bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular analysis of a phylogenetically conserved carrot gene: Developmental and environmental regulation
Authors: Seffens William S. , Almoguera Concepción , Wilde H. Dayton , Von der Haar Raymond A. , Thomas Terry L. 
Published: May 2005

AbstractExtensive studies of gene expression programs in carrot somatic embryos identified a gene, designated Dc3, that serves as a reliable molecular marker for the acquisition of embryogenic potential by carrot cells in culture. The complete sequence of a carrot genomic region, DcG3, encoding a Dc3‐like mRNA, was determined. The DcG3 transcription unit contains a single intron and encodes mRNA that is expressed at high levels in embryonic tissue but is undetectable in somatic tissue of carrot. The predicted protein sequence of DcG3 is 163 amino acids and includes two approximately 50 amino acid direct repeats which in turn include additional repetitive elements with an unusual distribution of charged amino acids. Dc3 and Dc3‐like mRNAs are encoded by a small divergent gene family. Furthermore, similarities of the Dc3 gene family with genes from other plant species that are expressed in response to environmental and developmental cues suggest a possible role in seed desiccation and possibly in more general water‐stiess responses in plants. Analysis of transgenic tobacco containing a β‐glucuronidase (GUS) reporter gene fused to a 1.7 kb 5′ upstream element of DcG3 defined a promoter/enhancer complex that confers developmentally and environmentally regulated expression of GUS activity. Thus, DcG3 is phylogenetically conserved together with the trans‐acting factors required for its regulated expression in transgenic tobacco.
Characterization and expression of two sea urchin homeobox gene sequences
Authors: Wang Gordon V. L. , Dolecki Gregory J. , Carlos Ruben , Humphreys Tom 
Published: May 2005

AbstractWe describe two homeobox sequences, TgHbox5 and TgHboxó, isolated from the Hawaiian sea urchin Tripneustes gratilla using a Drosophila Sex combs reduced probe. Sequence analysis shows that the encoded TgHbox5 home‐odomain shares only 30‐52% amino acid identity with homeodomains encoded by previously characterized genes, establishing that it is a divergent homeobox that is not in any known class of homeoboxes. TgHbox5 is expressed in the embryo as two major developmentally regulated transcripts. one at 5.0 kilobase (kb) appearing by blastula stage and the other at 2.7 kb appearing at pluteus stage. Multiple transcripts from TgHbox5 are present at a much lower level in adult tissues and are predominantly expressed in small and large intestines. The TgHbox6 homeobox is an Antennapedia‐class homeobox, which appears not to be expressed during embryogenesis but produces abundant 3.6 and 3.2 kb transcripts in the six adult tissues examined.
Different requirements for l(1)giant in two embryonic domains of Drosophila melanogaster
Authors: Petschek Jane P. , Mahowald Anthony P. 
Published: May 2005

AbstractL(1)giant is a zygotic lethal mutation which affects the embryonic development of both the labial/thoracic segments and a subset of posterior abdominal segments. Using antibodies specific for proteins encoded by several Drosophila genes to identify the compartmental origin of the defects, we show that the requirement of giant activity is different in these two embryonic domains. Anteriorly, the posterior compartment of the labial segment is missing at the blastoderm stage. Posteriorly, cells are specifically deleted by cell death within the anterior compartments of abdominal segments 5–7 during germ band elongation. In mature embryos, posterior compartment structures of the peripheral nervous system of A5–7 are fused. In addition to a different pattern of defect in the two parts of the embryo, the kind of action appears different. Anteriorly, giant resembles a gap mutation in that a particular region is missing from the blastoderm fate map, whereas in the abdominal domain, giant affects the development of anterior compartment‐specific structures.
Cis‐acting sequences and trans‐acting factors required for constitutive expression of a microinjected HSP70 gene after the midblastula transition of Xenopus laevis embryogenesis
Authors: Ovsenek Nick , Williams Gregg T. , Morimoto Richard I. , Heikkila John J. 
Published: May 2005

AbstractMicroinjected human HSP70 promoter‐chloramphenicol acetyl transferase (CAT) chimeric genes are constitutively expressed immediately after the midblastula transition of Xenopus embryogenesis. Analysis of a series of 5′‐deletion mutants in the HSP70 promoter revealed that sequences within 74 bases of the transcriptional start site were sufficient for strong basal activity. We investigated the role of specific sequences in the basal promoter by injecting HSP70‐CAT vectors containing linker‐scanner mutations in the basal elements (CCAAT, purine‐rich element, GC‐element, ATF/AP1, and 1ATA). Our data reveal that deletion of any of these cis‐acting elements in the basal promoter prevents expression after the midblastula stage of development. Furthermore, we have identified specific binding activities in embryonic nuclear extracts that complex with basal promoter elements (CCAAT, ATF, and GC) of the heterologous HSP70 promoter. These trans‐acting factors are detectable in nuclear extracts of early blastula embryos, and their respective binding activity increases dramatically after the midblastula transition. The expression of the human HSP70 gene after the midblastula transition of Xenopus embryogenesis requires an array of cisacting elements, which interact with specific Xenopus transcription factors.
Developmental expression of regionally specific cell surface antigens in the Xenopus gastrula
Authors: Litvin Judith , Grant Barth , Davis Lynn , Lou King Mary 
Published: May 2005

AbstractMolecular markers for specific cell lineages would be useful in studies of cellular differentiation. To isolate such markers monoclonal antibodies (MoABs) were raised against plasma membranes isolated from gastrulating Xenopus embryos. Those antibodies that recognized subsets of cells within the embryo were selected by indirect immunofluorescence. The analysis of eight such MoAbs is presented. Western blot analysis showed that all but one MoAb recognized a complex pattern of glycoconjugates associated with glycoproteins. All the antigens recognized by the MoAbs were maternal in origin and displayed similar spatial patterns of pregastrular expression. This pattern of immunoreactivity at the apical surface was inherited passively during cleavage by the resulting superficial blastomeres suggesting that ectodermal specific markers of maternal origin are pre‐localized to the cortical ooplasm in mature oocytes. We suggest that these maternal components may be specific glycosyl transferases. Three different patterns of expression were observed during gastrulation as exemplified by MoAbs 1F10C1, 3A4D1, and 6F10B6. MoAb 6F10B6 was specific for both neural and non‐neural epithelium. MoAb 3A4D1 was specific for non‐neural epidermis. MoAb 1F10C1 appeared to recognize a protein epitope on an extracellular component expressed by the superificial and involuting epithelial cells. The pattern of expression for the 1F10C1 antigen suggests that it may play a role in facilitating the movement of the involuting cells during gastrulation.
Endoreduplication of nuclear DNA in the developing maize endosperm
Authors: Kowles Richard V. , Srienc Friedrich , Phillips Ronald L. 
Published: May 2005

AbstractMultiparametric flow cytometry was used to analyze the development of the endosperm in Zea mays L. during the period from 8 to 20 days after pollination (dap). Nuclear size, DNA content per nucleus, and frequencies of nuclei with varying properties were measured in preparations that included all of the endosperm nuclei of single kernels of the inbred strain Al88. Characteristics of nuclear populations from different kernels on the same ear showed minimal variation. The dynamic changes of non‐mitotic cells involved in endosperm development consisted of alternating periods of DNA replication with non‐replication. Seven rounds of DNA replication had occurred in some nuclei in the later developmental stages with the rate averaging approximately one round per 24‐hour period. Analysis of the DNA levels in the nuclei showed an exact doubling pattern indicating an endoreduplication process, that is, replication of the entire genome during each round. The loosely organized polytenization of the chromatin occurred to varying extents among the nuclei within an endosperm. A weak positive correlation existed between DNA content and size of nuclei suggesting that DNA increases and nuclear growth may not be highly coordinated in this tissue. Increased proportions of the larger nuclei occurred in the later stages of endosperm development. Considering the entire endosperm, the average DNA content per nucleus at the 15‐dap peak level was approximately 12.8 C constituting a 2.7‐fold overall increase from 8 dap.
Temporal expression of genes encoding free radical–metabolizing enzymes is associated with higher mRNA levels during in utero development in mice
Authors: El‐hage Samar , Singh Shiva M. 
Published: May 2005

AbstractThe interaction of reactive oxygen metabolites with DNA is well characterized and may result in mutagenesis, chromosome aberrations, and modulation of gene expression. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH‐Px) catalyze enzymatic reactions to remove oxidant stresses, particularly O2− and H2O2. The role of these enzymes during in utero development of the embryo and the developmental pattern of expression of the embryonic genes encoding them is not known. We examined the in utero developmental expression and activity of the three free‐radical–metabolizing enzymes in mice. We collected mouse fetuses at different stages of development and examined total RNA populations by Northern and slot blots using gene‐specific cDNA probes. In addition to quantifying the probe‐specific RNAs, activities of the three enzymes were also evaluated on the same tissue samples.The gene‐specific RNAs and the associated enzyme activities are detectable with somite formation (day 8 postcoitus [p.c.]) in mice. The relative RNA values for each of the genes studied are higher in in utero stages as compared with the adult. The specific activities of these enzymes, on the other hand, follow a characteristic increase with development and growth. The relative RNA levels for each of the genes studied are higher during in utero growth and development than the relative enzyme activity values (between day 8 and day 18, third trimester) in the liver and carcass. This may suggest that the mRNA specific to these genes may accumulate in utero and are not translated immediately. Such accumulating transcripts are translated efficiently after birth, when these enzyme are particularly needed with the advent of aerobic respiration.
Gene interactions and epigenetic variation in transgenic plants
Authors: Matzke M. A. , Matzke A. J. M. 
Published: May 2005

AbstractUnusual gene interactions were observed in several doubly transformed tobacco plants which were obtained following sequential transformation steps using two T‐DNAs encoding different selection and screening markers. The expression of T‐DNA‐I, which encoded kanamycin resistance (Kanr) and nopaline synthase (NOS), was suppressed in some, but not all, of the double transformants after the introduction of T‐DNA‐II, which encoded hygromycin resistance (Hygr) and octopine synthase (OCS). Double transformants in which T‐DNA‐I had been inactivated could produce KanrNOS+ progeny, but these were shown to lack T‐DNA‐II, thus establishing the role of this T‐DNA in the suppression of T‐DNA‐I. Reversible cytosine methylation of the promoters of T‐DNA‐I genes was shown to correlate with their activation/inactivation cycle. In this paper we pursue further the questions of the mechanism of suppression of T‐DNA‐I genes by T‐DNA‐II, and also the timing and extent of demethylation of T‐DNA‐I promoters in Kanr progeny following the loss of T‐DNA‐II. We propose that the suppression is due to the competition between homologous regions on each T‐DNA for binding to nuclear sites with fixed locations. We further suggest that incomplete demethylation patterns of T‐DNA‐I promoters in Kanr progeny reflect the existence in the shoot apex meristem of two cell populations, which have either methylated or unmethylated T‐DNA‐I promoters, respectively. Thus, Kanr progeny are epigenetic chimeras with respect to the expression of T‐DNA‐I genes.
Bacterial and firefly luciferase genes in transgenic plants: Advantages and disadvantages of a reporter gene
Authors: Koncz Csaba , Langridge William H. R. , Olsson Olof , Schell Jeff , Szalay Aladar A. 
Published: May 2005

AbstractGenes encoding light‐emitting luciferase were recently isolated from luminous marine bacteria and fireflies. Expression of luciferase genes in diverse organisms is a unique way for studying gene expression by simple and sensitive measurement of light. Recent advances in application of luciferase reporter genes are reviewed and documented by examples of in vivo visualization of their expression in transgenic plants.
Chromatin structure of transferred genes in transgenic plants
Authors: Weising Kurt , Bohn Horst , Kahl Günter 
Published: May 2005

AbstractThe chromatin structure of foreign genes in transgenic tobacco plants was investigated by digestion of nuclei with DNase I and micrococcal nuclease, respectively, followed by restriction and Southern analysis of the digestion products. The results were compared to the differential expression of the different transgenes. Two model systems were used: plants harbouring vector DNA derived from the disarmed vector pGV 3850 and plants harbouring the light‐regulated and organ‐specifically expressed potato ST‐LS1 gene and the cotransferred ncpaline synthase (nos) reporter gene. Our results show that transferred genes are located in DNase l‐sensitive domains in all transformants. Slight variations of DNase l‐sensitivity of the transferred ST‐LS1 constructs in different transformants neither reflected the between‐transformant variability of expression nor the organ‐specific activity of the transgenes. A deletion event was found responsible for silencing the ST‐LS1 gene but not the nos gene in one of the transformants. Whereas no DNase l‐hypersensitive sites were found within the 3850‐T‐DNA and the ST‐LS1 gene, one prominent site was mapped to the nos promoter within the ST‐LS1 construct in all transformants. Digestion of chromatin harbouring 3850‐T‐DNA with micrococcal nuclease resulted in a blurred nucleosomal pattern as compared to nucleolar and bulk chromatin, the extent of blurring being independent of the expression of transferred genes. The present results favour the “permissive domain” hypothesis which capitalizes on the chromatin surrounding the integration site as the determining factor for the chromatin structure of incoming alien genes. However, between‐transformant variability of expression is not reflected by differential sensitivity to DNase I. Hence, other factors than chromatin structure must be involved in creating “position effects”.
Dosage compensation in Drosophila melanogaster male and female embryos generated by segregation distortion of the sex chromosomes
Authors: Polito Catello , Pannuti Antonio , Lucchesi John C. 
Published: May 2005

AbstractWe report the first practical application of a genetic scheme devised for the purpose of obtaining large quantities of embryos of a specific sex. The scheme, which is based on the meiotic drive system Segregation Distorter, results in the production of populations of zygotes that are almost exclusively of one sex. We have used this scheme to determine that the steady‐state levels of transcripts of X‐linked genes are the same in early male and female embryos, establishing that these genes are dosage compensated.
Separate molecular mechanisms regulate CAT2 gene expression before and after glyoxysome maturation in two genetic lines of maize
Authors: Skadsen Ronald W. , Ruzsa Stephanie M. , Scandalios John G. 
Published: May 2005

AbstractThe temporal expression pattern of the CAT‐2 catalase isozyme in scutella of Zea mays seedlings normally coincides with that of other major glyoxysomal enzymes. In standard genetic lines (e.g., W64A), the CAT‐2 enzyme is synthesized de novo after imbibition, reaches a peak at approximately 4 days later, and then declines steadily. In a high CAT‐2 genetic line, R6‐67, the enzyme accumulates in a linear fashion for at least 8 days after imbibition and reaches a level 3‐fold higher than in W64A. During the first 9 days of early seedling growth in W64A, the correlation between Cat2 mRNA levels and CAT‐2 protein suggests that pretranslational control governs Cat2 gene expression. In R6‐67, the steady rise in CAT‐2 protein appears to result from a pretranslational control mechanism in which Cat‐2 mRNA apparently never declines to levels which would limit the rate of accumulation of CAT‐2 protein. In addition, the amount of Cat2 mRNA bound to polysomes is 3‐fold higher in R6‐67 at day 9 relative to W64A at day 9, reflecting a much greater capacity to synthesize CAT‐2 later in development. Despite substantial differences in Cat2 mRNA levels between genetic lines, early CAT‐2 protein accumulation is similar until day 5, when other glyoxysomal enzymes also attain maximal activity levels. The early increase in CAT‐2, between day 2 and day 5 post‐imbibition, occurs despite a sharp decline in polysomal Cat2 mRNA. This is related to a transient decline in total extractable polysomes which paradoxically coincides with the peak in glyoxysomal enzyme activities. Early Cat2 gene expression is likely controlled by the compartmentalization of CAT‐2 in glyoxysomes.
Actin‐Associated proteins in Dictyostelium discoideum
Authors: Luna Elizabeth J. , Condeelis John S. 
Published: May 2005

AbstractThe cellular slime mold Dictyostelium discoideum is becoming the premier system for the explication of the biochemical and cellular events that occur during motile processes. Proteins associated with the actin cytoskeleton, in particular, appear to play key roles in cellular responses to many external stimuli. This review summarizes our present understanding of the actin‐associated proteins in Dictyostelium, including their in vitro activities and their structural and/or functional analogues in mammalian cells.
Mechanisms of amoeboid chemotaxis: An evaluation of the cortical expansion model
Authors: Condeelis J. , Bresnick A. , Demma M. , Dharmawardhane S. , Eddy R. , Hall A. L. , Sauterer R. , Warren V. 
Published: May 2005

AbstractIn this work we evaluate the cartical expansion model for amoeboid chemo‐taxis with regard to new information about molecular events in the cytoskeleton following chemo‐tactic stimulation of Dictyostelium amoebae. A rapid upshift in the concentration of chemoattrac‐tant can be used to synchronize the motile behavior of a large population of cells. This synchrony presents an opportunity to study the biochemical basis of morphological changes such as pseudopod extension that are required for amoeboid chemotaxis. Changes in the composition and activity of the cytoskeleton following stimulation can be measured with precision and correlated with important morphological changes. Such studies demonstrate that activation of actin nucleation is one of the first and most crucial events in the actin cytoskeleton following stimulation. This activation is followed by incorporation of specific actin cross‐linking proteins into the cytoskeleton, which are implicated in the extension of pseudopods and filopods. These results, as well as those from studies with mutants deficient in myosin, indicate that cortical expansion, driven by focal actin polymerization, cross‐linking and gel osmotic swelling, is an important force for pseudopod extension.It is concluded that whereas three forces, frontal sliding, tail contraction, and cortical expansion may cooperate to produce amoeboid movement, the cortical expansion model offers the simplest explanation of how focal stimulation with a chemoat‐tractant causes polarized pseudopod extension.
Intracellular vesicle movement, cAMP and myosin II in Dictyostelium
Authors: Soll David R. , Wessels Deborah , Murray John , Vawter Holly , Voss Edward , Bublitz Ann 
Published: May 2005

AbstractDictyostelium amoebae were analyzed before and after rapid addition of 10−6 M cAMP for cellular motility, dynamic shape changes, and intracellular particle movement. Before cAMP addition, amoebae moved in a persistent anterior fashion and were elongate with F‐actin localized predominantly in the anterior pseudopod. Intracellular particles moved rapidly and anteriorly. Within seconds after 10−6 M cAMP addition, cells stopped translocating, pseudopod formation ceased, intra‐cellular particle movement was depressed, and F‐actin was lost from the pseudopod and concomitantly relocalized in the cell cortex After 10 seconds, expansion zones reappeared but were small and no longer anteriorly localized. Vesicle movement partially rebounded but was no longer anteriorly directed. The myosin II null mutant HS2215 exhibited both depressed cellular translocation and vesicle movement. The addition of cAMP to HS2215 cells did not result in any detectable change in the random, depressed movement of particles. The results with HS2215 suggest that myosin II is essential for (1) rapid cellular translocation, (2) cellular polarity, (3) rapid particle movement, (4) anteriorly directed particle movement, and (5) the cAMP response. Electron micrographs suggest that at least half of the particles examined in this study contain in turn smaller membrane bound vesicles or multilameilar membrane bodies. The possible role of these vesicles is discussed.
Ponticulin, a developmentally‐regulated plasma membrane glycoprotein, mediates actin binding and nucleation
Authors: Luna Elizabeth J. , Wuestehube Linda J. , Chia Catherine P. , Shariff Aneesa , Hitt Anne L. , Ingalls Hilary M. 
Published: May 2005

AbstractPonticulin is a 17,000‐dalton transmembrane glycoprotein that is involved in the binding and nucleation of actin filaments by Dictyostelium discoideum plasma membranes. The major actin‐binding protein isolated from these membranes by F‐actin affinity chromatography, ponticulin also binds F‐actin on blot overlays. The actin‐binding activity of ponticulin in vitro is identical to that observed for purified plasma membranes: it resists extraction with 0.1 N NaOH, is sensitive to high salt concentrations, and is destroyed by heat, proteolysis, and thiol reduction and alkylation. A cytoplasmic domain of ponticulin mediates binding to actin because univalent antibody fragments directed against the cytoplasmic surface of this protein inhibit 96% of the actin‐membrane binding in sedimenlation assays. Antibody specific for ponticulin emoves both ponticu‐lin and the ability to reconstitute actin nucleation activity from detergent extracts of solubilized plasma membranes. Levels of plasma membrane ponticulin increase 2‐ to 3‐fold during aggregation streaming, when cells adhere to each other and are highly motile. Although present throughout the plasma membrane, ponticulin is preferentially localized to some actin‐rich membrane structures, including sites of cell‐cell adhesion and arched regions of the plasma membrane reminiscent of the early stages of pseudopod formation. Ponticulin also is present but not obviously enriched at phagocytic cups of log‐phase amebae. These results indicate that ponticulin may function in vivo to attach and nucleate actin filaments at the cytoplas‐mic surface of the plasma membrane. A 17,000‐dalton analogue of ponticulin has been identified in human polymorphonuclear leukocyte plasma membranes by immunoblotting and immunofluo‐rescence microscopy. These findings suggest that the structure and function of ponticulin in motile cells has been evolutionarily conserved.