bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell lineage analysis of the gynoecium of maize using the transposable element Ac
Authors: Dellaporta Stephen L. , Moreno Maria A. , Delong Alison 
Published: April 2021

Abstract
The maize gynoecium develops from a primordium comprising two distinct cell lineages: an epidermal LI and a subepidermal LII lineage. We have analyzed somatic gynoecial sectors marked with red flavonoid pigments by excision of Ac from the P locus. Somatic sector analysis indicates the epidermal lineage starts as a single cell layer at the base of the ovary and thickens into several cell layers, presumably by periclinal divisions, near the silk attachment point. The silk attachment point appears to be mainly an epidermal outgrowth of two of three fused carpels and presumably the silk contains only LI, or mostly LI, with only traces of subepidermal LII cells. The third carpel, covering the germinal face of the kernel, retains a multicellular LII and unicellular LI organization but fails to contribute substantially to stylar outgrowth. Ac transpositions in subepidermal somatic sectors are transmitted to the archesporial cell lineage. Ac transpositions that occur in epidermal sectors are not transmitted to offspring. These results demonstrate that the female megasporocyte is derived from subepidermal (LII) cells.
Homeotic genes controlling flower development in Antirrhinum
Authors: Coen Enrico S. , Doyle Sandra , Romero JOse M. , Elliott Robert , Magrath Ruth , Carpenter Rosemary 
Published: April 2021

Abstract
In order to study genes controlling flower development, we have carried out an extensive transposon-mutagenesis experiment in Antirrhinum majus. More than 15 independent homeotic mutations were obtained, allowing three categories of genes to be defined. The first includes floricaula (flo), a primary gene required for the initiation of the floral developmental pathway. In the absence of the wild-type flo product, proliferating inflorescence meristems arise in place of flowers. The flo gene has been isolated and shown to be expressed transiently in a subset of organ primordia in the floral meristem. The second category includes genes that affect the identity, and also sometimes the number, of whorls of organs in the flower. These genes act in overlapping domains so that each whorl has a distinct combination of gene functions, suggesting a model for the genetic control of whorl identity and number. Genes of the third category control differences between organs in the same whorl and hence the overall symmetry of the flower. We discuss how the basic plan of the flower and inflorescence may arise through the interactions between the three categories of genes.
Properties of deficiens, a homeotic gene involved in the control of flower morphogenesis in Antirrhinum majus
Authors: Sommer Hans , Nacken Wolfgang , Beltran Pio , Huijser Peter , Pape Heike , Hansen Rolf , Flor Peter , Saedler Heinz , Schwarz-Sommer Zsuzsanna 
Published: April 2021

Abstract
deficiens, together with other homeotic genes, is involved in the genetic control of floral morphogenesis in A. majus. Mutations in this gene cause homeotic transformations of petals to sepals and stamens to carpels, thus producing male sterile flowers.
The deduced DEF A protein shows homology to the DNA-binding domain of the transcription factors SRF of mammals (activating c-fos) and MCM1 of yeast (regulating mating type), suggesting that DEF A has a possible regulatory function as a transcription factor. Interestingly, DEF A belongs to a family of putative transcription factors, called the MADS box genes, whose DNA-binding domains show conserved homology.
Two members of this family correlate with known morphogenetic mutants of Antirrhinum.
DEF A is constantly expressed during flower development in all floral organs; it is strongly expressed in petals and stamens, but only at a low basal level in the other organs. Molecular, genetic and morphological observations with deficiens morphoalleles indicate that transcriptional and post-transcriptional control of deficiens specifies and diversifies its function in space and time.
Genetic analysis of pattern formation in the Arabidopsis embryo
Authors: Jürgens Gerd , Mayer Ulrike , Ruiz Ramon A. Torres , Berleth Thomas , Miséra Simon 
Published: April 2021

Abstract
Virtually nothing is known about the mechanisms that generate the basic body pattern in plant embryogenesis. As a first step towards the analysis of pattern formation, we have isolated and begun to characterise putative pattern mutants in the flowering plant, Arabidopsis thaliana. A large-scale screen for morphologically abnormal seedling mutants yielded about 250 lines for further study, and genetic evidence suggests saturation of the genome for this kind of mutation. The phenotypes of putative pattern mutants fall into distinct categories, classes and groups, which may reflect specific aspects of embryonic pattern formation. Mutant seedling phenotypes result from abnormal development in the early embryo. The implications of our findings are discussed with regard to the prospects for a mechanistic understanding of pattern formation in the plant embryo.
Gene activation in the amphibian mesoderm
Authors: Hopwood N. D. , Gurdon J. B. 
Published: April 2021

Abstract
Cell potency is progressively restricted in amphibian development by a series of cellular interactions called inductions. The mesoderm is believed to develop in response to the earliest known induction, in which vegetal cells of the blastula divert overlying animal hemisphere cells away from epidermal and towards mesodermal fates. We describe two early markers of mesodermal differentiation in Xenopus laevis, both mRNAs that encode DNA-binding proteins of the helixloop-helix family. One is a frog homologue of MyoD, a gene that in transfection experiments can convert cultured fibroblasts into myoblasts. Xenopus MyoD (XMyoD) is expressed in the early myotomes, from which the axial musculature develops. The accumulation of XMyoD RNA precedes that of transcripts from the cardiac actin gene, until now the earliest known marker of the muscle lineage, this result indicating that XMyoD could play a role in initiating muscle differentiation in normal development. We show by microinjection of synthetic RNA that XMyoD can indeed activate musclespecific gene expression in animal cap cells, which would normally form only ectoderm. However, the XMyoD-injected animal caps did not produce differentiated muscle, suggesting that additional specific factors are required for full myogenesis. The other mRNA is a relative of the twist gene of Drosophila, which is required for mesodermal differentiation in flies. This gene (Xtwi) is expressed widely in the early frog mesoderm, but not, however, in the myotomes, where XMyoD is expressed. Later, the Xtwi gene is activated, in response to a second induction, in the developing neural crest.
Isolation of temperature-sensitive diphtheria toxins in yeast and their effects on Drosophila cells
Authors: Bellen Hugo J. , D’Evelyn Diana , Harvey Michele , Elledge Stephen J. 
Published: April 2021

ABSTRACT
We have isolated temperature-sensitive diphtheria toxins (DT-At5) to develop a method that allows temporal impedement of cellular functions. Four DT-Ats genes were isolated in a mutagenesis screen using the yeast, Saccharomyces cerevisiae. When expressed in yeast, these DT-Ats arrest growth at 18°C but not at 30°C. Three DT-At5 were subsequently tested in the R1-R6 photoreceptor cells of transgenic fruit flies, Drosophila melanogaster. The toxins show similar temperature dependence in both organisms, suggesting that they may be useful in a wide range of non-homeothermic species. DNA sequence analysis revealed that three of the four DT-At5 mutations are novel. Interestingly, the fourth DT-Ats carries the same point mutation as the extensively characterized CRM197, an ADP ribosyltransferase-defective form of diphtheria toxin.
Synthesis and phosphorylation of uvomorulin during mouse early development
Authors: Sefton Mark , Johnson Martin H. , Clayton Lesley 
Published: April 2021

Abstract
The cell adhesion molecule, uvomorulin, is synthesised in both the 135×103Mr precursor and 120×103Mr mature forms on maternal mRNA templates in unfertilized and newly fertilized mouse oocytes. Synthesis on maternal message ceases during the 2-cell stage to resume later on mRNA encoded presumptively by the embryonic genome. Uvomorulin is detectable by immunoblotting at all stages upto the blastocyst stage, but shows variations in its total amount and processing with embryonic stage. Whilst only trace levels of phosphorylated uvomorulin are detectable in early and late 4-cell embryos, uvomorulin in 8-cell embryos is phosphorylated.
Development of surface pattern during division in Paramecium II. Defective spatial control in the mutant kin241
Authors: Jerka-Dziadosz Maria , Loubresse Nicole Garreau De , Beisson Janine 
Published: April 2021

Abstract
kin241 is a monogenic nuclear recessive mutation producing highly pleiotropic effects on cell size and shape, generation time, thermosensitivity, nuclear reorganization and cortical organization. We have analyzed the nature of the cortical disorders and their development during division, using various specific antibodies labelling either one of the cortical cytoskeleton components, as was previously done for analysis of cortical pattern formation in the wild type.
Several abnormalities in basal body properties were consistently observed, although with a variable frequency: extra microtubules in either the triplets or in the lumen; nucleation of a second kinetodesmal fiber; abnormal orientation of the newly formed basal body with respect to the mother one. The latter effect seems to account for the major observed cortical disorders (reversal, intercalation of supplementary ciliary rows). The second major effect of the mutation concerns the spatiotemporal map of cortical reorganization during division. Excess basal body proliferation occurs and is correlated with modified boundaries of some of the cortical domains identified in the wild type on the basis of their basal body duplication pattern.
This is the first mutant described in a ciliate in which both the structure and duplication of basal bodies and the body plan are affected. The data support the conclusion that the mutation does not alter the nature of the morphogenetic signal(s) which pervade the dividing cell, nor the competence of cytoskeletal structures to respond to signalling, but affects the local interpretation of the signals.
Gonad formation and development requires theabd-Adomain of the bithorax complex inDrosophila melanogaster
Authors: Cumberledge Susan , Szabad Janos , Sakonju Shigeru 
Published: April 2021

AbstractThe abdominal-A (abd-A) gene, a member of the bithorax complex, is required for the correct identity of parasegments (PS) 7 through 13. Mutations in iab-4, one of the crs-regulatory regions of abd-A, transform epidermal structures of PS 9 and also cause loss of gonads in adult flies. Here, we describe a developmental and molecular analysis of the role of iab-4 functions in gonadal development. In flies homozygous for a strong iab-4 allele, gonadogenesis is not initiated in the embryo because the mesodermal cells fail to encapsulate the pole cells. Flies homozygous for weaker iab-4 mutations sometimes form ovaries. The ovary-oviduct junctions are abnormal, however, and egg transfer from the ovary to the uterus is blocked in the adult. To localize the sites that require iab-4 function, we have analyzed animals chimeric for the mutant and wild-type cells. These chimeras were generated by three kinds of transplantation experiments: pole cells, embryonic somatic nuclei or larval ovaries. Our results suggest that iab-4 is required in the somatic cells of the gonadal primordia, but not the germ line. In addition, the formation of functional ovary-oviduct junctions and egg transfer also requires iab-4 functions in the somatic cells of the ovary and in at least one additional somatic tissue.
A transgene containing lacZ is expressed in primary sensory neurons in zebrafish
Authors: Bayer Thomas A. , Campos-Ortega José A. 
Published: April 2021

Abstract
In order to screen for developmentally active chromosomal domains during zebrafish embryogenesis, we generated transgenic fish by microinjecting two different lacZ reporter constructs into fertilized eggs. Transgenic fish were screened among the progeny of injected fish (Fo) crossed to non-injected fish. Groups of 15 to 20 progeny of each cross were tested for lacZ expression and/or transmission of injected sequences using PCR and Southern hybrizations. Progeny from 2 of 102 fish injected with super coiled constructs containing Rous sarcoma virus promoter sequences showed apparently spatially regulated β-galactosidase (β-Gal) activity. However, we were not able to detect this reporter construct in DNA from fins of F, fish. Injections of a linear reporter construct containing mouse heat-shock promoter sequences revealed transmission of injected sequences to Fi progeny in about 6% of cases (8 of 129 fish, tested with PCR). We found one ZacZ-expressing line that showed a spatially and temporally restricted expression of lacZ and, therefore, features typical characteristics of ‘enhancer trap’lines. In this line, lacZ expression starts at 16 hours post-fertilization in trigeminal ganglion cells. At about 24 hours lacZ expression can be detected in trigeminal ganglion neurons and Rohon-Beard neurons, indicating that the development of these two cell types shows common features. The reporter gene has integrated as a single copy. The founder fish was mosaic: 19% of its offspring (3 of 16 tested animals) carried the reporter construct in their fins; about 51% (13 of 27 tested animals) of the progeny of F, fish were β-Gal positive indicating full hemizygosity. We traced the heritability up to the 4th generation and showed that the reporter construct is stably integrated and inherited in a Mendelian manner. These results demonstrate that it is possible to generate “enhancer trap” lines in zebrafish, albeit with low efficiency.
Spatial and temporal expression of an epithelial mucin, Muc-1, during mouse development
Authors: Braga V. M. M. , Pemberton L. F. , Duhig T. , Gendler S. J. 
Published: April 2021

Abstract
The Muc-1 mucin is found as a transmembrane protein in the apical surface of glandular epithelia. To provide insight into possible functions, we have assessed the timing of expression and the distribution of the Muc-1 protein during mouse embryogenesis using three different techniques: RT-PCR, northern blots and immunohistochemistry. Our results indicate that Muc-1 expression correlates with epithelial differentiation in stomach, pancreas, lung, trachea, kidney and salivary glands. Once started, Muc-1 synthesis continually increases with time, mainly due to epithelial area growth. Our data suggest that expression of the Muc-1 gene is under spatial and temporal control during organogenesis. Although Muc-1 is present in different organs, its expression is not induced systemically, but according to the particular onset of epithelial polarization and branching morphogenesis of each individual organ. It is of particular interest that Muc-1 protein can be detected lining the apical surfaces of the developing lumens when the epithelium of these organs is still undergoing folding and branching, and glandular activity has not yet started. We speculate that Muc-1 may participate in epithelial sheet differentiation/lumen formation during early development of the organs known to express it. This speculation is based on: (1) the detection of Muc-1 expression early during organogenesis, (2) the defined apical localization in different epithelia, (3) the decrease in cell-cell interactions when Muc-1 protein is highly expressed and (4) the possible interaction of its cytoplasmic tail with the actin cytoskeleton. However, it remains to be established using in vitro systems, whether the temporal and local expression of the Muc-1 gene coincident with the morphogenetic events described here is relevant for the process.
Differential expression of acidic cytokeratins 18 and 19 during sexual differentiation of the rat gonad
Authors: Fridmacher Valérie , Locquet Odette , Magre Solange 
Published: April 2021

Abstract
The expression of cytokeratins (CKs) 8, 18 and 19 was analyzed in male and female rat gonads from the undifferentiated stage (12.5 days of gestation) until two weeks after birth by indirect immunofluorescence, using specific monoclonal antibodies anti-CK 8 (LE41), anti-CK 19 (LP2K) and anti-CK 18 (LE65 and RGE53). In the undifferentiated blastema, the somatic cells were stained for CK 8 and CK 19, whereas no detectable immunoreactivity for CK 18 was obtained. The same staining CK pattern was observed in ovaries, in the somatic cells of ovigerous cords and in primary follicles. The staining was progressively decreasing in growing follicles after one week after birth. At the onset of testicular differentiation, when the first Sertoli cells differentiate in the gonad of 13.5-day old male fetuses, positive staining for CK 18 became evident, in addition to CK 8 and CK 19 expression. In the following days,CK 8, CK 18 and CK 19 were detected in Sertoli cells in the differentiating seminiferous cords, but progressively the reactivity for CK 19 decreased and was no longer observed after 18.5-19.5 days of gestation. In all cases, CKs were found to be coexpressed with vimentin, and germ cells were negative for both vimentin and CKs. The results reported here show first, that CKs are expressed before sexual differentiation in gonadal blastema in which no epithelial organization is observed, and second, that there is a CK 18/CK 19 shift in expression during morphogenesis of the testis which is not observed in the differentiating ovary. Future studies will have to determine whether these differences in CK expression are due to epitope-masking phenomena or to the regulation of CK synthesis.
β-integrin is a maternal protein that is inserted into all newly formed plasma membranes during early Xenopus embryogenesis
Authors: Gawantka V. , Ellinger-Ziegelbauer H. , Hausen P. 
Published: April 2021

Abstract
A monoclonal antibody (mAb 8C8) that recognizes the Xenopus β1-integrin chain was used to study the appearance, synthesis and distribution of this integrin subunit during the early development of Xenopus. Both the precursor and the mature form of β1-integrin are provided maternally. They do not increase significantly in amount until early gastrula when the level of both forms begins to rise gradually.
Synthesis of β1-integrin from maternal mRNA is observed throughout the pregastrula phase, though it seems to add only little to the total β1-integrin of the embryo. Until late blastula only small amounts of precursor are processed into the mature form.
Starting with the formation of the first cleavage membrane, mature β1-integrin is inserted into the newly formed plasma membranes of all cells. The membrane domains forming the outer surface of the embryo remain devoid of the antigen. The data suggest an as yet unknown function of β1-integrin during the cleavage phase.
The neural tube/notochord complex is necessary for vertebral but not limb and body wall striated muscle differentiation
Authors: M.Rong P. , Teillet M.-A. , Ziller C. , Douarin N.M. Le 
Published: April 2021

ABSTRACT
The aim of this work was to investigate the role played by the axial organs, neural tube and notochord, on the differentiation of muscle cells from the somites in the avian embryo. Two of us have previously shown that neuralectomy and notochordectomy is followed by necrosis of the somites and consecutive absence of vertebrae and of most muscle cells derived from the myotomes while the limbs develop normally with muscles. Here we have focused our attention on muscle cell differentiation by using the 13F4 mAb that recognizes a cytoplasmic antigen specific of all types of muscle cells. We show that differentiation of muscle cells of myotomes can occur in the absence of notochord and neural tube provided that the somites from which they are derived have been in contact with the axial organs for a defined period of time, about 10 hours for the first somites formed at the cervical level, a duration that progressively reduces caudalward (i. e. for thoracic and lumbar somites). Either one or the other of the two axial organs, the neural tube or the noto-chord can prevent somitic cell death and fulfill the requirements for myotomal muscle cell differentiation. Separation of the neural tube/notochord complex from the somites by a surgical slit on one side of the embryo gave the same results as extirpation of these organs and provided a perfect control on the non-operated side. A striking finding was that limb and body wall muscles, although derived from the somites, differentiated in the absence of the axial organs. However, limb muscles that develop after excision of the neural tube started to degenerate from E10 onward due to lack of innervation. In vitro explantation of somites from different axial levels confirmed and defined precisely the chronology of muscle cell commitment in the myotomes as revealed by the in vivo experiments.
Overexpression of Dd PK2 protein kinase causes rapid development and affects the intracellular cAMP pathway of Dictyostelium discoideum
Authors: Anjard Christophe , Pinaud Stephane , Kay Robert R. , D. Reymond Christophe 
Published: April 2021

ABSTRACT
The Dd PK2 gene codes for a putative protein of 648 amino acids with a C-terminal half sharing high homology with protein kinase A catalytic subunits from other organisms. In order to find out more about the physiological role of the Dd PK2 kinase, its gene, and a version having a frame shift mutation in the middle of the catalytic region, were overexpressed in developing Dictyostelium cells. Both the intact gene (K-) and the frame shift mutant (Kdel-) caused rapid development with spores formed in 16-18 hours compared to the 24 hours required by their parent. This result was confirmed by the pattern of expression of some developmentally regulated genes. Other rapid developing strains (rde) are activated in the cAMP second messenger system. Both K- and Kdel-containing strains have lower cAMP levels than the parental strain during late development, thus resembling rdeC mutants. K-cells (but not Kdel-cells) produced bizarre fruiting bodies with many prostrate forms. The parallel with rde mutants was confirmed by demonstrating that K-cells are able to form spores in submerged monolayer culture. Furthermore, K-cells have about four times more protein kinase A (cAPK) activity than wild-type cells. These results indicate that the N-terminal domain of Dd PK2 is sufficient to influence cAMP levels and to provoke rapid development, whereas kinase activity seems to be required for the sporogenous phenotype. The association between elevated cAPK and Dd PK2 overexpression phenotype further indicates a role for cAPK in the formation of spores.
orthodenticle activity is required for the development of medial structures in the larval and adult epidermis of Drosophila
Authors: Wieschaus Eric , Perrimon Norbert , Finkelstein Robert 
Published: April 2021

ABSTRACT
Lethal alleles of orthodenticle (=otd) cause abnormalities in the embryonic head that reflect an early role in anterior pattern formation. In addition, otd activity is required for the development of the larval and adult epidermis. Clonal analysis of both viable and lethal alleles shows that the adult requirement for otd is restricted to medial regions of certain discs. When otd activity is reduced or removed, some medial precursor cells produce bristles and cuticle characteristic of more lateral structures. Similar medial defects are observed in the larval epidermis of embryos homozygous for lethal otd alleles. Antibodies to otd recognize a nuclear protein found at high levels in the medial region of the eye antennal discs, the leg discs, the genital discs and along the ventral midline of the ventral epidermis of the embryo. These results suggest that the otd gene product is required to specify medial cell fates in both the larval and adult epidermis.