bluuebunny/crossref_metadata_2025_split huggingface dataset:
A large cluster of highly expressed genes is dispensable for growth and development in Aspergillus nidulans.
Authors: Aramayo R , Adams T H , Timberlake W E 
Published: January 2021

Abstract
We investigated the functions of the highly expressed, sporulation-specific SpoC1 genes of Aspergillus nidulans by deleting the entire 38-kb SpoC1 gene cluster. The resultant mutant strain did not differ from the wild type in (1) growth rate, (2) morphology of specialized reproductive structures formed during completion of the asexual or sexual life cycles, (3) sporulation efficiency, (4) spore viability or (5) spore resistance to environmental stress. Thus, deletion of the SpoC1 gene cluster, representing 0.15% of the A. nidulans genome, had no readily detectable phenotypic effects. Implications of this result are discussed in the context of major alterations in gene expression that occur during A. nidulans development.
Characterization of the amdR-controlled lamA and lamB genes of Aspergillus nidulans.
Authors: Katz M E , Hynes M J 
Published: January 2021

Abstract
Four Aspergillus nidulans genes are known to be under the control of the trans-acting regulatory gene amdR. We describe the isolation and initial characterization of one of these amdR-regulated genes, lamA. The lam locus, however, was found to consist of two divergently transcribed genes, the lamA gene, and a new gene, also under amdR control, which we have designated lamB. Using recombinant DNA techniques we have constructed a strain of A. nidulans lacking a functional lamB gene. Experiments conducted with this strain demonstrate that lamB, like lamA, is involved in utilization of 2-pyrrolidinone in A. nidulans. Metabolism of a related compound, gamma-amino butyric acid (GABA) is not affected. We also provide evidence that the conversion of exogenous 2-pyrrolidinone to endogenous GABA requires a functional lamB gene. The expression of both lamA and lamB is subject to carbon and nitrogen metabolite repression in addition to amdR-mediated induction by omega-amino acids.
Rapid spread of transposable p elements in experimental populations of Drosophila melanogaster.
Authors: Good A G , Meister G A , Brock H W , Grigliatti T A , Hickey D A 
Published: January 2021

Abstract
The invasion of P elements in natural populations of Drosophila melanogaster was modeled by establishing laboratory populations with 1%, 5% and 10% P genomes and monitoring the populations for 20 generations. In one experiment, the ability of flies to either induce or suppress gonadal sterility in different generations was correlated with the amount of P element DNA. In a second experiment, the percentage of genomes that contained P elements, and the distribution of P elements among individual flies was monitored. The ability to induce gonadal dysgenesis increased rapidly each generation. However, the increase in P cytotype lagged behind by five to ten generations. The total amount of P element DNA and the frequency of flies containing P elements increased each generation. The number of P elements within individual genomes decreased initially, but then increased. Finally, the distribution of P elements within the genomes of individuals from later generations varied considerably, and this pattern differed from the parental P strain. These results suggest that the interaction between the assortment and recombination of chromosomal segments, and multiplicative transposition could result in the rapid spread of P elements in natural populations.
Genetic definition of two functional elements in a bacteriophage T4 host-range "cassette".
Authors: Snyder M , Wood W B 
Published: January 2021

Abstract
Gene 37 of T4 encodes the major subunit of the distal half of the tail fiber. The distal tip of the fiber, comprised of the carboxy-terminal ends of two molecules of gene 37 product (gp37), carries the principal determinant of the phage host range. The gp37 carboxyl termini recognize the bacterial surface during infection, and, in addition, include a site required for interaction with the product of gp38 during distal half-fiber assembly. In the absence of interaction with gp38, gp37 polypeptides do not dimerize. Eleven temperature-sensitive mutants with defects located near the promoter-distal end of gene 37 were tested at nonpermissive temperatures for production of an antigen that is diagnostic of distal half-fiber assembly. Six of the mutations prevent distal half-fiber assembly. The other five allow assembly of distal half fibers, which combine with proximal half fibers and attach to phage particles, but the resulting phage do not adsorb to bacteria. These two classes of mutations define two adjacent but separate genetic regions, corresponding to two different functional domains in gp37. These two regions and the neighboring gene 38 comprise a functional unit that can be considered as a host-range "cassette," with features that are strikingly similar to corresponding functional units in other unrelated as well as related phages.
Genic and allelic interactions in the carotenogenic response of myxococcus xanthus to blue light.
Authors: Martinez-Laborda A , Murillo F J 
Published: January 2021

Abstract
In the bacterium Myxococcus xanthus, the synthesis of carotenoids requires illumination with blue light. This stimulates transcription of the carB locus, which is positively required for carotenogenesis. Mutations at the carR locus and the only mutation known at carA cause constitutive expression of carB and thus remove the light requirement for carotenoid accumulation (Car(c) phenotype). The carR locus is unlinked, and carA is linked, to carB. We have now identified a novel class of car mutation, closely linked to carR, that block accumulation of carotenoids and transcription of carB, and are epistatic over the Car(c) mutations at carR but not over the Car(c) mutation at carA. We also report here the cloning of a 16-kb DNA fragment that contains the entire carA gene in a shuttle vector for DNA transfer between Escherichia coli and M. xanthus. The study of allelic interactions at this gene strongly indicate that carA is a cis-acting element for the control of carB expression. A regulatory model that satisfies all the indicated data is presented.
Cloning and characterization of the scarlet gene of Drosophila melanogaster.
Authors: Tearle R G , Belote J M , McKeown M , Baker B S , Howells A J 
Published: January 2021

Abstract
DNA from the scarlet (st) region of Drosophila melanogaster has been cloned by chromosome walking, using the breakpoints of a new X-ray-induced third chromosome inversion (In(3LR)st-a27) which breaks in the scarlet (73A3.4) and rosy (87D13-14) regions. Two spontaneous mutants of st(st1 and stsp) contain insertions of non-st DNA located within 3.0 kb of the site of the inversion breakpoint used to isolate the gene, and a second scarlet inversion breaks within 6.5 kb of this site. However no changes detectable by Southern blotting were found in 5 X-ray-induced st mutants with cytologically normal third chromosomes. A 2.3-kb transcript arising from the st gene region (as defined by mutant analysis and DNA transformation) has been detected. This transcript is present throughout development at low levels, with a peak level during the early to mid-pupal stage. The size and amount of this transcript is altered in st1, and its amount is drastically reduced in stsp. Flies carrying the white1 mutation show normal levels of expression of the st transcript, suggesting that the w+ gene does not regulate transcription of the st+ gene. Nucleotide homology between sequences from the st transcription unit and a fragment carrying coding information from the white gene has been detected. This suggests that the st and w proteins are related; they appear to belong to a family of membrane-spanning, ATP-binding proteins involved in the transport of pigment precursors into cells.
Is knowing the age-order of alleles in a sample useful in testing for selective neutrality?
Authors: Tavaré S , Ewens W J , Joyce P 
Published: January 2021

Abstract
The most powerful, and most frequently used, test of selective neutrality, based on data consisting of observed allelic frequencies in a sample of genes at some locus, is the procedure of G. A. Watterson. This procedure uses the sample homozygosity F* as the test statistic, and in effect leads to rejection of the hypothesis of selective neutrality if the observed value of F* differs significantly from neutral theory expectations. The homozygosity statistic is invariant under relabeling of the alleles and thus cannot use any further information on the alleles which might be available. We present results which suggest that information concerning the age order of the alleles cannot be used to provide a more powerful testing procedure than that of Watterson.
Genetic correlations and maternal effect coefficients obtained from offspring-parent regression.
Authors: Lande R , Price T 
Published: January 2021

Abstract
Additive genetic variances and covariances of quantitative characters are necessary to predict the evolutionary response of the mean phenotype vector in a population to natural or artificial selection. Standard formulas for estimating these parameters, from the resemblance between relatives in one or two characters at a time, are biased by natural selection on the parents and by maternal effects. We show how these biases can be removed using a multivariate analysis of offspring-parent regressions. A dynamic model of maternal effects demonstrates that, in addition to the phenotypic variance-covariance matrix of the characters, sufficient parameters for predicting the response of the mean phenotype vector to weak selection are the additive genetic variance-covariance matrix and a set of causal coefficients for maternal effects. These can be simultaneously estimated from offspring-parent regressions alone, in some cases just from the daughter-mother regressions, if all of the important selected and maternal characters have been measured and included in the analysis.
Role of gene duplications in the adaptation of Salmonella typhimurium to growth on limiting carbon sources.
Authors: Sonti R V , Roth J R 
Published: January 2021

Abstract
Duplication-containing cells are selected when growth of Salmonella typhimurium is limited by the availability of any one of several carbon and energy sources. Under conditions of extreme starvation, growth occurs almost exclusively in the duplication-containing fraction of the population. Cells with duplications of one large segment of the chromosome are repeatedly selected regardless of which of these carbon sources limits growth. The duplicated chromosomal segment encodes the transport systems for all of these carbon sources. This duplication is not selected during growth on a carbon source for which the permease is not included within the duplication segment. This suggests that the growth advantage conferred by the duplication may be due to increased transport of the limiting carbon source. Inclusion of the permease alone is not sufficient to explain the growth advantage of the duplications, since other common duplications that include the permease are not selected.
Position effects in ectopic and allelic mitotic recombination in Saccharomyces cerevisiae.
Authors: Lichten M , Haber J E 
Published: January 2021

Abstract
We have examined the role that genomic location plays in mitotic intragenic recombination. Mutant alleles of the LEU2 gene were inserted at five locations in the yeast genome. Diploid and haploid strains containing various combinations of these inserts were used to examine both allelic recombination (between sequences at the same position on parental homologs) and ectopic recombination (between sequences at nonallelic locations). Chromosomal location had little effect on mitotic allelic recombination. The rate of recombination to LEU2 at five different loci varied less than threefold. This finding contrasts with previous observations of strong position effects in meiosis; frequencies of meiotic recombination at the same five loci differ by about a factor of forty. Mitotic recombination between dispersed copies of leu2 displayed strong position effects. Copies of leu2 located approximately 20 kb apart on the same chromosome recombined at rates 6-13-fold higher than those observed for allelic copies of leu2. leu2 sequences located on nonhomologous chromosomes or at distant loci on the same chromosome recombined at rates similar to those observed for allelic copies. We suggest that, during mitosis, parental homologs interact with each other no more frequently than do nonhomologous chromosomes.
Xanthine dehydrogenase is transported to the Drosophila eye.
Authors: Reaume A G , Clark S H , Chovnick A 
Published: January 2021

Abstract
The rosy (ry) locus in Drosophila melanogaster codes for the enzyme xanthine dehydrogenase. Mutants that have no enzyme activity are characterized by a brownish eye color phenotype reflecting a deficiency in the red eye pigment. This report demonstrates that enzyme which is synthesized in some tissue other than the eye is transported and sequestered at the eye. Previous studies find that no leader sequence is associated with this molecule but a peroxisomal targeting sequence has been noted, and the enzyme has been localized to peroxisomes. This represents a rare example of an enzyme involved in intermediary metabolism being transported from one tissue to another and may also be the first example of a peroxisomal protein being secreted from a cell.
Interactions between pesticide genes: model and experiment.
Authors: Raymond M , Heckel D G , Scott J G 
Published: January 2021

Abstract
In response to years of intense selection pressure by organophosphate insecticides, several different insecticide resistance mechanisms have evolved in natural populations of the mosquito Culex pipiens. We examined interactions between two of the most important mechanisms using a four-compartment model of insecticide pharmacokinetics. The joint effect of different mechanisms of resistance can be expressed in terms of epistasis at the physiological level in this model. The type of epistasis predicted by the model depends on the particular physiological mechanisms of resistance involved. Resistance due to a reduced penetration of the insecticide combines multiplicatively with other resistance factors, but resistance due to detoxicative processes and to insensitivity of the target site combines additively. How the pattern of epistasis at the physiological level is translated into fitness epistasis in natural populations of this mosquito depends on the intensity and pattern of insecticide selection in the field.
No linkage between genes controlling female pheromone production and male pheromone response in the European corn borer, Ostrinia nubilalis Hübner (Lepidoptera; Pyralidae).
Authors: Löfstedt C , Hansson B S , Roelofs W , Bengtsson B O 
Published: January 2021

Abstract
The E and Z pheromonal strains of the European corn borer, Ostrinia nubilalis, are characterized by female production of and male preference for opposite blends of (E)-11-and (Z)-11-tetradecenyl acetate. It is known that the pheromone production is controlled by an autosomal gene and that the males' behavior is determined by a sex-linked gene. A third gene, autosomally inherited, has been shown to determine the organization of the male pheromone receptors. In the present study the linkage relationship between the autosomal genes controlling sex pheromone production and male olfactory sensilla was investigated. A recombination experiment showed unequivocally that the genes determining the variation in pheromone production and male pheromone receptors are not closely linked and are most likely inherited independently.
Molecular and genetic characterization of Mu transposable elements in Zea mays: behavior in callus culture and regenerated plants.
Authors: Planckaert F , Walbot V 
Published: January 2021

Abstract
Active Mutator lines of maize (Zea mays L.) have a high mutation rate and contain multiple hypomethylated 1.4-kb and 1.7-kb Mu transposable elements. Correlated with the inactivation of the Mutator system, these Mu elements cease to transpose and become more methylated. To determine whether the shock of tissue culture can affect Mutator activities, F1 progenies of outcrosses between active or inactive Mutator stocks and inbred line A188 were used to initiate embryogenic callus cultures. HinfI restriction digestion of genomic DNA isolated from 3-5-month-old cultures demonstrated that there is a very good correlation between the modification state of Mu elements in the cultures and the Mutator parent. Despite the dedifferentiation and rapid proliferation characteristic of tissue culture, the Mutator activity state is relatively stable during an extended tissue culture period. Cultures established from inactive Mutator lines were not reactivated; cultures established from active lines maintained a high Mu copy number, and most Mu elements remained unmodified. In contrast, weakly active Mutator parents gave rise to cultures in which Mu element modification could switch between low and high methylation during the culture period. Evidence for transposition was investigated with EcoRI digestion of genomic DNA isolated at different times during culture. The appearance of novel Mu-hybridizing fragments and a strong background hybridization are interpreted as evidence that transposition events occur during culture. Plants regenerated from such active cultures transmitted Mutator activity to their progeny.
Genetic instability of clathrin-deficient strains of Saccharomyces cerevisiae.
Authors: Lemmon S K , Freund C , Conley K , Jones E W 
Published: January 2021

Abstract
Saccharomyces cerevisiae strains carrying a mutation in the clathrin heavy chain gene (CHC1) are genetically unstable and give rise to heterogeneous populations of cells. Manifestations of the instability include increases in genome copy number as well as compensatory genetic changes that allow better growing clathrin-deficient cells to take over the population. Increases in genome copy number appear to result from changes in ploidy as well as alterations in normal nuclear number. Genetic background influences the frequency at which cells with increased genome content are observed in different Chc- strains. We cannot distinguish whether genetic background affects the rate at which aberrant nuclear division events occur or a growth advantage of cells with increased nuclear and/or genome content. However, survival of chc1-delta cells does not require an increase in genome copy number. The clathrin heavy chain gene was mapped 1-2 cM distal to KEX1 on the left arm of chromosome VII by making use of integrated 2 mu plasmid sequences to destabilize distal chromosome segments and allow ordering of the genes.
Mechanisms of gene conversion in Saccharomyces cerevisiae.
Authors: Roman H , Ruzinski M M 
Published: January 2021

Abstract
In red-white sectored colonies of Saccharomyces cerevisiae, derived from mitotic cells grown to stationary phase and irradiated with a light dose of x-rays, all of the segregational products of gene conversion and crossing over can be ascertained. Approximately 80% of convertants are induced in G1, the remaining 20% in G2. Crossing over, in the amount of 20%, is found among G1 convertants but most of the crossovers are delayed until G2. About 20% of all sectored colonies had more than one genotype in one or the other sector, thus confirming the hypothesis that conversion also occurs in G2. The principal primary event in G2 conversion is a single DNA heteroduplex. It is suggested that the close contact that this implies carries over to G2 when crossing over and a second round of conversion occurs.
Size selection identifies new genes that regulate Saccharomyces cerevisiae cell proliferation.
Authors: Prendergast J A , Murray L E , Rowley A , Carruthers D R , Singer R A , Johnston G C 
Published: January 2021

Abstract
A centrifugation procedure to enrich for enlarged cells has been used to isolate temperature-sensitive cdc mutants of the yeast Saccharomyces cerevisiae. Among these mutants are strains containing mutations that arrest proliferation at the regulatory step start. These new start mutations define two previously unidentified genes, CDC67 and CDC68, and reveal that a previously identified gene, DNA33 (here termed CDC65), can harbour start mutations. Each new start mutation permits significant biosynthetic activity after transfer of mutant cells to the non-permissive temperature. The cdc68-1 start mutation causes arrest of cell proliferation without inhibition of mating ability, while the cdc65-1 and cdc67-1 mutations inhibit zygote formation and successful conjugation. The identification of new start genes by a novel selection procedure suggests that the catalog of genes that influence start is large.
Dosage requirements of Ultrabithorax and bithoraxoid in the determination of segment identity in Drosophila melanogaster.
Authors: Smolik-Utlaut S M 
Published: January 2021

Abstract
The wild-type Ultrabithorax (Ubx) and bithoraxoid (bxd) functions are primarily responsible for establishing the identity of parasegment 6 (PS6) in the Drosophila embryo and thus the identity of the posterior compartment of the third thoracic segment (pT3) and the anterior compartment of the first abdominal segment (aA1) in the adult. The experiments described were designed to test the ability of an increased dosage of Ubx+ and bxd+ to affect the transformation of PS5 toward PS6. The results are consistent with the ideas that (1) multiple copies of Ubx+ and bxd+ cause some cells within PS5 to take on the characteristics of PS6 cells but do not cause an overall parasegmental transformation of PS5 toward PS6, (2) cellular identity depends not only on the activity of Ubx+ but on its concentration as well, and (3) that an interaction between Ubx+ and the wild-type Antennapedia (Antp) gene establishes segmental identity in pT2. In the first instar larvae carrying eight copies of Ubx+ and bxd+ the fine hairs of the T3 setal belt are transformed toward the hook-like structures of the A1 setal belt. Other structures within this segment are unaffected. In the adult, the haltere is reduced in size. The transformation of pT2 cells (wing) toward pT3 cells (haltere) is seen in adults carrying eight doses of wild type Ubx and bxd by decreasing the amount of the bithorax complex (BX-C) regulator Polycomb (Pc). However, the transformation of the T3 setal belt is not enhanced in the larvae of these animals. The interaction between the genes of the Antennapedia complex (ANT-C) and the Ubx+ and bxd+ functions in pT2 is dosage sensitive only when the animals carry one copy of Pc. In these animals, the transformation of wing toward haltere is significantly enhanced.
Genetic variation for sex ratio traits within a natural population of a parasitic wasp, Nasonia vitripennis.
Authors: Orzack S H , Parker E D 
Published: January 2021

Abstract
By analyzing isofemale strains extracted from a natural population of Nasonia vitripennis, we detected variation for the sex ratios produced in fresh hosts (first sex ratios) and in previously parasitized hosts (second sex ratios). Under simple assumptions of population structure, this between-strain heterogeneity of first sex ratios results in heterogeneity of fitnesses. There is approximately ten percent difference in average fitnesses between the strains. (The fitnesses of second sex ratios are analyzed in the accompanying paper.) Average first and average second sex ratios are uncorrelated. There is significant between-female heterogeneity within some strains for first sex ratios but not for second sex ratios. In addition, the average direct-developing and diapause first sex ratios (but not second sex ratios) are significantly correlated. There are significant correlations between the direct-developing and diapause sex ratios produced by the same female. The strains differ in their effects on the sex ratio and size of another female's brood in the same host. Data on these types of variation for sex ratio traits are essential for further progress in the study of sex ratio evolution.