Identification of a female-sterile mutation affecting yolk protein 2 in Drosophila melanogaster

Summary The three yolk proteins (YP1, YP2 and YP3) of Drosophila melanogaster are synthesised in the fat body and ovarian follicle cells and selectively accumulated in the developing oocytes to provide a nutrient source for embryogenesis. We have described the phenotype of a temperaturesensitive female-sterile mutant, fs(1) K313, and characterised its yolk proteins. This mutation affects the secretion of YP2 and is the first mutation affecting YP2 to be described. Using genetic and molecular tests we argue that the female-sterile phenotype results, at least in part, from the abnormal secretion of YP2 perturbing the follicle cell secretory pathway in general and thus causing defects in chorion protein secretion. The gene coding for YP2 in fs (1) K313 has been cloned and sequenced. Two amino acid substitutions have been found which probably cause the abnormal secretion of YP2 and the resulting female-sterile phenotype.     

Semidominant Effect of the l(1)ts403 (sbr 10) Mutation on Sex Chromosome Nondsjunction in Meiosis in Drosophila melanogaster Females Exposed to Heat

The sbrgene of Drosophila melanogasterbelongs to the NXF(nuclear export factor) family responsible for the mRNA transport from nucleus to cytoplasm. We have shown that in the heat-exposed (37°C, 1 h) females, the l(1)ts403(sbr ¹⁰) mutation leads, in particular, to the high-frequency nondisjunction and loss of sex chromosomes in meiosis. For this trait, the incomplete dominance of the sbr ¹⁰ mutation is observed. At the same time, the sbr ¹⁰ mutation is recessive for many other traits of the heat-exposed flies: reduced viability, low fertility, impaired synthesis of the heat shock proteins, etc. The females heterozygous for the null allele (Df(1)v ^L4, a deletion eliminating gene srb) do not differ from females homozygous for the wild-type allele in frequency of the heat shock-induced nondisjunction and loss of sex chromosomes in meiosis. Because of this, the sbr ¹⁰ mutation can be assigned to the gain-of-function alleles (those gaining the dominance function). Expression of the mutant sbr ¹⁰ allele against the background of the wild-type allele suggests that in the heat shock-exposed females, the heat-modified product of this ts allele has an active effect on sex chromosome disjunction in meiosis.     

Isolation of germ line-dependent female-sterile mutation that affects yolk specific sequestration and chorion formation in Drosophila

Two loci on the X chromosome have been implicated in choriogenesis by in situ hybridization of poly A-containing RNA from choriogenic eggchambers to Drosophila polytene chromosomes (A. C. Spradling and A. P. Mahowald (1979): 7E and 12E. At least two genes coding for major eggshell proteins map to region 7E (A. C. Spradling, M. E. Digan, A. P. Mahowald, M. Scott, and E. A. Craig (1980). In an effort to elucidate the functional role of the 12E gene product, 3600 EMS-treated X chromosomes were screened for recessive female-sterile mutations that mapped within the region 11F10-12F1. Four independent female-sterile mutations were recovered, three of which fell into one complementation group (fs29, fs117, and fs445). Mapping by analysis of recombinant progeny as well as of trans heterozygotes utilizing other deficiency chromosomes showed that the three noncomplementing mutations all mapped to region 12E1-12F1. Studies comparing chorion morphology and protein synthesis indicate localized perturbations in the extracellular assembly of eggshell components in mutant eggchambers. The germ line dependence of the mutations was established using germ line mosaics constructed by pole cell transplantation. Analysis of eggchamber protein accumulation patterns showed reduced amounts of yolk polypeptides (YPs) in the mutants. The elevated concentrations of YPs found in mutant hemolymph coupled with the normal YP biosynthetic patterns and active uptake of trypan blue by mutant oocytes suggest that 12E sequences play a role in yolk-specific sequestration.     

In vivo cloning of a carboxy-terminalrpoB allele which confers altered transcriptional properties

A 3′-terminal mutation of the gene encoding the β subunit ofEscherichia coli RNA polymerase was isolated using anin vivo polA(Ts) technique. Cloning of the allele was monitored by virtue of the fact that the deletion Δ(rpoB) 1570-1 resulted in an altered-size restriction fragment. DNA sequencing confirmed the predicted nature and location of the mutation: Δ(rpoB) 1570-1 involved an in-frame deletion of 186 bp (62 codons) encoding amino acid residues 967–1028. The phenotype conferred by Δ(rpoB) 1570-1 is discussed with respect to conserved domains within the β polypeptide. Dedicated to Dr. J. Spížek on the occasion of his 60th birthday     

Phenotypic consequences and genetic interactions of a null mutation in the Drosophila posterior Sex Combs gene

The Posterior Sex Combs (Psc) gene of Drosophila is a member of the Polycomb (Pc) group of transregulatory genes. Previous analyses of the function of this gene in Drosophila em-bryogenesis have been hampered by the lack of a null mutation. We recently isolated a mutation that deletes the 5′ end of the Psc gene. This allele appears to be a null mutation, and we have used it to determine the Psc zygotic null phenotype and to look at the interactions of a null allele of Psc with five other Pc group mutations. We find evidence for transformations along both the anterior-posterior and dorsal-ventral axes in embryos of a variety of genotypes that include a null mutation in Psc. The phenotypes of embryos that are doubly mutant for a null allele of Psc and a mutation in a second Pc group gene show dramatic synergistic effects, but in their specifics they are dependent on the identify of the second Pc group gene. This is different from the relatively uniform phenotypes seen among double mutants that contained the allele Psc¹, which has both gain and loss of function properties. The differences in the phenotypes of the doubly mutant embryos allow us to eliminate one class of molecular models to explain the dramatic synergism seen with mutations in this group of genes.     

Inhibition of F plasmid replication in htpR mutants of Escherichia coli deficient in sigma 32 protein

Summary In Drosophila melanogaster there are two glutamine synthetase (GS) (EC 6.3.1.2) isozymes. They are called GSI and GSII. The two enzymes have different subunits and different genetic determination. A DNA fragment that comprises 80% of the coding region of the glutamine synthetase gene of Chinese hamster ovary (CHO) cells allowed the identification and cloning of an homologous DNA fragment of Drosophila. This sequence is located at the 10B8-11 region on the X chromosome. Dose variation of a chromosomal segment from 9F3 to 10C1-2, which encompasses the 10B region, leads to proportional variations of GSII without apparently influencing the amount of GSI.     

Studies of fs(1)1621, a mutation producing ovarian tumors in Drosophila melanogaster

The ethyl methane sulfonate-induced mutation, fs(1)1621, resides at 11.7 on the genetic map and within segment 4F1-5A1 of the cytological map of the X chromosome. When homozygous, fs(1)1621 renders females semisterile but has no effect on their viability; nor does it affect the viability or fertility of hemizygous males. Heterozygous females are fertile and have cytologically normal ovaries. The ovaries of homozygous females first produce normal oocytes, which, if fertilized, can develop into adult males or females. After this period, ovarian chambers containing only pseudonurse cells are formed, and finally mutant germaria produce only tumors. These contain hundreds to thousands of cells that appear to be derived from germarial cystocytes, because they occasionally form clones of interconnected cells and also can differentiate into endopolyploid pseudonurse cells. Raising the temperature speeds the rate at which tumors form; lowering it increases the probability of pseudonurse cell differentiation. Df(1)C159 includes fs(1)1621. The pattern of ovarian chamber production is more temperature sensitive in hemizygous females than in homozygous ones. The morphology of hemizygous tumors and the number of dividing cells within them also differ from homozygotes. These observations support the hypothesis that fs(1)1621 is producing a product, that less is produced by one gene than by two, and that the product plays a role in the mitosis and cytokinesis of ovarian cystocytes.     

Association of CTG repeats and the 1-kbAlu insertion/deletion polymorphism at the myotonin protein kinase gene in the Japanese population suggests a common Eurasian origin of the myotonic dystrophy mutation

We have studied linkage disequilibrium between CTG repeats and anAlu insertion/deletion polymorphism at the myotonin protein kinase gene (DMPK) in 102 Japanese families, of which 93 were affected with myotonic dystrophy (DM). All of the affected chromosomes are in complete linkage disequilibrium with theAlu insertion allele. Among the normal chromosomes, alleles of CTG repeats 5 and 17 are exclusively associated with the insertion allele. On the other hand, intermediate alleles of 11-6 repeats show a significantly greater association with the deletion allele. A strikingly similar pattern of linkage disequilibrium observed in European populations suggests a common origin of the DM mutation in the Japanese and European populations.     

Out of the testis,into the ovary: biased outcomes of gene duplication and deletion in Drosophila

Gene turnover is a key source of adaptive variation. Yet most evolutionary studies have focused on gene duplication, dismissing gene deletion as a mechanism that simply eradicates redundancy. Here, I use genome‐scale sequence and multi‐tissue expression data from Drosophila melanogaster and Drosophila pseudoobscura to simultaneously assess the evolutionary outcomes of gene duplication and deletion in Drosophila. I find that gene duplication is more frequent than gene deletion in both species, indicating that it may play a more important role in Drosophila evolution. However, examination of several genic properties reveals that genes likely possess distinct functions after duplication that diverge further before deletion, suggesting that loss of redundancy cannot explain a majority of gene deletion events in Drosophila. Moreover, in addition to providing support for the well‐known “out of the testis” origin of young duplicate genes, analyses of gene expression profiles uncover a preferential bias against deletion of old ovary‐expressed genes. Therefore, I propose a novel “into the ovary” hypothesis for gene deletion in Drosophila, in which gene deletion may promote adaptation by salvaging genes that contribute to the evolution of female reproductive phenotypes. Under this combined “out of the testis, into the ovary” evolutionary model, gene duplication and deletion work in concert to generate and maintain a balanced repertoire of genes that promote sex‐specific adaptation in Drosophila.     

The relative importance of meiotic gene conversion,selection and mutation pressure,in population genetics and evolution

Disparity in the direction of meiotic gene conversion can change allele frequencies, favouring one allele of a pair in heterozygotes. Equilibrium allele frequencies for large diploid populations are examined by means of equations relating them to meiotic gene conversion, selection and mutation for deleterious recessives, deleterious dominants, and deleterious alleles with no dominance. Using observed conversion parameters from various fungi,Zea mays andDrosophila, it is shown that conversion is generally much more important than mutation pressure and may be of greater or lesser importance than selection, depending on dominance and the strength of selection and conversion forces for the alleles involved.     

Genetic and Phenotypic Analysis of <Emphasis Type="Italic">lax1-6</Emphasis>, a Mutant Allele of <Emphasis Type="Italic">LAX PANICLE1</Emphasis> in Rice

Proper function of the LAX1 gene is required for the development of axillary meristem in rice. Here, we report genetic and phenotypic characters of a novel recessive mutant allele of rice LAX1 gene, lax1-6, which showed abnormal panicle phenotypes with few numbers of elongated primary rachis branches. Beside typical lax mutant phenotype, abnormalities of lax1-6 mutant allele were observed with defect lemma and palea primordial in floral organs. The lax1-6 mutant locus was linked between SSR markers RM7594 and RM5389 on chromosome 1 with 1.02% and 1.0% recombination frequencies, respectively. Molecular analysis revealed that the lax1-6 mutant allele was caused by a transversion mutation of nucleotide T to G substitution that resulted in an amino acid substitution from serine (S) to alanine (A) at the 117^th position from amino terminus of a basic helix-loop-helix protein coded by LAX1 gene. Furthermore, we found that the Oryza sativa indica type cv. IRRI347 contained 24 nucleotide deletion in the upstream sequence in the LAX1 gene, but this deletion did not influence panicle morphology, which demonstrated that the deletion is a polymorphism in rice. All together, the lax1-6 mutant is a newly identified allele of LAX1 gene displaying the abnormal axillary meristems and inflorescences in rice.     

Analysis of DNA Interband Regions 3A5/A6, 3C5-6/C7, and 60E8-9/E10 in Polytene Chromosomes of Drosophila melanogaster

Using electron microscopic (EM) data on the formation of a novel band from theP-element material after its insertion in the interband and the procedure of P-target rescue, DNA interband regions 3A5/A6, 3C5-6/C7, and 60E8-9/E10 of Drosophila melanogasterpolytene chromosomes were cloned and sequenced. EM analysis of the 3C region have shown that the formation of the full-size 3C5-6/C7 interband requires a 880-bp DNA sequence removed by deletion Df(1)fa ^swb. A comparison of DNA sequences of six bands, two of which were obtained in the present work and four were described earlier, demonstrated the uniqueness of each of them in the Drosophilagenome and heterogeneity of their molecular organization. Interband 60E8-9/E10 contains gene rpl19transcribed throughout the development, in particular in salivary glands. In the other interbands examined 5" and 3" nontranslated gene regions are located. These results suggest that Drosophilainterbands may contain both housekeeping genes and regulatory sequences of currently inactive genes from adjacent bands.     

The functional <Emphasis Type="Italic">SLC11A1</Emphasis> gene polymorphisms are associated with sarcoidosis in Turkish population

Sarcoidosis (SA) is an immune-mediated multisystemic disorder of unknown etiology characterized by the accumulation of lymphocytes, mononuclear phagocytes and epithelioid cell granulomas involved in different organs and tissues. The belief that genetics contribute to SA etiology is supported by twin studies, disease clustering in families and racial differences in incidence rates. Involvements of SLC11A1 in macrophage function and activation, makes it an attractive candidate gene for immune-mediated and infectious diseases. We investigated the association between SA and four polymorphisms of the SLC11A1 gene, including a single nucleotide change in intron 4 (INT4); a nonconservative single-base substitution at codon 543 (D543N); a TGTG deletion in the 3′ untranslated region; and the functional (GT)_n repeat polymorphism in the 5′ region, in 95 Turkish SA patients and 150 healthy controls, by using amplification refractory mutation system–polymerase chain reaction and sequencing. We found significant association between SA and INT4 G/C allele frequency (P = 0.0000; odds ratio 2.75; 95% confidence interval 1.68–4.52) and 5′(GT)_n allele 2/3 frequency (P = 0.0000; odds ratio 2.69; 95% confidence interval 1.61–4.47) suggesting that SLC11A1 might be a plausible candidate gene for SA.