Influence of Parental Age on Endoreduplication of Giant Chromosomes and Some Quantitative Traits in Drosophila melanogaster Descendants

We studied the influence of parental age on the degree of polyteny of giant chromosomes and expressivity of mutation eyeless in Drosophila melanogaster descendants. The parental age equal to six days exerted an adverse effect on the function of endoreduplication of giant chromosomes in straineyeless. The highest degree of polyteny was observed in descendants of four- and ten-day imago. The maximum reduction of eye facets was observed in descendants of four-day imago, while in the progeny of older parents, the mutation expressivity was sharply reduced. Relations between the changes in chromosome polyteny, expressivity of mutation eyeless, and earlier studied components of adaptation were statistically analyzed in descendants of aging parents of this Drosophila strain.     

Effect of culture density and degree of expression of the trait "eyeless" and degree of polyteny of giant chromosomes in Drosophila melanogaster]

Effects of culture density on expressivity of character eyeless and polyteny of giant chromosomes were studied in Drosophila melanogaster. Larval crowding was shown to significantly reduce eye facets. The expression of eyeless was sex-dependent: in females, this character was expressed more strongly than in males. Larval crowding resulted in a decrease of chromosome polyteny in larval salivary glands. A strong negative correlation was established between the expressivity of eyeless and the degree of giant chromosome polyteny.     

Influence of genotype on endoreduplication of giant chromosomes and expressivity of character eyeless in Drosophila melanogaster

In Drosophila melanogaster lines LA (low activity), HA (high activity), and Oregon-R (wild type), the effect of genetic background on endoreplication in giant chromosomes of salivary glands, fecundity, and expression of mutation ey was studied. The degree of chromosome polyteny and the number of adult flies in saturated lines eyHA, eyBA, and eyOr were significantly higher than in the original lines. The degree of chromosome polyteny was correlated with fecundity. The expressivity of the ey character was shown to be far lower in lines eyLA, eyHA, and eyOr than in the original eyeless line. In the saturated lines, the eye facets were reduced to a similar degree. All the lines studied displayed clear-cut sexual distinctions in this parameter. In the eyHA line, the coefficients of variation for the degree of chromosome polyteny, fecundity, and expressivity of the ey mutation were much lower than in lines eyeless, eyLA, and eyOr.     

The effect of the genotype on the expressiveness of the vestigial trait and polyteny of chromosomes in Drosophila melanogaster Meig

The effects of the Bar (B) and white (w) mutations on the expressiveness of the character vestigial (vg) and the degree of polyteny of salivary gland giant chromosomes were studied in Drosophila melanogaster. Either mutation changed both the expressiveness of vestigial and the degree of chromsome polyteny. A negative association between the vg expressiveness and the degree of chromosome polyteny was revealed and proved to be stronger in females than in males. The parameters under study were shown to differ between females and males.     

The Effect of the Genotype on the Expressiveness of Character vestigial and Polyteny of Giant Chromosomes in Drosophila melanogaster Meig.

The effects of the Bar (B) andwhite (w) mutations on the expressiveness of the character vestigial (vg) and the degree of polyteny of salivary gland giant chromosomes were studied in Drosophila melanogaster.Either mutation changed both the expressiveness of vestigial and the degree of chromosome polyteny. A negative association between the vg expressiveness and the degree of chromosome polyteny was revealed and proved to be stronger in females than in males. The parameters under study were shown to differ between females and males.     

Hidden polyteny in giant embryonic nuclei of Drosophila melanogaster gnu mutants

Drosophila melanogaster embryos, whose mothers are homozygous for the gnu (a recessive lethal mutation with maternal effect) undergo DNA synthesis but are defective in nuclear division. This leads to formation of giant nuclei in the syncytial blastoderm. The interior spatial chromatin organization and possibility of obtaining polytene chromosomes in these nuclei was analysed. Partial conjugation of homologous chromatids, which is an evidence for cryptic polyteny in the gnu embryos nuclei, was shown.     

The influence of monoterpenoids and phenol derivatives on Drosophila melanogaster viability

The present study investigated the effect of mono/bicyclic terpenoids and phenol derivatives on the viability of Drosophila melanogaster and their influence on the multiplication of the nuclear genome. The fertility and viability of fruit flies were assessed after oral administration and inhalation exposure of compounds 1–5: guaiacol, eugenol, borneol, menthol and carvacrol. The influence of terpenoids and phenols on the degree of chromosomes polyteny in salivary gland cells of D. melanogaster larvae was determined. Among all tested compounds, carvacrol demonstrated the most significant impact on fecundity and insect survival when inhaled or adding to the culture medium. Oral administration of carvacrol had an impact on giant chromosomes increasing their average level of chromosome polyteny degree while eugenol adding to culture medium had the opposite effect. The possible mechanism of terpenoids and phenols action is discussed.     

Effect of culture density on the polyteny degree of giant chromosomes in inbred lines and hybrids of Drosophila melanogaster

The influence of culture density and genotype on the polyteny degree of giant chromosomes (PDC) in Drosophila melanogaster was investigated. The reliable depression of the polytene chromosomes endoreduplication function under increased culture density was revealed. The essential dependence of the PDC on the genotype was shown. Correlation between the PDC and the number of adaptive features was established. The certain parallelism between the increased heterosis effect on the number of quantitative characters and the superiority of the hybrids above the inbred lines on the PDC in conditions of high culture density was found out. The sex-dependent distinctions and maternal effect at the inheritance of the PDC in drosophila were shown.     

Influence of Genotype on Endoreduplication of Giant Chromosomes and Expressivity of Character eyelessin Drosophila melanogaster

In Drosophila melanogaster lines LA (low activity), HA (high activity), andOregon-R (wild type), the effect of genetic background on endoreplication in giant chromosomes of salivary glands, fecundity, and expression of mutation eywas studied. The degree of chromosome polyteny and the number of adult flies in saturated lines ey _L, ey _H, and ey _Or were significantly higher than in the original lines. The degree of chromosome polyteny was correlated with fecundity. The expressivity of the ey character was shown to be far lower in lines ey _L, ey _H, and ey _Or than in the original eyelessline. In the saturated lines, the eye facets were reduced to a similar degree. All the lines studied displayed clear-cut sexual distinctions in this parameter. In the ey _L line, the coefficients of variation for the degree of chromosome polyteny, fecundity, and expressivity of the ey mutation were much lower than in lines eyeless, ey _LAandey _Or.     

Three-dimensional organization of Drosophila melanogaster interphase nuclei. I. Tissue-specific aspects of polytene nuclear architecture

Interphase chromosome organization in four different Drosophila melanogaster tissues, covering three to four levels of polyteny, has been analyzed. The results are based primarily on three-dimensional reconstructions from unfixed tissues using a computer-based data collection and modeling system. A characteristic organization of chromosomes in each cell type is observed, independent of polyteny, with some packing motifs common to several or all tissues and others tissue-specific. All chromosomes display a right-handed coiling chirality, despite large differences in size and degree of coiling. Conversely, in each cell type, the heterochromatic centromeric regions have a unique structure, tendency to associate, and intranuclear location. The organization of condensed nucleolar chromatin is also tissue-specific. The tightly coiled prothoracic gland chromosomes are arrayed in a similar fashion to the much larger salivary gland chromosomes described previously, having polarized orientations, nonintertwined spatial domains, and close packing of the arms of each autosome, whereas hindgut and especially the unusually straight midgut chromosomes display striking departures from these regularities. Surprisingly, gut chromosomes often appear to be broken in the centric heterochromatin. Severe deformations of midgut nuclei observed during gut contractions in living larvae may account for their unusual properties. Finally, morphometric measurements of chromosome and nuclear dimensions provide insights into chromosome growth and substructure and also suggest an unexpected parallel with diploid chromatin organization.     

Modifications of Mean Ovariole Number, Fresh Weight of Adult Females and Developmental Time in DROSOPHILA MELANOGASTER Induced by Drosophila C Virus

Drosophila C virus, a picornavirus that has some influence on ovarian morphogenesis, was discovered in a French strain of Drosophila melanogaster. When the strain was infected by Drosophila C virus (DCV), the mean number of ovarian tubes and weights of the adult females increased, but the developmental time from egg to imago decreased. The maternal effects observed when DCV was present disappeared when the strain was DCV free but were restored by experimental contamination.     

Isolation of expressed sequence tags of Agaricus bisporus and their assignment to chromosomes.

The genome of the cultivated basidiomycete Agaricus bisporus Horst U1 and of its homokaryotic parents has been characterized by using an optimized method of pulsed-field gel electrophoresis. Expressed sequence tags obtained as expressed cDNAs from a primordial tissue-derived cDNA library and a number of previously isolated genes were used to identify the individual chromosomes of the parental lines of Horst U1. The genome consists of 13 chromosomes, and its total size is 31 Mb. For those chromosomes that could not be resolved by contour-clamped homogeneous electric field electrophoresis, the segregation of marker genes was studied in a set of 86 homokaryotic offspring of Horst U1. At least two markers were assigned to each individual chromosome. In this way all individual chromosomes were unequivocally identified. The large size difference observed between the homologous chromosomes IX, harboring the rDNA repeat, was shown to be largely due to a higher copy number of rDNA in parental strain H97 than in parental strain H39.     

Phototaxis and adaptation of the eyeless Drosophila melanogaster line]

An artificial selection on positive and negative phototaxis of eyeless (ey) Drosophila melanogaster line was carried out. Expression of the ey trait in imago was estimating during the selection. The fitness of the "+" and "-" selected lines was evaluated by such components as heat resistance, life span, fertility of flies. The genetic analysis of phototaxis inheritance was carried out. It was found that phototaxis selection results in changes of fertility whereas it doesn't affect other indices of fitness to environmental conditions as well as the ey expression. The main polygenic systems of phototaxis inheritance are located in chromosome 2 and chromosome 3.     

DNA synthesis in polytenic chromosomes of Anopheles atroparvus

DNA synthesis in polytenic chromosomes of Anopheles atroparvus has been studied during the third and fourth larval stages. The beginning of the replication cycle coincides with the moult. With increasing larval age the frequency of nuclei in synthesis decreases continuously to reach 1 per cent in the fourth instar at 48 hours of age. The beginning of synthesis is characterized by asynchrony both among larvae and among nuclei within the same larva. At the beginning of replication the polytenic chromosomes have a discontinuous labelling pattern. The same pattern was observed at the end of reduplication. Whole nuclei and single chromosomal regions seem to reach their maximum degree of polyteny during the third larval stage.     

Polyteny and endomitosis in supergiant trophoblast cells of the gray vole Microtus subarvalis

A cytomorphological study was made of peculiarly structured polytene chromosomes in supergiant trophoblast cells of Microtus subarvalis. The polyteny level was extremely high (over 1024C). The polytene chromosomes are characterized by a rather high degree of condensation of single chromosomes, and, as a consequence, close chromosome junctions and the typical disk pattern are lacking. The presence of complex nucleoli in the nuclei of these cells also testifies to a great detachment of chromonemes in polytene chromosomes of the studied supergiant trophoblast cells. Compared to other rodent species, a lower degree of chromoneme junction in the vole polytene chromosomes may cause their easy dissociation into single chromonemata, whose further condensation results in endomitotic chromosome formation. The chromosome depolytenization, earlier suggested from the analysis of interphase nucleus markers, has been traced here in detail. The process of polytene chromosome splitting was most obvious in the nucleolus-organizing chromosomes. A hony-combed nucleolus splits into numerous micronucleoli. The nucleus pattern becomes altered. Once in the polytene nucleus, chromosome bundles were located below the nuclear membrane and the central zone of the karyoplasm was not completely filled up. However, after dissociation of polytene chromosomes the whole karyoplasm was filled up with small nucleoli, and a thin layer of endomitotic chromosomes was seen beneath the nuclear membrane. The correlation between endomitosis and polyteny is discussed in terms of the dissociation of polytene chromosomes and formation of endomitotic chromosomes.     

Use of enlarged cells and nuclei for studying mitosis inNeurospora

Summary Mitotic division stages studied by light microscopy in differentNeurospora crassa cell types clearly resemble prophase, metaphase, anaphase, and telophase stages of higher eukaryotes. 1. When conidia are cultured in liquid medium containing 3.22 M ethylene glycol, they grow without cell division, forming giant spheres with multiple nuclei. In a few giant cells, nuclear numbers remain small (1 to 3) but the nuclei become very large. Seven large chromosomes are seen in some nuclei suggesting polyteny, 14 or more chromosomes are seen in other, very large nuclei, indicating polyploidy. Cell volume and nuclear volume are positively correlated in giant cells. Nuclear divisions are not synchronous within individual multinucleate giant cells. 2. Nuclear division stages were also observed in crosses heterozygous for the dominant mutant banana where haploid prefusion nuclei in late-forming croziers revert to mitosis. Swollen ascogenous hyphae become highly multinucleate after several rounds of mitosis. Mitosis is completely synchronous in nuclei of the same crozier cyst, providing replicate information for unambiguous identification of division stage. 3. Observations are also reported of mitosis in a cell-wall deficient slime strain. Previous observations on mitosis in large nuclei of the ascus are summarized for comparison. The nucleolus persists throughout mitosis in the giant cells, multinucleate reverted croziers, and in the cell-wall deficient slime strain. It is expelled from the dividing nuclei in the ascus. Spindles and spindle pole bodies, which are normally conspicuous in asci, are also seen in normal and reverted croziers, but they have not been clearly identified in the ethylene glycol-induced giant cells.     

Strain‐specific effects of parental age on offspring in Drosophila melanogaster

Maternal age is generally known to be negatively correlated with the lifespan of offspring in several animal models including yeast, rotifers, flies, and possibly in humans. However, several reports have shown positive effects of parental age on offspring lifespan. Thus, there was a need to investigate further the inconsistent results on the effect of parental age on lifespan. In this study, the effects of parental age on offspring fitness and lifespan were examined by using Drosophila melanogaster. The lifespan of offspring from old parents was significantly increased compared with that of the young counterparts in the Canton‐S (CS) strain but not in other D. melanogaster strains, such as Oregon‐R (OR) and w¹¹¹⁸. To find out why the lifespan is increased in the offspring from old parents in CS flies, fitness components that could modulate lifespan were examined in CS flies. Egg weight and body weight were reduced by parental aging and the offspring of old fathers or old mothers developed faster than that of the young. In addition, the offspring of old parents had increased resistance to oxidative and heat shock stresses. However, reproductive capacity, mating preference, and food intake were unaffected by parental aging. These results indicate that parental aging in CS strain D. melanogaster has beneficial effects on the lifespan and fitness of offspring. The presence of strain‐specific manner effects suggests that genetic background might be a significant factor in the parental age effect.     

Transplantation of insect giant chromosome nuclei into amphibian oocytes

Polytene salivary gland nuclei of Chironomus pallidivittatus were transplanted into oocytes of Xenopus laevis which were then cultured in vitro for 18 h. The giant chromosomes and nucleoli as well as the entire nuclei enlarged considerably in volume during this time. The polyteny and specific chromomere pattern of the chromosomes were maintained, and the puffing of the salivary gland-specific Balbiani rings was not noticeably changed. — Polytene nuclei from differentiated insect cells transplanted into Xenopus oocytes thus appear suited for exposing giant chromosomes in vivo to purified factors such as regulatory molecules. This paper is dedicated to Professor Wolfgang Beermann on the occasion of his 60th birthday     

Autosegregation of enzyme loci in agamospermous progenies of triploid plants of sugar beet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.)

The ratios of the phenotypic classes of glucosephosphate isomerase (GPI2) and malate dehydrogenase (MDH1 and MDH2) were studied in agamospermous progenies of triploid sugar beet plants. The ratio of the phenotypic classes of these enzymes corresponds to the calculations based on the assumption of polyteny of chromosomes carrying alleles of the enzyme loci accompanied by the loss of extra copies of the alleles in the first division of a cell entering embryogenesis. An increase in the gene dosage due to polyteny leads to the appearance in the progeny with a definite frequency of alleles that were absent in the original parental plant. The notions of “meiotic autosegregation” and “mitotic autosegregation” characteristic of meiotic and mitotic agamospermy are introduced, as well as the term locus polygenotype characterizing not only the allelic composition and the number of chromosomes, but also the number of chromatids carrying alleles of the marker locus in the cell before its entry into embryogenesis.     

Differential replication of male and female X-chromosomes in Drosophila

The replication patterns of larval salivary gland chromosomes of D. hydei and D. melanogaster were studied by autoradiography with tritiated thymidine injected in mid third instar larvae. The male X chromosome showed a different replication behavior in comparison to that of the female X chromosome and autosomes. It is concluded that the male X chromosome finishes its replication earlier than the female X chromosome. Moreover, the time needed for a complete replication cycle of individual identical replication units was found to be shorter in the male than in the female X chromosome. Although the whole X chromosomes behave different there were no differences observed in the sequence of the discontinuous labeling patterns of the two types of X chromosome. One autosomal replication unit was observed which showed a different replication behavior in males and females. The possible origin of the differential behavior of the two X chromosomes is discussed in terms of their difference in degree of polyteny.