied with molybdate, and the effects on plant physiology, morphology, and biochemistry were analyzed. When supplied with (colorless) molybdate Indian mustard (Brassica juncea) seedlings accumulated water-soluble blue crystals in their peripheral cell layers. Energy dispersive x-ray analysis showed that Mo accumulated predominantly in the vacuoles of the epidermal cells. Therefore, the blue crystals are likely to be a Mo compound. The x-ray absorption spectrum of the plant-accumulated Mo was different than that for molybdate, indicating complexation with a plant molecule. Because the blue compound was water soluble and showed a pH-dependent color change, possible involvement of anthocyanins was investigated. An anthocyanin-less mutant of Brassica rapa (“fast plants”) was compared with varieties containing normal or high anthocyanin levels. The anthocyanin-less mutant did not show accumulation of a blue compound when supplied with molybdate. In the anthocyanin-containing varieties, the blue compound colocalized with anthocyanins in the peripheral cell layers. Mo accumulation by the three B. rapa varieties was positively correlated with anthocyanin content. Addition of molybdate to purified B. rapa anthocyanin resulted in an in vitro color change from pink to blue. Therefore, Mo appears to be sequestered in vacuoles of the peripheral cell layers of Brassica spp. as a blue compound, probably a Mo-anthocyanin complex.
A New C-Type Cyclin-Dependent Kinase from Tomato Expressed in Dividing Tissues Does Not Interact with Mitotic and G1 Cyclins
Authors: Joubès Jérôme , Lemaire-Chamley Martine , Delmas Frédéric , Walter Jocelyne , Hernould Michel , Mouras Armand , Raymond Philippe , Chevalier Christian 
Published: October 2002

Abstract
Cyclin-dependent kinases (CDKs) form a conserved superfamily of eukaryotic serine-threonine protein kinases whose activity requires the binding of a cyclin protein. CDKs are involved in many aspects of cell biology and notably in the regulation of the cell cycle. Three cDNAs encoding a C-type CDK, and a member of each B-type CDK subfamily, were isolated from tomato (Lycopsersicon esculentum Mill.) and designated Lyces;CDKC;1 (accession no. AJ294903), Lyces; CDKB1;1 (accession no. AJ297916), and Lyces;CDKB2;1 (accession no. AJ297917). The predicted amino acid sequences displayed the characteristic PITAIRE (CDKC), PPTALRE (CDKB1), and PPTTLRE (CDKB2) motives in the cyclin-binding domain, clearly identifying the type of CDK. The accumulation of all transcripts was associated preferentially with dividing tissues in developing tomato fruit and vegetative organs. In contrast to that of CDKA and CDKBs, the transcription pattern of Lyces;CDKC;1 was shown to be independent of hormone and sugar supply in tomato cell suspension cultures and excised roots. This observation, together with the absence of a patchy expression profile in in situ hybridization experiments, suggests a non-cell cycle regulation of Lyces;CDKC;1. Using a two-hybrid assay, we showed that Lyces;CDKC;1 did not interact with mitotic and G1 cyclins. The role of plant CDKCs in the regulation of cell division and differentiation is discussed with regard to the known function of their animal counterparts.
Hydrogen Peroxide Is Involved in Abscisic Acid-Induced Stomatal Closure in Vicia faba
Authors: Zhang Xiao , Zhang Lin , Dong Facai , Gao Junfeng , Galbraith David W. , Song Chun-Peng 
Published: October 2002

Abstract
One of the most important functions of the plant hormone abscisic acid (ABA) is to induce stomatal closure by reducing the turgor of guard cells under water deficit. Under environmental stresses, hydrogen peroxide (H2O2), an active oxygen species, is widely generated in many biological systems. Here, using an epidermal strip bioassay and laser-scanning confocal microscopy, we provide evidence that H2O2 may function as an intermediate in ABA signaling in Vicia faba guard cells. H2O2 inhibited induced closure of stomata, and this effect was reversed by ascorbic acid at concentrations lower than 10−5 m. Further, ABA-induced stomatal closure also was abolished partly by addition of exogenous catalase (CAT) and diphenylene iodonium (DPI), which are an H2O2 scavenger and an NADPH oxidase inhibitor, respectively. Time course experiments of single-cell assays based on the fluorescent probe dichlorofluorescein showed that the generation of H2O2 was dependent on ABA concentration and an increase in the fluorescence intensity of the chloroplast occurred significantly earlier than within the other regions of guard cells. The ABA-induced change in fluorescence intensity in guard cells was abolished by the application of CAT and DPI. In addition, ABA microinjected into guard cells markedly induced H2O2 production, which preceded stomatal closure. These effects were abolished by CAT or DPI micro-injection. Our results suggest that guard cells treated with ABA may close the stomata via a pathway with H2O2 production involved, and H2O2 may be an intermediate in ABA signaling.
Phospholipase D and Phosphatidic Acid-Mediated Generation of Superoxide in Arabidopsis
Authors: Sang Yongming , Cui Decai , Wang Xuemin 
Published: October 2002

Abstract
Phospholipase D (PLD), which hydrolyzes phospholipids into free head groups and phosphatidic acid (PA), may regulate cellular processes through the production of lipid and lipid-derived messengers. We have genetically abrogated PLDα, the most prevalent isoform of PLD in plants, and the depletion of PLDα in Arabidopsis decreased the levels of PA and superoxide production in Arabidopsis leaf extracts. Addition of PA promoted the synthesis of superoxide in the PLDα-depleted plants, as measured by chemiluminescence and superoxide dismutase-inhibitable, NADPH-dependent reduction of cytochrome c and nitroblue tetrazolium. The PA-enhanced generation of superoxide was associated mainly with microsomal membranes. Among various lipids tested, PA was the most effective stimulator with the optimal concentrations between 100 and 200 μm. The PA-promoted production of superoxide was observed also in leaves directly infiltrated with PA. The added PA was more effective in stimulating superoxide generation in the PLDα-depleted leaves than in the PLDα-containing, wild-type leaves, suggesting that PA produced in the cell was more effective than added PA in promoting superoxide production. These data indicate that PLD plays a role in mediating superoxide production in plants through the generation of PA as a lipid messenger.
Isolation and Characterization of Kinase Interacting Protein 1, a Pollen Protein That Interacts with the Kinase Domain of PRK1, a Receptor-Like Kinase of Petunia
Authors: Skirpan Andrea L. , McCubbin Andrew G. , Ishimizu Takeshi , Wang Xi , Hu Yi , Dowd Peter E. , Ma Hong , Kao Teh-hui 
Published: October 2002

Abstract
Many receptor-like kinases have been identified in plants and have been shown by genetic or transgenic knockouts to play diverse physiological roles; however, to date, the cytosolic interacting proteins of relatively few of these kinases have been identified. We have previously identified a predominantly pollen-expressed receptor-like kinase of petunia (Petunia inflata), named PRK1, and we have shown by the antisense RNA approach that it is required for microspores to progress from the unicellular to bicellular stage. To investigate the PRK1-mediated signal transduction pathway,PRK1-K cDNA, encoding most of the cytoplasmic domain of PRK1, was used as bait in yeast (Saccharomyces cerevisiae) two-hybrid screens of pollen/pollen tube cDNA libraries of petunia. A protein named kinase interacting protein 1 (KIP1) was found to interact very strongly with PRK1-K. This interaction was greatly reduced when lysine-462 of PRK1-K, believed to be essential for kinase activity, was replaced with arginine (the resulting protein is named PRK1-K462R). The amino acid sequence of KIP1 deduced from full-length cDNA contains an EF-hand Ca2+-binding motif and nine predicted coiled-coil regions. The yeast two-hybrid assay and affinity chromatography showed that KIP1 interacts with itself to form a dimer or higher multimer.KIP1 is present in a single copy in the genome, and is expressed predominantly in pollen with a similar temporal pattern toPRK1. In situ hybridization showed thatPRK1 and KIP1 transcripts were localized in the cytoplasm of pollen. PRK1-K phosphorylated KIP1-NT (amino acids 1–716), whereas PRK1-K462R only weakly phosphorylated KIP1-NT in vitro.
Characterization of Rice Anthranilate Synthase α-Subunit GenesOASA1 and OASA2. Tryptophan Accumulation in Transgenic Rice Expressing a Feedback-Insensitive Mutant of OASA1
Authors: Tozawa Yuzuru , Hasegawa Hisakazu , Terakawa Teruhiko , Wakasa Kyo 
Published: October 2002

Abstract
Anthranilate synthase (AS) is a key enzyme in the synthesis of tryptophan (Trp), indole-3-acetic acid, and indole alkaloids. Two genes, OASA1 and OASA2, encoding AS α-subunits were isolated from a monocotyledonous plant, rice (Oryza sativa cv Nipponbare), and were characterized. A phylogenetic tree of AS α-subunits from various species revealed a close evolutionary relationship among OASA1 and Arabidopsis ASA2,Ruta graveolens ASα2, and tobacco ASA2, whereas OASA2, Arabidopsis ASA1, and R. graveolens ASα1 were more distantly related. OASA1 is expressed in all tissues tested, but the amount of its mRNA was greater in panicles than in leaves and roots. The abundance of OASA2 transcripts is similar among tissues and greater than that of OASA1transcripts; furthermore, OASA2 expression was induced by a chitin heptamer, a potent elicitor, suggesting that OASA2 participates in secondary metabolism. Expression of wild-typeOASA1 or OASA2 transgenes did not affect the Trp content of rice calli or plants. However, transformed calli and plants expressing a mutated OASA1 gene,OASA1(D323N), that encodes a protein in which aspartate-323 is replaced with asparagine manifested up to 180- and 35-fold increases, respectively, in Trp accumulation. These transgenic calli and plants were resistant to 300 μm 5-methyl-Trp, and AS activity of the calli showed a markedly reduced sensitivity to Trp. These results show that OASA1 is important in the regulation of free Trp concentration, and that mutation of OASA1 to render the encoded protein insensitive to feedback inhibition results in accumulation of Trp at high levels. The OASA1(D323N) transgene may prove useful for the generation of crops with an increased Trp content.
Harpin Induces Activation of the Arabidopsis Mitogen-Activated Protein Kinases AtMPK4 and AtMPK6
Authors: Desikan Radhika , Hancock John T. , Ichimura Kazuya , Shinozaki Kazuo , Neill Steven J. 
Published: October 2002

Abstract
Mitogen-activated protein kinases (MAPKs) are key enzymes that mediate adaptive responses to various abiotic and biotic stresses, including pathogen challenge. The proteinaceous bacterial elicitor harpin (secreted by Pseudomonas syringae pvsyringae) activates two MAPKs in suspension cultures of Arabidopsis var. Landsberg erecta. In this study, we show that harpin and exogenous hydrogen peroxide (H2O2) activate myelin basic protein kinases in Arabidopsis leaves. Using anti-AtMPK4 and anti-AtMPK6 antibodies, we identify the harpin-activated MAPKs in both leaves and suspension cultures as AtMPK4 and AtMPK6, and show that H2O2, generated by Arabidopsis cells in response to challenge with harpin, activates only AtMPK6. However, treatments with catalase, which removes H2O2, or diphenylene iodonium, which inhibits superoxide and H2O2 production, do not inhibit harpin-induced activation of AtMPK4 or AtMPK6. In addition, activation of AtMPK4 but not AtMPK6 is inhibited by the MAPK kinase inhibitor PD98059. Neither harpin nor H2O2 has any effect onAtMPK4 or AtMPK6 gene expression. In addition, the expression of AtMEKK1,AtMEK1, or AtMKK2, previously shown to be potential functional partners of AtMPK4, were not affected by either harpin or H2O2 treatments. These data suggest that harpin activates several signaling pathways, one leading to stimulation of the oxidative burst and others leading to the activation of AtMPK4 or AtMPK6.
Cold Acclimation-Induced WAP27 Localized in Endoplasmic Reticulum in Cortical Parenchyma Cells of Mulberry Tree Was Homologous to Group 3 Late-Embryogenesis Abundant Proteins
Authors: Ukaji Norifumi , Kuwabara Chikako , Takezawa Daisuke , Arakawa Keita , Fujikawa Seizo 
Published: October 2002

Abstract
We have shown that two 27-kD proteins, designated as WAP27A and WAP27B, were abundantly accumulated in endoplasmic reticulum-enriched fractions isolated from cortical parenchyma cells of mulberry tree (Morus bombycis Koidz.) during winter (N. Ukaji, C. Kuwabara, D. Takezawa, K. Arakawa, S. Yoshida, S. Fujikawa [1999] Plant Physiol 120: 480–489). In the present study, cDNA clones encoding WAP27A and WAP27B were isolated and characterized. The deduced amino acid sequences of WAP27A and WAP27BcDNAs had 12 repeats of an 11-mer amino acid motif that was the common feature of group 3 late-embryogenesis-abundant proteins. Under field conditions, transcripts of WAP27 genes were initially detected in mid-October, reached maximum level from mid-November to mid-December, and then gradually decreased. The transcript levels ofWAP27 genes in cortical parenchyma cells harvested in October was drastically induced by cold treatment within a few days, whereas those in cortical parenchyma cells harvested in August were low even by cold treatment for 3 weeks. Immunocytochemical analysis by electron microscopy confirmed that WAP27 was localized specifically in vesicular-form ER and also localized in dehydration-induced multiplex lamellae-form ER. The role of WAP27 in the ER is discussed in relation to acquisition of freezing tolerance of cortical parenchyma cells in mulberry tree during winter.
Sequence Architecture Downstream of the Initiator Codon Enhances Gene Expression and Protein Stability in Plants
Authors: Sawant Samir V. , Kiran Kanti , Singh Pradhyumna K. , Tuli Rakesh 
Published: October 2002

Abstract
Nucleotide positions conserved on the 3′ side of the initiator codon ATG and the corresponding N-terminal amino acid residues in a number of highly abundant plant proteins were identified by computational analysis of a dataset of highly expressed plant genes. The reporter genes uidA and gfp were modified to introduce these features. Insertion of GCT TCC TCC after the initiator codon ATG augmented expression for both the reporter genes. The insertion of each successive codon improved the expression of β-glucuronidase (GUS) in an incremental fashion in transient transformation of tobacco (Nicotiana tabacum) leaves. The insertion of alanine-serine (Ser)-Ser resulted in about a 2-fold increase in the stability of GUS. However, this did not account for the 30- to 40-fold increase in GUS activity between the constructs coding for methionine-alanine-Ser-Ser-GUS and the native enzyme. Substitution of the codon for Ser at the third amino acid residue with synonymous codons reduced GUS expression. The results suggest a role for the conserved nucleotides in the +4 to +11 region in augmenting posttranscriptional events in the expression of genes in plants.
Phylogenetic Relationships within Cation Transporter Families of Arabidopsis
Authors: Mäser Pascal , Thomine Sébastien , Schroeder Julian I. , Ward John M. , Hirschi Kendal , Sze Heven , Talke Ina N. , Amtmann Anna , Maathuis Frans J.M. , Sanders Dale , Harper Jeff F. , Tchieu Jason , Gribskov Michael , Persans Michael W. , Salt David E. , Kim Sun A , Guerinot Mary Lou 
Published: October 2002

Abstract
Uptake and translocation of cationic nutrients play essential roles in physiological processes including plant growth, nutrition, signal transduction, and development. Approximately 5% of the Arabidopsis genome appears to encode membrane transport proteins. These proteins are classified in 46 unique families containing approximately 880 members. In addition, several hundred putative transporters have not yet been assigned to families. In this paper, we have analyzed the phylogenetic relationships of over 150 cation transport proteins. This analysis has focused on cation transporter gene families for which initial characterizations have been achieved for individual members, including potassium transporters and channels, sodium transporters, calcium antiporters, cyclic nucleotide-gated channels, cation diffusion facilitator proteins, natural resistance-associated macrophage proteins (NRAMP), and Zn-regulated transporter Fe-regulated transporter-like proteins. Phylogenetic trees of each family define the evolutionary relationships of the members to each other. These families contain numerous members, indicating diverse functions in vivo. Closely related isoforms and separate subfamilies exist within many of these gene families, indicating possible redundancies and specialized functions. To facilitate their further study, the PlantsT database (http://plantst.sdsc.edu) has been created that includes alignments of the analyzed cation transporters and their chromosomal locations.
A Novel Superoxide Dismutase with a High Isoelectric Point in Higher Plants. Expression, Regulation, and Protein Localization
Authors: Karpinska Barbara , Karlsson Marlene , Schinkel Helga , Streller Steffen , Süss Karl-Heinz , Melzer Michael , Wingsle Gunnar 
Published: October 2002

Abstract
Several isoforms of superoxide dismutase (SOD) with a high isoelectric point (pI) have been identified by isoelectric focusing chromatography in protein extracts from Scots pine (Pinus sylvestris) needles. One of these isoforms, a CuZn-SOD with a pI of about 10 and thus denoted hipI-SOD, has been isolated and purified to apparent homogeneity. A cDNA encoding the hipI-SOD protein was cloned and sequenced. Northern hybridization of mRNA isolated from different organs and tissues showed that hipI-SOD has a markedly different pattern of expression compared with chloroplastic and cytosolic SOD. Furthermore, the transcript levels of hipI-SOD and cytosolic SOD were found to respond differently to mechanical wounding, treatment with oxidized glutathione, paraquat, and ozone. Immunogold electron microscopy localized the hipI-SOD in the plasma membrane of sieve cells and the Golgi apparatus of albuminous cells. Moreover, high protein density was also detected in extracellular spaces such as secondary cell wall thickenings of the xylem and sclerenchyma and in intercellular spaces of parenchyma cells.
Formation of Rhamnogalacturonan II-Borate Dimer in Pectin Determines Cell Wall Thickness of Pumpkin Tissue
Authors: Ishii Tadashi , Matsunaga Toshiro , Hayashi Noriko 
Published: October 2002

Abstract
Boron (B) deficiency results in inhibition of pumpkin (Cucurbia moschata Duchesne) growth that is accompanied by swelling of the cell walls. Monomeric rhamnogalacturonan II (mRG-II) accounted for 80% to 90% of the total RG-II in B-deficient walls, whereas the borate ester cross-linked RG-II dimer (dRG-II-B) accounted for more than 80% of the RG-II in control plants. The results of glycosyl residue and glycosyl linkage composition analyses of the RG-II from control and B-deficient plants were similar. Thus, B deficiency does not alter the primary structure of RG-II. The addition of10B-enriched boric acid to B-deficient plants resulted within 5 h in the conversion of mRG-II to dRG-II-10B. The wall thickness of the 10B-treated plants and control plants was similar. The formation and possible functions of a borate ester cross-linked RG-II in the cell walls are discussed.
A Medicago truncatula Homoglutathione Synthetase Is Derived from Glutathione Synthetase by Gene Duplication
Authors: Frendo Pierre , Jiménez Marı́a Jesús Hernández , Mathieu Christel , Duret Laurent , Gallesi Daniela , Van de Sype Ghislaine , Hérouart Didier , Puppo Alain 
Published: October 2002

Abstract
Glutathione (GSH) and homo-GSH (hGSH) are the major low-molecular weight thiols synthesized in Medicago truncatula. TwoM. truncatula cDNAs (gshs1 andgshs2) corresponding to a putative GSH synthetase (GSHS) and a putative hGSH synthetase (hGSHS) were characterized. Heterologous expression of gshs1 and gshs2 cDNAs in anEscherichia coli strain deficient in GSHS activity showed that GSHS1 and GSHS2 are a GSHS and an hGSHS, respectively. Leucine-534 and proline-535 present in hGSHS were substituted by alanines that are conserved in plant GSHS. These substitutions resulted in a strongly stimulated GSH accumulation in the transformed E. coli strain showing that these residues play a crucial role in the differential recognition of β-alanine and glycine by hGSHS. Phylogenetic analysis of GSHS2 and GSHS1 with other eukaryotic GSHS sequences indicated that gshs2 and gshs1are the result of a gene duplication that occurred after the divergence between Fabales, Solanales, and Brassicales. Analysis of the structure of gshs1 and gshs2 genes shows they are both present in a cluster and in the same orientation in the M. truncatula genome, suggesting that the duplication ofgshs1 and gshs2 occurred via a tandem duplication.
Transpiration Rate. An Important Factor Controlling the Sucrose Content of the Guard Cell Apoplast of Broad Bean
Authors: Outlaw William H. , De Vlieghere-He Xiaoyi 
Published: October 2002

Abstract
Evaporation of water from the guard cell wall concentrates apoplastic solutes. We hypothesize that this phenomenon provides two mechanisms for responding to high transpiration rates. First, apoplastic abscisic acid is concentrated in the guard cell wall. Second, by accumulating in the guard cell wall, apoplastic sucrose (Suc) provides a direct osmotic feedback to guard cells. As a means of testing this second hypothesized mechanism, the guard cell Suc contents at a higher transpiration rate (60% relative humidity [RH]) were compared with those at a lower transpiration rate (90% RH) in broad bean (Vicia faba), an apoplastic phloem loader. In control plants (constant 60% RH), the guard cell apoplast Suc content increased from 97 ± 81 femtomol (fmol) guard cell pair−1 to 701 ± 142 fmol guard cell pair−1 between daybreak and midday. This increase is equivalent to approximately 150 mm external, which is sufficient to decrease stomatal aperture size. In plants that were shifted to 90% RH before daybreak, the guard cell apoplast Suc content did not increase during the day. In accordance, in plants that were shifted to 90% RH at midday, the guard cell apoplast Suc content declined to the daybreak value. Under all conditions, the guard cell symplast Suc content increased during the photoperiod, but the guard cell symplast Suc content was higher (836 ± 33 fmol guard cell pair−1) in plants that were shifted to 90% RH. These results indicate that a high transpiration rate may result in a high guard cell apoplast Suc concentration, which diminishes stomatal aperture size.