bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluence and Wavelength Requirements for Arabidopsis CAB Gene Induction by Different Phytochromes
Authors: Hamazato F. , Shinomura T. , Hanzawa H. , Chory J. , Furuya M. 
Published: July 2002

Abstract
The roles of different phytochromes have been investigated in the photoinduction of several chlorophyll a/b-binding protein genes (CAB) of Arabidopsis thaliana. Etiolated seedlings of the wild type, a phytochrome A (PhyA) null mutant (phyA), a phytochrome B (PhyB) null mutant (phyB), and a phyA/phyB double mutant were exposed to monochromatic light to address the questions of the fluence and wavelength requirements for CAB induction by different phytochromes. In the wild type and the phyB mutant, PhyA photoirreversibly induced CAB expression upon irradiation with very-low-fluence light of 350 to 750 nm. In contrast, using the phyA mutant, PhyB photoreversibly induced CAB expression with low-fluence red light. The threshold fluences of red light for PhyA- and PhyB-specific induction were about 10 nmol m-2 and 10 [mu]mol m-2, respectively. In addition, CAB expression was photoreversibly induced with low-fluence red light in the phyA/phyB double mutant, revealing that another phytochrome(s) (PhyX) regulated CAB expression in a manner similar to PhyB. These data suggest that plants utilize different phytochromes to perceive light of varying wave-lengths and fluence, and begin to explain how plants respond so exquisitely to changing light in their environment.
Auxin Transport Is Required for Hypocotyl Elongation in Light-Grown but Not Dark-Grown Arabidopsis1
Authors: Jensen Philip J. , Hangarter Roger P. , Estelle Mark 
Published: July 2002

Abstract
Many auxin responses are dependent on redistribution and/or polar transport of indoleacetic acid. Polar transport of auxin can be inhibited through the application of phytotropins such as 1-naphthylphthalamic acid (NPA). WhenArabidopsis thaliana seedlings were grown in the light on medium containing 1.0 μm NPA, hypocotyl and root elongation and gravitropism were strongly inhibited. When grown in darkness, however, NPA disrupted the gravity response but did not affect elongation. The extent of inhibition of hypocotyl elongation by NPA increased in a fluence-rate-dependent manner to a maximum of about 75% inhibition at 50 μmol m−2 s−1 of white light. Plants grown under continuous blue or far-red light showed NPA-induced hypocotyl inhibition similar to that of white-light-grown plants. Plants grown under continuous red light showed less NPA-induced inhibition. Analysis of photoreceptor mutants indicates the involvement of phytochrome and cryptochrome in mediating this NPA response. Hypocotyls of some auxin-resistant mutants had decreased sensitivity to NPA in the light, but etiolated seedlings of these mutants were similar in length to the wild type. These results indicate that light has a significant effect on NPA-induced inhibition in Arabidopsis, and suggest that auxin has a more important role in elongation responses in light-grown than in dark-grown seedlings.
Formate Dehydrogenase, an Enzyme of Anaerobic Metabolism, Is Induced by Iron Deficiency in Barley Roots1
Authors: Suzuki Kazuya , Itai Reiko , Suzuki Koichiro , Nakanishi Hiromi , Nishizawa Naoko-Kishi , Yoshimura Etsuro , Mori Satoshi 
Published: July 2002

Abstract
To identify the proteins induced by Fe deficiency, we have compared the proteins of Fe-sufficient and Fe-deficient barley (Hordeum vulgare L.) roots by two-dimensional polyacrylamide gel electrophoresis. Peptide sequence analysis of induced proteins revealed that formate dehydrogenase (FDH), adenine phosphoribosyltransferase, and the Ids3gene product (for Fe deficiency-specific) increased in Fe-deficient roots. FDH enzyme activity was detected in Fe-deficient roots but not in Fe-sufficient roots. A cDNA encoding FDH (Fdh) was cloned and sequenced. Fdh expression was induced by Fe deficiency. Fdh was also expressed under anaerobic stress and its expression was more rapid than that induced by Fe deficiency. Thus, the expression of Fdh observed in Fe-deficient barley roots appeared to be a secondary effect caused by oxygen deficiency in Fe-deficient plants.
Isolation of the Ornithine-δ-Aminotransferase cDNA and Effect of Salt Stress on Its Expression inArabidopsis thaliana1
Authors: Roosens Nancy H.C.J. , Thu Tran T. , Iskandar Hayati M. , Jacobs Michel 
Published: July 2002

AbstractTo evaluate the relative importance of ornithine (Orn) as a precursor in proline (Pro) synthesis, we isolated and sequenced a cDNA encoding the Orn-δ-aminotransferase (δ-OAT) from Arabidopsis thaliana. The deduced amino acid sequence showed high homology with bacterial, yeast, mammalian, and plant sequences, and the N-terminal residues exhibited several common features with a mitochondrial transit peptide. Our results show that under both salt stress and normal conditions, δ-OAT activity and mRNA in young plantlets are slightly higher than in older plants. This appears to be related to the necessity to dispose of an easy recycling product, glutamate. Analysis of the expression of the gene revealed a close association with salt stress and Pro production. In young plantlets, free Pro content, Δ1-pyrroline-5-carboxylate synthase mRNA, δ-OAT activity, and δ-OAT mRNA were all increased by salt-stress treatment. These results suggest that for A. thaliana, the Orn pathway, together with the glutamate pathway, plays an important role in Pro accumulation during osmotic stress. Conversely, in 4-week-old A. thaliana plants, although free Pro level also increased under salt-stress conditions, the δ-OAT activity appeared to be unchanged and δ-OAT mRNA was not detectable. Δ1-pyrroline-5-carboxylate synthase mRNA was still induced at a similar level. Therefore, for the adult plants the free Pro increase seemed to be due to the activity of the enzymes of the glutamate pathway.
Potent Inhibition of Ribulose-Bisphosphate Carboxylase by an Oxidized Impurity in Ribulose-1,5-Bisphosphate1
Authors: Kane Heather J. , Wilkin Jean-Marc , Portis Archie R. , John Andrews T. 
Published: July 2002

Abstract
Oxidation of d-ribulose-1,5-bisphosphate (ribulose-P2) during synthesis and/or storage producesd-glycero-2,3-pentodiulose-1,5-bisphosphate (pentodiulose-P2), a potent slow, tight-binding inhibitor of spinach (Spinacia oleracea L.) ribulose-P2 carboxylase/oxygenase (Rubisco). Differing degrees of contamination with pentodiulose-P2 caused the decline in Rubisco activity seen during Rubisco assay time courses to vary between different preparations of ribulose-P2. With some ribulose-P2 preparations, this compound can be the dominant cause of the decline, far exceeding the significance of the catalytic by-product, d-xylulose-1,5-bisphosphate. Unlike xylulose-1,5-bisphosphate, pentodiulose-P2 did not appear to be a significant by-product of catalysis by wild-type Rubisco at saturating CO2 concentration. It was produced slowly during frozen storage of ribulose-P2, even at low pH, more rapidly in Rubisco assay buffers at room temperature, and particularly rapidly on deliberate oxidation of ribulose-P2with Cu2+. Its formation was prevented by the exclusion of transition metals and O2. Pentodiulose-P2 was unstable and decayed to a variety of other less-inhibitory compounds, particularly in the presence of some buffers. However, it formed a tight, stable complex with carbamylated spinach Rubisco, which could be isolated by gel filtration, presumably because its structure mimics that of the enediol intermediate of Rubisco catalysis. Rubisco catalyzes the cleavage of pentodiulose-P2 by H2O2, producing P-glycolate.
Developmental Expression and Substrate Specificities of Alfalfa Caffeic Acid 3-O-Methyltransferase and Caffeoyl Coenzyme A 3-O-Methyltransferase in Relation to Lignification1
Authors: Inoue Kentaro , Sewalt Vincent J.H. , Murray Ballance G. , Ni Weiting , Stürzer Cornelia , Dixon Richard A. 
Published: July 2002

Abstract
The biosynthesis of monolignols can potentially occur via two parallel pathways involving free acids or their coenzyme A (CoA) esters. Caffeic acid 3-O-methyltransferase (COMT) and caffeoyl CoA 3-O-methyltransferase (CCOMT) catalyze functionally identical reactions in these two pathways, resulting in the formation of mono- or dimethoxylated lignin precursors. The activities of the two enzymes increase from the first to the sixth internode in stems of alfalfa (Medicago sativa L.), preceding the deposition of lignin. Alfalfa CCOMT is highly similar at the amino acid sequence level to the CCOMT from parsley, although it contains a six-amino acid insertion near the N terminus. Transcripts encoding both COMT and CCOMT are primarily localized to vascular tissue in alfalfa stems. Alfalfa CCOMT expressed in Escherichia coli catalyzesO-methylation of caffeoyl and 5-hydroxyferuloyl CoA, with preference for caffeoyl CoA. It has low activity against the free acids. COMT expressed in E. coli is active against both caffeic and 5-hydroxyferulic acids, with preference for the latter compound. Surprisingly, very little extractableO-methyltransferase activity versus 5-hydroxyferuloyl CoA is present in alfalfa stem internodes, in which relativeO-methyltransferase activity against 5-hy-droxyferulic acid increases with increasing maturity, correlating with increased lignin methoxyl content.
Computation of Surface Electrical Potentials of Plant Cell Membranes
Authors: Kinraide Thomas B. , Yermiyahu Uri , Rytwo Giora 
Published: July 2002

Abstract
A Gouy-Chapman-Stern model has been developed for the computation of surface electrical potential (ψ0) of plant cell membranes in response to ionic solutes. The present model is a modification of an earlier version developed to compute the sorption of ions by wheat (Triticum aestivum L. cv Scout 66) root plasma membranes. A single set of model parameters generates values for ψ0 that correlate highly with published ζ potentials of protoplasts and plasma membrane vesicles from diverse plant sources. The model assumes ion binding to a negatively charged site (R − = 0.3074 μmol m−2) and to a neutral site (P 0 = 2.4 μmol m−2) according to the reactions R − +I Ζ ⇌RI Ζ−1 and P 0 + I Ζ⇌ PI Ζ, whereI Ζ represents an ion of charge Ζ. Binding constants for the negative site are 21,500m −1 for H+, 20,000m −1 for Al3+, 2,200m −1 for La3+, 30m −1 for Ca2+ and Mg2+, and 1 m −1 for Na+ and K+. Binding constants for the neutral site are 1/180 the value for binding to the negative site. Ion activities at the membrane surface, computed on the basis of ψ0, appear to determine many aspects of plant-mineral interactions, including mineral nutrition and the induction and alleviation of mineral toxicities, according to previous and ongoing studies. A computer program with instructions for the computation of ψ0, ion binding, ion concentrations, and ion activities at membrane surfaces may be requested from the authors.
The Down-Regulation of Mt4-Like Genes by Phosphate Fertilization Occurs Systemically and Involves Phosphate Translocation to the Shoots1
Authors: Burleigh Stephen H. , Harrison Maria J. 
Published: July 2002

Abstract
Mt4 is a cDNA representing a phosphate-starvation-inducible gene from Medicago truncatula that is down-regulated in roots in response to inorganic phosphate (Pi) fertilization and colonization by arbuscular mycorrhizal fungi. Split-root experiments revealed that the expression of the Mt4 gene in M. truncatula roots is down-regulated systemically by both Pi fertilization and colonization by arbuscular mycorrhizal fungi. A comparison of Pi levels in these tissues suggested that this systemic down-regulation is not caused by Pi accumulation. Using a 30-bp region of the Mt4 gene as a probe, Pi-starvation-inducible Mt4-like genes were detected in Arabidopsis and soybean (Glycine max L.), but not in corn (Zea mays L.). Analysis of the expression of the Mt4-like Arabidopsis gene,At4, in wild-type Arabidopsis and pho1, a mutant unable to load Pi into the xylem, suggests that Pi must first be translocated to the shoot for down-regulation to occur. The data from the pho1 and split-root studies are consistent with the presence of a translocatable shoot factor responsible for mediating the systemic down-regulation of Mt4-like genes in roots.
Delivery of a Secreted Soluble Protein to the Vacuole via a Membrane Anchor1
Authors: Barrieu François , Chrispeels Maarten J. 
Published: July 2002

Abstract
To further understand how membrane proteins are sorted in the secretory system, we devised a strategy that involves the expression of a membrane-anchored yeast invertase in transgenic plants. The construct consisted of a signal peptide followed by the coding region of yeast invertase and the transmembrane domain and cytoplasmic tail of calnexin. The substitution of a lysine near the C terminus of calnexin with a glutamic acid residue ensured progression through the secretory system rather than retention in or return to the endoplasmic reticulum. In the transformed plants, invertase activity and a 70-kD cross-reacting protein were found in the vacuoles. This yeast invertase had plant-specific complex glycans, indicating that transport to the vacuole was mediated by the Golgi apparatus. The microsomal fraction contained a membrane-anchored 90-kD cross-reacting polypeptide, but was devoid of invertase activity. Our results indicate that this membrane-anchored protein proceeds in the secretory system beyond the point where soluble proteins are sorted for secretion, and is detached from its membrane anchor either just before or just after delivery to the vacuole.
Expression of Endoxyloglucan Transferase Genes inacaulis Mutants of Arabidopsis
Authors: Akamatsu Taku , Hanzawa Yoshie , Ohtake Yuhko , Takahashi Taku , Nishitani Kazuhiko , Komeda Yoshibumi 
Published: July 2002

Abstract
A mutant of Arabidopsis with reduced internodal cell length, acaulis5 (acl5), has recently been shown to have reduced transcript levels of a gene for endoxyloglucan transferase, EXGT-A1 (Y. Hanzawa, T. Takahashi, Y. Komeda [1997] Plant J 12: 863–874). In the present study, we cloned genomic fragments of five members of theEXGT gene family, EXGT-A1,EXGT-A3, EXGT-A4, XTR2, and XTR3, and examined their expression in the wild type and in a series of acl mutants. In wild-type plants, theEXGT-A3 gene showed higher expression in lower internodes (internodes between nodes bearing axillary shoots) than in upper and young internodes, in which EXGT-A1 was highly expressed. EXGT-A4 was preferentially expressed in roots and XTR3 in siliques. The XTR2 gene was constitutively expressed. In acl1, acl3, and acl4 mutants, which have a severe defect in leaf expansion as well as in internode elongation, theEXGT-A1 gene showed reduced levels of expression before bolting of plants. In contrast, XTR3 was increased in these mutant seedlings. Reduction of EXGT-A1 expression was also detected after bolting of all acl mutants except acl2, whose growth defect is restricted to lower internodes. These results suggest the involvement of each EXGT in different aspects of organ development.
Purification of a Jojoba Embryo Fatty Acyl-Coenzyme A Reductase and Expression of Its cDNA in High Erucic Acid Rapeseed
Authors: Metz James G. , Pollard Michael R. , Anderson Lana , Hayes Thomas R. , Lassner Michael W. 
Published: July 2002

Abstract
The jojoba (Simmondsia chinensis) plant produces esters of long-chain alcohols and fatty acids (waxes) as a seed lipid energy reserve. This is in contrast to the triglycerides found in seeds of other plants. We purified an alcohol-forming fatty acyl-coenzyme A reductase (FAR) from developing embryos and cloned the cDNA encoding the enzyme. Expression of a cDNA in Escherichia coliconfers FAR activity upon those cells and results in the accumulation of fatty alcohols. The FAR sequence shows significant homology to an Arabidopsis protein of unknown function that is essential for pollen development. When the jojoba FAR cDNA is expressed in embryos ofBrassica napus, long-chain alcohols can be detected in transmethylated seed oils. Resynthesis of the gene to reduce its A plus T content resulted in increased levels of alcohol production. In addition to free alcohols, novel wax esters were detected in the transgenic seed oils. In vitro assays revealed that B. napus embryos have an endogenous fatty acyl-coenzyme A: fatty alcohol acyl-transferase activity that could account for this wax synthesis. Thus, introduction of a single cDNA into B. napus results in a redirection of a portion of seed oil synthesis from triglycerides to waxes.
Differential Regulation of Plastidial and Cytosolic Isoforms of Peptide Methionine Sulfoxide Reductase in Arabidopsis
Authors: Sadanandom Arivananthan , Poghosyan Zaruhi , Fairbairn David J. , Murphy Denis J. 
Published: July 2002

Abstract
We report the characterization of two members of a gene family from Arabidopsis that encode, respectively, cytosolic (cPMSR) and plastid-targeted (pPMSR) isoforms of the oxidative-stress-repair enzyme peptide methionine sulfoxide reductase. Overexpression of these proteins in Escherichia coli confirmed that each had PMSR enzyme activity with a synthetic substrate,N-acetyl-[3H]-methionine sulfoxide, or a biological substrate, α-1 proteinase inhibitor. The pPMSR was imported into intact chloroplasts in vitro with concomitant cleavage of its approximately 5-kD N-terminal signal peptide. The two PMSR isoforms exhibited divergent pH optima, tissue localization, and responses to developmental and environmental effects. Analysis of the Arabidopsis database indicated that there are probably at least twop-pmsr-like genes and three c-pmsr-like genes in the Arabidopsis genome. Expression of thep-pmsr genes and their protein products was restricted to photosynthetic tissues and was strongly induced following illumination of etiolated seedlings. In contrast, thec-pmsr genes were expressed at moderate levels in all tissues and were only weakly affected by light. Exposure to a variety of biotic and abiotic stresses showed relatively little effect onpmsr gene expression, with the exception of leaves subjected to a long-term exposure to the cauliflower mosaic virus. These leaves showed a strong induction of the c-pmsrgene after 2 to 3 weeks of chronic pathogen infection. These data suggest novel roles for PMSR in photosynthetic tissues and in pathogen defense responses in plants.
Brassinosteroid-Insensitive-1 Is a Ubiquitously Expressed Leucine-Rich Repeat Receptor Serine/Threonine Kinase
Authors: Friedrichsen Danielle M. , Joazeiro Claudio A.P. , Li Jianming , Hunter Tony , Chory Joanne 
Published: July 2002

AbstractBrassinosteroid (BR) mutants of Arabidopsis have pleiotropic phenotypes and provide evidence that BRs function throughout the life of the plant from seedling development to senescence. Screens for BR signaling mutants identified one locus, BRI1, which encodes a protein with homology to leucine-rich repeat receptor serine (Ser)/threonine (Thr) kinases. Twenty-seven alleles of this putative BR receptor have been isolated to date, and we present here the identification of the molecular lesions of 14 recessive alleles that represent five new mutations. BR-insensitive-1 (BRI1) is expressed at high levels in the meristem, root, shoot, and hypocotyl of seedlings and at lower levels later in development. Confocal microscopy analysis of full-length BRI1 fused to green fluorescent protein indicates that BRI1 is localized in the plasma membrane, and an in vitro kinase assay indicates that BRI1 is a functional Ser/Thr kinase. Among thebri1 mutants identified are mutants in the kinase domain, and we demonstrate that one of these mutations severely impairs BRI1 kinase activity. Therefore, we conclude that BRI1 is a ubiquitously expressed leucine-rich repeat receptor that plays a role in BR signaling through Ser/Thr phosphorylation.
Inward Potassium Channel in Guard Cells As a Target for Polyamine Regulation of Stomatal Movements
Authors: Liu Kun , Fu Huihua , Bei Qixin , Luan Sheng 
Published: July 2002

Abstract
A number of studies show that environmental stress conditions such as drought, high salt, and air pollutants increase polyamine levels in plant cells. However, little is understood about the physiological function of elevated polyamine levels. We report here that polyamines regulate the voltage-dependent inward K+ channel in the plasma membrane of guard cells and modulate stomatal aperture, a plant “sensor” to environmental changes. All natural polyamines, including spermidine, spermine, cadaverine, and putrescine, strongly inhibited opening and induced closure of stomata. Whole-cell patch-clamp analysis showed that intracellular application of polyamines inhibited the inward K+ current across the plasma membrane of guard cells. Single-channel recording analysis indicated that polyamine regulation of the K+ channel requires unknown cytoplasmic factors. In an effort to identify the target channel at the molecular level, we found that spermidine inhibited the inward K+ current carried by KAT1 channel that was functionally expressed in a plant cell model. These findings suggest that polyamines target KAT1-like inward K+ channels in guard cells and modulate stomatal movements, providing a link between stress conditions, polyamine levels, and stomatal regulation.
Regulation and Function of the ArabidopsisABA-insensitive4Gene in Seed and Abscisic Acid Response Signaling Networks
Authors: Söderman Eva M. , Brocard Inès M. , Lynch Tim J. , Finkelstein Ruth R. 
Published: July 2002

AbstractWe have characterized developmental, environmental, and genetic regulation of abscisic acid-insensitive (ABI)4 gene expression in Arabidopsis. Although expressed most strongly in seeds,ABI4 transcripts are also present at low levels in vegetative tissue; vegetative expression is not induced by abscisic acid (ABA) or stress treatments. Comparison of transcript levels in mature seeds of ABA-insensitive, ABA-hypersensitive, ABA-deficient, or heterochronic mutants indicates that ABI4 expression is altered in only two of the backgrounds, the ABA-insensitive mutantsabi1-1 and abi3-1. To determine whetherABI4 is necessary and/or sufficient for ABA response, we assayed the effects of loss of ABI4 function and ectopicABI4 expression on growth and gene expression. We examined genetic interactions among three ABA response loci,ABI3, ABI4, and ABI5, by comparing phenotypes of mutants, ectopic expression lines, mutants carrying an ectopically expressed transgene, and the corresponding wild-type lines. Our results indicate some cross-regulation of expression among ABI3, ABI4, andABI5 and suggest that they function in a combinatorial network, rather than a regulatory hierarchy, controlling seed development and ABA response.