bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of developmentally interesting genes cloned from higher plants by insertional mutagenesis
Authors: Chandlee Joel M.
Published: May 2005

The ability of transposable elements to generate gene mutations by excising from one site in the genome and reintegrating into new, different sites elsewhere in the genome has led to the development of procedures whereby the elements can be used to tag specific gene sequences for eventual isolation and analysis through gene cloning. This transposon tagging strategy is particularly useful in those situations where limited knowledge of the biochemistry of the target gene precludes gene cloning by conventional strategies. This approach, in conjunction with the more general insertional mutagenesis approach using T‐DNA, has led to the cloning and subsequent analysis of several genes from higher plants involved in particular developmental processes. Studies of this nature should eventually shed light on the precise molecular mechanisms utilized to regulate and control cellular differentiation in plants.
Cellular morphogenesis in the Saccharomyces cerevisiae cell cycle: Localization of the CDC11 gene product and the timing of events at the budding site
Authors: Ford Susan K. , Pringle John R.
Published: May 2005

The Saccharomyces cerevisiae CDC3, CDC10, CDC11, and CDC12 genes encode a family of homologous proteins that are not closely related to other known proteins [Haarer BK, Ketcham SR, Ford SK, Ashcroft DJ, and Pringle JR (submitted)]. Temperature‐sensitive mutants defective in any of these four genes display essentially identical pleiotropic phenotypes that include abnormal cell‐wall deposition and bud growth, an inability to complete cytokinesis, and a failure to form the ring of 10 nm filaments that normally lies directly subjacent to the plasma membrane in the neck region of budding cells. We showed previously that the CDC3 and CDC12 gene products localize to the region of the mother‐bud neck and are probably constituents of the ring of 10 nm filaments. We now report the generation of polyclonal antibodies specific for the CDC11 product (Cdc11p) and the use of these antibodies in immunofluorescence experiments with wild‐type and mutant cells. The results suggest that Cdc11p is also a constituent of the filament ring, and thus support the hypothesis that the S. cerevisiae 10 nm filaments represent a novel type of eukaryotic cytoskeletal element. Cdc11p and actin both localize to the budding site well in advance of bud emergence and at approximately the same time, and both proteins also remain localized at the old budding site for some time after cytokinesis. Cdc11p also localizes to regions of cell‐wall reorganization in mating cells and in cells responding to purified mating pheromone. Surprisingly, most preparations of affinity purified Cdc11p‐specific antibodies also stained the nuclear and cytoplasmic microtubules. Although this staining probably reflects the existence of an epitope shared by Cdc11p and some microtubule‐associated protein, the possibility that a fraction of the Cdc11 p is associated with the microtubules could not be eliminated.
Expression of gap junction genes during postnatal neural development
Authors: Belliveau Daniel J. , Kidder Gerald M. , Naus Christian C. G.
Published: May 2005

The timing of appearance of mRNAs encoding gap junction proteins was examined during development of the rat and mouse brain. Complementary DNAs (cDNAs) specific for the mRNA for the liver‐type gap junction protein, connexin32, and the heart‐type gap junction protein, connexin43, were used to probe Northern blots of total RNA isolated from the forebrain and hindbrain of mice and rats at various times before and after birth. Prior to postnatal day 10, connexin32 mRNA is detectable only at low levels. By postnatal days 10 to 16, a sharp increase occurs in the level of this mRNA. This increase is detectable first in the hindbrain, and subsequently in the forebrain. In contrast, connexin43 mRNA is readily detectable at birth, and the level of this mRNA also increases during subsequent development. The developmental appearance of the gap junction proteins, connexin32 and connexin43, was similar to that of their respective mRNAs. These results indicate that the genes encoding connexin32 and connexin43 are differentially expressed during neural development.
Sequence of swallow, a gene required for the localization of bicoid message in Drosophila eggs
Authors: Chao Yu‐Chan , Donahue Kathleen M. , Pokrywka Nancy J. , Stephenson Edwin C.
Published: May 2005

We report the sequence of the Drosophila maternal effect gene swallow, one of the genes whose product is required for the localization of bicoid message during Drosophila oo‐genesis. The inferred swallow protein contains a domain that is predicted to be an amphipathic α‐helix similar to those implicated in protein:protein associations in other systems. Another part of the predicted protein appears to be a diverged RNA‐binding motif. We discuss these structural features in light of the function of the swallow protein in the bicoid message localization process.
Phenotypic consequences and genetic interactions of a null mutation in the Drosophila posterior Sex Combs gene
Authors: Adler Paul N. , Martin Elisabeth C. , Charlton Jeannette , Jones Katherine
Published: May 2005

The Posterior Sex Combs (Psc) gene of Drosophila is a member of the Polycomb (Pc) group of transregulatory genes. Previous analyses of the function of this gene in Drosophila em‐bryogenesis have been hampered by the lack of a null mutation. We recently isolated a mutation that deletes the 5′ end of the Psc gene. This allele appears to be a null mutation, and we have used it to determine the Psc zygotic null phenotype and to look at the interactions of a null allele of Psc with five other Pc group mutations. We find evidence for transformations along both the anterior‐posterior and dorsal‐ventral axes in embryos of a variety of genotypes that include a null mutation in Psc. The phenotypes of embryos that are doubly mutant for a null allele of Psc and a mutation in a second Pc group gene show dramatic synergistic effects, but in their specifics they are dependent on the identify of the second Pc group gene. This is different from the relatively uniform phenotypes seen among double mutants that contained the allele Psc1, which has both gain and loss of function properties. The differences in the phenotypes of the doubly mutant embryos allow us to eliminate one class of molecular models to explain the dramatic synergism seen with mutations in this group of genes.
Mosaicism of tyrosinase‐locus transcription and chromatin structure in dark vs. light melanocyte clones of homozygous chinchilla‐mottled mice
Authors: Porter Susan , Larue Lionel , Mintz Beatrice
Published: May 2005

The chinchilla‐mottled (cm) mutation at the mouse tyrosinase‐encoding locus leads to a transversely striped pattern of dark‐ and light‐grey coat colors in homozygotes. The same basic pattern occurs in various other genotypes and has previously been found to represent the clonal developmental history of melanocytes. In a homozygote such as cm/cm, cis‐acting mechanisms would be expected to account for the color differences. To search for these mechanisms, the genomic structure of the mutation was examined and compared with the wild‐type, and its function was compared in cultured melanocyte clones of the respective colors. Evidence from restriction mapping indicated that the coding region of the mutant gene resembles that of the fully and uniformly pigmented wild‐type. However, the upstream sequences are rearranged in the mutation. The rearrangement begins 5 kb 5′ of the transcription initiation site and is estimated to encompass at least 30 kb of distal upstream sequence. At least two stable functional states of the cm gene were detectable: Light‐cell clones have low levels of tyrosinase‐specific transcription, reduced DNAase I sensitivity of tyrosinase chromatin, and no detectable hypersensitive sites near the gene; dark‐cell clones have higher (but subnormal) levels of transcription, greater sensitivity of chromatin to DNAase I, and a hypersensitive site in the promoter region. The changed relation between the structural gene and its upstream region may separate it from cis‐acting control elements, resulting in reduced and variable ability to achieve the appropriate chromatin configuration near the time of melanocyte determination; differences in expression among clonal initiator cells are then mitotically perpetuated. © 1992 Wiley‐Liss, Inc.
Adoptive transfer of the hematopoietic system of trisomic mice with limited life span: Stem cells from six different trisomies are capable of survival
Authors: Herbst Eberhard W. , Winking Heinz
Published: May 2005

The life span of murine trisomies is limited to the fetal or early postnatal period. However, rescue of the hematopoietic system of fetal mice with trisomies (Ts) 12, 13, 14, 16, 18, and 19 is possible by transplanting hematopoietic stem cells from the liver into lethally irradiated adult hosts. Thus, radiation chimeras with permanent and almost complete trisomic hematopoietic and lymphocytopoietic systems were constructed. The longest documented survival of a trisomic graft was 12 months in Ts 19 chimeras. Blood counts in trisomic chimeras reveal a marked anemia in Ts 16 chimeras; lymphocytopenia in Ts 12, Ts 16, and Ts 19 chimeras; and granulocytopenia in Ts 18 chimeras. Survival rates of Ts 12, Ts 18, and Ts 19 chimeras were not different from those of the respective controls, whereas survival rates of chimeras with Ts 13 and Ts 16 hematopoiesis were markedly reduced and that of Ts 14 chimeras only slightly reduced. These results indicate that transplanted hematopoietic stem cells from Ts 13, Ts 14, and Ts 16 fetuses exhibit relevant genetically determined defects, resulting in a reduced restoration capacity of hematopoietic organs and/or deficiencies of differentiated blood cells. © 1992 Wiley‐Liss, Inc.
Pheromone 4 gene of Euplotes octocarinatus
Authors: Meyer Frank , Schmidt Helmut J. , Heckmann Klaus
Published: May 2005

We have cloned and sequenced a 1.7 kb macronuclear chromosome encoding the pheromone 4 gene of Euplotes octocarinatus. The sequence of the secreted pheromone is preceded by a 42 amino acid leader peptide, which ends with a lysine residue. The sequence coding for the leader peptide contains information for a putative signal peptide and is interrupted by a 772 bp intron as shown by comparison with a cDNA clone. A 64 bp intron and a 145 bp intron interrupt the sequence coding for the secreted pheromone. The three introns contain typical 5′ and 3′ splice junctions and a putative branch point site. The small introns have a low GC content. The large intron has a GC content similar to that of the pheromone 4 gene exons. The amino acid sequence of pheromone 4, deduced from both the genomic DNA and the cDNA of pheromone 4, shows that the secreted pheromone consists of 85 amino acids. One of its amino acids is encoded by a UGA codon. Since it has been shown for pheromone 3 of E. octocarinatus that UGA is translated as cysteine, it is assumed that the UGA codon encodes cysteine in pheromone 4 as well. The 164 bp noncoding region upstream of the leader peptide is AT‐rich and contains an inverted repeat capable of forming a stem‐loop structure with a stem of 11 bp. The 151 bp noncoding region at the 3′ end of the chromosome contains a putative polyadenylation sequence and an inverted repeat. The macro‐nuclear molecule is flanked by telomeres and carries the pentanucleotide motif TTGAA, located at a distance of 17 nucleotides from the telomeres. This motif has been suggested to be involved in the formation of macronuclear chromosomes. © 1992 Wiley‐Liss, Inc.
Ciliary polypeptides and glycoconjugates of wild‐type and mutant Tetrahymena thermophila: Starved versus nonstarved
Authors: Cheng Lee‐Ju , Hufnagel Linda A.
Published: May 2005

To investigate the role of cilia in mating interactions of Tetrahymena thermophila, ciliary membrane‐rich fractions were isolated from two wild‐type strains, a non‐discharge mucocyst mutant which possesses mating behavior similar to wild‐type, and a mating mutant which is able to costimulate cells of complementary mating type but cannot enter into pair formation. In each case, proteins from the ciliary membrane‐rich fractions of starved, mating‐competent (“initiated”) cells were compared with those from non‐starved, mating‐incompetent (“non‐initiated”) cells, by gel electro‐phoresis and lectin blotting. In stained gels, a 43 kDa polypeptide was reduced or absent in initiated cells but present in non‐initiated cells, in all strains. In silver‐stained gels, a 25 kDa polypeptide was present in all strains, both initiated and non‐initiated. In blots probed with Con A‐peroxidase, a 25 kDa glycoprotein was present in ciliary membrane fractions from non‐initiated cells and absent in membranes of initiated cells of the two wild‐type strains and the mucocyst mutant, but is present in initiated and non‐initiated cells of the mating mutant (several hypotheses are presented to explain these findings). In addition, ciliary proteins of the mating mutant included at least two unique Con A‐binding polypeptides. Our results support the idea that development of mating competence during starvation involves an extensive remodeling of ciliary membranes, and identify a 25 kDa glyco‐conjugate as having a potential role in control of pair formation during mating. © 1992 Wiley‐Liss, Inc.
Mapping the mating type locus of Tetrahymena thermophila: Meiotic linkage of mat to the ribosomal RNA gene
Authors: Bleyman Lea K. , Baum Mary P. , Bruns Peter J. , Orias Eduardo
Published: May 2005

Tetrahymena thermophila has a multiple mating type system. While a sexually mature cell usually expresses only one mating type, its germline (micronucleus) carries the genetic potential for 5 to 7 mating types. The set of allowed mating types is specified by the mat locus. The choice of which particular mating type is expressed by a cell reflects a somatically inherited, developmentally programmed differentiation of the somatic nucleus (macronucleus). In this work we report that the mat locus maps to the left arm of chromosome 2, as determined by nullisomic deletion mapping. We also report a distance of 29 cM between the mat locus and the ribosomal RNA gene, previously mapped to chromosome 2L. This represents another (rare) case of meiotic linkage in Tetrahymena. © 1992 Wiley‐Liss, Inc.
Development of sexual maturity in the ciliate Euplotes crassus: Sources of variation in the timing of maturity
Authors: Dini Fernando , Nyberg Dennis
Published: May 2005

The life styles of ciliated protists are particularly suitable for experimental analyses of certain aspects of developmental and genetic biology. The progression from sexual immaturity tomaturity to senescence represents one of the most intriguing aspects of developmental programs. The extent to which progeny clones, their subclones, and testers used in the assay result in different lengths of immaturity has been investigated in Euplotes crassus. Six subclones from each of 12 progeny clones from a cross between stocks EC1 and EC2 were tested for maturity with stocks EC3, EC4, and EC5 on every transfer. Analysis of variance was used to partition thetotal variation in fissions to maturity into parts due to clones, subclones, and testers and the interactions between these levels. The error, interaction of subclones and testers, corresponds to a standard deviation of only 4.1 fissions, while the within clone within tester means range from 15.2 to 46.7 fissions; all levels except testers contribute significantly to the total variation. Most of the variability is attributable to clones (66%), the next most to error (16%), the next most to interaction of clones by testers (13%), and the least to subclones (5%). An a posteriori analysis examined whether the differences among clones were due to the cytoplasm of the clone ancestor (exconjugant), its mat (mating‐type) locus genotype, or the mated pair it came from. None of these characteristics was able to interpret simply the large variability among clones. These results provide evidence that the transition from immaturity to maturity is quantitative and complex rather than a jump from one well‐defined state to another. © 1992 Wiley‐Liss, Inc.
Developmental expression of macronuclear specific antigen in Paramecium caudatum
Authors: Fujishima Masahiro , Inoue Yasutake , Sawada Tomoo , Fukumoto Tetsuo
Published: May 2005

We obtained a monoclonal antibody (MA‐1) specific for macronuclei of the ciliate Paramecium caudotum and P. dubosqui. Immunoblotting showed that the antigen was a poly‐peptide of 50 kilodalton (kDa). During the process of nuclear differentiation in P. caudatum, the MA‐1 antigens appeared in the macronuclear anlagen immediately after four out of eight post zygotic nuclei differentiated morphologically into the macro‐nuclear anlagen. Afterwards, the antigens could be detected in the macronucleus through the cell cycle, and disappeared when the macronucleus began to degenerate in exconjugant cells. These results suggest that the antigens may play a role in the differentiation and function of the macronucleus. © 1992 Wiley‐Liss, Inc.
Scrambled actin I gene in the micronucleus of Oxytricha nova
Authors: Prescott David M. , Greslin Arthur F.
Published: May 2005

In the hypotrichous ciliate Oxytricha nova the cloned precursor gene from the micronuclear genome that encodes actin I is composed of highly disordered blocks of deoxynucle‐otide sequences. We present and illustrate in detail a recombination model that explains how the actin I gene may be unscrambled during macronuclear development after cell mating. The model was described in a previous publication (Greslin et al.: Proc Natl Acad Sci USA 86:6264‐6268, 1989). Here we show the data, described in the earlier publication, that support the model. The data show that scrambling is not an artifact of cloning. They rule against the presence of an unscrambled copy of the actin I gene in the micronucleus, which means that unscrambling must be a part of macro‐nuclear development. Finally, the data prove that the actin I gene in O. trifallax is scrambled in a pattern that resembles the pattern in O. nova. © 1992 Wiley‐Liss, Inc.
Stable and unstable transformation by microinjection of macronucleoplasm in Paramecium
Authors: Harumoto Terue , Hiwatashi Koichi
Published: May 2005

Transformation by microinjection of macronucleoplasm in Paramecium caudatum was investigated. Macronucleoplasm with three genetic markers (behavior, trichocyst, and mating type) was injected into the macronucleus. To facilitate microinjection, in most cases, paramecia were immobilized in a gelatin (7.5%) solution. The injected cells began to express a dominant gene (cnrA+ or cnrB+) of the donor 9–24 hr after injection. Expression did not require cell division suggesting injected macronucleoplasm was capable of expressing a phenotype. The amount of injected macronucleoplasm appears to correlate with the frequency of successful expression but not to correlate with the time required for expression. After a number of fissions, the injected cells produced clones which had cells expressing the phenotype of the donor. This suggests that injected macronucleoplasm was replicated and expressed in the recipient cell lines. The transformed clones were classified into two groups. In one group, transformation was stable. All cell lines derived from the injected cells expressed a phenotype similar to the heterozygote of donor and recipient cells. In the other group, transformation was unstable. During the first five to seven fissions after injection, at each division, cells produced one daughter cell which later reverted to the recipient phenotype. After this unstable period, cells no longer produced the recipient phenotype but produced the donor phenotype exclusively. Donor and recipient phenotypes were, thus, segregated in different cell lines. Observation of genetic markers and analysis by computer simulation shed light on the mode of transmission of injected macronucleoplasm. In stable transformation, injected macronucleoplasm appears to be distributed equally to daughter cells. In unstable transformation, injected macronucleoplasm is distributed only to one of the daughter cells at every division until about the fifth to seventh fission after injection and then begins to assort equally to daughter cells. The cell cycle stage at injection may influence the mode of transformation. Interspecific microinjection of macronucleoplasm from P. multimicronucleatum and P. tetraurelia to P. caudatum. resulted in the expression of foreign genes in P. caudatum. In one case, injection of macronucleoplasm of P. tetraurelia produced a stable transformant indicating replication of foreign macronucleoplasm in P. caudatum. This work reveals the mode of transformation by injected macronucleoplasm and shows the possibility of transformation among Paramecium species, which is significant in the study of the conservation of gene products and the mechanism of gene expression in different species. © 1992 Wiley‐Liss, Inc.
Inheritance of the group I rDNA intron in Tetrahymena pigmentosa
Authors: Nielsen Henrik , Simon Ellen M. , Engberg Jan
Published: May 2005

We have previously argued from phylogenetic sequence data that the group I intron in the rRNA genes of Tetrahymena was acquired by different Tetrahymena species at different times during evolution. We have now approached the question of intron mobility experimentally by crossing intron+ and intron− strains looking for a strong polarity in the inheritance of the intron (intron homing). Based on the genetic analysis we find that the intron in T. pigmentosa is inherited as a neutral character and that intron+ and intron− alleles segregate in a Mendelian fashion with no sign of intron homing. In an analysis of vegetatively growing cells containing intron+ and intron− rDNA, initially in the same macronucleus, we similarly find no evidence of intron homing.

During the course of this work, we observed to our surprise that progeny clones from some crosses contained three types of rDNA. One possible explanation is that T. pigmentosa has two rdn loci in contrast to the single locus found in T. thermophila. Some of the progeny clones from the genetic analysis were expanded for several hundred generations, and allelic assortment of the rDNA was demonstrated by subcloning analysis. © 1992 Wiley‐Liss, Inc.
Immunocytochemical analysis of secretion mutants of Tetrahymena using a mucocyst‐specific monoclonal antibody
Authors: Turkewitz Aaron P. , Kelly Regis B.
Published: May 2005

Dense‐core granules represent an adaptation of specialized secretory cell to facilitate stimulus‐regulated release of stored proteins. Such granules are a prominent feature of mammalian neuroendocrine and exocrine cells and are also well developed in the ciliates. In Tet‐rahymena thermophila, the ability to generate mutants in dense‐core granule biosynthesis and fusion presents a versatile system for dissecting steps in regulated exocytosis. We have previously shown that defective granules in such mutants could be characterized by several biochemical criteria, including buoyant density, which increases during maturation, and the degree of proteolytic processing of the content precursors. We have now used indirect immunofluorescence, taking advantage of a monoclonal antibody directed against a granule protein, to visualize the morphology and distribution of both granules and putative granule intermediates in mutant and wild‐type cells. The results are consistent with the biochemical analysis and extend our characterization of the mutants, allowing us to distinguish four classes. In addition, the assay represents a powerful technique for diagnosis of new mutants. © 1992 Wiley‐Liss, Inc.
Genetic characterization of Tetrahymena thermophila mutants unable to secrete capsules
Authors: Gutierrez Juan Carlos , Orias Eduardo
Published: May 2005

Under appropriate conditions, Alcian Blue‐induced exocytosis of Tetrahymena mucocysts leads to formation of a capsule that surrounds the cell. This phenomenon is an example of regulated secretion, a mechanism of fundamental significance in eukaryotic cells. In order to dissect genetically the mechanism of mucocyst biogenesis and regulated exocytosis, mutants unable to form capsules (Caps–) were isolated. In this paper we report a genetic characterization of Caps– mutants in this collection. The mutations in mutants SB255 and SB281 behave as single recessive Men‐delian mutations. The mutation in SB251 is restricted to the macronucleus, and could not be further characterized by the genetic methods we used. Complementation tests suggest the existence of at least 2 genes, named exoA and exoB; additional mutant loci are likely to be included in the mutant collection. Deletion mapping using nulli‐somic strains showed that exoA and exoB are located on the left arm of chromosome 4. The exo‐3 mutation, which behaves as recessive and complements with exoA1 in SB255 and exoB2 in SB281, maps to chromosome 3. These Caps– mutants may be useful for the elucidation of the developmental pathway of mucocyst biogenesis and the control of regulated secretion in eukaryotic cells. © 1992 Wiley‐Liss, Inc.
Locus‐dependent profiles of the rescue of nonexcitable behavioral mutants during conjugation in Tetrahymena thermophila
Authors: Takahashi Mihoko
Published: May 2005

The Tetrahymena nonreversal (TNR) mutants of Tetrahymena thermophila are behavioral mutants with nonexcitable membranes. When cells of the tnrB mutant were mated with wild type, a phenotypic change occurred about l h after pair formation. The pairs began to lose their heterotypic character in stimulation solution containing high potassium and, within 1 1/2h, they were not distinguishable from the wild‐type homotypic pairs. On the contrary, although pairs of the tnrA and wild type also lost their heterotypic character about 1 1/2 h after pair formation, they never showed a full response as wild‐type homotypic pairs. When tnrA was mated with tnrB more than 50% of pairs expressed a heterotypic pair character 2 h after pair formation, consistent with the tnrB defect having been rescued but not the tnrA defect. Thus, conjugation rescue of the mutant phenotype is locus dependent and probably reflects the nature of the gene products controlling voltage‐dependent Ca2+ channels. © 1992 Wiley‐Liss, Inc.
Genes and structural patterns in ciliates: Vance tartar and the “cellular architects”
Authors: Frankel Joseph
Published: May 2005

The one form of cytoplasmic inheritance that has not been assimilated into the Central Dogma is the inheritance of surface structural patterns, a phenomenon most clearly expressed in cilates. Vance Tartar, although he worked with a genetically undomesticated organism (Stentor coeruleus), provided early evidence for the crucial role of clonally propagated features of the cell cortex. He showed that the capacity for development of cortical organelle systems is associated with a particular relational feature, the “locus of stripe contrast” (LSC), and that clonally inherited cortical variants (homopolar doublets) could be created at will by microsurgical operations that duplicated the LSC. Tartar also hoped to demonstrate the existence of what David Nanney called “cellular architects” by provoking stentors to carry out entirely novel types of morphogenetic performances. He eventually acknowledged failure, although the bizarre juxtapositions by which he attempted to elicit such novel performances did bring about specific and illuminating defects in cortical development. Subsequent analyses of similar defects in other ciliates revealed not the unitary “pattern factor” postulated by Tartar, but rather a hierarchy of distinct patterning mechanisms. Nonetheless, by pursuing an embryological approach toward morphogenesis in a highly regulative ciliate, Tartar uncovered relational aspects of pattern‐determination; this, in my view, delineates the major problem that we must solve to gain understanding of intracellular patterning. © 1992 Wiley‐Liss, Inc.
Structural deficiency of 180°‐rotated ciliary rows in Tetrahymena: Implications on the inheritance and development of a non‐genically acquired cortical trait during vegetative propagation
Authors: Lau Kin Mang , Ng Stephen F.
Published: May 2005

The present study reveals a deficiency in the number of ciliated basal bodies along 180° rotated ciliary rows (IRs) in Tetrahymena. This feature is common to IRs recently generated in young clones with stable corticotypes (total number of ciliary rows per cell), irrespective of the number of IRs present per cell or their cellular location, and is found before the cell loses any of the IRs. In cells bearing three IRs, the IRs on the two sides of the inversion immediately next to normal ciliary rows (junctures) exhibit an even greater deficiency in ciliated basal bodies, compared to the IR located internally between two other IRs; the normal ciliary rows flanking the inversion are also somewhat deficient. These observations show that the IRs of Tetrahymena are structurally deficient, hence developmentally defective, and suggest that they are intrinsically unstable. We propose that basal body development along IRs tends to be truncated before the stage of ciliation; such basal bodies would fail to acquire the potential to serve as nucleating centers for new basal body development in the next round of basal body proliferation, leading to the eventual loss of the IRs. © 1992 Wiley‐Liss, Inc.
Lithium‐Induced respecification of pattern in Paramecium
Authors: Beisson Janine , Ruiz Françoise
Published: May 2005

The long‐known teratogenic effects (dorsalisation) of lithium on amphibian embryos has recently raised renewed interest. As it is known that lithium blocks the polyphosphoinositide (PI) cycle, causing a depressed level of myo‐inositol, and as injections of myo‐inostiol have been shown to rescue the effects of Li+, it was postulated that Li+ causes a flattening of gradients of PI cycle activity underlying the developmental polarities. We have studied the effect of Li+ on the morphogenesis of the unicellular organism, Paramecium. We show (1) that exposure to 25 mM Li+ during division yields precise distorsions of the cortical pattern that can be explained by a uniformisation of surface growth i.e. partial suppression of the right/left and antero/posterior asymmetries and (2) that Li+ effects are rescued by injection of myo‐ inositol. These results suggest that spatially graded activity of the PI cycle (ensuring in turn a spatially graded distribution of secondary messengers directly involved in the morphogenetic processes) appeared early in evolution. © 1992 Wiley‐Liss, Inc.
Directed positioning of nuclei in living Paramecium tetraurelia: Use of the laser optical force trap for developmental biology
Authors: Aufderheide Karl J. , Du Qing , Fry Edward S.
Published: May 2005

We have constructed a laser optical force trap (“laser tweezers”) by coupling an Nd:YAG laser to an optical microscope with a high numerical aperture objective. The laser beam (approximately 0.1 W power) is focused to a diffraction‐limited spot at the specimen plane of the objective: the wavelength chosen (1,064 nm) is not strongly absorbed by most biological materials and is thus not ablative. Because the intensity of the laser beam increases towards the center of the focal spot, small particles brought near the spot will be attracted to the center and held there. Movement of the laser beam will tend to move any trapped particles with it. The laser tweezers can permit precise, nondestructive repositioning of small structures inside a living cell, without recourse to micromanipulators. Initial work has involved the use of laser tweezers on cells of Paramecium tet‐raurelia held by a rotocompressor. We have been able to trap and reposition small organelles, especially the highly refractile structures known as crystals. Using a trapped crystal as a “tool”, we have been able to push micronuclei and other structures for many micrometers to virtually any desired location in a cell. In spite of extended exposure of specific structures and of individual cells to the laser beam, no damage has been detectible. Exposed cells, which were removed from the rotocompres‐sor and cultured, showed complete viabilty. The laser tweezers technique shows tremendous potential for applications to the study of many fundamental cellular and developmental phenomena in paramecia and other ciliates. For example, we intend to use this technique to investigate temporal and spatial characteristics of nuclear determining regions during sexual reorganization in Paramecium. © 1992 Wiley‐Liss, Inc.
Isolation of the Lembadion‐factor, A morphogenetically active signal, that induces Euplotes cells to change from their ovoid form into a larger lateral winged morph
Authors: Kusch Jürgen , Heckmann Klaus
Published: May 2005

A morphogenetically active substance released by the predatory ciliate Lem‐badion bullinum is recognized by ciliates of the genus Euplotes, which are potential prey organisms of Lembadion. The substance (L‐factor) induces cells of the genus Euplotes to become less compact, which reduces their likelihood of becoming engulfed. Under the influence of this Lembadion‐ derived signal, E. octocarinatus develops extended wings and dorsal and ventral ridges and transforms within a few hours from its typical ovoid morph into an enlarged circular morph. This takes place without cell division. We have isolated the L‐factor and report that it is a protein with a mass of 31,500 Da. The factor has been purified to chromatographic and electrophoretic homogeneity and was found to be active at concentrations as low as 10−12 mol/L. © 1992 Wiley‐Liss, Inc.
Generation of Minute phenotypes by a transformed antisense ribosomal protein gene
Authors: Patel Rekha , Jacobs‐Lorena Marcelo
Published: May 2005

Antisense RNAs have been used for gene interference experiments in many cell types and organisms. However, relatively few experiments have been conducted with antisense genes integrated into the germ line. In Drosophila reduced ribosomal protein (r‐protein) gene function has been hypothesized to result in a Minute phenotype. In this report we examine the effects of antisense r‐protein 49 expression, a gene known to correspond to a Minute mutation An antisense rp49 gene driven by a strong and inducible promoter was transformed into the Drosophila germ line. Induction of this gene led to the development of flies with weak Minute phenotypes and to the transient arrest of oogenesis. Parameters that may affect the success of antisense gene inactivation are discussed. © 1992 Wiley‐Liss, Inc.
Broad‐Complex function during oogenesis in Drosophila melanogaster
Authors: Huang Ruea‐Yea , Orr William C.
Published: May 2005

The Broad‐Complex (BR‐C) appears to encode factors that mediate ecdysone effects during the larva‐adult transition. The main goal of this study was to gain insight into what roles the BR‐C might play during oogenesis. The main findings are as follows. First, as determined by heteroallele studies and clonal analysis, de12 is a somatic line mutation that appears to fall into the broad domain of the BR‐C. Second, the de12 mutation is associated with the insertion of the gypsy transposon at position 169.5 (Chao and Guild, Embo J, 1986, 5:143–150) in the BR‐C domain. In its new context this gypsy element exhibits ovarianspecific activation. Both this gypsy activation and the de12 phenotype are partially suppressible by su(f) and su(Hw). Third, we have identified a set of transcripts that cross‐hybridize with BR‐C sequence spanning the gypsy insertion site (166–179). There are significant differences in these cross‐hybridizing species, both in size and relative abundance, between de12 and its parent strain. Finally we have determined that in de12 there is a premature arrest of chorion gene amplification in the late stages of oogenesis. © 1992 Wiley‐Liss, Inc.
Sequential up‐regulation of thyroid hormone β receptor, ornithine transcarbamylase, and carbamyl phosphate synthetase mRNAs in the liver of Rana catesbeiana tadpoles during spontaneous and thyroid hormone‐induced metamorphosis
Authors: Helbing Caren , Gergely Gus , Atkinson Burr G.
Published: May 2005

During both spontaneous and thyroid hormone (TH)‐induced metamorphosis, the Rana catesbeiana tadpole undergoes postembryonic developmental changes in its liver which are necessary for its transition from an ammonotelic larva to a ureotelic adult. Although this transition ultimately results from marked increases in the activities and/or de novo synthesis of the urea cycle enzymes, the precise molecular means by which TH exerts this tissue‐specific response are presently unknown. Recent reports, using RNA from whole Xenopus laevis tadpole homogenates and indirect means of measuring TH receptor (TR) mRNAs, suggest a correlation between the up‐regulation of TRβ‐mRNAs and the general morphological changes occurring during amphibian metamorphosis. To assess whether or not this same relationship exists in a TH‐responsive tissue, such as liver, we isolated and characterized a cDNA clone containing the complete nucleotide sequence for a R. catesbeiana urea cycle enzyme, ornithine transcarbamylase (OTC), as well as a genomic clone containing a portion of the hormone‐binding domain of a R. catesbeiana TRβ gene. Through use of these homologous sequences and a heterologous cDNA fragment encoding rat carbamyl phosphate synthetase (CPS), we directly determined the relative levels of the TRβ, OTC, and CPS mRNAs in liver from spontaneous and TH‐induced tadpoles. Our results establish that TH affects an up‐regulation of mRNAs for its own receptor prior to up‐regulating CPS and OTC mRNAs. Moreover, results with cultured tadpole liver demonstrate that TH, in the absence of any other hormonal influence, can affect an up‐regulation of both the TRβ and OTC mRNAs. © 1992 Wiley‐Liss, Inc.
The genetic program for preimplantation development
Authors: Kidder Gerald M.
Published: May 2005

This review summarizes information on accumulation profiles of individual gene transcripts in preimplantation development. Most of the information is from the mouse, but some data from other species are reviewed as well. The principal finding is that the transcription of most genes is not temporally linked with any of the three morphogenetic transitions (compaction, cavitation, and blastocoel expansion) that characterize this period. Most genes that are expressed during pre‐implantation development of the mouse are already being transcribed in the 4‐cell stage, and some clearly begin as early as the 2‐cell stage. Once activated, a gene continues to be transcribed at least into the blastocyst stage, resulting in continuous mRNA accumulation. Thus the pattern of gene transcription established at the time of genomic activation in the 2‐cell stage is perpetuated into the blastocyst, with a few additions along the way. This information is interpreted in light of previous findings concerning the sensitivity of morphogenetic transitions to inhibition of gene expression. The lack of a clear relationship between the timing of expression of most genes and the schedule of morphogenesis leads one to conclude that temporal regulation is imposed downstream of transcription and translation. This conclusion is substantiated by a consideration of factors controlling the events of compaction. © 1992 Wiley‐Liss, Inc.
Sequence and expression of IMP‐L1, an ecdysone‐inducible gene expressed during Drosophila imaginal disc morphogenesis
Authors: Natzle Jeanette E. , Robertson Jeannette P. , Majumdar Arindam , Vesenka Gwendolyn D. , Enlow Brett , Clark Katherine E.
Published: May 2005

Drosophila imaginal discs are induced by the steroid hormone 20‐hydroxy‐ecdysone to initiate morphogenesis leading to formation of the adult appendages and thoracic epidermis at the end of the third larval instar. Ecdysone‐dependent transcriptional activation of a set of genes that encode imaginal disc transcripts found on membrane‐bound polysomes precedes and may be responsible for some aspects of the cellular changes that mediate epithelial morpho‐genesis in this system. A 1.35 kb transcript from one of these genes, IMP‐L1, is first observed in vivo at or just prior to pupariation, as ecdysone titers are peaking and beginning to decline. Expression is initiated in proximal areas of the antennal disc, later spreading to a more widespread but nonuniform distribution throughout other thoracic imaginal discs. IMP‐L1 is not, however, expressed in other ecdysone target tissues such as salivary glands or fat body. The IMP‐L1 gene encodes a novel protein product containing a signal peptide, a possible transmembrane domain, two highly charged domains and a proline rich C‐terminal domain. We suggest that the delayed timing of expression of this secondary response gene is necessary for proper ordering of cellular events associated with disc morphogenesis. © 1992 Wiley‐Liss, Inc.
Cloning and sequence comparison of the mouse, human, and chicken engrailed genes reveal potential functional domains and regulatory regions
Authors: Logan C. , Hanks M. C. , Noble‐Topham S. , Nallainathan D. , Provart N. J. , Joyner A. L.
Published: May 2005

We have isolated and characterized genomic DNA clones for the human and chicken homologues of the mouse En‐1 and En‐2 genes and determined the genomic structure and predicted protein sequences of both En genes in all three species. Comparison of these vertebrate En sequences with the Xenopus En‐2 (Hemmati‐Brivanlou et al., 1991) and invertebrate engrailed‐ like genes showed that the two previously identified highly conserved regions within the En protein [reviewed in Joyner and Hanks, 1991] can be divided into five distinct subregions, designated EH1 to EH5. Sequences 5′ and 3′ to the predicted coding regions of the vertebrate En genes were also analyzed in an attempt to identify cis‐acting DNA sequences important for the regulation of En gene expression. Considerable sequence similarity was found between the mouse and human homologues both within the putative 5′ and 3′ untranslated as well as 5′ flanking regions. Between the mouse and Xenopus En‐2 genes, shorter stretches of sequence similarity were found within the 3′ untranslated region. The 5′ untranslated regions of the mouse, chicken and Xenopus En‐2 genes, however, showed no similarly conserved stretches. In a preliminary analysis of the expression pattern of the human En genes, En‐2 protein and RNA were detected in the embryonic and adult cerebellum respectively and not in other tissues tested. These patterns are analogous to those seen in other vertebrates. Taken together these results further strengthen the suggestion that En gene function and regulation has been conserved throughout vertebrate evolution and along with the five highly conserved regions within the En protein, raise an interesting question about the presence of conserved genetic pathways. © 1992 Wiley‐Liss, Inc.
Mutations in the glutamine synthetase I (gsI) gene produce embryo‐lethal female sterility in Drosophila melanogaster
Authors: Caggese Corrado , Caizzi Ruggiero , Barsanti Paolo , Bozzetti Maria Pia
Published: May 2005

A female‐sterile mutation (fs(2) PM11‐19) was recovered in a screen for P‐M hybrid dysgenesis induced mutations uncovered by a deletion of region 21B and was identified as an allele of the gene encoding the Drosophila glutamine synthetase I (GSI) mitochondrial isozyme.

Molecular analysis has shown that fs(2)PM11‐19 contains a 5 kb insert within 500 bp upstream of the transcriptional start site of the gsI gene. Mutant flies have extremely low levels of gsl transcription and GSI activity. A pre‐existing deficiency (Df(2L) netpm1) with a breakpoint near the transcription start site was also found to be a female‐sterile allele of gsl.

All eggs laid by PM11‐19 homozygous females, as well as by females heterozygous for this mutation and a deletion or any of several recessive lethal alleles of the gsl gene, fail to hatch. We conclude that an adequate level of maternally supplied GSI activity is necessary in the early stages of Drosophila embryonic development. © 1992 Wiley‐Liss, Inc.
Use of a yeast site‐specific recombinase to generate embryonic mosaics in Drosophila
Authors: Dang Duyen T. , Perrimon Norbert
Published: May 2005

An efficient method for generating embryonic mosaics using a yeast site‐specific recombinase (FLP), under the control of a heat shock promoter, is described. FLP‐recombinase can promote mitotic exchange between homologous chromosomes that contain FRT (FLP Recombination Target) sequences. To demonstrate the efficiency of FLP‐recombinase to generate embryonic mosaics, clones of the recessive and cell autonomous mutation armadillo (arm), detected by their ability to differentiate ectopic denticles in the naked cuticle of each abdominal segment, have been induced. We have analyzed the parameters of FLP‐recombinase induced embryonic mitotic recombination and have demonstrated that clones can be efficiently induced during the postblastoderm mitotic divisions. We discuss applications of this technique for the analyses of the roles of various mutations during embryonic patterning. © 1992 Wiley‐Liss, Inc.
Characterization of REC104, a gene required for early meiotic recombination in the yeast Saccharomyces cerevisiae
Authors: Galbraith Anne M. , Malone Robert E.
Published: May 2005

The REC104 gene was initially defined by mutations that rescued the inviability of a rad52 spo13 haploid strain in meiosis. We have observed that rec104 mutant strains undergo essentially no induction of meiotic gene conversion, and we have not been able to detect any meiotic crossing over in such strains. The REC104 gene has no apparent role in mitosis, since mutations have no observable effect on growth, mitotic recombination, or DNA repair. The DNA sequence of REC104 reveals that it is a previously unknown gene with a coding region of 549‐bp, and genetic mapping has localized the gene to chromosome VIll near FUR1. Expression of the REC104 gene is induced in meiosis, and it appears that the gene is not transcribed in mitotic cells. Possible roles for the REC104 gene product in meiosis are discussed. © 1993 Wiley‐Liss, Inc.
Searching for synaptonemal complex proteins and their genes
Authors: Moens Peter B. , Spyropoulos Barbar , Dobson Melanie , Karaiskakis Angelo , Pearlman Ronald E.
Published: May 2005

As an alternative to the production and use of monoclonal antisynaptonemal complex (SC) antibodies to isolate SC genes, we have explored the use of polyclonal anti‐SC antibodies to identify SC genes from a cDNA expression library. The method proved relatively simple, reliable, and fast and has yielded two SC genes. A homologue of one of these genes from a different species has previously been isolated in another laboratory. © 1993 Wiley‐Liss, Inc.