bluuebunny/crossref_metadata_2025_split huggingface dataset:
How Malleable is the Eukaryotic Genome? Extreme Rate of Chromosomal Rearrangement in the GenusDrosophila
Authors: Ranz José Marı́a , Casals Ferran , Ruiz Alfredo 
Published: July 2002

During the evolution of the genusDrosophila, the molecular organization of the major chromosomal elements has been repeatedly rearranged via the fixation of paracentric inversions. Little detailed information is available, however, on the extent and effect of these changes at the molecular level. In principle, a full description of the rate and pattern of change could reveal the limits, if any, to which the eukaryotic genome can accommodate reorganizations. We have constructed a high-density physical map of the largest chromosomal element inDrosophila repleta(chromosome 2) and compared the order and distances between the markers with those on the homologous chromosomal element (3R) inDrosophila melanogaster. The two species belong to different subgenera (DrosophilaandSophophora, respectively), which diverged 40–62 million years (Myr) ago and represent, thus, the farthest lineages within theDrosophilagenus. The comparison reveals extensive reshuffling of gene order from centromere to telomere. Using a maximum likelihood method, we estimate that 114 ± 14 paracentric inversions have been fixed in this chromosomal element since the divergence of the two species, that is, 0.9–1.4 inversions fixed per Myr. Comparison with available rates of chromosomal evolution, taking into account genome size, indicates that theDrosophilagenome shows the highest rate found so far in any eukaryote. Twenty-one small segments (23–599 kb) comprising at least two independent (nonoverlapping) markers appear to be conserved betweenD. melanogasterandD. repleta. These results are consistent with the random breakage model and do not provide significant evidence of functional constraint of any kind. They support the notion that theDrosophilagenome is extraordinarily malleable and has a modular organization. The high rate of chromosomal change also suggests a very limited transferability of the positional information from theDrosophilagenome to other insects.[The sequence data described in this paper have been submitted to the GenBank data library under accession no,AF319441.]
Uncoupled Defense Gene Expression and Antimicrobial Alkaloid Accumulation in Elicited Opium Poppy Cell Cultures
Authors: Facchini P. J. , Johnson A. G. , Poupart J. , De Luca V. 
Published: July 2002

Abstract
Treatment of opium poppy (Papaver somniferum L.) cell cultures with autoclaved mycelial homogenates of Botrytis sp. resulted in the accumulation of sanguinarine. Elicitor treatment also caused a rapid and transient induction in the activity of tyrosine/dopa decarboxylase (TYDC, EC 4.1.1.25), which catalyzes the conversion of L-tyrosine and L-dopa to tyramine and dopamine, respectively, the first steps in sanguinarine biosynthesis. TYDC genes were differentially expressed in response to elicitor treatment. TYDC1-like mRNA levels were induced rapidly but declined to near baseline levels within 5 h. In contrast, TYDC2-like transcript levels increased more slowly but were sustained for an extended period. Induction of TYDC mRNAs preceded that of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) mRNAs. An elicitor preparation from Pythium aphanidermatum was less effective in the induction of TYDC mRNA levels and alkaloid accumulation; however, both elicitors equally induced accumulation of PAL transcripts. In contrast, treatment with methyl jasmonate resulted in an induction of TYDC but not PAL mRNAs. The calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and the protein kinase inhibitor staurosporine partially blocked the fungal elicitor-induced accumulation of sanguinarine. However, only staurosporine and okadaic acid, an inhibitor of protein phosphatases 1 and 2A, blocked the induction of TYDC1-like transcript levels, but they did not block the induction of TYDC2-like or PAL tanscript levels. These data suggest that activation mechanisms for PAL, TYDC, and some later sanguinarine biosynthetic enzymes are uncoupled.
Cold-Shock Regulation of the Arabidopsis TCH Genes and the Effects of Modulating Intracellular Calcium Levels
Authors: Polisensky D. H. , Braam J. 
Published: July 2002

Abstract
The Arabidopsis TCH genes, which encode calmodulin-related proteins and a xyloglucan endotransglycosylase, are shown to be up-regulated in expression following cold shock. We investigated a possible role of fluctuations in intracellular calcium ion concentra- tions ([Ca2+]) in the cold-shock-induced TCH gene expression. Transgenic plants harboring the apoaequorin gene were generated to monitor [Ca2+] and to test the necessity of cold-induced [Ca2+] increases for TCH expression. Cold-shock-induced [Ca2+] increases can be blocked by La3+ and Gd3+, putative plasma membrane Ca2+ channel blockers, and 1,2-bis(o-aminophenoxy)ethane-N,N,N[prime],N[prime]- tetraacetic acid, an extracellular Ca2+ chelator. Cold-shock-induced expression of the TCH genes is inhibited by levels of La3+, Gd3+, and 1,2-bis(o-aminophenoxy)ethane-N,N,N[prime],N[prime]-tetraacetic acid, that have been shown to block [Ca2+] increases. These data support the hypotheses that (a) intracellular [Ca2+] increases following cold shock require extracellular Ca2+ and may derive from a Ca2+ influx mediated by plasmalemma Ca2+ channels, and (b) cold up-regulation of expression of at least a subset of the TCH genes requires an intracellular [Ca2+] increase. The inhibitors are also shown to have stimulus-independent effects on gene expression, providing strong evidence that these commonly used chemicals have more complex effects than generally reported.
Expression and RNA Splicing of the Maize Glutathione S-Transferase Bronze2 Gene Is Regulated by Cadmium and Other Stresses
Authors: Marrs K. A. , Walbot V. 
Published: July 2002

Abstract
The Bronze2 (Bz2) gene in maize (Zea mays) encodes a glutathione S-transferase that performs the last genetically defined step in anthocyanin biosynthesis[mdash]tagging anthocyanin precursors with glutathione, allowing for recognition and entry of anthocyanins into the vacuole. Here we show that Bz2 gene expression is highly induced by heavy metals such as cadmium. Treatment of maize seedlings with cadmium results in a 20-fold increase in Bz2 message accumulation and a 50-fold increase in the presence of the unspliced, intron-containing transcript. The increase in message levels during cadmium stress appears to result, at least in part, from activation of an alternative mRNA start site approximately 200 nucleotides upstream of the normal start site; this site is not used in unstressed or heat-stressed tissues. The effect of cadmium on the RNA splicing of Bz2 seems to be specific: splicing of other intron-containing maize genes, including a maize actin gene under the control of the cadmium-inducible Bz2 promoter, is unaffected by cadmium stress. Conversely, Bz2 intron splicing is not affected by other stress conditions that induce Bz2 gene expression, such as abscisic acid, auxin, or cold stress. Surprisingly, the increase in Bz2 mRNA during cadmium stress does not result in an increase in Bz2 glutathione S-transferase activity. We propose that an alternative protein may be encoded by Bz2 that has a role during responses to heavy metals.
Complementary DNAs Encoding Eukaryotic-Type Cytidine-5[prime]-Diphosphate-Diacylglycerol Synthases of Two Plant Species
Authors: Kopka J. , Ludewig M. , Muller-Rober B. 
Published: July 2002

Abstract
Cytidine diphosphate (CDP)-diacylglycerol synthase (cytidine triphosphate:phosphatidate cytidyltransferase, EC 2.7.7.41) catalyzes the formation of CDP-diacylglycerol, which is the precursor of phosphatidylinositol, phosphatidylglycerol, and cardiolipin. We report the first cloning, to our knowledge, of two plant cDNAs, StCDS1 and AtCDS1, coding for CDP-diacylglycerol synthases from potato (Solanum tuberosum) and Arabidopsis thaliana, respectively. The two proteins belong to the eukaryotic type of CDP-diacylglycerol synthases and contain eight predicted transmembrane-spanning domains. We analyzed gene expression in shoot and root tissues of potato plants and demonstrated enzyme activity by expression of N-terminally truncated, recombinant StCDS1 in Escherichia coli.
Xyloglucan Galactosyl- and Fucosyltransferase Activities from Pea Epicotyl Microsomes
Authors: Faik A. , Chileshe C. , Sterling J. , Maclachlan G. 
Published: July 2002

Abstract
Microsomal membranes from growing tissue of pea (Pisum sativum L.) epicotyls were incubated with the substrate UDP-[14C]galactose (Gal) with or without tamarind seed xyloglucan (XG) as a potential galactosyl acceptor. Added tamarind seed XG enhanced incorporation of [14C]Gal into high-molecular-weight products (eluted from columns of Sepharose CL-6B in the void volume) that were trichloroacetic acid-soluble but insoluble in 67% ethanol. These products were hydrolyzed by cellulase to fragments comparable in size to XG subunit oligosaccharides. XG-dependent galactosyltransferase activity could be solubilized, along with XG fucosyltransferase, by the detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate. When this enzyme was incubated with tamarind (Tamarindus indica L.) seed XG or nasturtium (Tropaeolum majus L.) seed XG that had been partially degalactosylated with an XG-specific β-galactosidase, the rates of Gal transfer increased and fucose transfer decreased compared with controls with native XG. The reaction products were hydrolyzed by cellulase to 14C fragments that were analyzed by gel-filtration and high-performance liquid chromatography fractionation with pulsed amperometric detection. The major components were XG subunits, namely one of the two possible monogalactosyl octasaccharides (-XXLG-) and digalactosyl nonasaccharide (-XLLG-), whether the predominant octasaccharide in the acceptor was XXLG (as in tamarind seed XG) or XLXG (as in nasturtium seed XG). It is concluded that the first xylosylglucose from the reducing end of the subunits was the Gal acceptor locus preferred by the solubilized pea transferase. These observations are incorporated into a model for the biosynthesis of cell wall XGs.
Heat Treatment Results in a Loss of Transgene-Encoded Activities in Several Tobacco Lines
Authors: Neumann K. , Droge-Laser W. , Kohne S. , Broer I. 
Published: July 2002

Abstract
Heat treatment (37[deg]C) of transgenic tobacco (Nicotiana tabacum) plants led to a reversible reduction or complete loss of transgene-encoded activities in about 40% of 10 independent transformants carrying the luciferase-coding region fused to the 35S cauliflower mosaic virus or the soybean small subunit promoter and the nopaline synthase promoter driving the neomycin phosphotransferase gene, whereas the other lines had temperature-tolerant activities. Temperature sensitivity or tolerance of transgene-encoded activities was heritable. In some of the lines, temperature sensitivity of the transgene-encoded activities depended on the stage of development, occurring in either seedlings (40% luciferase and 50% neomycin phosphotransferase) or adult plants (both 40%). The phenomenon did not correlate with copy numbers or the homo- or hemizygous state of the transgenes. In lines harboring a temperature-sensitive luciferase activity, reduction of bioluminescence was observed after 2 to 3 h at 37[deg]C. Activity was regained after 2 h of subsequent cultivation at 25[deg]C. Irrespective of the reaction to the heat treatment, the level of luciferase RNA was slightly increased at 37[deg]C. Only in lines showing temperature sensitivity of transgene-encoded activities was the amount of luciferase and neomycin phosphotransferase strongly reduced. In sterile culture, heat treatment for 15 d did not cause visible damage or changes in plant morphology. In all plants tested a slight induction of the heat-shock response was observed at 37[deg]C.
Evidence That Heat and Ultraviolet Radiation Activate a Common Stress-Response Program in Plants That Is Alterd in the uvh6 Mutant of Arabidopsis thaliana
Authors: Jenkins M. E. , Suzuki T. C. , Mount D. W. 
Published: July 2002

Abstract
The uvh6 mutant of Arabidopsis was previously isolated in a screen for increased sensitivity to ultraviolet (UV) radiation. uvh6 mutant plants were killed by incubation at 37[deg]C for 4 d, a treatment not lethal to wild-type plants. Furthermore, under permissive conditions, uvh6 plants were yellow-green with an approximately one-third lower chlorophyll content. Genetic analysis of the uvh6 mutant strongly suggested that all three mutant phenotypes were due to mutation at the same genetic locus. To understand UVH6 function more fully, the response of wild-type plants to growth at elevated temperatures and exposure to UV radiation was analyzed. Wild-type plants grown at 30[deg]C were as UV-hypersensitive and yellow-green as uvh6 mutant plants grown at 24[deg]C. Mutant uvh6 plants induced heat-shock protein HSP21 at a lower threshold temperature than wild-type plants, indicating that the uvh6 mutant was exhibiting signs of heat stress at a 4 to 5[deg]C lower temperature than wild-type plants. We propose that UV damage and heat induce a common stress response in plants that leads to tissue death and reduced chloroplast function, and that the UVH6 product is a negative regulator of this response.
Developmental and Hormonal Regulation of Genes Coding for Proline-Rich Proteins in Female Inflorescences and Kernels of Maize1
Authors: Josè-Estanyol Matilde , Puigdomènech Pere 
Published: July 2002

Abstract
The pattern of expression of two genes coding for proteins rich in proline, HyPRP(hybrid proline-rich protein) and HRGP(hydroxyproline-rich glycoprotein), has been studied in maize (Zea mays) embryos by RNA analysis and in situ hybridization. mRNA accumulation is high during the first 20 d after pollination, and disappears in the maturation stages of embryogenesis. The two genes are also expressed during the development of the pistillate spikelet and during the first stages of embryo development in adjacent but different tissues. HyPRPmRNA accumulates mainly in the scutellum and HRGP mRNA mainly in the embryo axis and the suspensor. The two genes appear to be under the control of different regulatory pathways during embryogenesis. We show that HyPRP is repressed by abscisic acid and stress treatments, with the exception of cold treatment. In contrast, HRGP is affected positively by specific stress treatments.
Temporal Regulation of Somatic Embryogenesis by Adjusting Cellular Polyamine Content in Eggplant1
Authors: Singh Yadav Jitender , Venkat Rajam Manchikatla 
Published: July 2002

Abstract
Four critical stages of embryogenesis, including callus induction, cellular acquisition of morphogenetic competence, expression of embryogenic program, and development and maturation of somatic embryos during somatic embryogenesis from leaf discs of eggplant (Solanum melongena L.), were identified by scanning electron microscopy. Temporal changes in arginine decarboxylase (ADC) activity and polyamines (PAs) during critical stages of embryogenesis revealed that high levels of PAs (especially putrescine [PUT]), due to higher ADC activity in discs from the apical region (with high embryogenic capacity) than from the basal region of the leaf (with poor embryogenic capacity), were correlated with differential embryogenesis response. Kinetic studies of the up- and down-regulation of embryogenesis revealed that PUT and difluoromethylarginine pretreatments were most effective before the onset of embryogenesis. Basal discs pretreated with PUT for 4 to 7 d showed improved embryogenesis that was comparable to apical discs. PA content at various critical steps in embryogenesis from basal discs were found to be comparable to that of apical discs following adjustments of cellular PA content by PUT. In contrast, pretreatment of apical discs with difluoromethylarginine for 3 d significantly reduced ADC activity, cellular PA content, and embryogenesis to levels that were comparable to basal discs. Discs from the basal region of leaves treated with PUT for 3 d during the identified stages of embryogenesis improved their embryogenic potential.
Soybean Lipoxygenase-1 Oxidizes 3Z-Nonenal
Authors: Gardner Harold W. , Grove Marilyn J. 
Published: July 2002

Abstract
In previous work with soybean (Glycine max), it was reported that the initial product of 3Z-nonenal (NON) oxidation is 4-hydroperoxy-2E-nonenal (4-HPNE). 4-HPNE can be converted to 4-hydroxy-2E-nonenal by a hydroperoxide-dependent peroxygenase. In the present work we have attempted to purify the 4-HPNE-producing oxygenase from soybean seed. Chromatography on various supports had shown that O2 uptake with NON substrate consistently coincided with lipoxygenase (LOX)-1 activity. Compared with oxidation of LOX's preferred substrate, linoleic acid, the activity with NON was about 400- to 1000-fold less. Rather than obtaining the expected 4-HPNE, 4-oxo-2E-nonenal was the principal product of NON oxidation, presumably arising from the enzyme-generated alkoxyl radical of 4-HPNE. In further work a precipitous drop in activity was noted upon dilution of LOX-1 concentration; however, activity could be enhanced by spiking the reaction with 13S-hydroperoxy-9Z,11E-octadecadienoic acid. Under these conditions the principal product of NON oxidation shifted to the expected 4-HPNE. 4-HPNE was demonstrated to be 83% of the 4S-hydroperoxy-stereoisomer. Therefore, LOX-1 is also a 3Z-alkenal oxygenase, and it exerts the same stereospecificity of oxidation as it does with polyunsaturated fatty acids. Two other LOX isozymes of soybean seed were also found to oxidize NON to 4-HPNE with an excess of 4S-hydroperoxy-stereoisomer.
ADP-Glucose Pyrophosphorylase from Potato Tubers. Site-Directed Mutagenesis Studies of the Regulatory Sites1
Authors: Ballicora Miguel A. , Fu Yingbin , Nesbitt Natasha M. , Preiss Jack 
Published: July 2002

AbstractSeveral lysines (Lys) were determined to be involved in the regulation of the ADP-glucose (Glc) pyrophosphorylase from spinach leaf and the cyanobacteriumAnabaena sp. PCC 7120 (K. Ball, J. Preiss [1994] J Biol Chem 269: 24706–24711; Y. Charng, A.A. Iglesias, J. Preiss [1994] J Biol Chem 269: 24107–24113). Site-directed mutagenesis was used to investigate the relative roles of the conserved Lys in the heterotetrameric enzyme from potato (Solanum tuberosumL.) tubers. Mutations to alanine of Lys-404 and Lys-441 on the small subunit decreased the apparent affinity for the activator, 3-phosphoglycerate, by 3090- and 54-fold, respectively. The apparent affinity for the inhibitor, phosphate, decreased greater than 400-fold. Mutation of Lys-441 to glutamic acid showed even larger effects. When Lys-417 and Lys-455 on the large subunit were mutated to alanine, the phosphate inhibition was not altered and the apparent affinity for the activator decreased only 9- and 3-fold, respectively. Mutations of these residues to glutamic acid only decreased the affinity for the activator 12- and 5-fold, respectively. No significant changes were observed on other kinetic constants for the substrates ADP-Glc, pyrophosphate, and Mg2+. These data indicate that Lys-404 and Lys-441 on the small subunit are more important for the regulation of the ADP-Glc pyrophosphorylase than their homologous residues in the large subunit.
Acclimation of Photosynthesis to Elevated CO2under Low-Nitrogen Nutrition Is Affected by the Capacity for Assimilate Utilization. Perennial Ryegrass under Free-Air CO2 Enrichment
Authors: Rogers Alistair , Fischer Bernt U. , Bryant Jonathan , Frehner Marco , Blum Herbert , Raines Christine A. , Long Stephen P. 
Published: July 2002

Abstract
Acclimation of photosynthesis to elevated CO2 has previously been shown to be more pronounced when N supply is poor. Is this a direct effect of N or an indirect effect of N by limiting the development of sinks for photoassimilate? This question was tested by growing a perennial ryegrass (Lolium perenne) in the field under elevated (60 Pa) and current (36 Pa) partial pressures of CO2(pCO2) at low and high levels of N fertilization. Cutting of this herbage crop at 4- to 8-week intervals removed about 80% of the canopy, therefore decreasing the ratio of photosynthetic area to sinks for photoassimilate. Leaf photosynthesis, in vivo carboxylation capacity, carbohydrate, N, ribulose-1,5-bisphosphate carboxylase/oxygenase, sedoheptulose-1,7-bisphosphatase, and chloroplastic fructose-1,6-bisphosphatase levels were determined for mature lamina during two consecutive summers. Just before the cut, when the canopy was relatively large, growth at elevatedpCO2 and low N resulted in significant decreases in carboxylation capacity and the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase protein. In high N there were no significant decreases in carboxylation capacity or proteins, but chloroplastic fructose-1,6-bisphosphatase protein levels increased significantly. Elevated pCO2resulted in a marked and significant increase in leaf carbohydrate content at low N, but had no effect at high N. This acclimation at low N was absent after the harvest, when the canopy size was small. These results suggest that acclimation under low N is caused by limitation of sink development rather than being a direct effect of N supply on photosynthesis.
Embryo-Specific Gene Expression in Microspore-Derived Embryos ofBrassica napus.An Interaction between Abscisic Acid and Jasmonic Acid1,2
Authors: Hays Dirk B. , Wilen Ronald W. , Sheng Chuxing , Moloney Maurice M. , Pharis Richard P. 
Published: July 2002

AbstractThe induction of napin and oleosin gene expression in Brassica napus microspore-derived embryos (MDEs) was studied to assess the possible interaction between abscisic acid (ABA) and jasmonic acid (JA). Napin and oleosin transcripts were detected sooner following treatment with ABA than JA. Treatment of MDEs with ABA plus JA gave an additive accumulation of both napin and oleosin mRNA, the absolute amount being dependent on the concentration of each hormone. Endogenous ABA levels were reduced by 10-fold after treatment with JA, negating the possibility that the observed additive interaction was due to JA-induced ABA biosynthesis. Also, JA did not significantly increase the uptake of [3H-ABA] from the medium into MDEs. This suggests that the additive interaction was not due to an enhanced carrier-mediated ABA uptake by JA. Finally, when JA was added to MDEs that had been treated with the ABA biosynthesis inhibitor fluridone, napin mRNA did not increase. Based on these results with the MDE system, it is possible that embryos of B. napus use endogenous JA to modulate ABA effects on expression of both napin and oleosin. In addition, JA could play a causal role in the reduction of ABA that occurs during late stages of seed development.