bluuebunny/crossref_metadata_2025_split huggingface dataset:
A genetic switch, based on negative regulation, sharpens stripes in Drosophila embryos
Authors: Edgar Bruce A. , Odell Garrett M. , Schubiger Gerold 
Published: May 2005

AbstractThe pair‐rule genes hairy, runt, even‐skipped, and fushi tarazu express their mRNAs and proteins in striped patterns in the Drosophila embryo at the blastoderm stage. Previous studies have shown that the generation of these patterns depends upon products of the gap genes and upon interactions between the pair‐rule genes themselves. Here we show that blocking protein synthesis induces expression of each of the pair‐rule mRNAs in virtually all regions of the embryo. Our observations together with genetic studies carried out in other laboratories suggest that negative feedback between the pair‐rule genes plays a key role in striped expression of pair‐rule genes. We propose that stable proteins, present in all regions of the embryo, first activate transcription ofthese pair‐rule genes constitutively. Then, various combinations of unstable proteins repress their transcription in a patterned fashion; each stripe of accumulated products of a given pair‐rule gene marks a region where it was not repressed. We develop this idea in mathematical form and demonstrate that a network of mutual repression by pair‐rule genes can make each blastoderm nucleus into a genetic switch with two stable states. If preexisting gap gene patterns provide initial bias to the blastoderm nuclei, then the “bistable switch behavior” of the nuclei can refine an initially weak spatial bias into a final pattern of sharp stripes.
Cloning and dosage compensation of the 6‐phosphogluconate dehydrogenase gene (Pgd+) of Drosophila melanogaster
Authors: Gutierrez Anthony G. , Christensen Alan C. , Manning Jerry E. , Lucchesi John C. 
Published: May 2005

AbstractUsing a heterologous rat cDNA probe, we have identified a 14.7 kbp Drosophila melanogaster genomic clone containing the X‐linked gene Pgd+, which encodes the enzyme 6‐phosphogluconate dehydrogenase (6PGD). We used in situ hybridization to larval polytene chromosomes, a somatic transient expression assay for enzyme activity, and the rescue of the lethal Pgd− phenotype by germline transformation to verify the identity of the gene. A 7.4 kbp fragment including the gene and approximately 1.2 kbp of upstream and 1.8 kbp of downstream sequences was relocated to autosomal ectopic sites by germline transformation; this transduced gene exhibits levels of enhanced activity in males comparable to those of the indigenous gene at its normal X chromosome locus. We conclude that the sequences responsible for dosage compensation of Pgd+ are included in this fragment.
Analysis of Adh gene regulation in Drosophila: Studies using somatic transformation
Authors: Shen Nancy L. L. , Subrahmanyam Guttina , Clark Wendy , Martin Presley , Sofer William 
Published: May 2005

AbstractWe have used in vitro mutagenesis and somatic transformation [Sofer and Martin, 1987a; Martin et al., 1986] to investigate the role of cis‐acting sequences in the control of alcohol dehydrogenase gene expression in larvae of Drosophila melanogaster. Two sets of experiments were carried out. In the first, a series of aeletions were constructed in the region upstream of the proximal transcriptional start site. In the second, one or both introns were removed from within the structural gene. These constructs (on circular plasmids) were injected into Adh‐null embryos and ADH activity was assayed in third instar larvae of the injected generation. The first set of experiments indicated that there are at least three distinct regulatory regions essential for larval activity located in the 5′ flanking region of the gene. One, in an area that includes the TATA box, was found to be necessary but not sufficient for larval ADH activity. Two others, further upstream, seemed to have enhancer‐like properties because their absence could be compensated by a second copy of the Adh gene on the same plasmid molecule. The second set of experiments showed that neither the tis‐sue distribution nor amount of ADH activity was affected by the removal of one or both introns from the Adh gene.
Larval fat body‐specific gene expression in D. melanogaster
Authors: Deutsch Jean , Laval Monique , Lepesant Jean‐Antoine , Maschat Florence , Pourrain Francine , Rat Luce 
Published: May 2005

AbstractThe P1 gene, together with the LSP‐1a, ‐1β, and ‐ly, LSP‐2, and P6 genes, is expressed exclusively in the larval fat body of D. melanogaster during the third instar. In vivo mapping of the cis‐acting regulatory sequences of the P1 gene was carried out using hybrid constructs with three different reporter genes and a combination of transient and germline transformation assays. This revealed that regulatory elements involved in the setting up of the temporal and spatial specificities of transcription of the P1 gene are located in a short DNA region immediately upstream of the mRNA transcription start. This region includes on element that behaves as a fat‐body transcriptional enhancer and element(s) required for ecdysone inducibility of transcription of the P1 gene.
Molecular genetics of dopa decarboxylase and biogenic amines in Drosophila
Authors: Hirsh J. 
Published: May 2005

AbstractThe gene Ddc encodes two isoforms of the enzyme dopa decarboxylase in Drosophila. These gene products catalyze the final steps in the synthesis of the biogenic amines sero‐tonin and dopamine. This article summarizes recent progress in understanding the tissue‐ and cell‐specific regulation of Ddc, which occurs at both the transcription and alternate splicing levels. In addition, results that are pertinent to understanding the roles of biogenic amines in the neurophysiology of Drosophila are discussed.
Molecular genetics ofDelta, a locus required for ectodermal differentiation inDrosophila
Authors: Alton Althea K. , Fechtel Kim , Kopczynski Casey C. , Shepard Scott B. , Kooh Pamela J. , Muskavitch Marc A. T. 
Published: May 2005

AbstractDelta(Dl) is one of the six known zygotic neurogenic genes, each of which is essential for proper segregation of the embryonic ectoderm into neural and epidermal lineages. Molecular analysis ofDlreveals that it is a transcriptionally complex locus that yields multiple maternal and zygotic transcripts. DNA sequence analysis suggests that the predominant product of the locus is a putative transmembrane protein exhibiting homology to blood coagulation factors and epidermal growth factor of vertebrates. The structure of this product is consistent with the hypothesis thatDlparticipates in cell‐cell interactions that are central to establishment of the epidermal lineage within the developing ectoderm. Genetic analyses demonstrate thatDlmutations can modify the imaginal phenotypes that result from heterozygosity forNotch (N)mutations as well as the interaction between particular alleles ofNotch (N)andEnhancer of split [E(spl)]two other members of the neurogenic gene set. Vital interactions also occur betweenDlandN.Given the structures of products encoded byN,Dl, andE(spl), we suggest that the synergistic phenotypic interactions observed among mutations in these three loci result from physical, as opposed to regulatory, interactions.
Hemin increases production of β‐like globin RNA transcripts in human erythroleukemia K‐562 cells
Authors: Tsiftsoglou Asterios S. , Wong Willie , Robinson Stephen H. , Hensold Jack 
Published: May 2005

AbstractPrevious studies have indicated that control and hemin‐treated human eryth‐roleukemia K‐562 cells fail to produce adult‐type β‐globin mRNA transcripts and to translate them into nascent β‐globin chains. Expression of the β‐globin DNA sequences in K‐562 cells can occur, however, under certain conditions. To readdress this issue and to examine the possibility of whether these cells produce immature and untranslatable β‐globin RNA transcripts, we prepared total cyto‐plasmic RNA from control and inducer‐treated cells and performed Northern blot hybridization analysis using 5′ end‐labeled fragments of the human β‐globin DNA rather than 3′ end fragments as probes. Although hybridization of both cytoplasmic and nuclear K‐562 RNA with a32P‐labeled 3′ end fragment (1.6kb Bam H1 cut) coding for a large part of the first exon of β‐globin failed to detect β‐globin RNA transcripts, hybridization with a 5′ end 32P‐labeled 2.0kb Bam H1 fragment (coding for the third exon and part of the second) revealed the presence of relatively small (<7S) RNA molecules both in nuclear and cytoplasmic fraction. S1 nuclease mapping of both cytoplasmic and nuclear RNA with the use of 5′ end‐labeled 2.0 kb Bam H1 fragment of human β‐globin DNA indicated protection of a small portion located 64bp 5′ upstream from the Bam H1 site of the second exon. The amount of protected portion was relatively higher in K‐562 cells undergoing erythroid maturation. These findings suggest that control and differentiating K‐562 cells synthesize β‐globin‐like RNA transcripts that are 3′ end short, immature, and unable to give rise to adult β‐globin chains. These results also indicate that K‐562 cells may lack factors that are unique for transcription and processing of the human β‐globin RNA transcripts.
Heat‐shock proteins during pollen development in maize
Authors: Frova Carla , Taramino Graziana , Binelli Giorgio 
Published: May 2005

AbstractIn contrast to sporophytic tissues, mature pollen of higher plants does not synthesize the typical set of heat‐shock proteins (HSPs) in response to a marked temperature upshift. Immature grains, however, seem able to do so, at least partially. We investigated the characteristics of HSP synthesis throughout the male gametophytic phase in maize and compared gametophytic and sporophytic heat‐shock responses. One‐dimensional Sodium dodecyl sulfate‐polyacryl‐amide gel electrophoresis technique (SDS‐PAGE) of newly synthesized proteins revealed that immature pollen synthesizes HSPs, some of which are not induced in sporophytic tissues. The heat‐shock response appeared to be related to microgametophytic developmental stages. The strongest response was found in uninucleate microspores: at this stage, in addition to the sporophytic 102, 84, 72, and 18 kD HSPs, three other polypeptides of 74, 56, and 46 kD were observed. In the binucleate and trinucleate stages, only a reduced synthesis of few HSPs could be induced, and differences between genotypes were observed. In germinating pollen, HSP synthesis was not induced under a voriety of heat‐stress conditions; however, the consti‐tutive synthesis of two polypeptides of the same molecular weight, 72 and 64 kD, as two HSPs was observed. The biological significance of these results is discussed.
Hyperinsulinemia in transgenic mice carrying multiple copies of the human insulin gene
Authors: Marban S. L. , Deloia J. A. , Gearhart J. D. 
Published: May 2005

AbstractWe are investigating human insulin gene expression in transgenic mice. An 8.8 kilobase (kb) human genomic DNA fragment, including the insulin gene (1.4 kb) and 2 kb of 5′ human flanking sequences, was introduced into mouse embryos by pronuclear microinjection. Two lines of transgenic mice have been established, both of which carry the intact human gene in multiple copies. Animals from both lines have significantly higher insulin levels than control mice, and the degree of hyperinsulinemia shows a positive correlation with human gene copy number in the two lines. Expression of the human gene is confirmed by the detection of human C‐peptide in plasma. Tissue specificity of expression is maintained, with human insulin mRNA detectable only in the pancreas. The transgenics maintain normal fasting blood glucose in spite of their high insulin levels, but preliminary studies show them to be glucose intolerant when given a glucose load. These mice provide a model system for further studies on the regulation of insulin gene expression and on the effects of chronic hyperinsulinemia on glucose homeostasis.
Developmental effects of modifiers of the vg mutant in Drosophila melanogaster
Authors: Cavicchi Sandro , Guerra Daniela , Natali Vanna , Giorgi Gianfranco , Pezzoli Cristina , Villani Luigi 
Published: May 2005

AbstractAn analysis of the modifiers affecting the expression of the vg gene was performed. We selected for weak and strong expression of the vg mutant in 2 segregating populations obtained by crossing a vestigial stock with an Oregon laboratory stock (O) and with a wild strain (B) captured near Bologna, Italy. The selection for enlarged wings was more effective in the vg B population where wild wings appeared from the lCth generation. The assay of the three major chromosomes showed that the modifiers are located on chromosomes 2 and 3. The mutant imaginal disc cell death phenotype is evident in vg/vg strains that have a wild‐type wing phenotype. It is suggested that the selected modifiers do not prevent cell death but induce regenerative growth.
Patterns of developmental and heritable change in methylation of the Suppressor‐mutator transposable element
Authors: Banks Jo Ann , Fedoroff Nina 
Published: May 2005

AbstractGenetic inactivation of the Suppressor‐mutator (Spm) element is correlated with methylation of sequences surrounding the element's transcription initiation site. Several stages in the development of the plant have been identified during which element methylation is reproducibly altered. Loss of element methylation occurs during development of the embryo and early in vegetative growth of the tiller. Element methylation increases during vegetative growth and during development of male and female inflorescences. The susceptibility of element methylation to change during development correlates with the genetic stability of the element's phase of activity. Increases in methylation of sites both upstream and downstream of the Spm element's transcription initiation site parallel increases in the genetic stability of the inactive phase. These results strengthen the likelihood that methylation of C residues within specific regions of the element is important in maintaining the element in an inactive phase and is a component of the molecular mechanism that regulates element expression in plant development.
Transposable element‐induced mutations of the viviparous‐1 gene in maize
Authors: McCarty Donald R. , Carson Christian B. , Lazar Mark , Simonds S. Caprice 
Published: May 2005

AbstractThe viviparous‐1 (vp1) locus in maize is a developmental gene that controls diverse aspects of the maturation phase of seed development. Mutations of vp1 alter embryo sensitivity to the hormone abscisic acid and block formation of anthocyanin pigment. Molecular cloning of a Robertson Mutator‐induced mutant allele, vp1‐mum‐1, by transposable element tagging has allowed analysis of several transposon‐induced vp1 mutants. In the vp1‐Mc mutation, the gene is disrupted by 4.0 kbp insertion, which results in expression of a 3′ truncated mRNA. Phenotypically, this allele is at least partially functional in causing embryo dormancy, but is ineffective in controlling anthocyanin expression. This result suggests that disruption of the C‐terminal domain of the Vp1 protein specifically affects regulation of the anthocyanin pathway. A second Mutator‐ derived allele, vp1‐mum2, exhibits an unusual form of somatic mutability in which endosperm cells revert from wild‐type vp1 expression to a mutant condition. The vp1‐mum2 allele contains a 1.5 kbp Insertion that has no detectable homology to known Mu elements. This element is retained In wild‐type germinal revertants derived from vp1‐mum2 An apparent DNA modification affecting cleavage at an internal Sstl restriction site in the element correlates with vp1‐mum2 states that exhibit wild‐type Vp1 expression. A model involving mitotic assortment of modified and unmodified DNA strands during development is proposed for vp1‐mum2 somatic mutation.
Developmental and genetic aspects of Mutator excision in maize
Authors: Levy Avraham A. , Britt Anne Bagg , Luehrsen Kenneth R. , Chandler Vicki L. , Warren Christine , Walbot Virginia 
Published: May 2005

AbstractThe regulation of excision of Mu elements of the Mutator transposable element family of maize is not well understood. We have used somatic instability of Mu receptor elements from the Bronze 1 and Bronze 2 loci to monitor the frequency and the timing of excision of Mu elements in several tissues. We show that spot size in the aleurone of a bz2::mu1 stock varies between one to approximately 256 cells. This indicates that excision events begin eight divisions prior to full aleurone differentiation and end after the last division of the aleurone. We show that excision is equally biased for late events in all other tissues studied. A locus on chromosome 5 has been identified that affects spot size, possibly by altering the timing of Mu excision.Using somatic excision as an assay of Mutator activity, we found that activity can change in small sectors of the tassel; however, there are no overall activity changes in the tassel during the period of pollen shedding. We also report the recovery of germinal revertants for the bz1::mu1 and bz2::mu1 alleles. One of these revertant alleles was characterized by Southern blot analysis and found to be similar to the progenitor of the mutable allele.
w4‐Mutable line in soybean
Authors: Palmer R. G. , Hedges B. R. , Benavente R. S. , Groose R. W. 
Published: May 2005

AbstractAn unstable mutation for anthocyanin pigmentation in soybean (Giycine max [L.] Merr.) was identified in 1983. The mutability is conditioned by an allele at the w4 locus that is recessive to wild type. The population containing the mutable allele is known as the w4‐mutable line. Most plants in the line have chimeric flowers with purple sectors on a near‐white background. The mutable allele yields germinal revertants at a rate that varies from 5 to 10% per generation, and the revertant alleles are stable. Approximately 1% of the progenies derived from germinal revertant plants contain mutations at other loci These features, as well as the occurrence of pale flower phenotypes and changes of state, suggest that a transposable element system is producing the unstable phenotype.Several new mutants were isolated in an experiment designed to tag loci. The first three chlorophyll‐deficient mutants found (CD‐1, CD‐2, and CD‐3) are inherited as single‐gene recessives. Each of the mutants lacks the same two mitochondrial malate dehydrogenase (MDH) bands. No recombination has been detected between the MDH phenotype and the chlorophyll‐deficient phenotype. Genetic data indicate that the three mutants are allelic, and additional evidence suggests that each of the CD mutants is the result of a deletion. In the CD‐1, CD‐2, and CD‐3 mutants, the deletions result in the silencing of an MDH locus, atypical chloroplast development, and an altered chlorophyll composition. Additional mutants for root necrosis, partial and near sterility, chlorophyll deficiency, and flower color isolated from the transposon tagging study have provided material for future research.
Gene tagging in Petunia hybrida using homologous and heterologous transposable elements
Authors: Gerats Anton G. M. , Beld Marcel , Huits Henk , Prescott Andy 
Published: May 2005

AbstractIn this paper we describe the current state of knowledge of transposable element systems in Petunia hybrida. The main features of the unstable An1 alleles are discussed. The data on derivative (un)stable alleles at different loci are summarized. A simple strategy is outlined for random versus directed gene tagging using endogenous and heterologous elements. The progress in the cloning of endogenous elements is presented.
Temporal and spatial expression of a cytoskeletal actin gene in the ascidian Styela clava
Authors: Beach Rebecca L. , Jeffery William R. 
Published: May 2005

AbstractWe have cloned and characterized the temporal and spatial expression of ScCAl5, a cDNA clone encoding an actin gene in the ascidian Styela clava. The partial nucleotide and derived amino acid sequences of this single‐ copy gene suggest that it is a cytoskeletal actin. Northern analysis shows that ScCAl5 corresponds to a 1.8‐kb mRNA that is transcribed during oogenesis, during embryonic development, and in the adult. In situ hybridization shows that maternal ScCA15 mRNA is distributed uniformly in the cyto‐ plasm of the oocyte and unfertilized egg. During the period of ooplasmic segregation following fertilization, however, ScCAl5 mRNA appears to be translocated into the ectoplasm, a specialized cytoplasmic region of the egg. During the early cleavages, the ectoplasmic transcripts are partitioned to ectodermal cells in the animal hemisphere, which are precursors of the epidermis and nervous system of the larva. Maternal ScCA15 mRNA is degraded just before gastrulation and replaced by zygotic transcripts which begin to accumulate between the neurula and mid‐tailbud stages. Zygotic ScCAl5 mRNA accumulates primarily in the epidermal and neural cells, although lower levels of these transcripts may also be present in tail muscle cells. These results show that two mechanisms are used to concentrate ScCA15mRNA in the ectodermal cells during development: (1) localization and differential segregation of maternal transcripts and (2) specific expression of the ScCA15 gene. ScCAl5 mRNA is detected by in situ hybridization in the testes, ovaries, alimentary tract, and endostyle of adults. In the testes, ScCA15 mRNA is present in developing sperm, whereas in the ovary, these transcripts are present in the germinal epithelium and developing oocytes. In the alimentary tract, ScCAl5 mRNA is confined to the gastric epithelium of the esophagus, stomach, and intestine. Since the ScCA15 gene is expressed in embryonic and adult tissues that are undergoing rapid cell division, this actin is likely to function in some aspect of cell proliferation.
Stages of cell hair construction in Drosophila
Authors: Mitchell Herschel K. , Edens Jean , Petersen Nancy S. 
Published: May 2005

AbstractThe construction of cell hairs (trichomes) on the wings of Drosophila occurs in synchrony on 30,000 cells over a period of about 20 hr. Changes in both morphology and patterns of protein synthesis occur rapidly during this time period. In this report we describe the use of stressinduced (heat shock) abnormalities in morphogenesis to provide further details on the stepwise processes of differentiation within single wing cells. A cartoon summary of the overall process and a discussion of some possible mechanisms is included.
Expression of soybean lectin gene deletions in tobacco
Authors: Lindstrom Jon T. , Vodkin Lila O. , Harding Roy W. , Goeken Robert M. 
Published: May 2005

AbstractA series of constructs containing the developmentally regulated soybean lectin gene (Le1) were used to transform tobacco plants in order to assess developmental and quantitative regulation conferred by flanking sequences. The largest of the lectin constructs contained approximately 3,00 base pairs (bp) of Le1 5′ flanking region and 1,500 bp of the 3′ flanking region. The smallest construct contained no 5′ flanking region and 194 bp of the 3′ flanking region. ELISA assays of lectin in individual tobacco seeds and Southern blot analyses confirmed that most constructs were inherited as unique insertion events. Maximal expression of Le1 required more than 338 bp of 5′ sequence, indicating that far upstream factors are involved in quantitative control of lectin expression. Lectin expression declined more than 80% between deletions with 1,700 versus 338 bp of 5′ flanking sequence. In contrast, developmental control of lectin expression was maintained by Le1 inserts with only 190 bp of 5′ sequence. The lectin promoter offers a potential means to target high levels of gene expression to the developing seeds of soybean or other dicotyledonous plants.