bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phytoremediation of Organomercurial Compounds via Chloroplast Genetic Engineering
Authors: Ruiz Oscar N. , Hussein Hussein S. , Terry Norman , Daniell Henry 
Published: July 2003

Abstract
Mercury (Hg), especially in organic form, is a highly toxic pollutant affecting plants, animals, and man. In plants, the primary target of Hg damage is the chloroplast; Hg inhibits electron transport and photosynthesis. In the present study, chloroplast genetic engineering is used for the first time to our knowledge to enhance the capacity of plants for phytoremediation. This was achieved by integrating a native operon containing the merA and merB genes (without any codon modification), which code for mercuric ion reductase (merA) and organomercurial lyase (merB), respectively, into the chloroplast genome in a single transformation event. Stable integration of the merAB operon into the chloroplast genome resulted in high levels of tolerance to the organomercurial compound, phenylmercuric acetate (PMA) when grown in soil containing up to 400 μm PMA; plant dry weights of the chloroplast transformed lines were significantly higher than those of wild type at 100, 200, and 400 μm PMA. That the merAB operon was stably integrated into the chloroplast genome was confirmed by polymerase chain reaction and Southern-blot analyses. Northern-blot analyses revealed stable transcripts that were independent of the presence or absence of a 3′-untranslated region downstream of the coding sequence. The merAB dicistron was the more abundant transcript, but less abundant monocistrons were also observed, showing that specific processing occurs between transgenes. The use of chloroplast transformation to enhance Hg phytoremediation is particularly beneficial because it prevents the escape of transgenes via pollen to related weeds or crops and there is no need for codon optimization to improve transgene expression. Chloroplast transformation may also have application to other metals that affect chloroplast function.
Phosphate Starvation Triggers Distinct Alterations of Genome Expression in Arabidopsis Roots and Leaves
Authors: Wu Ping , Ma Ligeng , Hou Xingliang , Wang Mingyi , Wu Yungrong , Liu Feiyan , Deng Xing Wang 
Published: July 2003

Abstract
Arabidopsis genome expression pattern changes in response to phosphate (Pi) starvation were examined during a 3-d period after removal of Pi from the growth medium. Available Pi concentration was decreased after the first 24 h of Pi starvation in roots by about 22%, followed by a slow recovery during the 2nd and 3rd d after Pi starvation, but no significant change was observed in leaves within the 3 d of Pi starvation. Microarray analysis revealed that more than 1,800 of the 6,172 genes present in the array were regulated by 2-fold or more within 72 h from the onset of Pi starvation. Analysis of these Pi starvation-responsive genes shows that they belong to wide range of functional categories. Many genes for photosynthesis and nitrogen assimilation were down-regulated. A complex set of metabolic adaptations appears to occur during Pi starvation. More than 100 genes each for transcription factors and cell-signaling proteins were regulated in response to Pi starvation, implying major regulatory changes in cellular growth and development. A significant fraction of those regulatory genes exhibited distinct or even contrasting expression in leaves and roots in response to Pi starvation, supporting the idea that distinct Pi starvation response strategies are used for different plant organs in response to a shortage of Pi in the growth medium.
An Isoleucine Residue within the Carboxyl-Transferase Domain of Multidomain Acetyl-Coenzyme A Carboxylase Is a Major Determinant of Sensitivity to Aryloxyphenoxypropionate But Not to Cyclohexanedione Inhibitors
Authors: Délye Christophe , Zhang Xiao-Qi , Chalopin Claire , Michel Séverine , Powles Stephen B. 
Published: July 2003

Abstract
A 3,300-bp DNA fragment encoding the carboxyl-transferase domain of the multidomain, chloroplastic acetyl-coenzyme A carboxylase (ACCase) was sequenced in aryloxyphenoxypropionate (APP)-resistant and -sensitive Alopecurus myosuroides (Huds.). No resistant plant contained an Ile-1,781-Leu substitution, previously shown to confer resistance to APPs and cyclohexanediones (CHDs). Instead, an Ile-2,041-Asn substitution was found in resistant plants. Phylogenetic analysis of the sequences revealed that Asn-2,041 ACCase alleles derived from several distinct origins. Allele-specific polymerase chain reaction associated the presence of Asn-2,041 with seedling resistance to APPs but not to CHDs. ACCase enzyme assays confirmed that Asn-2,041 ACCase activity was moderately resistant to CHDs but highly resistant to APPs. Thus, the Ile-2,041-Asn substitution, which is located outside a domain previously shown to control sensitivity to APPs and CHDs in wheat (Triticum aestivum), is a direct cause of resistance to APPs only. In known multidomain ACCases, the position corresponding to the Ile/Asn-2,041 residue in A. myosuroides is occupied by an Ile or a Val residue. In Lolium rigidum (Gaud.), we found Ile-Asn and Ile-Val substitutions. The Ile-Val change did not confer resistance to the APP clodinafop, whereas the Ile-Asn change did. The position and the particular substitution at this position are of importance for sensitivity to APPs.
Induction of Volatile Terpene Biosynthesis and Diurnal Emission by Methyl Jasmonate in Foliage of Norway Spruce
Authors: Martin Diane M. , Gershenzon Jonathan , Bohlmann Jörg 
Published: July 2003

Abstract
Terpenoids are characteristic constitutive and inducible defense chemicals of conifers. The biochemical regulation of terpene formation, accumulation, and release from conifer needles was studied in Norway spruce [Picea abies L. (Karst)] saplings using methyl jasmonate (MeJA) to induce defensive responses without inflicting physical damage to terpene storage structures. MeJA treatment caused a 2-fold increase in monoterpene and sesquiterpene accumulation in needles without changes in terpene composition, much less than the 10- and 40-fold increases in monoterpenes and diterpenes, respectively, observed in wood tissue after MeJA treatment (D. Martin, D. Tholl, J. Gershenzon, J. Bohlmann [2002] Plant Physiol 129: 1003–1018). At the same time, MeJA triggered a 5-fold increase in total terpene emission from foliage, with a shift in composition to a blend dominated by oxygenated monoterpenes (e.g. linalool) and sesquiterpenes [e.g. (E)-β-farnesene] that also included methyl salicylate. The rate of linalool emission increased more than 100-fold and that of sesquiterpenes increased more than 30-fold. Emission of these compounds followed a pronounced diurnal rhythm with the maximum amount released during the light period. The major MeJA-induced volatile terpenes appear to be synthesized de novo after treatment, rather than being released from stored terpene pools, because they are almost completely absent from needle oleoresin and are the major products of terpene synthase activity measured after MeJA treatment. Based on precedents in other species, the induced emission of terpenes from Norway spruce foliage may have ecological and physiological significance.
Structural and Biochemical Dissection of Photorespiration in Hybrids Differing in Genome Constitution betweenDiplotaxis tenuifolia(C3-C4) and Radish (C3)
Authors: Ueno Osamu , Bang Sang Woo , Wada Yoshiharu , Kondo Ayumu , Ishihara Kuni , Kaneko Yukio , Matsuzawa Yasuo 
Published: July 2003

AbstractWe compared the structural, biochemical, and physiological characteristics involved in photorespiration of intergeneric hybrids differing in genome constitution (DtDtR, DtDtRR, and DtRR) between the C3-C4 intermediate species Diplotaxis tenuifolia (DtDt) and the C3 species radish (Raphanus sativus; RR). The bundle sheath (BS) cells in D. tenuifolia included many centripetally located chloroplasts and mitochondria, but those of radish had only a few chloroplasts and mitochondria. In the hybrids, the numbers of chloroplasts and mitochondria, the ratio of centripetally located organelles to total organelles, and the mitochondrial size in the BS cells increased with an increase in the constitution ratio of the Dt:R genome. The P-protein of glycine decarboxylase (GDC) was confined to the BS mitochondria in D. tenuifolia, whereas in radish, it accumulated more densely in the mesophyll than in the BS mitochondria. In the hybrids, more intense accumulation of GDC in the BS relative to the mesophyll mitochondria occurred with an increase in the Dt:R ratio. These structural and biochemical features in the hybrids were reflected in the gas exchange characteristics of leaves, such as the CO2 compensation point. Our data indicate that the leaf structure, the intercellular pattern of GDC expression, and the gas exchange characteristics of C3-C4 intermediate photosynthesis are inherited in the hybrids depending on the constitution ratio of the parent genomes. Our findings also demonstrate that the apparent reduced photorespiration in C3-C4 intermediate plants is mainly due to the structural differentiation of mitochondria and chloroplasts in the BS cells combined with the BS-dominant expression of GDC.
Potato Plants Lacking the CDSP32 Plastidic Thioredoxin Exhibit Overoxidation of the BAS1 2-Cysteine Peroxiredoxin and Increased Lipid Peroxidation in Thylakoids under Photooxidative Stress
Authors: Broin Mélanie , Rey Pascal 
Published: July 2003

Abstract
The CDSP32 protein (chloroplastic drought-induced stress protein of 32 kD) is a thioredoxin participating in the defense against oxidative damage. We recently have identified in vitro the BAS1 2-Cys peroxiredoxin, a peroxide-detoxifying enzyme, as a target for CDSP32. Here, we report the characterization under stress conditions of transgenic potato (Solanum tuberosum) plants lacking CDSP32 with regard to the BAS1 redox state and the level of lipid peroxidation. Under control conditions, BAS1 is present at similar levels both in wild-type (WT) and transgenic plants. Under drought and methyl viologen treatment, CDSP32-lacking plants display, compared with WT, an increased proportion of BAS1 monomer corresponding to an overoxidized form of the protein. Leaf discs from transgenic plants treated with methyl viologen exhibit earlier degradation of BAS1 than WT plants do. Using several approaches, i.e. a probe emitting fluorescence when reacting with peroxides, high-performance liquid chromatography determination of lipid hydroxy fatty acid content, and measurement of chlorophyll thermoluminescence, we show a higher lipid peroxidation level under methyl viologen treatment in thylakoids from CDSP32-lacking plants compared with WT. These data show that CDSP32 is a critical component in the defense system against lipid peroxidation in photosynthetic membranes, likely as a physiological electron donor to the BAS1 peroxiredoxin.
The Distribution of Arsenate and Arsenite in Shoots and Roots of Holcus lanatus is Influenced by Arsenic Tolerance and Arsenate and Phosphate Supply
Authors: Quaghebeur Mieke , Rengel Zdenko 
Published: July 2003

Abstract
The recent discovery that phytochelatins are important for arsenic (As) detoxification in terrestrial plants results in the necessity to understand As speciation and metabolism in plant material. A hydroponic study was therefore conducted to examine the effects of different levels of phosphate and arsenate [As(V)] on As speciation and distribution in tolerant and non-tolerant clones of Holcus lanatus. Speciation of As in tissue (using high-performance liquid chromatography-inductively coupled plasma mass spectrometry) revealed that the predominant species present were the inorganic As species (As(V) and arsenite [As(III)]), although small levels (&lt;1%) of organic As species (dimethylarsinic acid and monomethylarsonic acid) were detected in shoot material. In roots, the proportion of total As present as As(III) generally increased with increasing levels of As(V) in the nutrient solution, whereas in shoots, the proportion of total As present as As(III) generally decreased with increasing levels of As(V). H. lanatus plants growing in the high-phosphorus (P) (100 μm) solution contained a higher proportion of As(V) (with regard to total As) in both roots and shoots than plants supplied with low P (10 μm); in addition, tolerant clones generally contained a higher proportion of As(V) with regard to total As than non-tolerant clones. The study further revealed that As(V) can be reduced to As(III) in both roots and shoots. Although the reduction capacity was limited, the reduction was closely regulated by As influx for all treatments. The results therefore provide a new understanding about As metabolism in H. lanatus.
Cold Tolerance of C4 photosynthesis in Miscanthus × giganteus: Adaptation in Amounts and Sequence of C4 Photosynthetic Enzymes
Authors: Naidu Shawna L. , Moose Stephen P. , AL-Shoaibi Abdul K. , Raines Christine A. , Long Stephen P. 
Published: July 2003

Abstract
Field-grown Miscanthus × giganteus maintains high photosynthetic quantum yields and biomass productivity in cool temperate climates. It is related to maize (Zea mays) and uses the same NADP-malic enzyme C4 pathway. This study tests the hypothesis that M. × giganteus, in contrast to maize, forms photosynthetically competent leaves at low temperatures with altered amounts of pyruvate orthophosphate dikinase (PPDK) and Rubisco or altered properties of PPDK. Both species were grown at 25°C/20°C or 14°C/11°C (day/night), and leaf photosynthesis was measured from 5°C to 38°C. Protein and steady-state transcript levels for Rubisco, PPDK, and phosphoenolpyruvate carboxylase were assessed and the sequence of C4-PPDK from M. × giganteus was compared with other C4 species. Low temperature growth had no effect on photosynthesis in M. × giganteus, but decreased rates by 80% at all measurement temperatures in maize. Amounts and expression of phosphoenolpyruvate carboxylase were affected little by growth temperature in either species. However, PPDK and Rubisco large subunit decreased &gt;50% and &gt;30%, respectively, in cold-grown maize, whereas these levels remained unaffected by temperature in M. × giganteus. Differences in protein content in maize were not explained by differences in steady-state transcript levels. Several different M. × giganteus C4-PPDK cDNA sequences were found, but putative translated protein sequences did not show conservation of amino acids contributing to cold stability in Flaveria brownii C4-PPDK. The maintenance of PPDK and Rubisco large subunit amounts in M. × giganteus is consistent with the hypothesis that these proteins are critical to maintaining high rates of C4 photosynthesis at low temperature.
Arabidopsis UVH6, a Homolog of Human XPD and Yeast RAD3 DNA Repair Genes, Functions in DNA Repair and Is Essential for Plant Growth
Authors: Liu Zongrang , Hong Suk-Whan , Escobar Mindy , Vierling Elizabeth , Mitchell David L. , Mount David W. , Hall Jennifer D. 
Published: July 2003

Abstract
To evaluate the genetic control of stress responses in Arabidopsis, we have analyzed a mutant (uvh6-1) that exhibits increased sensitivity to UV light, a yellow-green leaf coloration, and mild growth defects. We have mapped the uvh6-1 locus to chromosome I and have identified a candidate gene, AtXPD, within the corresponding region. This gene shows sequence similarity to the human (Homo sapiens) XPD and yeast (Saccharomyces cerevisiae) RAD3 genes required for nucleotide excision repair. We propose that UVH6 is equivalent to AtXPD because uvh6-1 mutants carry a mutation in a conserved residue of AtXPD and because transformation of uvh6-1 mutants with wild-type AtXPD DNA suppresses both UV sensitivity and other defective phenotypes. Furthermore, the UVH6/AtXPD protein appears to play a role in repair of UV photoproducts because the uvh6-1 mutant exhibits a moderate defect in the excision of UV photoproducts. This defect is also suppressed by transformation with UVH6/AtXPD DNA. We have further identified a T-DNA insertion in the UVH6/AtXPD gene (uvh6-2). Plants carrying homozygous insertions were not detected in analyses of progeny from plants heterozygous for the insertion. Thus, homozygous insertions appear to be lethal. We conclude that the UVH6/AtXPD gene is required for UV resistance and is an essential gene in Arabidopsis.
Evidence for Nuclear Processing of Plant Micro RNA and Short Interfering RNA Precursors
Authors: Papp István , Mette M. Florian , Aufsatz Werner , Daxinger Lucia , Schauer Stephen E. , Ray Animesh , van der Winden Johannes , Matzke Marjori , Matzke Antonius J.M. 
Published: July 2003

Abstract
The Arabidopsis genome encodes four Dicer-like (DCL) proteins, two of which contain putative nuclear localization signals. This suggests one or more nuclear pathways for processing double-stranded (ds) RNA in plants. To study the subcellular location of processing of nuclear-encoded dsRNA involved in transcriptional silencing, we examined short interfering (si) RNA and micro (mi) RNA accumulation in transgenic Arabidopsis expressing nuclear and cytoplasmic variants of P19, a viral protein that suppresses posttranscriptional gene silencing. P19 binds specifically to DCL-generated 21- to 25-nucleotide (nt) dsRNAs with 2-nt 3′ overhangs and reportedly suppresses the accumulation of all size classes of siRNA. Nuclear P19 resulted in a significant reduction of 21- to 22-nt siRNAs and a 21-nt miRNA, but had a lesser effect on 24-nt siRNAs. Cytoplasmic P19 did not decrease the quantity but resulted in a 2-nt truncation of siRNAs and miRNA. This suggests that the direct products of DCL cleavage of dsRNA precursors of 21- to 22-nt siRNAs and miRNA are present in the nucleus, where their accumulation is partially repressed, and in the cytoplasm, where both normal sized and truncated forms accumulate. DCL1, which contains two putative nuclear localization signals, is required for miRNA production but not siRNA production. DCL1-green fluorescent protein fusion proteins localize to nuclei in transient expression assays, indicating that DCL1 is a nuclear protein. The results are consistent with a model in which dsRNA precursors of miRNAs and at least some 21- to 22-nt siRNAs are processed in the nucleus, the former by nuclear DCL1 and the latter by an unknown nuclear DCL.
Nitric Oxide and Cyclic GMP Are Messengers in the Indole Acetic Acid-Induced Adventitious Rooting Process
Authors: Pagnussat Gabriela Carolina , Lanteri María Luciana , Lamattina Lorenzo 
Published: July 2003

AbstractThis report describes part of the signaling pathway and some of the molecules involved in the auxin-induced adventitious root formation in cucumber (Cucumis sativus). Previous results showed that nitric oxide (NO) mediates the auxin response during adventitious root formation (Pagnussat et al., 2002). To determine the order of action of indole acetic acid (IAA) and NO within the signal transduction pathway and to elucidate the target molecules that are downstream of NO action, cucumber hypocotyl cuttings were submitted to a pretreatment leading to endogenous auxin depletion. The auxin depletion treatment provoked a 3-fold reduction of the root number in comparison to the nondepleted explants. The NO-donor sodium nitroprusside was able to promote adventitious rooting in auxin-depleted explants, whereas the specific NO scavenger cPTIO prevented the effect of sodium nitroprusside. The endogenous NO level was monitored in both control and auxin-depleted explants using a NO-specific fluorescent probe. The NO level was 3.5-fold higher in control (nondepleted) explants than in auxin-depleted ones. The exogenous application of IAA restored the NO concentration to the level found in nondepleted explants. Because NO activates the enzyme guanylate cyclase (GC), we analyzed the involvement of the messenger cGMP in the adventitious root development mediated by IAA and NO. The GC inhibitor LY83583 reduced root development induced by IAA and NO, whereas the cell-permeable cGMP derivative 8-Br-cGMP reversed this effect. The endogenous level of cGMP is regulated by both the synthesis via GC and its degradation by the phosphodiesterase activity. When assayed, the phosphodiesterase inhibitor sildenafil citrate was able to induce adventitious rooting in both nondepleted and auxin-depleted explants. Results indicate that NO operates downstream of IAA promoting adventitious root development through the GC-catalyzed synthesis of cGMP.
Enhanced Low Oxygen Survival in Arabidopsis through Increased Metabolic Flux in the Fermentative Pathway
Authors: Ismond Kathleen P. , Dolferus Rudy , De Pauw Mary , Dennis Elizabeth S. , Good Allen G. 
Published: July 2003

Abstract
We manipulated the enzyme activity levels of the alcohol fermentation pathway, pyruvate decarboxylase (PDC), and alcohol dehydrogenase (ADH) in Arabidopsis using sense and antisense overexpression of the corresponding genes (PDC1, PDC2, and ADH1). Transgenic plants were analyzed for levels of fermentation and evaluated for changes in hypoxic survival. Overexpression of either Arabidopsis PDC1 or PDC2 resulted in improved plant survival. In contrast, overexpression of Arabidopsis ADH1 had no effect on flooding survival. These results support the role of PDC as the control step in ethanol fermentation. Although ADH1 null mutants had decreased hypoxic survival, attempts to reduce the level of PDC activity enough to see an effect on plant survival met with limited success. The combination of flooding survival data and metabolite analysis allows identification of critical metabolic flux points. This information can be used to design transgenic strategies to improve hypoxic tolerance in plants.
Interacting Transcription Factors from the Three-Amino Acid Loop Extension Superclass Regulate Tuber Formation
Authors: Chen Hao , Rosin Faye M. , Prat Salomé , Hannapel David J. 
Published: July 2003

Abstract
Using the yeast (Saccharomyces cerevisiae) two-hybrid system and a potato (Solanum tuberosum) KNOX protein, designated POTH1, as bait, we have identified seven distinct interacting proteins from a stolon library of potato. All seven cDNAs are members of the BEL1-like family of transcription factors. Among these proteins, there are at least four regions of high sequence conservation including the homeodomain, the proline-tyrosine-proline three-amino acid loop extension, the SKY box, and a 120-amino acid region upstream from the homeodomain. Through deletion analysis, we identified a protein-binding domain present in the carboxy end of the KNOX domain of POTH1. The protein-binding domain in the BEL1 protein is located in the amino-terminal one-half of the 120-residue conserved region of the BELs. RNA-blot analysis showed differential patterns of RNA accumulation for the BELs in various potato organs. The level of StBEL5 mRNA increased in response to a short-day photoperiod in both leaves and stolons. Similar to sense mutants of POTH1, transgenic lines that overexpressed StBEL5 exhibited enhanced tuber formation even under noninductive conditions. Unlike POTH1 sense lines, however, these BEL lines did not exhibit the extreme leaf and stem morphology characteristic of KNOX overexpressers and displayed a more rapid rate of growth than control plants. Both StBEL5 and POTH1 sense lines exhibited an increase in cytokinin levels in shoot tips. StBEL5 lines also exhibited a decrease in the levels of GA 20-oxidase1 mRNA in stolon tips from long-day plants. Our results demonstrate an interaction between KNOX and BEL1-like transcription factors of potato that may potentially regulate processes of development.