Localization of genes affecting species differences in male courtship song between Drosophila virilis and D. littoralis

The males of six species of the Drosophila virilis group (including D. virilis) keep their wings extended while producing a train of sound pulses, where the pulses follow each other without any pause. The males of the remaining five species of the group produce only one sound pulse during each wing extension/vibration, which results in species-specific songs with long pauses (in D. littoralis about 300 ms) between successive sound pulses. Genetic analyses of the differences between the songs of D. virilis and D. littoralis showed that species-specific song traits are affected by genes on the X chromosome, and for the length of pause, also by genes on chromosomes 3 and 4. The X chromosomal genes having a major impact on pulse and pause length were tightly linked with white, apricot and notched marker genes located at the proximal third of the chromosome. A large inversion in D. littoralis, marked by notched, prevents more precise localization of these genes by classical crossing methods.     

Microinjection of the monoclonal anti-tubulin antibody YL1/2 inhibits cleavage of sand dollar eggs

Two monoclonal antibodies against alpha-tubulin (YL1/2 and D2D6) were microinjected into the egg of the sand dollar Clypeaster japonicus, and their effects on cleavage of the egg were investigated. They had already been shown by immunoblotting to react specifically with egg tubulin and by immunofluorescence to stain the mitotic apparatus [OKA et al., (1990). Cell Motil. Cytoskel. 16:239-250]. Injection of YL1/2 prevented chromosome movement and cleavage, although the cleavage furrow developed in some cases. In all eggs injected at prometaphase, metaphase, or anaphase, the birefringence of the mitotic apparatus disappeared immediately after injection. Injection of D2D6 had no significant effect on mitosis or cleavage of whole eggs injected after nuclear disappearance, although it prevented the disappearance of the nuclear envelope in 54% of the eggs injected before the disappearance. FITC-conjugated D2D6 did not accumulate in the spindle when injected into the dividing sand dollar egg. These results indicate that YL1/2 disassembled microtubules, whereas D2D6 did not bind to microtubules in the living cell.     

Temperature sensitivity of mutations in species of the virillis group of Drosophila. III. The maternal influence and dominance of lethals in D. virillis Sturt. X D. littoralis Sokolov hybrids]

Lethal mutations sensitive to the temperatures 17 and 31 degrees were found in D. virilis. The phenocritical stage for the heat-sensitive mutation begins from the 2nd half of the 3rd larval instar. The specific stage for the cold-sensitive mutation was not found. The mutations are recessive under intraspecific and interspecific (D. littoralis female XD. virilis hermaphrodite) crossing. They are inherited as dominant in the hybrids D. virilis female XD. littoralis hermaphrodite due to the maternal effect of the D. virillis egg cytoplasm.     

The temperature sensitivity of mutations in species of the virilis group of Drosophila. II. The effect of temperature on the maternal effect on the puffed marker following hybridization

The influence of temperature (17 and 31 degrees) on the maternal effect of mutation Puffed (Pu) in Drosophila hybrids has been studied. In the hybrids female D. littoralis +/+ x male D. virilis Pu/Pu, the stage of formation of black ring on anterior spiracles in the 3rd larval instar is sensitive to 31 degrees. In the hybrids female D. virilis Pu/Pu x male D. littoralis +/+, the expression of Pu gene manifests the maternal effect and as a result, two temperature-sensitive stages are found. The first one--onset of embryogenesis (2 to 4 hrs). At the temperature 17 degrees, the penetrance of Pu increases. The second stage is sensitive to 31 degrees and coincides with the period of black rings formation on anterior spiracles in the 3rd laval instar. It has been shown that at least two genetic systems take part in the formation of this feature. One group of genes controls the maternal effect and is sensitive to low temperature in the early embryogenesis of the hybrids female D. virilis x male D. littoralis. The second one--Pu gene and its modifiers--is active during the 2nd half of the 3rd larval instar and is heat-sensitive.     

New mutations fts-36, lts-33, and ftsW clustered in the mra region of the Escherichia coli chromosome induce thermosensitive cell growth and division.

Three new mutants of Escherichia coli showing thermosensitive cell growth and division were isolated, and the mutations were mapped to the mra region at 2 min on the E. coli chromosome map distal to leuA. Two mutations were mapped closely upstream of ftsI (also called pbpB), in a region of 600 bases; the fts-36 mutant showed thermosensitive growth and formed filamentous cells at 42 degrees C, whereas the lts-33 mutant lysed at 42 degrees C without forming filamentous cells. The mutation in the third new thermosensitive, filament-forming mutant, named ftsW, was mapped between murF and murG. By isolation of these three mutants, about 90% of the 17-kilobase region from fts-36-lts-33 to envA could be filled with genes for cell division and growth, and the genes could be aligned.     

The site of function of the Y chromosome in Drosophila melanogaster males

Summary The Y chromosome is essential for fertility in D. melanogaster males. An analysis of 126 pal-induced Y chromosome mosaics indicated that its function is only required in the germ line of fertile males. This analysis also showed that approximately 1/4 of all pal-induced Y chromosome mosaics had an XO/XYY constitution and hence that they resulted from somatic nondisjunction. Preliminary evidence suggests that pal-induced somatic nondisjunction can occur at the second or subsequent cleavage divisions.     

Independence of genetic geographical variation between photoperiodic diapause, circadian eclosion rhythm, and Thr-Gly repeat region of the period gene in Drosophila littoralis

Drosophila littoralis is a latitudinally widespread European species of the Drosophila virilis group. The species has ample genetic variation in photoperiodism (adult diapause) and circadian rhythmicity (pupal eclosion rhythm), with adaptive latitudinal clines in both of them. The possible common genetic basis between the variability of photoperiodism and circadian rhythms was studied by a long-term crossing experiment. A northern strain (65 degrees N) having long critical day length (CDL = 19.9 h) for diapause, early phase of the entrained rhythm in LD 3:21 (psi(LD3:21) = 12.3 h), and short period (tau= 18.8 h) of the free-running rhythm for the eclosion rhythm was crossed with a southern strain (42 degrees N) having short CDL (12.4 h), late eclosion phase (psi(LD3:21) = 20.2 h), and long period (tau= 22.8 h). After 54 generations, including free recombination, artificial selection, and genetic drift, a novel strain resulted, having even more "southern" diapause and more "northern" eclosion rhythm characteristics than found in any of the geographical strains. The observed complete separation of eclosion rhythm characteristics from photoperiodism is a new finding in D. littoralis; in earlier studies followed for 16 generations, the changes had been mostly parallel. Evidently, the genes controlling the variability of the eclosion rhythm and photoperiodism in D. littoralis are different but closely linked. To test for the possible gene loci underlying the observed geographical variability, the period gene was studied in 10 strains covering all the known clock variability in D. littoralis. The authors sequenced the most suspected Thr-Gly region, which is known to take part in the adaptive clock variability in Drosophila melanogaster. No coding differences were found in the strains, showing that this region is not included in the adaptive clock variability in D. littoralis.     

Mécanisme cytologique de la tétraploïdie expérimentale chez le Triton Pleurodeles waltlii

When the eggs of the newt Pleurodeles waltlii, at the beginning of the first furrow formation, are submitted for 10 minutes to a sudden increase in temperature (37.2 to 37.3 degrees C), the subsequently developing embryos are tetraploid. The percentage obtained of viable individuals is about 30% of the number of treated eggs. A temperature between 36.2 and 36.4 degrees C applied at the same period and for the same length of time may lead to viable animals diplo-tetraploid mosaics as previously reported.--Cytological examination showed that at the formation of the first furrow the egg contains two interphase nuclei. During heat treatment, cytoplasmic cleavage regresses resulting in an uncleaved egg with two interphase nuclei. About 2 1/2 hours after heat treatment the egg divides again into two cells. Tetraploidy results from doubling of chromosomes of both nuclei instead of the second mitotic division. The mechanism which leads to tetraploidy consists in inhibition of the movement of the two asters and aberration of spindle formation.--The mosaic animals develop from eggs in which only one of the nuclei became tetraploid while the other one divided normally.     

A New Mutant Controlling Mitotic Chromosome Disjunction in DROSOPHILA MELANOGASTER

A new mutant, mit (mitotic loss inducer), is described. The mutant is recessive and maternal in action, producing gynandromorphs and haplo-4 mosaics among the progeny of homozygous mit females. Mosaic loss of maternal or paternal chromosomes can occur. The probabilities of either maternal or paternal X chromosome loss are equal. mit has been mapped to approximately 57 on the standard X chromosome map.-Using gyandromorphs generated by mit, a morphogenetic fate map, placing the origins of 40 cuticular structures on the blastoderm surface, has been constructed. This fate map is consistent with embryological data and with the two other fate maps generated in different ways.     

Nuclear division and migration during early embryogenesis of Bradysia tritici coquillet (syn. Sciara ocellaris) (diptera : Sciaridae)

Nuclear division and migration of cleavage nuclei in the embryos of Bradysia tritici (Diptera : Sciaridae) have been studied by light microscopy and nuclear staining. There are 8 cleavage cycles up to the syncytial blastoderm stage (4.5 hr), and during the 11th cycle cellularization begins (6.5 hr). The first 3 divisions take about 30 min each. During the 5th and 6th cycles, the maximum rate of division is reached (12 min/cycle at 22°C). After pole cell formation, the duration of the following mitotic cycles increases progressively. During nuclear migration, the presumptive germ line nuclei reach the egg cortex first, followed by anterior somatic nuclei and finally, posterior somatic nuclei reach the egg cortex. Possibly as a result of this region-specific nuclear migration, nuclear divisions become parasynchronous after 3 hr of embryogenesis (4th cycle). Several mitotic cycles later, between the 8th and 10th cycle in different embryos, X-chromosome elimination in somatic nuclei begins at the anterior egg pole and progresses in anteroposterior direction. Our observations suggest that the observed region-specific differences may be due to the activity of localized factors in the egg that control migration and nuclear cycle of the somatic nuclei.     

Development of Microtubule-Dependence of the Chromosome Cycle at the Midblastula Transition in Xenopus laevis Embryos

Animal-cap cells isolated from Xenopus laevis morulae and blastulae are cultured for 2 to 6 hr in medium containing nocodazole, Colcemid or taxol, at concentrations completely inhibiting cell division. At 20°C, cells from each control embryo undergo synchronous cell cycles up to the 12th, with a period of 32 min, of which 60% represents the chromosome condensation (mitotic or M-) phase, and the average mitotic index remains near 50%. Cells treated with nocodazole, Colcemid or taxol before 12th cleavage undergo chromosome cycles with a similar period as controls, albeit without chromosome segregation, and the average mitotic index remains near 50%. From the 12th to 15th cycles, control cycles become asynchronous, their period gradually increases 2 to 3 times, and the mitotic index declines to 10%. In cells treated after 12th cleavage with taxol, the mitotic index declines, similarly to control cells. However, in nocodazole-treated cells, it increases steadily, and exceeds 70% at 2 hr of treatment, but gradually declines to 40% at 6 hr. Therefore, while inhibition of microtubule activities does not significantly alter the timing of chromosome condensation cycles during synchronous cleavage, inhibition of microtubule assembly can prolong M-phase during asynchronous cleavage after the midblastula transition.     

Die Zytologie der bisexuellen und parthenogenetischen Fortpflanzung von Heteropeza pygmaea Winnertz,einer Gallmücke mit pädogenetischer Vermehrung

Heteropeza pygmaea (syn. Oligarces paradoxus) can reproduce as larvae by paedogenesis or as imagines (Fig. 1). The eggs of imagines may develop after fertilization or parthenogenetically. The fertilized eggs give rise to female larvae, which develop into mother-larvae with female offspring (Weibchenmütter). Only a few of the larvae which hatch from unfertilized eggs become motherlarvae with female offspring; the others die. Spermatogenesis is aberrant, as it is in all gall midges studied to date. The primary spermatocyte contains 53 or 63 chromosomes. The meiotic divisions give rise to two sperms each of which contains only 7 chromosomes (Figs. 5–11). The eggs of the imago are composed of the oocyte and the nurse-cell chamber. In addition to the oocyte nucleus and the nurse-cell nuclei there are three other nuclei in the eggs (Figs. 15–17). They are called small nuclei (kleine Kerne). In prometaphase stages of the first cleavage division it could be seen that these nuclei contain about 10 chromosomes. Therefore it is assumed that these nuclei originate from the soma of the mother-larva. The chromosome number of the primary oocyte is approximately 66. The oocyte completes two meiotic divisions. The reduced egg nucleus contains approximately 33 chromosomes. The polar body-nuclei degenerate during the first cleavage divisions. The fertilized egg contains 2–3 sperms. The primary cleavage nucleus is formed by the egg nucleus and usually all of the sperm nuclei and the small nuclei (Figs. 21–29). The most frequent chromosome numbers in the primary cleavage nuclei are about 77 and 67. The first and the second cleavage divisions are normal. A first elimination occurs in the 3rd, 4th, and 5th cleavage division (Fig. 30). All except 6 chromosomes are eliminated from the future somatic nuclei. Following a second elimination (Figs. 33, 34), the future somatic nuclei contain 5 chromosomes. No elimination occurs in the divisions of the germ line nucleus. In eggs which develop parthenogenetically the primary cleavage nucleus is formed by the egg nucleus and 2–3 small nuclei. It's chromosome number is therefore about 53 or 63. After two eliminations, which are similar to the ones which occur in fertilized eggs, the soma contains 5 chromosomes. The somatic nuclei of male larvae which arrise by paedogenesis contain 5 chromosomes; while the somatic nuclei of female larvae of paedogenetic origin contain 10 chromosomes. It was therefore assumed earlier that sex was determined by haploidy or diploidy. But the above results show that larvae from fertilized as well as from unfertilized eggs of imagines have 5 chromosomes in the soma, but are females, and the female paedogenetic offspring of larvae from unfertilized eggs have either 5 or 10 chromosomes in their somatic cells. Therefore sex determination is not by haploidy-diploidy but by some other, unknown, mechanism. The cytological events associated with paedogenetic, bisexual, and parthenogenetic reproduction in Heteropeza pygmaea are compared (Fig. 37). The occurrence and meaning of the small nuclei which are found in the eggs of most gall midges are discussed. It has been shown here that these nuclei function to restore the chromosome number in fertilized eggs; it is suggested that they function similarity in certain other gall midges. Consideration of the mode of restoration of the germ-line chromosome number leads to the conclusion that in Heteropeza few, if any, of the chromosomes are limited to the germ-line, i.e. can never occur in somatic cells (p. 124).     

Induction of cell division in a temperature-sensitive division mutant of Escherichia coli by inhibition of protein synthesis.

Synchronous cells of the thermosensitive division-defective Escherichia coli strain MACI (divA) divided at the restrictive temperature (42 degrees C) if they were allowed to grow at 42 degrees C for a certain period before protein synthesis was inhibited by adding chloramphenicol (CAP) or rifampicin. The completion of chromosome replication was not required for such divA-independent division. Synchronous cells of strain MACI divided in the presence of an inhibitor of DNA synthesis, nalidixic acid, if they were shifted to 42 degrees C and CAP or rifampicin was added after some time; cells of the parent strain MC6 (div A+) treated in the same way did not divide. These data suggest that coupling of cell division to DNA synthesis depends on the divA function. The ability to divide at 42 degrees C, whether or not chromosome termination was allowed, was directly proportional to the mean cell volume of cultures at the time of CAP addition, suggesting that cells have to be a certain size to divide under these conditions. The period of growth required for CAP-induced division had to be at the restrictive temperature; when cells were grown at 30 degrees C, in the presence of nalidixic acid to prevent normal division, they did not divide on subsequent transfer to 42 degrees C followed, after a period, by protein synthesis inhibition. A model is proposed in which the role of divA as a septation initiator gene is to differentiate surface growth sites by converting a primary unregulated structure, with the capacity to make both peripheral wall and septum, to a secondary structure committed to septum formation.     

Viable diploid progeny induced from sperm of Chinese tetraploid pond loach by cold‐shock androgenesis

Natural tetraploid loach (Misgurnus anguillicaudatus) living in the Changjiang River basin and adjacent area in China has been considered a true genetic tetraploidy (4n = 100) with four sets of homologous chromosomes. Here, we reported its further supporting evidence provided by the cold‐shock androgenesis. Viable androgenetic progeny appeared when eggs were cold‐shocked at 3°C for 60 min, starting 5 min after fertilization with sperm of natural tetraploid males, although the survival rate was significantly lower than control group. The majority (87%) of androgenetic embryos were diploid (2n = 50) and all‐paternal inheritance was verified in larval stage by microsatellite genotypes. Microscopic observations confirmed the elimination of both egg nucleus and second polar body from a fertilized egg, followed by the cleavage exclusively with sperm nucleus. Thus, the appearance of normal diploid androgenetic progeny from sperm of natural tetraploid loach revealed the presence of four chromosome sets in tetraploid males.     

Site of the previous meiotic division defines cleavage orientation in the mouse embryo

The conservation of early cleavage patterns in organisms as diverse as echinoderms and mammals suggests that even in highly regulative embryos such as the mouse, division patterns might be important for development. Indeed, the first cleavage divides the fertilized mouse egg into two cells: one cell that contributes predominantly to the embryonic part of the blastocyst, and one that contributes to the abembryonic part. Here we show, by removing, transplanting or duplicating the animal or vegetal poles of the mouse egg, that a spatial cue at the animal pole orients the plane of this initial division. Embryos with duplicated animal, but not vegetal, poles show abnormalities in chromosome segregation that compromise their development. Our results show that localized factors in the mammalian egg orient the spindle and so define the initial cleavage plane. In increased dosage, however, these factors are detrimental to the correct execution of division.     

Meiosis in garden roses

Summary Meiosis in 96 varieties of garden roses was studied. While the euploid numbers were most frequent, in exceptional cases, aneuploid numbers were recorded. Intervarietal variation in chromosome pairing is reflected in the varying degrees of expression of univalents, heteromorphic bivalents, bivalents with double secondary constrictions and multivalents. Supernumerary fragments in addition to the euploid chromosome complement were recorded in three varieties. Three varieties of floribundas and one of hybrid polyanthas were chromosome numerical mosaics.A part of Ph. D. thesis submitted by the senior author to the Post Graduate School, Indian Agricultural Research Institute, New Delhi, India.     

Study of the Lpm-system of mink allotypes in relation to Aleutian mink disease

Data on comparative study of the Lpm system of allotypes in minks of sovkhoz populations affected and nonaffected by Aleutian disease are presented. Significant interpopulational differences for frequencies of several Lpm genes of the second category (of corresponding haplo-, allo- and phenotypes) are revealed. This category includes genes species-specific for Mustela vison which make the main contribution to Lpm polymorphism. Seven minks with Lpm 3, 4, 6, 9, 10, 11 and Lpm 3, 4, 6, 7, 9, 10, 11 phenotypes, unknown earlier, have been found in the stationary hotbeds of Aleutian disease. They are most probably caused by the appearance and spreading of the recombinant haplotype Lpm in these populations. The data obtained are discussed from the point of view of their possible connection with epizootic of Aleutian disease.     

Genetic variation in wheat endosperm proteins: an analysis by two-dimensional electrophoresis using intervarietal chromosomal substitution lines

Summary The major endosperm proteins in a range of genotypes of hexaploid wheat have been fractionated by two-dimensional electrophoresis. The genotypes included nine varieties and forty four intervarietal substitution lines in which chromosomes 1A, 1B, 1D, 6A, 6B or 6D from eight of the varieties have been introduced one at a time into a common genetic background. The appearance of different protein subunits was often correlated with a chromosome substitution. This showed that many of the genes for the high molecular weight protein subunits (molecular weight range 55,000 to 140,000 determined by SDS polyacrylamide gel electrophoresis) are specified by chromosomes 1A, 1B and 1D while many of the lower molecular weight subunits (molecular weight range 30,000 to 45,000) are specified by chromosomes 6A, 6B and 6D. The different protein subunits correlated with chromosome substitution could not always be recognised in the varietal source of the substituted chromosome. The different subunits specified by homologous chromosomes in different wheat varieties may differ in isoelectric point and/or molecular weight.     

On the location of the gene(s) harbouring the advantageous variant that maintains the X/4 fusion of Drosophila americana

Weak selection is maintaining the Drosophila americana X/4 fusion chromosomal frequency cline. The gene(s) harbouring the advantageous variant(s) that is responsible for the establishment and maintenance of this chromosomal frequency gradient must be located in a region of the X and/or 4th chromosome that is genetically isolated between the X/4 fusion and non-fusion forms. The limits of these regions must thus be determined before an attempt is made to identify these genes. For this purpose, the correspondence between the D. virilis X and 4th chromosome genome scaffolds sequence and the D. americana gene order was established. Polymorphism levels and patterns at seven genes located at the base of the D. americana X chromosome, as well as three genes located at the base of the 4th chromosome, were analysed. The data suggest that the D. americana X/4 fusion is no more than 29,000 years old. At the base of the X chromosome, there is suppression of recombination within X/4 fusion and non-fusion chromosomes, and little recombination between the two chromosomal forms. Apparent fixed silent and replacement differences are found in three of seven genes analysed located at the base of the X chromosome. There is no evidence for suppression of recombination between fusion and non-fusion chromosomes at the base of the 4th chromosome. The advantageous variant responsible for the establishment in frequency and maintenance of the X/4 fusion is thus inferred to be in the D. americana X centromere-inversion Xc basal breakpoint region.