Effects of the “sexcombless” chromosome (In(1)sx) on males and females ofDrosophila melanogaster

Summary The chromosome which carries the mutationsexcombless (In(1)sx) affects males and females ofD. melanogaster. In the male foreleg basitarsi the number of sexcomb teeth is dramatically reduced from 10 to 0.7 and the number of transverse rows of bristles is increased from 6 to 8. Females homozygous forIn(1)sx show a normal bristle pattern in the foreleg basitarsus. The genital disc derivatives of both male and femaleIn(1)sx flies are strongly affected. While the external genitalia show a duplicated or a reduced bristle pattern, the internal genitalia are mostly absent. However, the sexually dimorphic tergites and sternites of the abdomen remain unaffected. The male-specific effect on the basitarsus and the general effects on the genital disc derivatives are proposed to represent two different phenotypic effects ofIn(1)sx which may derive from mutations at different gene loci in the inverted chromosome.     

The effect of sexcombless in genetic mosaics ofDrosophila melanogaster

Summary Gynandric basitarsi possessing areas heterozygous for the sexlinked mutant sexcombless (sx) and hemizygous for it, and mosaic basitarsi possessingsx/+,sx/sx and +/+ areas have been studied for the developmental expression ofsx andsx/sx patches in the sex comb region. The mosaic basitarsi were obtained as the result of somatic crossing over following X-ray exposure of larvae. In order to observe the sex comb-forming potencies in these XX tissues the flies had been made homozygous for the genetra which transforms females into phenotypic males. The development ofsx/+;tra/tra females is greatly prolonged over that of normal females.Five of the 63 gynandric and two of the 39 radiation-induced mosaics showed a single typical tooth, a sixth gynandric basitarsus had two teeth. In all other cases intermediate bristles, or macrochaetae, or both, have been found iny sn sx hemizygous or homozygous patches irrespective of their size.Thesx-initiated distortion of bristle arrangement found in non-mosaicsx male basitarsi has also been seen in many mosaic patches.The mutant genesx acts autonomously and interferes with the process of seta-cell to tooth determination at a relatively early stage in development of a bristle organ.With 38 Figures in the Text     

Sperm competition in the Drosophila female

Summary Modified B ^S translocation males were developed at 26.0° C where univalentbearing gametes are recovered with less than half the frequency than at 18.0° C. Upon eclosion the males were stored for definite time periods at either temperature before mating individually to single y free-X females. the transfer cultures of the females show a higher frequency of recovery of univalent-bearing progeny regardless of the temperature or storage treatment of the male. In addition, postmeiotic temperature treatment does not appear to fundamentally alter the overall frequency of recovery of univalent-bearing gametes which is presumably determined by the developmental temperature of the male. A similar trend is observed for matings of y females to single X.Y^SY^L/O males in which the males were developed and stored at 26.0° C; namely, a higher frequency of recovery of attached-XY gametes in the transfer cultures.     

Frequency of x-ray induced mitotic recombination in genotypes with different X-Y-combination-chromosomes in Drosophila melanogaster

Summary In first and second instar larvae of Drosophila melanogaster mitotic recombination has been induced by X-rays. Resulting mosaic spots were analysed in the eyes of adult females. The five examined genotypes varied in the combination of different X-chromosomes and in the presence or absence of the duplication Dp(1;3)N ^264-58. X-chromosomes used have been elongated by proximally or distally linked arms of the Y-chromosome. The portion of Y-heterochromatin in the genome is negatively correlated with the frequency of twin mosaic spots (Fig. 1). The frequency of these spots is lower in flies bearing the duplication than in those without the duplication. With respect to the X-chromosome combinations, there are no marked differences in the frequencies of single mosaic spots (Fig. 2); with respect to the duplication they are absent. In the genotype Y ^S X/X.Y ^S prophases of neuroblast mitoses (Fig. 4) show normal pairing of homologous chromosome sections. Reasons for the different spot frequencies are discussed.

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Vorgelegt von E. Hadorn     

Bristle patterns and clones along a compartment border in the anterior wing margin ofDrosophila hydei

Summary The bristle pattern along the first longitudinal vein of the wing ofD. hydei differs from that ofD. melanogaster. Instead of a triple row,D. hydei and some allied species show a pattern of five parallel bristle rows of which the medial row (MR) is comparable to the medial triple row (MTR) ofD. melanogaster. Cells of the MR can be made homozygousyellow (y) by induction of mitotic recombination in heterozygousy/y ⁺ females. Until 70 h after egg laying (AEL), the MR clones inD. hydei overlap with one or more of the accompanying dorsal and ventral bristle rows. Between 70 and 120 h AEL the MR clones only overlap with dorsal bristle rows. Some time later they also become separated from both dorsal rows. The resulting MR clone pattern fits with the overall longitudinal clone pattern in the wing blade ofD. melanogaster described by Bryant (1970) and others. The MR clones inD. hydei, however, often show a fragmented appearance with many indentations of the surroundingy ⁺ tissue even when induced after fixation of the DV compartment boundary. This result contrasts with the commonly held notion, derived from work withD. melanogaster, that compartment boundaries are smooth lines.     

The suppressor of Hairy-wing binding region is required for gypsy mutagenesis

Summary We undertook a deletional analysis of the gypsy retrotransposon in order to determine which sequences of the element are required for its mutagenic effect. We show that a phenotype indistinguishable from that ofy ² flies can be generated by transformingy ^– flies with a construct containing theyellow gene and a gypsy element located at the same insertion site inyellow as found iny ² flies. When flies are transformed with similar constructs in which increasing amounts of the 5 transcribed untranslated region of gypsy have been removed, either a partialy ² revertant or a completely revertant phenotype is obtained. These results yield direct proof that the region of gypsy to which thesu(Hw) protein binds is required for the generation of mutant phenotypes by this retrotransposon.     

A transmissible dicentric chromosome in Drosophila melanogaster

A transmissible dicentric chromosome was recovered in Drosophila melanogaster. The radiation-induced secondary chromosome rearrangement consists essentially of the entire Y and fourth chromosomes joined by 2R heterochromatin. The Y ^S · Y ^L 2Rh4 · chromosome pairs with the X and the free fourth chromosome to form a trivalent in meiosis that is unusual because it forms few chromosome bridges in primary spermatocytes and is transmitted at high frequency. We suggest that the orientation of the weaker fourth chromosome kinetochore eventually fails when opposing the stronger Y kinetochore so that the Y ^S · Y ^L 2Rh4 · moves to the pole to which the Y kinetochore is oriented. There is however an increased frequency of sex chromosome nondisjunction (14%) and of chromosome laggards (6%) in primary spermatocytes; the frequency of exceptional progeny of males containing the Y ^S · Y ^L 2Rh4 · was 7.44% compared with 0.25% in the controls. Disruption of normal sex chromosome disjunction also occurs in females containing the Y ^S · Y ^L 2Rh4 · and a compound X chromosome; the frequency of exceptional progeny was 2.55% versus 0.91% in the controls. Chromosome nondisjunction appears to occur when orientation of the X and Y kinetochores to the same pole is stabilized through tension by the orientation of one or both fourth chromosome kinetochores to the opposite pole. During anaphase, the orientation of the fourth chromosome kinetochore of the Y ^S · Y ^L 2Rh4 · appears to fail and the X and Y ^S · Y ^L 2Rh4 · chromosomes move to the same pole. Y ^S · Y ^L 2Rh4 · chromosome laggards occur with both the Y and fourth chromosome kinetochores amphitelically oriented. This orientation appears to be stable as a result of equal opposing forces toward opposite poles.     

Bristle patterns,clones and cell competition along the anterior margin ofNotch wings ofDrosophila hydei

Summary The bristle pattern along the anterior margin ofNotch (N1-22.3) wings ofDrosophila hydei and the occurrence ofyellow (y 1–38.8) marked clones induced by X-ray irradiation during various larval stages are described. UnirradiatedN/N ⁺ wings show gaps (notches) in the longitudinal bristle rows along the 1st longitudinal vein, with tufts of bristles particularly near gaps. X-ray irradiation increases the number and total length of the gaps. The patterning of bristles along the margin depends on theN ⁽⁺⁾ genotype of the induced clones. RecombinantN ⁺/N ⁺ clones from irradiated wings show excessive growth with an autonomous wildtype bristle pattern. Characteristically, these clones do not respect the dorso-ventral compartment boundary along the wing margin, do not follow an exponential (2ⁿ) growth pattern, tend to fill the gaps with bristles and theiryellow medial row bristles are less often interspersed withy ⁺ bristles than described forN ⁺/N ⁺ wings. HomozygousN appears to be a cell lethal condition inD. hydei as it is inD. melanogaster. When y clones were kept phenotypicallyNotch (viz.,N/N/N ⁺) as the background cells, we found a lower number ofy bristles, a lower percentage of mosaic wings but also a reltive deficiency ofy ⁺ interspersions. The latter is discussed in relation to a possible clonal originof the notches.     

Identification of an uncommon haptoglobin type using DNA and protein analysis

The inherited variations in haptoglobin phenotypes are attributed to the homozygous and heterozygous combinations of three common autosomal alleles:HP ^* 1F,HP ^* 1S andHP ^* 2.HP ^* 1F andHP ^* 1S encode polypeptides that differ by two amino acids at positions 51 and 53. The formation ofHP ^* 2 is postulated to have resulted from a breakage and subsequent reunion event at non-homologous positions of twoHP ^* 1 alleles. The most common form ofHP ^* 2 isHP ^* 2FS in which the 5 end ofHP ^* 2 resemblesHP ^* 1F and the 3 end resemblesHP ^* 1S. Homologous crossing over betweenHP ^* 2 and either anHP ^* 1F orHP ^* 1S allele inHP ^* 2/HP ^* 1 heterozygotes can change the usual type ofHP ^* 2 to three other forms:HP ^* 2SS,HP ^* 2FF orHP ^* 2SF. We describe a nuclear family in which the uncommon genotypeHP ^* 2SS in one parent caused initial confusion in assigning genotypes to the rest of the nuclear family. The data demonstrate the need for a cautious approach when deducing haptoglobin genotypes from molecular analysis alone.     

Callus induction and regeneration in<Emphasis Type="Italic"> Spirodela</Emphasis> and<Emphasis Type="Italic"> Lemna</Emphasis>

The development of tissue culture systems in duckweeds has, to date, been limited to species of the genus Lemna. We report here the establishment of an efficient tissue culture cycle (callus induction, callus growth and plant regeneration) for Spirodela oligorrhiza Hegelm SP, Spirodela punctata 8717 and Lemna gibba var. Hurfeish. Significant differences were found among the three duckweed species pertaining to carbohydrate and phytohormone requirements for callus induction, callus growth and frond regeneration. In vitro incubation with poorly assimilated carbohydrates such as galactose (S. oligorrhiza SP and L. gibba var. Hurfeish) and sorbitol (S. punctata 8717) as sole carbon source yielded high levels of callus induction on phytohormone-supplemented medium. Sorbitol is required for optimal callus growth of S. oligorrhiza SP and S. punctata 8717, while sucrose is required for callus growth of L. gibba var. Hurfeish. Sucrose either alone (S. oligorrhiza SP, L. gibba var. Hurfeish) or in addition to sorbitol (S. punctata 8717) is required for frond regeneration.Abbreviations ABA: (±)-Abscisic acid - BA: N⁶-Benzyladenine - 2,4-D 2,4-Dichlorophenoxyacetic acid - Dicamba: 3,6-Dichloro-2-methoxybenzoic acid - 2iP: N⁶-(2-Isopentenyl)adenine - NAA: -Naphthaleneacetic acid - PCA: p-Chlorophenoxy acetic acid - Picloram: 4-Amino-3,5,6-trichloropicolinic acid - TDZ: Thidiazuron Communicated by A. AltmanJ. Li and M. Jain contributed equally to the research reported in this article.     

Cytological and genetical studies of the hybrid ofGossypium herbaceum L. andG. triphyllum Hoch

Cytological and genetical studies are reported on the hybrid and later generations ofGossypium herbaceum (A₁ genome) xG. triphyllum (Hg genome). Chromosome pairing between the two genomes was high, and their chromosomes are considered, with minor exceptions, to be strueturally similar. Studies of the F₁ and segregating families showed thatG. triphyllum carries the complementary factorsR _inf2 ^supΘS R _infa ^supGO for petal spot,Y _a(Y_b) Y _infc ^supP for cream petal,pa for cream pollen, andY _ap for depression of yellow petal pigment. Leaf ahape ofG. triphyllum was dominant to the leaf shape ofG. herbaceum. The blue petal color ofG. triphyllum was recovered only in the backeross of the F₁ to this species. Contribution from the Agricultural Experiment Stations of Arizona and Texas. Part of this work was done under Regional Research Project S-1 of the Hatch Act (Amended). 1. Address of first author; 2. Address of second author.     

Interaction of alleles of therelA, relC andspoT genes inEscherichia coli: Analysis of the interconversion of GTP, ppGpp and pppGpp

Summary Mutants in thespoT gene have been isolated as stringent second site revertants of therelC mutation. These show varying degrees of the characteristics associated with thespoT1 gene,viz relative amount and absolute levels of both pppGpp and ppGpp and the decay rate of the latter. The entry of³H-guanosine into GTP and ppGpp pools inspoT ⁺ andspoT1 cells either growing exponentially or during amino acid starvation was determined, and the rate of ppGpp synthesis and its decay constant calculated. During exponential growth the ppGpp pool is 2-fold higher, its decay constant 10-fold lower, and its synthesis rate 5-fold lower inspoT ^- than inspoT ⁺ cells; during amino acid starvation the ppGpp pool is 2-fold higher, its decay constant 20-fold lower, and its synthesis rate 10-fold lower inspoT than inspoT ⁺ cells. In one of the “intermediate”spoT mutants the rate of entry of³H-guanosine into GTP, ppGpp and pppGpp was measured during amino acid starvation. The data form the basis of a model for the interconversion of the guanosine nucleotides in which the flow is:GDP→GTP→pppGpp→ppGpp→Y. Calculations of the rates of synthesis and conversion of pppGpp and ppGpp under various conditions in variousspoT ⁺ andspoT ^- strains indicate that the ppGpp concentration indirectly controls the rate of pppGpp synthesis. ThespoT1 allele was introduced into various relaxed mutants. It was shown that many phenomena associated with the relaxed response ofrelC and “intermediate”relA mutants were phenotypically suppressed when thespoT1 allele was introduced into these mutants. These double mutants exhibit ppGpp accumulation, rate of RNA accumulation, rate of β-galactosidase synthesis, and heat lability of β-galactosidase synthesized during amino acid starvation similar to the stringent wild-type. It is concluded that the relaxed response is due directly to the lack of ppGpp and that the stringest response is due directly to ppGpp.     

Distribution of similar self-incompatibility (<Emphasis Type="Italic">S</Emphasis>) haplotypes in different genera,<Emphasis Type="Italic"> Raphanus</Emphasis> and<Emphasis Type="Italic"> Brassica</Emphasis>

The nucleotide sequences of ten SP11 and nine SRK alleles in Raphanus sativus were determined, and deduced amino acid sequences were compared with those of Brassica SP11 and SRK. The amino acid sequence identity of class-I SP11s in R. sativus was about 30% on average, the highest being 52.2%, while that of the S domain of class-I SRK was 77.0% on average and ranged from 70.8% to 83.9%. These values were comparable to those of SP11 and SRK in Brassica oleracea and B. rapa. SP11 of R. sativus S-21 was found to be highly similar to SP11 of B. rapa S-9 (89.5% amino acid identity), and SRK of R. sativus S-21 was similar to SRK of B. rapa S-9 (91.0%). SP11 and SRK of R. sativus S-19 were also similar to SP11 and SRK of B. oleracea S-20, respectively. These similarities of both SP11 and SRK alleles between R. sativus and Brassica suggest that these S haplotype pairs originated from the same ancestral S haplotypes.     

Contribution of the geneextramacrochaetae to the precise positioning of bristles inDrosophila

We examine the effect of mutations in theextramacrochaetae (emc) gene on the positioning of macrochaetes on the notum ofDrosophila. We show that, inemc mutants, most of the precursor cells appear earlier than in wild-type individuals, consistent with an antagonizing effect ofemc on the action of the proneural genesachaete andscute. We also show that reducingemc function affects the position of three bristles and/or of their precursors, but has no marked effect on the positioning of the other bristles.     

Heterochromatin of the Drosophila melanogaster Y chromosome as modifier of position effect variegation: the time of its action.

Summary Addition of heterochromatin suppresses while subtraction enhances position effect variegation. The heterochromatin-sensitive period has been determined in white/white-apricot variegated eyes of Y ^S w ^a /w ^a ; Dp (1;3) w ^265-58 flies. When such larvae, carrying a Y-short (Y ^S ) arm at the distal end of one X chromosome, are X-rayed, mitotic recombination leads to one daughter cell with two Y ^S arms and an adjacent daughter cell with no Y ^S arm. When induced after clonal initiation, the frequency of dark clones developing from daughter cells with two Y ^S arms is significantly higher than the frequency of dark clones in the rest of the eye; and this frequency is. even higher when induced before clonal initiation. The modifying action of the Y-heterochromatin is exerted, therefore, during and after clonal initiation. Surprisingly, the frequency of dark clones developing from cells with no Y ^S arm is not lower than the frequency of dark clones in the rest of the eye.     

The utilization ofL-amino acids as carbon source by yeasts of the generaHansenula andTrichosporon

The assimilation of singleL-amino acids as carbon source in the absence of added nitrogen has been studied for all the described species in the generaHansenula andTrichosporon. The range in the number of amino acids used by individual species varied in the two genera, inHansenula from 0 to 6, inTrichosporon from 0 to 16. These characters were considered in relation to the phylogenetic scheme and ecological origin ofHansenula.     

Influence of genetic markers and of the fusing agent polyethylene glycol on chromosomal gene transfer inSpiroplasma citri

Gene transfer-recombination involving three different chromosomal markers (Ars^R, Van^R, and Xyl^R) and influence of the fusing agent PEG on transfer efficiency were investigated in matings between single-resistant or single and double-resistant strains ofSpiroplasma citri. Efficiency and kinetics vary, inS. citri, with the markers involved in the crosses and are not enhanced by the membrane fusion effect of PEG. These features allow one to distinguish the chromosomal gene transfer inS. citri from the closely related transfer by protoplast fusion in Gram-positive bacteria. However, the results may be explained by a spontaneous high frequency of the membrane fusion events ofS. citri cells and the existence of variations in the recombination frequency of the markers. Indeed, inS. citri, the formation of the heterozygotic polyploid structure formed after membrane fusion may be considered as a nonlimiting step of the mechanism and allows one, accordingly, to point out differences in recombination frequencies of the markers.     

Sense organs in the femur of the stick insect and their relevance to the control of position of the femur-tibia-joint

Summary The sensory innervation pattern is described for the femur of the middle and the hind legs ofCarausius morosus. — In one of the nerves (F121) extracellular recordings show a unit which mirrors the tension of the flexor tibiae muscle (tension receptor). The tension receptor increases the firing rate of the slow extensor tibiae motoneuron. It measures the tension of one or more muscle fibres of the anterior side near the distal end of the muscle. The anatomical basis of this receptor is uncertain. — Another receptor was found on the ventral side of the distal end of the apodeme of the extensor tibiae muscle (apodeme receptor). Recordings from this receptor could not be obtained inCarausius. But inExtatosoma tiaratum it responded to stretching of the nerve. In the natural position it shows a minimum of excitation in the 90°-position of the femur-tibia-joint and an increase in firing rate for both flexion and extension. — Tactile hairs react phasically and have no special sensitivity for one direction. Two receptors at the dorsal side of the femur-tibia-joint (RDAL and RDPL), which are situated in the same position as inSchistocerca hind legs, react phasically to extension movements and fire tonically in the most extended position of the joint. — The influence of these receptors on the position of the femur-tibia-joint is only weak.Supported by Deutsche Forschungsgemeinschaft     

Interaction ofFLC and late-flowering mutations inArabidopsis thaliana

The phenotype caused by mutations that affect the timing of flowering inArabidopsis thaliana has been most extensively analyzed in the Landsbergerecta (Ler) genetic background. In Ler, the late-flowering phenotype ofFRIGIDA and mutations inLUMINIDEPENDENS is suppressed by the Ler allele ofFLC. In this study, the interactions of nine mutations conferring late flowering with theFLC allele of the Columbia ecotype (FLC-Col), which does not suppress late flowering, were examined. The effect on flowering time of combining six of the mutations withFLC-Col was additive; plants containingFLC-Col withfd, gi, fwa, fha, ft, andfe flowered slightly later than plants containing these mutations with theLer allele ofFLC. In contrast, a synergistic effect was observed betweenFLC-Col and three mutations;fca, fpa, andfve plants became extremely late flowering when combined withFLC-Col. Maximum delay in flowering for the majority of the mutant strains requiredFLC-Col in a homozygous state, although forfpa andfe a single copy ofFLC-Col allowed maximum lateness. In addition, thefd andfe mutations became more dominant in the presence ofFLC-Col.     

Sex determination in<Emphasis Type="Italic"> Drosophila melanogaster</Emphasis> and<Emphasis Type="Italic"> Musca domestica</Emphasis> converges at the level of the terminal regulator<Emphasis Type="Italic"> doublesex</Emphasis>

Sex-determining cascades are supposed to have evolved in a retrograde manner from bottom to top. Wilkins 1995 hypothesis finds support from our comparative studies in Drosophila melanogaster and Musca domestica, two dipteran species that separated some 120 million years ago. The sex-determining cascades in these flies differ at the level of the primary sex-determining signal and their targets, Sxl in Drosophila and F in Musca. Here we present evidence that they converge at the level of the terminal regulator, doublesex (dsx), which conveys the selected sexual fate to the differentiation genes. The dsx homologue in Musca, Md-dsx, encodes male-specific (MdDSX^M) and female-specific (MdDSX^F) protein variants which correspond in structure to those in Drosophila. Sex-specific regulation of Md-dsx is controlled by the switch gene F via a splicing mechanism that is similar but in some relevant aspects different from that in Drosophila. MdDSX^F expression can activate the vitellogenin genes in Drosophila and Musca males, and MdDSX^M expression in Drosophila females can cause male-like pigmentation of posterior tergites, suggesting that these Musca dsx variants are conserved not only in structure but also in function. Furthermore, downregulation of Md-dsx activity in Musca by injecting dsRNA into embryos leads to intersexual differentiation of the gonads. These results strongly support a role of Md-dsx as the final regulatory gene in the sex-determining hierarchy of the housefly.Edited by D. Tautz