bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphatidic Acid Induces Leaf Cell Death in Arabidopsis by Activating the Rho-Related Small G Protein GTPase-Mediated Pathway of Reactive Oxygen Species Generation
Authors: Park Jumok , Gu Ying , Lee Yuree , Yang Zhenbiao , Lee Youngsook 
Published: January 2004

AbstractPhosphatidic acid (PA) level increases during various stress conditions. However, the physiological roles of this lipid in stress response remain largely unknown. In this study, we report that PA induced leaf cell death and elevated the levels of reactive oxygen species (ROS) in the whole leaf and single cells. To further elucidate the mechanism of PA-induced cell death, we then examined whether Rho-related small G protein (ROP) 2, which enhanced ROS production in an in vitro assay, is involved in PA-induced ROS production and cell death. In response to PA, transgenic leaves of Arabidopsis expressing a constitutively active rop2 mutant exhibited earlier cell death and higher levels of ROS than wild type (WT), whereas those expressing a dominant-negative rop2 mutant exhibited later cell death and lower ROS. However, in the absence of exogenous PA, no spontaneous cell death or elevated ROS was observed in constitutively active rop2 plants, suggesting that the activation of ROP GTPase alone is insufficient to activate the ROP-mediated ROS generation pathway. These results suggest that PA modulates an additional factor required for the active ROP-mediated ROS generation pathway. Therefore, PA may be an important regulator of ROP-regulated ROS generation and the cell death process during various stress and defense responses of plants.
Osmotic Effects on the Electrical Properties of Arabidopsis Root Hair Vacuoles in Situ
Authors: Lew Roger R. 
Published: January 2004

Abstract
To assess the role of the vacuole in responses to hyperosmotic and hypo-osmotic stress, the electrical properties of the vacuole were measured in situ. A double-barrel micropipette was inserted into the vacuole for voltage clamping. A second double-barrel micropipette was inserted into the cytoplasm to provide a virtual ground that separated the electrical properties of the vacuole from those of the plasma membrane. Osmotic stress causes immediate electrical responses at the plasma membrane (Lew RR [1996] Plant Physiol 97: 2002-2005) and ion flux changes and turgor recovery (Shabala SN, Lew RR [2002] 129: 290-299) in Arabidopsis root cells. In situ, the vacuole also responds rapidly to changes in extracellular osmotic potential. Hyperosmotic treatment caused a very large increase in the ionic conductance of the vacuole. Hypo-osmotic treatment did not affect the vacuolar conductance. In either case, the vacuolar electrical potential was unchanged. Taken in concert with previous studies of changes at the plasma membrane, these results demonstrate a highly coordinated system in which the vacuole and plasma membrane are primed to respond immediately to hyperosmotic stress before changes in gene expression.
Molecular and Cell Biology of a Family of Voltage-Dependent Anion Channel Porins in Lotus japonicus
Authors: Wandrey Maren , Trevaskis Ben , Brewin Nick , Udvardi Michael K. 
Published: January 2004

Abstract
Voltage-dependent anion channels (VDACs) are generally considered as the main pathway for metabolite transport across the mitochondrial outer membrane. Recent proteomic studies on isolated symbiosome membranes from legume nodules indicated that VDACs might also be involved in transport of nutrients between plants and rhizobia. In an attempt to substantiate this, we carried out a detailed molecular and cellular characterization of VDACs in Lotus japonicus and soybean (Glycine max). Database searches revealed at least five genes encoding putative VDACs in each of the legumes L. japonicus, Medicago truncatula, and soybean. We obtained and sequenced cDNA clones from L. japonicus encoding five full-length VDAC proteins (LjVDAC1.1–1.3, LjVDAC2.1, and LjVDAC3.1). Complementation of a yeast (Saccharomyces cerevisiae) mutant impaired in VDAC1, a porin of the mitochondrial outer membrane, showed that LjVDAC1.1, LjVDAC1.2, LjVDAC2.1, and LjVDAC3.1, but not LjVDAC1.3, are functional and targeted to the mitochondrial outer membrane in yeast. Studies of the expression pattern of the five L. japonicus VDAC genes revealed largely constitutive expression of each throughout the plant, including nodules. Antibodies to LjVDAC1.1 of L. japonicus and the related POM36 protein of potato (Solanum tuberosum) recognized several proteins between 30 and 36 kD on western blots, including LjVDAC1.1, LjVDAC1.2, LjVDAC1.3, and LjVDAC2.1. Immunolocalization of VDACs in L. japonicus and soybean root nodules demonstrated their presence on not only mitochondria but also on numerous, small vesicles at the cell periphery. No evidence was found for the presence of VDACs on the symbiosome membrane. Nonetheless, the data indicate that VDACs may play more diverse roles in plants than suspected previously.
Characterization of Mutants in Arabidopsis Showing Increased Sugar-Specific Gene Expression, Growth, and Developmental Responses
Authors: Baier Margarete , Hemmann Georg , Holman Rachel , Corke Fiona , Card Rod , Smith Caroline , Rook Fred , Bevan Michael W. 
Published: January 2004

AbstractSugars such as sucrose serve dual functions as transported carbohydrates in vascular plants and as signal molecules that regulate gene expression and plant development. Sugar-mediated signals indicate carbohydrate availability and regulate metabolism by co-coordinating sugar production and mobilization with sugar usage and storage. Analysis of mutants with altered responses to sucrose and glucose has shown that signaling pathways mediated by sugars and abscisic acid interact to regulate seedling development and gene expression. Using a novel screen for sugar-response mutants based on the activity of a luciferase reporter gene under the control of the sugar-inducible promoter of the ApL3 gene, we have isolated high sugar-response (hsr) mutants that exhibit elevated luciferase activity and ApL3 expression in response to low sugar concentrations. Our characterization of these hsr mutants suggests that they affect the regulation of sugar-induced and sugar-repressed processes controlling gene expression, growth, and development in Arabidopsis. In contrast to some other sugar-response mutants, they do not exhibit altered responses to ethylene or abscisic acid, suggesting that the hsr mutants may have a specifically increased sensitivity to sugars. Further characterization of the hsr mutants will lead to greater understanding of regulatory pathways involved in metabolite signaling.
Characterization and Functional Identification of a Novel Plant 4,5-Extradiol Dioxygenase Involved in Betalain Pigment Biosynthesis in Portulaca grandiflora
Authors: Christinet Laurent , Burdet Frédéric X. , Zaiko Maïa , Hinz Ursula , Zrÿd Jean-Pierre 
Published: January 2004

Abstract
Betalains are pigments that replace anthocyanins in the majority of families of the plant order Caryophyllales. Betalamic acid is the common chromophore of betalains. The key enzyme of the betalain biosynthetic pathway is an extradiol dioxygenase that opens the cyclic ring of dihydroxy-phenylalanine (DOPA) between carbons 4 and 5, thus producing an unstable seco-DOPA that rearranges nonenzymatically to betalamic acid. A gene for a 4,5-DOPA-dioxygenase has already been isolated from the fungus Amanita muscaria, but no homolog was ever found in plants. To identify the plant gene, we constructed subtractive libraries between different colored phenotypes of isogenic lines of Portulaca grandiflora (Portulacaceae) and between different stages of flower bud formation. Using in silico analysis of differentially expressed cDNAs, we identified a candidate showing strong homology at the level of translated protein with the LigB domain present in several bacterial extradiol 4,5-dioxygenases. The gene was expressed only in colored flower petals. The function of this gene in the betalain biosynthetic pathway was confirmed by biolistic genetic complementation in white petals of P. grandiflora genotypes lacking the gene for color formation. This gene named DODA is the first characterized member of a novel family of plant dioxygenases phylogenetically distinct from Amanita sp. DOPA-dioxygenase. Homologs of DODA are present not only in betalain-producing plants but also, albeit with some changes near the catalytic site, in other angiosperms and in the bryophyte Physcomitrella patens. These homologs are part of a novel conserved plant gene family probably involved in aromatic compound metabolism.
Towards Functional Proteomics of Membrane Protein Complexes in Synechocystis sp. PCC 6803
Authors: Herranen Mirkka , Battchikova Natalia , Zhang Pengpeng , Graf Alexander , Sirpiö Sari , Paakkarinen Virpi , Aro Eva-Mari 
Published: January 2004

Abstract
The composition and dynamics of membrane protein complexes were studied in the cyanobacterium Synechocystis sp. PCC 6803 by two-dimensional blue native/SDS-PAGE followed by matrix-assisted laser-desorption ionization time of flight mass spectrometry. Approximately 20 distinct membrane protein complexes could be resolved from photoautotrophically grown wild-type cells. Besides the protein complexes involved in linear photosynthetic electron flow and ATP synthesis (photosystem [PS] I, PSII, cytochrome b6f, and ATP synthase), four distinct complexes containing type I NAD(P)H dehydrogenase (NDH-1) subunits were identified, as well as several novel, still uncharacterized protein complexes. The dynamics of the protein complexes was studied by culturing the wild type and several mutant strains under various growth modes (photoautotrophic, mixotrophic, or photoheterotrophic) or in the presence of different concentrations of CO2, iron, or salt. The most distinct modulation observed in PSs occurred in iron-depleted conditions, which induced an accumulation of CP43′ protein associated with PSI trimers. The NDH-1 complexes, on the other hand, responded readily to changes in the CO2 concentration and the growth mode of the cells and represented an extremely dynamic group of membrane protein complexes. Our results give the first direct evidence, to our knowledge, that the NdhF3, NdhD3, and CupA proteins assemble together to form a small low CO2-induced protein complex and further demonstrate the presence of a fourth subunit, Sll1735, in this complex. The two bigger NDH-1 complexes contained a different set of NDH-1 polypeptides and are likely to function in respiratory and cyclic electron transfer. Pulse labeling experiments demonstrated the requirement of PSII activity for de novo synthesis of the NDH-1 complexes.
Engineering Plant Shikimate Pathway for Production of Tocotrienol and Improving Herbicide Resistance
Authors: Rippert Pascal , Scimemi Claire , Dubald Manuel , Matringe Michel 
Published: January 2004

Abstract
Tocochromanols (tocopherols and tocotrienols), collectively known as vitamin E, are essential antioxidant components of both human and animal diets. Because of their potential health benefits, there is a considerable interest in plants with increased or customized vitamin E content. Here, we have explored a new strategy to reach this goal. In plants, phenylalanine is the precursor of a myriad of secondary compounds termed phenylpropanoids. In contrast, much less carbon is incorporated into tyrosine that provides p-hydroxyphenylpyruvate and homogentisate, the aromatic precursors of vitamin E. Therefore, we intended to increase the flux of these two compounds by deriving their synthesis directly at the level of prephenate. This was achieved by the expression of the yeast (Saccharomyces cerevisiae) prephenate dehydrogenase gene in tobacco (Nicotiana tabacum) plants that already overexpress the Arabidopsis p-hydroxyphenylpyruvate dioxygenase coding sequence. A massive accumulation of tocotrienols was observed in leaves. These molecules, which were undetectable in wild-type leaves, became the major forms of vitamin E in the leaves of the transgenic lines. An increased resistance of the transgenic plants toward the herbicidal p-hydroxyphenylpyruvate dioxygenase inhibitor diketonitril was also observed. This work demonstrates that the synthesis of p-hydroxyphenylpyruvate is a limiting step for the accumulation of vitamin E in plants.
TheULTRACURVATA2Gene of Arabidopsis Encodes an FK506-Binding Protein Involved in Auxin and Brassinosteroid Signaling
Authors: Pérez-Pérez José Manuel , Ponce María Rosa , Micol José Luis 
Published: January 2004

AbstractThe dwarf ucu (ultracurvata) mutants of Arabidopsis display vegetative leaves that are spirally rolled downwards and show reduced expansion along the longitudinal axis. We have previously determined that the UCU1 gene encodes a SHAGGY/GSK3-like kinase that participates in the signaling pathways of auxins and brassinosteroids. Here, we describe four recessive alleles of the UCU2 gene, whose homozygotes display helical rotation of several organs in addition to other phenotypic traits shared with ucu1 mutants. Following a map-based strategy, we identified the UCU2 gene, which was found to encode a peptidyl-prolyl cis/trans-isomerase of the FK506-binding protein family, whose homologs in metazoans are involved in cell signaling and protein trafficking. Physiological and double mutant analyses suggest that UCU2 is required for growth and development and participates in auxin and brassinosteroid signaling.
Hypobaric Biology: Arabidopsis Gene Expression at Low Atmospheric Pressure
Authors: Paul Anna-Lisa , Schuerger Andrew C. , Popp Michael P. , Richards Jeffrey T. , Manak Michael S. , Ferl Robert J. 
Published: January 2004

AbstractAs a step in developing an understanding of plant adaptation to low atmospheric pressures, we have identified genes central to the initial response of Arabidopsis to hypobaria. Exposure of plants to an atmosphere of 10 kPa compared with the sea-level pressure of 101 kPa resulted in the significant differential expression of more than 200 genes between the two treatments. Less than one-half of the genes induced by hypobaria are similarly affected by hypoxia, suggesting that response to hypobaria is unique and is more complex than an adaptation to the reduced partial pressure of oxygen inherent to hypobaric environments. In addition, the suites of genes induced by hypobaria confirm that water movement is a paramount issue at low atmospheric pressures, because many of gene products intersect abscisic acid-related, drought-induced pathways. A motivational constituent of these experiments is the need to address the National Aeronautics and Space Administration's plans to include plants as integral components of advanced life support systems. The design of bioregenerative life support systems seeks to maximize productivity within structures engineered to minimize mass and resource consumption. Currently, there are severe limitations to producing Earth-orbital, lunar, or Martian plant growth facilities that contain Earth-normal atmospheric pressures within light, transparent structures. However, some engineering limitations can be offset by growing plants in reduced atmospheric pressures. Characterization of the hypobaric response can therefore provide data to guide systems engineering development for bioregenerative life support, as well as lead to fundamental insights into aspects of desiccation metabolism and the means by which plants monitor water relations.
A Post Genomic Characterization of Arabidopsis Ferredoxins
Authors: Hanke Guy Thomas , Kimata-Ariga Yoko , Taniguchi Isao , Hase Toshiharu 
Published: January 2004

Abstract
In higher plant plastids, ferredoxin (Fd) is the unique soluble electron carrier protein located in the stroma. Consequently, a wide variety of essential metabolic and signaling processes depend upon reduction by Fd. The currently available plant genomes of Arabidopsis and rice (Oryza sativa) contain several genes encoding putative Fds, although little is known about the proteins themselves. To establish whether this variety represents redundancy or specialized function, we have recombinantly expressed and purified the four conventional [2Fe-2S] Fd proteins encoded in the Arabidopsis genome and analyzed their physical and functional properties. Two proteins are leaf type Fds, having relatively low redox potentials and supporting a higher photosynthetic activity. One protein is a root type Fd, being more efficiently reduced under nonphotosynthetic conditions and supporting a higher activity of sulfite reduction. A further Fd has a remarkably positive redox potential and so, although redox active, is limited in redox partners to which it can donate electrons. Immunological analysis indicates that all four proteins are expressed in mature leaves. This holistic view demonstrates how varied and essential soluble electron transfer functions in higher plants are fulfilled through a diversity of Fd proteins.
The CesA Gene Family of Barley. Quantitative Analysis of Transcripts Reveals Two Groups of Co-Expressed Genes
Authors: Burton Rachel A. , Shirley Neil J. , King Brendon J. , Harvey Andrew J. , Fincher Geoffrey B. 
Published: January 2004

Abstract
Sequence data from cDNA and genomic clones, coupled with analyses of expressed sequence tag databases, indicate that the CesA (cellulose synthase) gene family from barley (Hordeum vulgare) has at least eight members, which are distributed across the genome. Quantitative polymerase chain reaction has been used to determine the relative abundance of mRNA transcripts for individual HvCesA genes in vegetative and floral tissues, at different stages of development. To ensure accurate expression profiling, geometric averaging of multiple internal control gene transcripts has been applied for the normalization of transcript abundance. Total HvCesA mRNA levels are highest in coleoptiles, roots, and stems and much lower in floral tissues, early developing grain, and in the elongation zone of leaves. In most tissues, HvCesA1, HvCesA2, and HvCesA6 predominate, and their relative abundance is very similar; these genes appear to be coordinately transcribed. A second group, comprising HvCesA4, HvCesA7, and HvCesA8, also appears to be coordinately transcribed, most obviously in maturing stem and root tissues. The HvCesA3 expression pattern does not fall into either of these two groups, and HvCesA5 transcript levels are extremely low in all tissues. Thus, the HvCesA genes fall into two general groups of three genes with respect to mRNA abundance, and the co-expression of the groups identifies their products as candidates for the rosettes that are involved in cellulose biosynthesis at the plasma membrane. Phylogenetic analysis allows the two groups of genes to be linked with orthologous Arabidopsis CesA genes that have been implicated in primary and secondary wall synthesis.
Impact of Unusual Fatty Acid Synthesis on Futile Cycling through β-Oxidation and on Gene Expression in Transgenic Plants
Authors: Moire Laurence , Rezzonico Enea , Goepfert Simon , Poirier Yves 
Published: January 2004

Abstract
Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12-epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxyalkanoate (PHA) from the intermediates of the peroxisomal β-oxidation cycle. Both the quantity and monomer composition of the PHA synthesized in transgenic plants expressing the 12-epoxygenase and 12-hydroxylase in developing seeds revealed the presence of a futile cycle of degradation of the corresponding unusual fatty acids, indicating a limitation in their stable integration into lipids. The expression profile of nearly 200 genes involved in fatty acid biosynthesis and degradation has been analyzed through microarray. No significant changes in gene expression have been detected as a consequence of the activity of the 12-epoxygenase or the 12-hydroxylase in developing siliques. Similar results have also been obtained for transgenic plants expressing the Cuphea lanceolata caproyl-acyl carrier protein thioesterase and accumulating high amounts of caproic acid. Only in developing siliques of the tag1 mutant, deficient in the accumulation of triacylglycerols and shown to have a substantial futile cycling of fatty acids toward β-oxidation, have some changes in gene expression been detected, notably the induction of the isocitrate lyase gene. These results indicate that analysis of peroxisomal PHA is a better indicator of the flux of fatty acid through β-oxidation than the expression profile of genes involved in lipid metabolism.
Characterization of Geraniol Synthase from the Peltate Glands of Sweet Basil
Authors: Iijima Yoko , Gang David R. , Fridman Eyal , Lewinsohn Efraim , Pichersky Eran 
Published: January 2004

Abstract
The monoterpene fraction of the lemon-scented sweet basil (Ocimum basilicum) cv Sweet Dani consists mostly of citral (a mixture of geranial and neral), with lower levels of geraniol and nerol. These compounds are stored in the peltate glands found on the leaf epidermis. Younger leaves, which have a higher density of such glands, also have a higher content of monoterpenes than older leaves. Geraniol synthase (GES) activity, generating geraniol from geranyl diphosphate, was shown to be localized exclusively or almost exclusively to glands. GES activity resides in a homodimeric protein that was purified to near homogeneity. Basil GES requires Mn2+ as a divalent metal cofactor for activity and produces only geraniol from geranyl diphosphate. K m values of 21 and 51 μm were obtained for geranyl diphosphate and Mn2+, respectively. In the presence of 18O-labeled water, GES catalyzed the formation of 18O-geraniol from geranyl diphosphate, indicating that the reaction mechanism of GES is similar to that of other monoterpene synthases and is different from the action of phosphatases. A GES cDNA was isolated based on analysis of a glandular trichome expressed sequence tag database, and the sequence of the protein encoded by this cDNA shows some similarity to sequences of other terpene synthases. The expression of the GES cDNA in Escherichia coli resulted in a protein with enzymatic activity essentially identical to that of plant-purified GES. RNA gel-blot analysis indicated that GES is expressed in glands but not in leaves of basil cv Sweet Dani, whose glands contain geraniol and citral, and not in glands or leaves of another basil variety that makes other monoterpenes but not geraniol or citral.