bluuebunny/crossref_metadata_2025_split huggingface dataset:
GTPase Activity and Biochemical Characterization of a Recombinant Cotton Fiber Annexin1
Authors: Shin Heungsop , Brown R. Malcolm 
Published: July 2002

Abstract
A cDNA encoding annexin was isolated from a cotton (Gossypium hirsutum) fiber cDNA library. The cDNA was expressed in Escherichia coli, and the resultant recombinant protein was purified. We then investigated some biochemical properties of the recombinant annexin based on the current understanding of plant annexins. An “add-back experiment” was performed to study the effect of the recombinant annexin on β-glucan synthase activity, but no effect was found. However, it was found that the recombinant annexin could display ATPase/GTPase activities. The recombinant annexin showed much higher GTPase than ATPase activity. Mg2+ was essential for these activities, whereas a high concentration of Ca2+ was inhibitory. A photolabeling assay showed that this annexin could bind GTP more specifically than ATP. The GTP-binding site on the annexin was mapped into the carboxyl-terminal fourth repeat of annexin from the photolabeling experiment using domain-deletion mutants of this annexin. Northern-blot analysis showed that the annexin gene was highly expressed in the elongation stages of cotton fiber differentiation, suggesting a role of this annexin in cell elongation.
Two SNF1-Related Protein Kinases from Spinach Leaf Phosphorylate and Inactivate 3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase, Nitrate Reductase, and Sucrose Phosphate Synthase in Vitro1
Authors: Sugden Christopher , Donaghy Paul G. , Halford Nigel G. , Hardie D. Grahame 
Published: July 2002

AbstractWe resolved from spinach (Spinacia oleracea) leaf extracts four Ca2+-independent protein kinase activities that phosphorylate the AMARAASAAALARRR (AMARA) and HMRSAMSGLHLVKRR (SAMS) peptides, originally designed as specific substrates for mammalian AMP-activated protein kinase and its yeast homolog, SNF1. The two major activities, HRK-A and HRK-C (3-hydroxy-3-methylglutaryl-coenzyme Areductase kinase A andC) were extensively purified and shown to be members of the plant SnRK1 (SNF1-related proteinkinase 1) family using the following criteria: (a) They contain 58-kD polypeptides that cross-react with an antibody against a peptide sequence characteristic of the SnRK1 family; (b) they have similar native molecular masses and specificity for peptide substrates to mammalian AMP-activated protein kinase and the cauliflower homolog; (c) they are inactivated by homogeneous protein phosphatases and can be reactivated using the mammalian upstream kinase; and (d) they phosphorylate 3-hydroxy-3-methylglutaryl-coenzyme A reductase from Arabidopsis at the inactivating site, serine (Ser)-577. We propose that HRK-A and HRK-C represent either distinct SnRK1 isoforms or the same catalytic subunit complexed with different regulatory subunits. Both kinases also rapidly phosphorylate nitrate reductase purified from spinach, which is associated with inactivation of the enzyme that is observed only in the presence of 14-3-3 protein, a characteristic of phosphorylation at Ser-543. Both kinases also inactivate spinach sucrose phosphate synthase via phosphorylation at Ser-158. The SNF1-related kinases therefore potentially regulate several major biosynthetic pathways in plants: isoprenoid synthesis, sucrose synthesis, and nitrogen assimilation for the synthesis of amino acids and nucleotides.
Isolation of Tobacco Isoperoxidases Accumulated in Cell-Suspension Culture Medium and Characterization of Activities Related to Cell Wall Metabolism1
Authors: de Marco Ario , Guzzardi Patricia , Jamet Élisabeth 
Published: July 2002

Abstract
All of the most important guaiacol-type peroxidase (POX) isoforms accumulated in the culture medium of BY-2 tobacco (Nicotiana tabacumL. cv Bright Yellow 2) cells have been isolated. Five basic and two acidic isoforms were found. The four major isoforms (B2, B3, P1, and P2), all strongly basic, have been purified to homogeneity and partially sequenced. B2 and B3 are new isoforms showing high homology to only one POX isolated so far. Amino acid sequencing and specific activities indicated that basic isoPOXs constitute two pairs of strictly related isoforms (P1/P2 and B2/B3). Their specific activities measured in the presence of different substrates, as monolignols and NAD(P)H, indicated possible specialized functions in cell wall metabolism. Only P-type POXs were able to oxidize indoleacetic acid. Variations in pH could play a regulatory role by changing the relative contribution of different isoforms to total POX activity. Apart from cell culture medium, polyclonal antibodies obtained against P1 and P2 detected P1 in roots and in lower parts of stems. Immunocytochemical labeling indicated that P-type POXs were expressed in stem phloem and in phloem and epidermal cells of roots.
Photosynthesis and Carbon Partitioning in Transgenic Tobacco Plants Deficient in Leaf Cytosolic Pyruvate Kinase1
Authors: Grodzinski Bernard , Jiao Jirong , Knowles Vicki L. , Plaxton William C. 
Published: July 2002

Abstract
Whole-plant diurnal C exchange analysis provided a noninvasive estimation of daily net C gain in transgenic tobacco (Nicotiana tabacum L.) plants deficient in leaf cytosolic pyruvate kinase (PKc−). PKc− plants cultivated under a low light intensity (100 μmol m−2 s−1) were previously shown to exhibit markedly reduced root growth, as well as delayed shoot and flower development when compared with plants having wild-type levels of PKc (PKc+). PKc− and PKc+ source leaves showed a similar net C gain, photosynthesis over a range of light intensities, and a capacity to export newly fixed 14CO2 during photosynthesis. However, during growth under low light the nighttime, export of previously fixed 14CO2 by fully expanded PKc− leaves was 40% lower, whereas concurrent respiratory14CO2 evolution was 40% higher than that of PKc+ leaves. This provides a rationale for the reduced root growth of the PKc− plants grown at low irradiance. Leaf photosynthetic and export characteristics in PKc− and PKc+ plants raised in a greenhouse during winter months resembled those of plants grown in chambers at low irradiance. The data suggest that PKc in source leaves has a critical role in regulating nighttime respiration particularly when the available pool of photoassimilates for export and leaf respiratory processes are low.
Determination of the Motif Responsible for Interaction between the Rice APETALA1/AGAMOUS-LIKE9 Family Proteins Using a Yeast Two-Hybrid System1
Authors: Moon Yong-Hwan , Kang Hong-Gyu , Jung Ji-Young , Jeon Jong-Seong , Sung Soon-Kee , An Gynheung 
Published: July 2002

AbstractA MADS family gene,OsMADS6, was isolated from a rice (Oryza sativa L.) young flower cDNA library usingOsAMDS1 as a probe. With this clone, various MADS box genes that encode for protein-to-protein interaction partners of the OsMADS6 protein were isolated by the yeast two-hybrid screening method. On the basis of sequence homology, OsMADS6 and the selected partners can be classified in theAPETALA1/AGAMOUS-LIKE9 (AP1/AGL9) family. One of the interaction partners,OsMADS14, was selected for further study. Both genes began expression at early stages of flower development, and their expression was extended into the later stages. In mature flowers theOsMADS6 transcript was detectable in lodicules and also weakly in sterile lemmas and carpels, whereas theOsMADS14 transcript was detectable in sterile lemmas, paleas/lemmas, stamens, and carpels. Using the yeast two-hybrid system, we demonstrated that the region containing of the 109th to 137th amino acid residues of OsMADS6 is indispensable in the interaction with OsMADS14. Site-directed mutation analysis revealed that the four periodical leucine residues within the region are essential for this interaction. Furthermore, it was shown that the 14 amino acid residues located immediately downstream of the K domain enhance the interaction, and that the two leucine residues within this region play an important role in that enhancement.
Mannose Induces an Endonuclease Responsible for DNA Laddering in Plant Cells
Authors: Stein Joshua C. , Hansen Geneviève 
Published: July 2002

Abstract
The effect of d-mannose (Man) on plant cells was studied in two different systems: Arabidopsis roots and maize (Zea mays) suspension-cultured cells. In both systems, exposure to d-Man was associated with a subset of features characteristic of apoptosis, as assessed by oligonucleosomal fragmentation and microscopy analysis. Furthermore,d-Man induced the release of cytochrome cfrom mitochondria. The specificity of d-Man was evaluated by comparing the effects of diastereomers such as l-Man,d-glucose, and d-galactose. Of these treatments, only d-Man caused a reduction in final fresh weight with concomitant oligonucleosomal fragmentation. Man-induced DNA laddering coincided with the activation of a DNase in maize cytosolic extracts and with the appearance of single 35-kD band detected using an in-gel DNase assay. The DNase activity was further confirmed by using covalently closed circular plasmid DNA as a substrate. It appears thatd-Man, a safe and readily accessible compound, offers remarkable features for the study of apoptosis in plant cells.
The Arabidopsis Homolog of Yeast TAP42 and Mammalian α4 Binds to the Catalytic Subunit of Protein Phosphatase 2A and Is Induced by Chilling
Authors: Harris Darby M. , Myrick Tammy L. , Rundle Sabine J. 
Published: July 2002

AbstractType 2A serine/threonine protein phosphatases (PP2A) have been implicated as important mediators of a number of plant growth and developmental processes. In an effort to identify plant PP2A substrates and/or regulators, we performed a yeast two-hybrid screen using an Arabidopsis PP2A catalytic subunit cDNA as bait. All true positives identified by this screen were derived from the same gene, which we have named TAP46 (2A phosphatase associated protein of 46 kD). The TAP46 gene appears to be a single-copy gene and is expressed in all Arabidopsis organs. Transcripts derived from this gene are induced by chilling treatment but not by heat or anaerobic stress. Immunoprecipitation assays using antibodies generated to a peptide spanning amino acids 356 to 366 of TAP46 indicate that TAP46 is associated with a type 2A protein phosphatase in vivo. A search of the database identified TAP46 as a homolog of Saccharomyces cerevisiae TAP42 and mammalian α4. These two proteins are known to bind to the catalytic subunit of PP2A and to function in the target-of-rapamycin signaling pathway. Our results identify TAP46 as a plant PP2A-associated protein, with a possible function in the chilling response, and suggest that a target-of-rapamycin-like signaling pathway may exist in plants.
Cloning Two Genes for Nicotianamine Aminotransferase, a Critical Enzyme in Iron Acquisition (Strategy II) in Graminaceous Plants
Authors: Takahashi Michiko , Yamaguchi Hirotaka , Nakanishi Hiromi , Shioiri Takayuki , Nishizawa Naoko-Kishi , Mori Satoshi 
Published: July 2002

Abstract
Nicotianamine aminotransferase (NAAT), the key enzyme involved in the biosynthesis of mugineic acid family phytosiderophores (MAs), catalyzes the amino transfer of nicotianamine (NA). MAs are found only in graminaceous plants, although NA has been detected in every plant so far investigated. Therefore, this amino transfer reaction is the first step in the unique biosynthesis of MAs that has evolved in graminaceous plants. NAAT activity is dramatically induced by Fe deficiency and suppressed by Fe resupply. Based on the protein sequence of NAAT purified from Fe-deficient barley (Hordeum vulgare) roots, two distinct cDNA clones encoding NAAT, naat-A andnaat-B, were identified. Their deduced amino acid sequences were homologous to several aminotransferases, and shared consensus sequences for the pyridoxal phosphate-binding site lysine residue and its surrounding residues. The expression of bothnaat-A and naat-B is increased in Fe-deficient barley roots, while naat-B has a low level of constitutive expression in Fe-sufficient barley roots. No detectable mRNA from either naat-A or naat-B was present in the leaves of either Fe-deficient or Fe-sufficient barley. One genomic clone with a tandem array of naat-B andnaat-A in this order was identified.naat-B and naat-A each have six introns at the same locations. The isolation of NAAT genes will pave the way to understanding the mechanism of the response to Fe in graminaceous plants, and may lead to the development of cultivars tolerant to Fe deficiency that can grow in calcareous soils.
A Novel Alliinase from Onion Roots. Biochemical Characterization and cDNA Cloning
Authors: Lancaster Jane E. , Shaw Martin L. , Joyce Meeghan D. Pither , McCallum John A. , McManus Michael T. 
Published: July 2002

Abstract
We have purified a novel alliinase (EC 4.4.1.4) from roots of onion (Allium cepa L.). Two isoforms with alliinase activity (I and II) were separated by concanavalin A-Sepharose and had molecular masses of 52.7 (I) and 50.5 (II) kD on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 51 (I) and 57.5 (II) kD by gel filtration fast-protein liquid chromatography. Isoform I had an isoelectric point of 9.3, while isoform II had isoelectric points of 7.6, 7.9, 8.1, and 8.3. The isoforms differed in their glycosylation. Both contained xylose/fucose containing complex-type N-linked glycans, and isoform II also contained terminal mannose structures. Both isoforms had activity with S-alk(en)yl-l-cysteine sulfoxides. Unlike other allium alliinases, A. cepa root isoforms had cystine lyase activity. We cloned a gene from A. cepa root cDNA and show that it codes for A. cepa root alliinase protein. Homology to other reported allium alliinase genes is 50%. The gene coded for a protein of mass 51.2 kD, with two regions of deduced amino acid sequence identical to a 25- and a 40-amino acid region, as determined experimentally. The A. cepa root alliinase cDNA was expressed mainly in A. cepa roots. The structure and function of the alliinase gene family is discussed.
Molecular Cloning and Targeting of a Fibrillarin Homolog from Arabidopsis
Authors: Pih Kyoung Tae , Yi Min Joo , Liang Ying Shi , Shin Bong Jeong , Cho Moo Je , Hwang Inhwan , Son Daeyoung 
Published: July 2002

Abstract
Fibrillarin is a nucleolar protein known to be involved in the processing of ribosomal RNA precursors. We isolatedAtFbr1, a cDNA encoding a homolog of fibrillarin in Arabidopsis. The cDNA is 1.2 kb in size and encodes a polypeptide of 310 amino acid residues with a molecular mass of 33 kD.AtFbr1 is expressed at high levels in the flower and root tissue and at a slightly lower level in leaf tissue, whereas it was nearly undetectable in siliques. Expression ofAtFbr1 was compared with that of the FLP(fibrillarin-like protein) gene identified by the Arabidopsis genome project. Abscisic acid treatment resulted in the down-regulation of the expression of both AtFbr1 and FLP genes in seedlings, although the degree of suppression was higher forFLP than for AtFbr1. In addition, the expression level of FLP decreased with the age of the seedlings, whereas AtFbr1 did not exhibit any detectable change. The subcellular localization of AtFbrl was studied with an in vivo targeting approach using a fusion protein, and was found to be correctly targeted to the nucleolus in protoplasts when expressed as a green fluorescent fusion protein (GFP). Deletion experiments showed that the N-terminal glycine- and arginine-rich region is necessary and sufficient to target AtFbr1 to the nucleolus.
Ozone Sensitivity in Hybrid Poplar Correlates with Insensitivity to Both Salicylic Acid and Jasmonic Acid. The Role of Programmed Cell Death in Lesion Formation
Authors: Koch Jennifer Riehl , Creelman Robert A. , Eshita Steven M. , Seskar Mirjana , Mullet John E. , Davis Keith R. 
Published: July 2002

Abstract
Our earlier studies demonstrated that the ozone-sensitive hybrid poplar clone NE-388 displays an attenuated level of ozone-, wound-, and phytopathogen-induced defense gene expression. To determine if this reduced gene activation involves signal transduction pathways dependent on salicylic acid (SA) and/or jasmonic acid (JA), we compared the responses of NE-388 and an ozone-tolerant clone, NE-245, to these signal molecules. JA levels increased in both clones in response to ozone, but only minimal increases in SA levels were measured for either clone. Treatment with SA and methyl jasmonate induced defense gene expression only in NE-245, indicating that NE-388 is insensitive to these signal molecules. DNA fragmentation, an indicator of programmed cell death (PCD), was detected in NE-245 treated with either ozone or an avirulent phytopathogen, but was not detected in NE-388. We conclude that these clones undergo two distinct mechanisms of ozone-induced lesion formation. In NE-388, lesions appear to be due to toxic cell death resulting from a limited ability to perceive and subsequently activate SA- and/or JA-mediated antioxidant defense responses. In NE-245, SA-dependent PCD precedes lesion formation via a process related to the PCD pathway activated by phytopathogenic bacteria. These results support the hypothesis that ozone triggers a hypersensitive response.
Starch-Branching Enzymes Preferentially Associated with A-Type Starch Granules in Wheat Endosperm
Authors: Peng Mingsheng , Gao Ming , Båga Monica , Hucl Pierre , Chibbar Ravindra N. 
Published: July 2002

Abstract
Two starch granule-bound proteins (SGP), SGP-140 and SGP-145, were preferentially associated with A-type starch granules (&gt;10 μm) in developing and mature wheat (Triticum aestivum) kernels. Immunoblotting and N-terminal sequencing suggested that the two proteins were different variants of SBEIc, a 152-kD isoform of wheat starch-branching enzyme. Both SGP-140 and SGP-145 were localized to the endosperm starch granules but were not found in the endosperm soluble fraction or pericarp starch granules younger than 15 d post anthesis (DPA). Small-size starch granules (&lt;10 μm) initiated before 15 DPA incorporated SGP-140 and SGP-145 throughout endosperm development and grew into full-size A-type starch granules (&gt;10 μm). In contrast, small-size starch granules harvested after 15 DPA contained only low amounts of SGP-140 and SGP-145 and developed mainly into B-type starch granules (&lt;10 μm). Polypeptides of similar mass and immunologically related to SGP-140 and/or SGP-145 were also preferentially incorporated into A-type starch granules of barley (Hordeum vulgare), rye (Secale cereale), and triticale (× Triticosecale Wittmack) endosperm, which like wheat endosperm have a bimodal starch granule size distribution.
Can Meristematic Activity Determine Variation in Leaf Size and Elongation Rate among Four Poa Species? A Kinematic Study
Authors: Fiorani Fabio , Beemster Gerrit T.S. , Bultynck Lieve , Lambers Hans 
Published: July 2002

Abstract
We studied inherent variation in final leaf size among fourPoa spp. that live at different elevations. The average final length of leaf 7 of the main stem of the smallest species (Poa alpina) was only one-half that of the largest species (Poa trivialis); it was correlated with leaf elongation rate, but not with the duration of leaf elongation. A faster rate of leaf elongation rate was associated with (a) larger size of the zone of cell expansion, and (b) faster rates of cell production (per cell file) in the meristem, which in turn were due to greater numbers of dividing cells, whereas average cell division rates were very similar for all species (except Poa annua). Also we found that the proliferative fraction equaled 1 throughout the meristem in all species. It was remarkable that rates of cell expansion tended to be somewhat higher in the species with slower growing leaves. We discuss the results by comparing the spatial and material viewpoints, which lead to different interpretations of the role of cell division. Although the presented data do not strictly prove it, they strongly suggest a regulatory role for cell division in determining differences in growth rate among the present four Poa spp.
Spatial Distribution of Cell Division Rate Can Be Deduced from that of p34cdc2 Kinase Activity in Maize Leaves Grown at Contrasting Temperatures and Soil Water Conditions
Authors: Granier Christine , Inzé Dirk , Tardieu François 
Published: July 2002

Abstract
We have investigated the spatial distributions of cell division rate, p34cdc2 kinase activity, and amount of p34cdc2a in maize (Zea mays) leaves grown at contrasting temperatures and soil water conditions. An original method for calculating cell division rate in all leaf tissues is proposed. In all studied conditions, cell division rate was stable and maximum in the first 2 cm beyond the leaf insertion point, declined afterward, and reached zero at 7 cm from the insertion point. The spatial distribution of p34cdc2 kinase activity, expressed on a per cell basis, followed the same pattern. In contrast, the amount of p34cdc2a was maximum in the first centimeter of the leaf, declined afterward, but remained at 20% of maximum in more distal zones with a near-zero cell division rate. A mild water deficit caused a reduction in cell division rate and p34cdc2 kinase activity by approximately 45% in all leaf zones, but did not affect the amount of p34cdc2a. Growth temperature affected to the same extent cell division rate and p34cdc2 kinase activity, but only if p34cdc2 kinase activity was assayed at growth temperature, and not if a standard temperature was used in all assays. A common linear relationship between cell division rate and p34cdc2 kinase activity applied to all causes of changes in cell division rate, i.e. cell aging, water deficit, or changes in temperature. It is shown that temperature has two distinct and additive effects on p34cdc2 kinase activity; first, an effect on the rate of the reaction, and second, an effect on the amount of p34cdc2a.
Lipid Peroxidation Is an Early Symptom Triggered by Aluminum, But Not the Primary Cause of Elongation Inhibition in Pea Roots
Authors: Yamamoto Yoko , Kobayashi Yukiko , Matsumoto Hideaki 
Published: July 2002

Abstract
Pea (Pisum sativum) roots were treated with aluminum in a calcium solution, and lipid peroxidation was investigated histochemically and biochemically, as well as other events caused by aluminum exposure. Histochemical stainings were observed to distribute similarly on the entire surface of the root apex for three events (aluminum accumulation, lipid peroxidation, and callose production), but the loss of plasma membrane integrity (detected by Evans blue uptake) was localized exclusively at the periphery of the cracks on the surface of root apex. The enhancement of four events (aluminum accumulation, lipid peroxidation, callose production, and root elongation inhibition) displayed similar aluminum dose dependencies and occurred by 4 h. The loss of membrane integrity, however, was enhanced at lower aluminum concentrations and after longer aluminum exposure (8 h). The addition of butylated hydroxyanisole (a lipophilic antioxidant) during aluminum treatment completely prevented lipid peroxidation and callose production by 40%, but did not prevent or slow the other events. Thus lipid peroxidation is a relatively early symptom induced by the accumulation of aluminum and appears to cause, in part, callose production, but not the root elongation inhibition; by comparison, the loss of plasma membrane integrity is a relatively late symptom caused by cracks in the root due to the inhibition of root elongation.