bluuebunny/crossref_metadata_2025 huggingface dataset:
A dedifferentiation‐defective mutant of Dictyostelium that retains the capacity to aggregate in the absence of chemotaxis
Authors: Soll David R. , Mitchell Lee H. , Hedberg Christopher , Varnum Barbara
Published: May 2005

During slime mold development, cells acquire the capacity to rapidly recapitulate morphogenesis in roughly a tenth the original time. When developing cells are disaggregated and refed, they completely loss this capacity in a rapid and synchronous step referred to as the “erasure event.” The erasure event sets in motion a program of dedifferentiation during which developmentally acquired functions are lost at different times. In this report, we describe the phenotype of HI4, which is a mutant partially defective in the dedifferentiation program but normal in all aspects of growth, morphogenesis, and rapid recapitulation. HI4 cells progress through the erasure event, losing in a relatively normal fashion (I) the capacity to rapidly recapitulate later stages of morphogenesis, (2) the capacity to release a cAMP signal, and (3) the capacity to respond chemotactically to a cAMP signal. However, erased HI4 cells abnormally retain the capacity to rapidly reaggregate, even though they have lost chemotactic functions. Erased HI4 cells also abnormally retain EDTA‐resistant cohesion (contact sites A) and the surface glycoprotein gp80. It appears that erased HI4 cells rapidly reaggregate owing to random collisions followed by tight cell cohesion.
The Notch locus of Drosophila melanogaster: A molecular analysis
Authors: Artavanis‐Tsakonas Spyros , Grimwade Brian G. , Harrison Richard G. , Markopoulou Katerina , Muskavitch Marc A. T. , Schlesinger‐Bryant Ruth , Wharton Kristi , Yedvobnick Barry
Published: May 2005

Genetic analysis has suggested that neurogenesis in D melanogaster is under the control of a small number of genes. We have initiated a molecular study of the genes involved in this developmental event and started our analysis with the Notch locus, which is one of the best characterized loci in D melanogaster in terms of its genetic structure and developmental effects. In this paper we report on the molecular characterization of the Notch locus.

We describe the molecular cloning of Notch and present evidence that the entire locus is defined by approximately 40 kb of genomic DNA. The transcriptional activity of these sequences during development has been examined and the results indicate that an approximately 10.5‐kb‐long poly A+ RNA is essential for wild type Notch activity. Mapping of this RNA within the physical map of Notch indicates that it is the processed product of an approximately 40‐kb primary transcription unit spanning the entire Notch locus. More detailed analysis of the 10.5 kb RNA localizes several exons and identifies a small repetitive sequence that seems to be present in the mature Notch transcript. Structural details of a selected number of Notch locus mutations are presented and discussed. Preliminary data on the molecular structure of Notch‐homologous DNA sequences in closely related species are also presented.
The regulation and function of small heat‐shock protein synthesis
Authors: Berger Edward M.
Published: May 2005

The four small heat shock protein genes of Drosophila are tightly linked at the level of DNA, and are coordinately regulated. In cultured cell lines their expression is induced by high temprature shock and by physiological doses of ecdysterone. In vivo, small heat shock gene expression is developmentally regulated. Using recombinant DNA clones we have characterized and compared small hsp gene induction in response to the two independent stimuli.
Expression of the developmentally regulated catalase (cat) genes in maize
Authors: Scandalios J. G. , Tsaftaris A. S. , Chandlee J. M. , Skadsen R. W.
Published: May 2005

The catalase (H2O2:H2O2 oxidoreductase; E.C.1.11.1.6; CAT) gene‐enzyme system in Zea mays L (maize) represents an ideal model for studying the molecular basis of developmental gene regulation in higher eukaryotes. This system comprises a family of structural genes that are highly regulated, both temporally and spatially, during maize development.

In maize, there are four distinct forms (isozymes) of catalase that are readily discernible by convetional separation procedures. Three of the catalases have been studied in detail from a genetic and biochemical viewpoint. The catalases CAT‐1, CAT‐2, and CAT‐3 are encoded by the distinct, unlinked genes Cat1, Cat2, and Cat3, respectively. Each of the structural genes is highly regulated both spatially and temporally in its expression. Cat1 is expressed primarily in the endosperm, aleurone, pericarp, and scutellum of developing kernels, and in the root, shoot, and scutellum of very young seedlings. Cat2 is expressed primarily in the scutellum and leaf during postgerminative sporophytic development. Cat3 is expressed, for the most part, in the shoot and pericarp of young seedlings.

A number of regulatory variants have been recovered that affect the developmental program of expression of the catalases. Analysis of one variant allowed for the identification of a temporal regulatory gene (Car1) that specifically alters the developmental program of the Cat2 structural gene by acting to regulate the rate of CAT‐2 protein synthesis. Cat1 has been mapped on chromosome 1S, 37 map units (m.u.) from the Cat2 structural gene. Another variant line has been isolated which lacks expression of the Cat2 gene in its tissues at all stages of development. Isolated polysomes from this line (A16) were translated in vitro, and the products were immunoprecipitated with CAT‐2‐specific antibodies. No CAT‐2 was detectable in the A16 labeled immunoprecipitates, whereas CAT‐2 was readily detected in the normal line, W64A, under similar conditions.

The temporal and spatial expression of the Cat structural genes is not only influenced by genetic factors (as above), but is also responsive to exogenously applied environmental signals: light, hormones, and temperature. The mechanisms by which such signals specifically affect CAT‐2 expression will be discussed.
A Molecular approach to chromosome organization
Authors: Spierer Pierre
Published: May 2005

A 315 kb walk in the genetically well characterized rosy region of the Drosophila chromosomes permits a molecular analysis of chromosome organization. Polytene chromosome bands in this region range from less than 7 kb to about 160 kb and the level of DNA replication is constant within bands and among bands and interbands. A good numerical and topographical correspondence is found between chromomeric units and genetic units.
Minimal selection requirements for the correlation between heterozygosity and growth, and for the deficiency of heterozygotes, in oyster population
Authors: Zouros E. , Foltz D. W.
Published: May 2005

We examine several models that may account for the observation that in populations of marine molluscs in general, and of the American oyster (Crassostrea virginica) in particular, the growth of an individual is related to its degree of heterozygosity and, also, that the number of heterozygous individuals in the population is less than expected on the assumption of random mating and no selection. We classify these models into nonselective, selective, and mixed models. We conclude that mixed models are the most likely to apply to real populations, but cannot exclude selective models. Nonselective models appear least likely. Current evidence favors a model that assumes that heterozygotes enjoy a fitness advantage as adults, primarily because of their faster growth, and that the lower numbers of heterozygotes in the population result from some form of nonrandom fertilization. One possible source of nonrandom fertilization is variation in the time of spawning of individuals due to differences in body size.
Natural selection for the control of alcohol dehydrogenase activity in populations of Drosophila melanogaster
Authors: Birley A. J.
Published: May 2005

The control of alcohol dehydrogenase (ADH) activity in natural populations of Drosophila melanogaster is chromosomally diverse and due to variation in allotype, enzyme level, and possibly post‐translational modification. A comparative study of evolution in Adh structural gene variations with those loci modifying ADH expression has been carried out in large model populations maintained in environments that varied in temperature and food. Broadly based measures of gene expression were obtained as ADH activity and ADH protein level (determined immunologically) from individual flies whose allotype was also determined. The response to selection by “regulatory” or modifier loci compared with ADH allotypes was found to vary with environment, and its direction was not necessarily predictable from the kinetic properties of allele products. Selection for dominance modification of ADH activity in relation to Adh allotype was also observed. Analysis of genotype‐environment interaction discerned two main types of response. Two major classes of chromosomal types, identified from restriction endonuclease map variations in a 12‐kb region of DNA containing the Adh transcriptional unit, were present in the population. These two types of chromosome were in turn associated with the two types of interaction between genotypes and the environment. The results implicate polylmorphism for the control of genotypeenvironment interaction in populations, a genetically complex unit of selection, and a degree of evolutionary independence between structural and regulatory genes.
Spatial variation of biochemical and ecological phenotypes in Drosophila: Electrophoretic and quantitative variation
Authors: Hoffmann A. A. , Nielsen K. M. , Parsons P. A.
Published: May 2005

Electrophoretic variation at three enzyme loci‐alcohol dehydrogenase (Adh), glycerophosphate dehydrogenase (Gpdh), triosephosphate isomerase (Tpi)‐ is compared in Australian Drosophila melanogaster populations at three levels of spatial heterogeneity; among breeding sites, within populations, and between populations at the geographic level. Heterogeneity at the breeding site level greatly exceeds that among adults within populations, indicating greater intermixing at the mobile adult stage than at the developmentally immature and less migratory larval stage. Heterogeneity at the microspatial level is large relative to the geographic level at two of these loci.

Spatial patterns of variation in ecological phenotypes are also considered. It is argued that electrophoretic variants may contribute little to an understanding of this quantitative variation, and that a more useful approach in ecological genetics is to consider ecological phenotypes as primary data.
Gene expression during gonadal differentiation in the rat: A two‐dimensional gel electrophoresis investigation
Authors: Müller Ulrich , Schindler Hubert , Schempp Werner , Schott Klaus , Neuhoff Volker
Published: May 2005

Gonadal protein patterns were studied during development in the rat by two‐dimensional micro‐gel electrophoresis. Specific proteins were detected in both the male and the female sex at the morphologically indifferent state (two female‐ and one male‐specific) and during differentiation. At the onset of gonadal differentiation (day 14) two additional sex‐specific proteins were discovered in the male and two in the female. These proteins remained expressed during further development. One testicular protein was restricted to the cytosol of the tunica albuginea. The other one was absent from the tunica. In the female gonad, the two proteins were membrane‐specific, one present in germ cells, the other in somatic cells. In the testis, one additional protein was discovered at postnatal day 1. Thus according to biochemical criteria there is no indifferent state of gonadal development. The testis and ovary express sex‐specific genes both before and after the onset of gonadal differentiation.
Karyonidal inheritance of mating types in tetrahymena malaccensis
Authors: Simon Ellen M. , Nanney David L.
Published: May 2005

Mating type determination in Tetrahymena malaccensis is karyonidal, ie, the four new macronuclei developing in a single conjugating pair are independently determined as to which of the six known mating types they will express. Occasional selfing clones are similar to those in T thermophila, in that any one is capable of stabilizing at a restricted range of mating types. The genetic basis of mating type potentialities is incompletely resolved. T malaccensis may, like T thermophila and T canadensis, have a single multiallelic locus that controls the array of types. Quantitative considerations suggest, however, that other loci may be involved.
Allelic differences in initial expression of paternal alleles at an isocitrate dehydrogenase locus in rainbow trout (Salmo gairdneri)
Authors: Danzmann Roy G. , Ferguson Moira M. , Allendorf Fred W.
Published: May 2005

We examined a temporal series of embryos from 14 full‐sib families of rainbow trout with starch gel electrophoresis to determine the time of initial detection of enzyme produced by ldh‐3. Maternal enzyme was detected in unfertilized eggs, whereas paternal alleles showed evidence of initial expression after gastrulation and epiboly. Two alleles, 40 and 71, were expressed synchronously several days before the 114 allele. Measurement of enzyme activity by spectrophotometric analysis and serial dilution supported these observations. The degree of delay of expression of the 114 allele between families was coupled with other estimates of developmental rate. These data suggest the existence of allelic variation at a cis‐acting genetic element controlling the pattern of ontogenetic expression of structural alleles at Idh‐3.
Avian developmental antigens: Expression on erythrocytes of chickens, Japanese quail, and quail‐chicken hybrids
Authors: Hartwell D. P. , Dietert R. R. , Sanders B. G.
Published: May 2005

Monoclonal and polyclonal antibodies were used to examine the expression of three erythroid developmental antigen systems in the chicken, Japanese quail, and quail‐chicken hybrid. Chicken fetal antigen (CFA), quail fetal antigen (QFA), and chicken adult antigen (CAA) each represent a series of cell‐surface glycorproteins associated with the development of avian hematopoietic cells. Monoclonal anti‐CFA antibodies from clones 190‐4 and 288‐1.1.1.2 supernatants were shown to react against epitopes associated with CFA determinants 8 and 2, respectively. Using complement‐mediated microcytotoxicity, these reagents permitted the identification of different erythroid subpopulations in the neonatal chicken and hybrid; therefore, heterogeneity in cell surface CFA determinants among mature peripheral erythrocytes should serve as a useful tool for analyzing erythroid development. In the case of CAA, erythrocytes from adult hybrids were found to express the same complement of CAA determinants identified in the chicken, and CAA appeared much earlier in the hybrid than in either of the parental species. Similarly, two species‐restricted fetal antigens associated with similar glycoproteins, CFA8 and QFA, had similar developmental profiles in their respective species, the chicken and quail. In contrast, these antigens were dominantly expressed but exhibited different developmental profiles on erythrocytes from the hybrids. While quail‐chicken hybrids exhibited apparent genomic interactions in the expression of these developmental antigens, no evidence for the existence of hybrid‐specific fetal antigens was obtained.
Mating type differentiation in tetrahymena thermophila: Characterization of the delayed refeeding effect and its implications concerning intranuclear coordination
Authors: Orias Eduardo , Baum Mary P.
Published: May 2005

Mating type determination in Tetrahymena thermophila involves developmentally programmed, heritable alterations of the macronucleus, localized to the mtd locus. This determination can be predictably controlled by the environmental conditions during macronuclear development, eg, temperature and time of refeeding. In this article we have further characterized the effects of delayed refeeding on mating type determination, as revealed by the frequency of mating types among the progeny of a cross. Our results show that 1) the magnitude of this starvation effect decreases with temperature of conjugation and becomes undetectable at 18°C; 2) starvation during the interval 14 to 22 hr (after conjugation is induced at 30°C) is a necessary and sufficient condition for the induction of starvation effects; 3) relative mating type frequencies vary monotonically with nutrient concentration present during this critical period; and 4) sister macronuclei, developing under starvation conditions in the same cytoplasm, differentiate majority mating types characteristic of early or late refeeding; sister macronuclei show no apparent correlation with each other. On the basis of our observations on early and late refed cells, we propose that the composition of the newly developed macronucleus is the outcome of two key events: 1) mating type determination at the mtd locus and 2) differential molecular cloning of generally one or two autonomously replicating fragments (ARFs) of the macronuclear DNA bearing the mtd locus.
Rearrangement of the 5S ribosomal RNA gene clusters during the development and replication of the macronucleus in Tetrahymena thermophila
Authors: Allen Sally Lyman , Ervin Paul R. , White Theodore C. , McLaren Ning C.
Published: May 2005

The organization of the 5S rRNA genes in the MACronuclear genome of Tetrahymena thermophila was examined during MAC development and replication. The 5S genes are arranged in several tandem arrays of alternating transcribed and spacer sequences in both MICronucleus and MAC. The number of EcoRI fragments bearing 5S gene clusters is similar in MIC and MAC. Most fragments occur in both the MIC and newly formed MAC genomes, a few being MIC‐limited and a few MAC‐limited. The same rearrangements are seen in the MACs of all four caryonides of a mating pair, and most rearrangements are seen in the newly formed MACs of different inbred strains. During replication of the MAC about half the fragments bearing 5S gene clusters disappear in different cell lines, and new fragments containing 5S genes appear. These fragments differ in size from those present in the MIC or newly formed MAC. These alterations occur in the MACs of all strains except strain B, which is more resistant to vegetative rearrangement. The losses and gains of fragments occur during clonal propagation of cell lines. The process begins by 35 fissions following conjugation, but once an alteration occurs, it is stably propagated. Clonal variation occurs with respect to which losses and gains occur, although a nonrandom distribution is seen among cell clones. We conclude that the alterations in MAC fragment size occur at two stages in the life cycle of Tetrahymena. The first stage occurs during conjugation, when the MAC develops from the MIC. The second stage becomes manifest during vegetative growth, when DNA replication occurs in the MAC and daughter molecules are distributed “amitotically” to daughter nuclei. The two‐stage character to MAC alterations for the 5S genes is interpreted in terms of the two steps previously described for MAC differentiation: determination and phenotypic assortment. Possible molecular mechanisms are also discussed.
Bromodeoxyuridine inhibits the rDNA compensatory response of Drosophila melanogaster
Authors: Krider H. M. , Levine B. I.
Published: May 2005

The compensatory response is a regulatory event influencing the redundancy of the ribosomal RNA cistrons (rDNAs) of Drosophila melanogaster. In this report we attempt to demonstrate that the compensatory event and the thymidine analogue bromodeoxyuridine (BrdU) specifically interact. We conclude that the drug inhibits the compensatory response of Drosophila melanogaster XO males and argue that the compensatory event is not the passive consequence of replicational dominance known to occur in Drosophila polytene tissues.
Patterns of protein synthesis in the chick blastula: A comparison of the component areas of the epiblast and the primary hypoblast
Authors: Zagris Nikolas , Matthopoulos Demetrios
Published: May 2005

The patterns of protein synthesis are examined in the hypoblast and in the areas that comprise the epiblast, that is, the area opaca, the marginal zone, and the central area, during the blastula stage which marks the beginning of the interaction between the epiblast and hypoblast for induction of the primitive streak. The results demonstrate that there are distinct qualitative and quantitative differences in protein patterns in individual areas of blastoderm, the differences being most distinct between the hypoblast and any of the component areas of the epiblast. These differences in patterns of proteins suggest that the component areas of the chick blastula have already diverged to different developmental fates before any apparent morphogenetic differentiation, that is, the appearance of the primitive streak.
Stage‐specific regulation of actin genes in Drosophila wing cells
Authors: Petersen Nancy S. , Bond Beverly J. , Mitchell Herschel K. , Davidson Norman
Published: May 2005

Extreme and rapid changes in the synthesis of messenger RNAs and proteins accompany differentiation in wing tissues of Drosophila. Of the six actin genes, at least three are expressed in wing cells, some during the most extreme changes in cell shape. However, different messages of the set appear, decay, and reappear on a regulated temporal program. These results show that actin expression is stage‐specific in a single cell type.
Spatial relationships between the anterior centriole and the mitotic center during interphase in the amoebae of the myxomycete Physarum polycephalum
Authors: Wright M. , Mir L. , Moisand A.
Published: May 2005

Amoebae of the Myxomycete Physarum polycephalum in the interphase state typically contain only one proflagellar apparatus in which the anterior kinetosome (anterior centriole) is attached to the microtubule organizing center 1 (mtoc 1). We built strains possessing more than one mtoc 1 and a variable number of anterior centrioles to allow the appearance of new structures. In 8% of the amoebae of these strains, the 1:1 attachment between the anterior centriole and the mtoc 1 is not always respected. In nine cases studied using tridimensional reconstructions from ultrastructural thin sections, the pattern of attachment was more complex. A mtoc 1 could be linked to several anterior centrioles, and/or reciprocally an anterior centriole could be linked to several mtoc 1. In one case, an anterior centriole was not linked to a mtoc 1 and in three cases, a single centriole exhibited anterior and posterior characteristics. These observations suggest that (1) each pair of centrioles constitutes a morphological and physiological entity that is distinct from the mitotic center (mtoc 1); (2) the attachment of the anterior centriole to the mtoc 1 occurs at the end of each mitosis; (3) there is an inductory process during the morphogenesis of the link between the anterior centriole and the mtoc 1; (4) the anterior characteristics of a centriole can be present in the absence of the link with the mtoc 1; (5) the anterior and posterior characteristics of a centriole are not exclusive of each other, ruling out the existence of a lineage corresponding to the anterior centriole and a lineage corresponding to the posterior centriole; and (6) the differences between anterior and posterior centrioles result from a maturation process.
Effects of high‐temperature treatments on development, viability, and heat‐shock response in a temperature‐sensitive cell‐lethal mutant of Drosophila melanogaster
Authors: Cladera Jorge L. , Bryant Peter J.
Published: May 2005

Pulses of various durations at temperatures between 29 and 38°C were applied to developing larvae of Drosophila melanogaster carrying the temperature‐sensitive cell‐lethal mutation 1 (1)ts726. The results show that it is not possible to reduce the time required for the induction of abnormalities in the mutant by treating larvae with heat pulses at temperatures higher than 29°C. Instead, treatment with high temperature leads to fewer abnormalities than 29°C treatments. Furthermore with high temperature treatments, the mutation has less effect on viability than is seen at 29°C. It is suggested that 1 (1)ts726 leads to abnormalities and death by a temperature‐induced imbalance between different physiological or development events, rather than by interfering with the ability of the cell or the organism to withstand high temperature in general.
Gene dosage compensation in trisomies of Drosophila melanogaster
Authors: Devlin Robert H. , Grigliatti Thomas A. , Holm David G.
Published: May 2005

Production of trisomic‐3L Drosophila melanogaster has allowed further investigation of compensated levels of gene expression in autosomal trisomies. We find that four enzyme loci on this arm produce diploid levels of gene product in trisomic‐3L larvae. For one of these genes, we show that all three alleles are expressed at similar levels. Two genes on 3L display dose‐dependent levels of gene product, and their location, relative to the four compensating loci, indicates that these two classes of genes are not regionally separated. In trisomic‐2R larvae, the level of enzyme produced from on 2R‐linked gene was dose dependent. In contrast, measurements of five loci on the X chromosome in metafemales (X trisomies) suggest that most genes are compensated in these individuals. Heat‐shock gene expression in trisomic‐3L salivary glands was qualitatively similar to diploids. The quantities of the small hsps (from the 67B cluster on 3L) suggest that these four genes respond independently to the trisomic condition; two produce compensated levels of protein, whereas the other two produce dose‐dependent levels of protein. The amount of hsp 83 produced in trisomies was similar to diploids (compensated). However, quantification of hsp 83 RNA showed that a dose‐dependent level of transcript was produced. This implies that hsp 83 compensation is controlled post‐transcriptionally.
Coh A, a mutation affecting the post aggregative related (par) cohesive system of Dictyostelium discoideum
Authors: Chadwick C. M. , Collodi P. R. , Kasbekar D. P. , Katz E. R. , Sussman M.
Published: May 2005

Three stage‐specific cohesive systems operate in D. discoideum: VEG, elaborated by vegetative cells: AR, by aggregation competent cells; and PAR, by post aggregation stage cells. Previous study of a mutant strain JC‐5 had shown the stability of its PAR system (but not the AR) to be temperature sensitive. However, the phenotypic expression of this mutation termed Coh A is complicated by the presence in that strain of a preexisting mutant gene Rde A, which accelerates developmental events generally and alters the pattern of morphogenesis. Genetic evidence presented here indicates that the two mutations have been separated by parasexual recombination yielding a Coh A, Rde A+ segregant class of which strain JC‐36 is a prototype.

At the permissive temperature, JC‐36 follows a morphogenetic sequence like that of the wild type in respect to timing, morphogenetic pattern, and spore appearance. At the restrictive temperature, it forms normal aggregates at the usual time but exhibits two morphogenetic aberrancies during post aggregative development. First, fruit construction is arrested at a stage approximating the 16 hr “Bottle” stage of the wild type, though more squat and blunt tipped, and then the aggregate regresses. Cytodifferentiation into spores and stalk cells is also blocked. Second, a shift of slugs migrating normally at the permissive temperature to the restrictive causes the latter to disintegrate progressively as they leave clumps of cells behind them within the flattened sheath.

JC‐36 cells developing at the restrictive temperature also exhibited a decrease in EDTA resistant cohesivity attributable on two grounds to the sensitivity of the PAR system. In addition, the disappearance of the AR system completed in the wild type by the Mexicanhat (18–19 hr) stage is indefinitely arrested at an intermediate level in JC‐36.
The recessive phenotype of forked can be uncovered by heat shock in Drosophila
Authors: Mitchell Herschel K. , Petersen Nancy S.
Published: May 2005

Heat shock uncovers the recessive forked phenotype when heterozygotes between f36a and wild‐type are heated during sensitive periods in pupal development. We call the phenocopy of a mutant in such a heterozygote a heterocopy. The heterocopy in f36a/+ is virtually identical to the mutant phenotype; however, bristles on different parts of the body are affected during different sensitive periods. We discuss the hypothesis that the heat shock acts by affecting expression of the wild‐type gene product corresponding to the mutant gene. The sensitive period for heterocopy induction in a specific tissue is proposed to correspond to the normal time of gene expression for the forked gene product in a particular tissue.
Rapid amplification and fixation of new restriction sites in the ribosomal dna repeats in the derivatives of a cross between maize and Tripsacum dactyloides
Authors: Lin Liang‐Shiou , Ho Tuan‐Hua David , Harlan J. R.
Published: May 2005

Some of the derivatives of a cross of maize (Zea mays L.) × Tripsacum dactyloides (L) L (2n = 72) have abnormal development leading to strange and striking morphologies. The Tripsacum chromosomes in these “tripsacoid” maize plants (with Tripsacum‐like characteristics) were eliminated and the maize chromosomes were recovered through repeated backcrossing to maize. As an initial attempt to analyze the DNA alterations in tripsacoid maize, we have detected a few restriction site changes in the ribosomal DNA repeat of these plants (Hpa II, Bal I, Sst I, Mbo II, and Sph I) and a new Sph I site was mapped to the spacer region between the 26S and 17S genes. Several possible mechanisms for the generation of a new restriction site are discussed, and we propose that the transient presence of Tripsacum genome during the backcrossing in some way induced a rapid amplification and fixation of new restriction sites in a relatively short period of time.
Macronuclear persistence of sequences normally eliminated during development in Tetrahymena thermophila
Authors: White Theodore C. , Allen Sally Lyman
Published: May 2005

During conjugation in the ciliated protozoan, Tetrahymena thermophila, a somatic MAC‐ronucleus develops from the germinal MICronucleus. Ten to 20 percent of the MIC genome is eliminated during this process. Three repetitive families have been identified which have different levels of repetition in the MIC and are eliminated to different degrees in the MAC. Some members of two of these families persist in the MAC. In this study, we have looked at these persistent sequences in the MAC of cell lines from a variety of sources including several inbed strains, two sets of caryonides, caryonidal subclones, and vegetatively aged cell clones. The results suggest that the sequences that remain in the MAC have a genetic predisposition to persist. However, epigenetic variations occur as the MAC develops so that only some of the persistent sequences are actually observed in a particular MAC. Polymorphisms may be generated if alternative processing of a single MIC segment occurs. These polymorphisms can later be resolved by phenotypic assortment during vegetative growth. These facultatively persistent sequences appear to differ from sequences previously described in this organism.
Spatial and temporal relationships between cell death and tissue overgrowth in imaginal wing disks of the Drosophila mutant I(3)C43hs1
Authors: Sedlak Bonnie Joy
Published: May 2005

The temperature‐sensitive mutant l(3)c43hs1 is lethal at the restrictive temperature late in the last larval instar and has wing disks that show excessive growth when larvae are reared at 25°C. Such mutant disks give rise to defective wings showing duplications and deficiencies. Abnormal folding patterns are localized to the region between the wing pouch and the area where adepithelial cells are found; the disks retain an epithelial morphology. Apoptotic cell death is distributed throughout the wing disks without any obvious concentration of dead cells in a specific area. Cell death is seen as early as 12 hr after a shift to the restrictive temperature. Temperature shift experiments also show that cell death precedes the onset of overgrowth, but since the spatial distribution of death is not localized to the regions of abnormal folds, it is unlikely that cell death and overgrowth are causally related.
How the mirror‐image pattern specified by a janus mutation of Tetrahymena thermophila comes to expression
Authors: Frankel Joseph , Nelsen E. Marlo
Published: May 2005

The initial changes of cell‐surface organization that occurred as the recessive janAl (janus) mutation of Tetrahymena thermophila first became expressed were elucidated in a special mating scheme in which old macronuclei homozygous for janA+ were synchronously replaced by new macronuclei homozygous for janAl. During this period of onset of expression, the number, regularity, and asymmetry of the ciliary rows remained unchanged. New normal (primary) oral apparatuses (OAs) continued to be formed posterior to old OAs, as in normal cells. At about four fissions after conjugation, abnormal (secondary) OAs with a partial reversal of asymmetry began to appear nearly opposite to the primary OAs, close to but not at the eventual circumferential position of janAl secondary OAs. The array of contractile vacuole pores (CVPs), normally located adjacent to two ciliary rows centered near 22% of the cell circumference to the righ of the primary oral meridian, underwent a two‐step transformation: first, the number of adjacent ciliary rows bearing CVPs increased to 3, 4, and sometimes 5, then “skipped” rows appeared within this broadened CVP‐arc to split the single set of CVPs into two separated subsets. The CVP transformations occurred gradually and progressively. They began prior to the expression of secondary OAs but accelerated as secondary OAs appeared. As the CVP are became broader, its midpoint shifted somewhat to the right, away from the primary oral meridian, but ended up close to halfway between the primary and secondary oral meridians. The data provide a better fit to an intercalation model than to an alternative double gradient model, suggesting that the janAl mutation alters the large‐scale organization of positional values by preventing the expression of a subset of these values and thus provoking reverse‐intercalation of the remainder.
Analysis of the Drosophila female sterile mutation fs(1) 1304 by pole cell transplantation experiments
Authors: Lamnissou Klea M. , Gelti‐Douka Helen
Published: May 2005

The Drosophila melanogaster mutant fs(1)1304 is an ovary autonomous female sterile mutant that causes abnormal morphology of the egg. Vitellogenesis proceeds at an abnormally slow rate in homozygous females. We have used pole cell transplantation to construct germ line mosaics in order to determine whether the 1304 defect depends upon the genotype of the germ line cells (oocyte or nurse cells) or the somatic line (follicle cells). We have found that the germ line is the primary target tissue where the mutant gene is expressed.
Phenogenetics of triploid intersexes in Drosophila melanogaster
Authors: Mann Rebecca , Hake Lisa , Lucchesi John C.
Published: May 2005

Triploid intersexes homozygous for a mutant (msl‐2) known to impede the hyperactivation of the X chromosome in diploid males differentiate into adults, sexually indistinguishable from their heterozygous sibs. A shift toward female sexual differentiation mediated by manipulating the rearing temperature is accompanied by an apparent increase in the level of an X‐linked gene product. This unexpected result is rationalized in terms of differential lethality of individuals at the two extremities of the distribution of X‐activity levels in intersexes raised at a particular temperature. No evidence of a mosaicism comparable to the sexual mosaicism exhibited could be found with respect to an X‐linked gene product in triploid intersexes.
Wing reduction and cell death in Drosophila hydei: Analysis of the mutants Notch and Costal‐nick
Authors: Langhout Bart W. Van Zijll , Van Breugel Frans M. A.
Published: May 2005

Cell death and its effect on wing size have been described in some wing mutants of Drosophila hydei. Dead cells in the imaginal discs were localized by Nile‐bule and acridine‐orange staining. Various Notch (N) alleles, the mutation Costal‐nick (Cnk) and the compound N/Cnk show characteristic patterns of cell death in the imaginal wing disc. Some but not all of the structural features of the adult wing can be related to the site of cell death during larval stages. In NAx types, extensive cell death is followed by regenerative growth, invalidating a simple relation between size of the disk and size of the wing. In Nts/Cnk cell death and wing morphology depend on the breeding temperature. From temperature experiments we conclude that cell death starts between day 4 and 5 after egg laying and can be induced by a shift to the restrictive temperature during the critical phase. Patterns of wing incisions and cell death in Nts/Cnk genotypes seem not to be delimited by any of the known compartment boundaries.
Developmental changes in the sensitivity of Volvox to ultraviolet light
Authors: Baran George J. , Huskey Robert J.
Published: May 2005

The response of Volvox to ultraviolet irradiation was analyzed. Young individuals isolated from a synchronous culture were exposed to UV light (120 J/m2) and subjected to variable lenght periods of dark following irradiation. The major effect of the UV treatment was the inability of the gonidia present in the colonies at the time of irradiation to continue and complete the developmental program. Individuals show a heightened sensitivity to UV for a limited period immediately following inversion and are insensitive at other stages of development. The cytotoxic effect of UV during this interval is completely reversed by the immediate exposure to white light and is increased with longer periods of dark treatment prior to exposure to white light. The temporal profile of the sensitivity defines a smooth curve in which the maximal sensitivity occurs three hours after inversion. The response to higher doses of UV (up to 500 J/m2) is a nonlinear increase in cytotoxicity and is disproportionanately greater in those individuals just prior to the period of maximal sensitivity than those later in development. The results suggest that Volvox has at least two pathways for the repair of UV damage and that one of these, the principal dark repair pathway, is temporarily deficient in the gonidia of young individuals.
Germ line and somatic instability of a white mutation in Drosophila mauritiana due to a transposable genetic element
Authors: Haymer David S. , Marsh J. Lawrence
Published: May 2005

A spontaneous white mutation recovered in Drosophila mauritiana is unstable and reverts to normal eye color at a frequency greater than 4 per 1,000 ×‐chromosomes. Germ line reversion occurs at a high rate in D. mauritiana males and in interspecific hybrid females, while the rate is depressed in D. mauritiana females. These events are not restricted to the germ line, as cases of variegated patterns of eye pigmentation, indicating somatic reversion, are recovered at a frequency comparable to that of the male germ line reversion rate. Germ line reversion events are genetically stable, while the somatic variegation patterns are not heritable. The patterns of eye pigment variegation produced suggests that reversion events are occurring throughout development. Whole genome DNA digests blotted and probed with the cloned D. melanogaster white gene indicate that this unstable white mutation in D. mauritiana is associated with an insertion of DNA that is lost upon reversion to wild type, indicating that this DNA insert is in fact a transposable element.
Complementation between alleles at the ovarian tumor locus of Drosophila melanogaster
Authors: King Robert C. , Mohler Dawson , Riley Shawn F. , Storto Patrick D. , Nicolazzo Peter S.
Published: May 2005

The (ovarian tumor) otu gene resides at 23.2 on the genetic map of the X chromosome and near 7F1 on the cytological map. This germ line‐expressed locus behaves as if it encodes a gene product which is required during certain steps in the transformation of oogonia into functional oocytes. On the basis of their ovarian morphologies 17 ethyl methane sulfonate (EMS)‐induced mutants have been distributed among three developmental classes as follows: quiescent (eight), oncogenic (four), and differentiated (five). The otu13 and otu14 alleles interact to yield fertile females, and many other heteroallelic combinations show partial complementation. Since many mutant alleles interact beneficially, the functional product of the otu gene may be a multimer. We conclude, from an analysis of heteroallelic interactions and dosage effects, that the abnormal phenotypes observed are graded consequences of reduced levels of functional gene product and that the minimum concentration required for development increases as oogenesis proceeds.
Developmental profiles of three embryo‐lethal maize mutants lacking leaf primordia: ptd*‐1130, cp*‐1418, and bno*‐747B
Authors: Sheridan William F. , Thorstenson Yvonne R.
Published: May 2005

The defective kernel (dek) mutants of maize are altered in both their embryo and endosperm development. Earlier studies have indicated that some of the dek mutants are unable to form shoot apical meristems or leaf primoirda. We have examined three embryo lethal dek mutants of this type, ptd*‐1130, cp*‐1418, and bno*‐747B, to obtain a developmental profile for each. Allelism tests show that these three mutants are not allelic. Embryos were examined in early, mid‐, and late kernel development as well as at kernel maturity by dissection and sectioning procedures and also at kernel maturity by scanning electron microscopy. All three mutants lag behind normal embryos in their rate of development. Embryos of ptd*‐1130 reached the transition stage by early kernel development and progressed no further but underwent cell enlargement and necrosis during late kernel development. Embryos of cp*‐1418 reached an early coleoptilar stage by midkernel development. They subsequently increased in size but did not form any leaf primordia. At kernel maturity, they no longer had a shoot apical meristem but often had a well formed root meristem. They appeared to remain healthy and did not become necrotic. Embryos of bno*747B reached the early coleoptilar stage by early kernel development but progressed no further. By kernel maturity, they had grown into masses of irregularly shaped embryonic tissue that no longer resembled any normal embryo stage but were not necrotic. None of these three mutants responded to attempts to support continued embryo development when cultured, but all three mutants formed callus on N6 and MS media supplemented with 2,4‐D. These results indicate that these mutants are all uniformly blocked at specific stages early in embryonic development, have different subsequent developmental fates, and represent three different genes performing unique functions that are essential for embryogenesis.
A comparison of genome modifications leading to genetic and epigenetic tumorous transformation in Nicotiana spp. tissue cultures
Authors: Durante Mauro , Geri Chiara , Buiatti Marcello , Ciomei Marina , Cecchini Edi , Martini Guido , Parenti Roberto , Giorgi Livio
Published: May 2005

A single system is presented, where both genetic and epigenetic control of tumor induction can be studied at the same time. This system is offered by the amphidiploid tumorous hybrid Nicotiana glauca × N. langsdorffii, a nontumorous mutant of it and the nontumorous parent species N. glauca and N. langsdorffii. The aim of the present paper is to compare long‐term in vitro cultures of tumorous (genetic and habituated), and nontumorous strains, through the characterization of their genomes according to several physico‐chemical parameters. The data reported show that both qualitative and quantitative differences in DNA complexity are correlated with the tumorous transformation. Particularly, a high degree of mismatching between the DNAs of the tumorous and nontumorous hybrids and the lack, in the second genotype (nontumorous), of three DNA peaks in Ag+−Cs2SO4 analytical ultracentrifugation profile seem to support the hypothesis, suggested in a previous paper, of the presence, in the nontumorous mutant, of a gross chromosomal rearrangement, probably a deletion. Amplification and underreplication of specific sequences also seemed to be correlated with changes from the normal to the tumorous state, highly repetitive sequences being present in higher amounts in the normal strains and in the habituated N. glauca than in the case of the tumorous hybrid.

Finally, DNA bound ion contents were found to be strikingly higher in tumorous than in nontumorous tissues. The results are discussed in the frame of the general hypothesis of high somatic genomic plasticity in plants.
Decreased methylation of the major mouse long interspersed repeated DNA during aging and in myeloma cells
Authors: Mays‐Hoopes Laura , Chao Wei , Butcher Henry C. , Huang Ru Chin C.
Published: May 2005

Sequences of DNA that hybridize on Southern blots with cloned EcoR1 1.3 kb (ER1) of long interspersed repeated sequence (L1Md) of mouse have been examined in genomic DNA of neonatal mice, livers and brains of adult mice (3, 10, 27, and 30 mo old), and the solid myeloma tumor MOPC‐315. The isoschizomers Hpa II (CCGG or mCCGG) and Msp I (CCGG or CmCGG) were used to assess methylation. We found that the L1Md sequence is fully methylated in young animals but demethylated in myeloma. Demethylation of L1Md sequence also occurred in aged animals. By scanning the autoradiogram, we found that approximately 8% of the 104–105 copies have been demethylated in 27‐mo‐old liver.
Epididymides of sex‐reversed XX mice lack the initial segment
Authors: LeBarr Deborah K. , Blecher Stan R.
Published: May 2005

The genetic factor Sxr causes sex reversal of chromosomally female (XX or XO) mice to phenotypic maleness by inducing development of testes that produce androgens. It has been considered that these sex‐reversed animals, called pseudomales, confirm the principle originally developed by Jost that adequate androgenization produces normal phenotypic maleness in mammals, irrespective of chromosomal sex. However, wepreviously discovered that the epididymis of sex‐reversed XX mice (pseudomales of genotype XXSxr) lacks EH 9 cells (epididymal head, cell type No. 9, the principal cell' of the initial segment). The purpose of the present study was to determine whether cell type EH 9 of XXSxr pseudomales is replaced by a principal cell of a different appearance, or whether the initial segment itself is actually absent. We made serial sections of entire epididymal heads and did microdissections to unravel the highly coiled epididymal duct. Using these two approaches, we studied the sequence of epididymal segments, and estimated lengths of the relevant portion of the epididymal duct; we found that the initial segment of XXSxr pseudomales is truly absent. This is the first report of a mutant genotype causing absence of a segment of the epididymis. The XXSxr mutant appears to be an exception to Jost's principle. This finding shows that, even in full androgenization, male phenotype may not always be independent of chromosomal sex.
Intron‐delay and the precision of expression of homoeotic gene products in Drosophila
Authors: Gubb D.
Published: May 2005

It is suggested that the time taken in transcribing the large introns within homoeotic transcription units will reduce the quantity of mature transcript synthesised per nuclear division cycle. This could provide an additional level of control that would affect the ratios of fate‐determining gene products to each other. Determination of regional fate depends on both the large domains of homoeotic genes and the small, serially repeated domains of segmentation genes. As a consequence, each row of cells along the anteroposterior axis of the embryo could be assigned a precise, and unique, fate. This precision is apparently not dependent on cell lineage discontinuities.