Polymorphism of yellow locus in Drosophila melanogaster from natural populations

We studied molecular characteristics of yellow (y; 1-0.0) locus, which determines the body coloration of phenotypically wild-type and mutant alleles isolated from geographically distant populations of Drosophila melanogaster in different years. According to Southern data, restrictions map of yellow locus of all studied strains differ from each other as well as from that of Oregon stock. FISH analysis shows that in the neighborhood of yellow locus in X chromosome neither P nor hobo elements are found in y1-775 stock, while only hobo is found there in y1-859 and y1-866 stocks, only P element in y+sn849 stock, and both elements in y1-719 stock. Thus, all studied mutant variants of yellow are of independent origin. Yellow locus residing at the very end of X chromosome (region 1A5-8 of cytologic map) carries significantly more transposon than retrotransposon-induced mutations, as compared to white locus (regions 3C2). It is possible that transposons are more active than retrotransposons at the chromosomal ends of D. melanogaster.     

The effect of genetic environment on locus-specific instability of the yellow gene in Uman' population of Drosophila melanogaster

The effects of genotype of the laboratory strains, C(1)DX, ywf/Y, 23.5 MRF/CyL4, and C(1)DX,yf; pi2, on locus-specific instability in the yellow gene of the strains y(2-717, y(2-715), and y(2-700 ) from Uman' population of Drosophila melanogaster was studied. Crosses of the males from Uman'-derived lines with the C(1)DX, ywf/Y females yielded a cascade of derivatives, mostly consisting of y+ and y2 alleles, while their crosses with the 23.5 MRF/CyL4 and C(1)DX,yf; pi2 females mostly resulted in the appearance of y+ and y(1) derivatives. The genomes of laboratory strains used in the study contained the full-sized hobo elements, which could differ from one another relative to the structure of variable region and affinity to different DNA sequences.     

应用果蝇yellow基因的分子模式分析基因转应作用(英文)

基因转应作用（ｔｒａｎｓｖｅｃｔｉｏｎ）是基因表达的一种方式,这种方式是由等位基因配对及其相互作用所介导的。基因转应作用的现象已在果蝇的多种基因中发现。这种作用可产生正负两种效应。而且,在其它物种中,也逐渐发现了类似的现象。例如,在植物中的基因沉默现象（ｇｅｎｅｓｉｌｅｎｃｉｎｇ）以及在小鼠中的基因转激活作用（ｔｒａｎｓａｃｔｉｖａｔｉｏｎ）等。因此,阐明基因转应作用的机理,将有助于了解基因表达调节及增强子调控活动的分子基础。本文应用果蝇ｙｅｌｏｗ基因为模式来探讨基因转应作用的分子机制。前期研究表明,ｙｅｌｏｗ基因转应作用发生于ｇｙｐｓｙ诱导的ｙ２突变种和ｙｅｌｏｗ亚等位基因（ｙｈ）之间。为了证实是否ｇｙｐｓｙ是基因转应作用所必需的ＤＮＡ元件,我们鉴定了一种新的ｙｅｌｏｗ突变种,称为ｙ２３７４。ｙ２３７４突变是一种基因表达的组织特异性改变,这一改变使ｙ２３７４果蝇在翅和身体部位表皮着色呈突变型。通过遗传分析表明,ｙ２３７４也可与ｙｈ（如ｙ１＃８）产生基因转应作用。ｙ１＃８是一种无效的ｙｅｌｏｗ等位基因,它包含一个启动子和部分编码区序列的缺失。然而,当ｙ２３７４与ｙ１＃８杂交后,其杂交后代的表现型可由ｙ２３７     

Participation of mobile element hobo in transposition events in the long-term instability system of Drosophila melanogaster]

The lines with an active hobo elements as well as those without any hobo fragments were hybridized with the y2sc1waG line. This resulted in the appearance of a number of mutations at the white, miniature, and some other loci. The authors analysed, in which way the hobo transposable elements take part in mutagenesis in these crosses. Most of the white mutants obtained were analysed and transpositions of hobo and Stalker elements were demonstrated. Both independent and simultaneous transpositions were found. It was shown by means of the Southern blot analysis that additional hobo or Stalker insertion into or close to the parental unknown waG insertion resulted in mutant white phenotype's shift toward both extreme and partial reversion. Possible participation in mutagenesis of other mobile elements is also under debate.     

Molecular analysis of insertional mutations in the yellow gene region of Drosophila

We have cloned 70 kb of DNA from the yellow (y) gene region and analyzed two y null alleles. These alleles are caused by different DNA elements that have inserted into different sites of the y gene coding region.     

"Mode for mutation" in the natural population of Drosophila melanogaster from Umani is caused by distribution of a hobo-induced inversion in the regulatory region of the yellow gene

A mutation outburst of the yellow gene occurred in a Drosophila melanogaster population from the town of Uman' from 1982 to 1991 and was associated with the instability of several alleles. Molecular genetic analysis revealed a deletion variant of the hobo transposable element in the same site of the regulatory region of yellow in the mutant alleles and their derivatives. The outburst of the yellow-2 mutations was attributed to the spreading of the X chromosome, which contained an inversion of the yellow regulatory region, through the population. Reinversion resulted in the wild-type phenotype. Crossing lines carrying the inversion with laboratory line C(1)DX, ywf induced instability of the yellow alleles, which was associated with duplication or multiplication of a fragment of the yellow gene. Most derivative lines eventually became stable. The loss of instability was not associated with phenotypic changes; molecular genetic changes included a loss of the duplicated sequences or a deletion of the inverted regulatory region of the yellow gene.     

Persistent locus-specific instability of yellow(27-717) and Noth(Uc-1) in Drosophila melanogaster coincides with hobo multiplication

According to FISH data the presence of multiple hobo element copies in the unstable yellow and Notch loci in y(2-717) and Uc-1 Drosophila melanogaster stocks, respectively, was found. Locus-specific instability in these strains is caused by hobo multiplication in the respective loci and its subsequent recombination with neighboring hobo copies rather than its insertion-excision.     

Suppressors that permit A-signal-independent developmental gene expression in Myxococcus xanthus.

Progression through the early stages of Myxococcus xanthus fruiting body development requires the cell-to-cell transmission of soluble material called A signal. During these early stages, expression from the gene identified by Tn5 lac insertion omega 4521 increases. A DNA probe of the omega 4521 gene was constructed. Use of this probe showed that accumulation of mRNA corresponding to the omega 4521 gene depends upon A signal. A-signal-deficient (asg) mutants fail to accumulate this RNA, and the external addition of A signal restores accumulation. To identify links between A signal and its responsive gene, omega 4521, suppressors of an asg mutation were generated. All of the suppressor alleles restored lacZ expression from omega 4521 in the absence of A signal, and they were demonstrated to be neither reversions of the asgB mutation nor mutations in the promoter of omega 4521. Fifteen suppressor mutations map to two loci, sasA and sasB (for suppressor of asg). sasA and sasB mutants differ phenotypically during growth and development. Mid-logarithmic-phase sasA asgB double mutants, like sas+ asg+ strains, express low levels of lacZ, whereas sasB asgB double mutants express high levels. sasA asg+ mutants form abnormal colonies, are less cohesive than wild type, and are defective in fruiting body formation and sporulation. In contrast, sasB asg+ mutants form normal colonies, are as cohesive as wild type, and appear to develop normally. The characteristics of sasA suppressors implicate the sasA+ product as a negative regulator in the A-signal-dependent regulation of omega 4521.     

Mobilization of hobo elements residing within the decapentaplegic gene complex: suggestion of a new hybrid dysgenesis system in Drosophila melanogaster

We present results demonstrating that the hobo family of transposable elements can promote high rates of chromosomal instability. Using strains with a hobo element inserted within the decapentaplegic gene complex (DPP-C), we have recovered numerous DPP-C mutations involving chromosomal rearrangements and deletions with one endpoint in the vicinity of the pre-existing hobo element. This hypermutability occurred in the germ lines of hybrid progeny from crosses involving strains containing hobo elements to strains lacking them. In some crosses, the offspring had rudimentary gonads, reminiscent of GD sterility. The germline hypermutability and infertility are similar to those produced by P-element-mediated hybrid dysgenesis. Given the many genetic and molecular similarities of the P and hobo systems, we propose that a system analogous to P-M hybrid dysgenesis has been activated in the hobo+ X hobo- crosses.     

In Vivo Analysis of Saccharomyces Cerevisiae Cox2 mRNA 5''-Untranslated Leader Functions in Mitochondrial Translation Initiation and Translational Activation

We have used mutational and revertant analysis to study the elements of the 54-nucleotide COX2 5'-untranslated leader involved in translation initiation in yeast mitochondria and in activation by the COX2 translational activator, Pet111p. We generated a collection of mutants with substitutions spanning the entire COX2 5'-UTL by in vitro mutagenesis followed by mitochondrial transformation and gene replacement. The phenotypes of these mutants delimit a 31-nucleotide segment, from -16 to -46, that contains several short sequence elements necessary for COX2 5'-UTL function in translation. The sequences from -16 to -47 were shown to be partially sufficient to promote translation in a foreign context. Analysis of revertants of both the series of linker-scanning alleles and two short deletion/insertion alleles has refined the positions of several possible functional elements of the COX2 5'-untranslated leader, including a putative RNA stem-loop structure that functionally interacts with Pet111p and an octanucleotide sequence present in all S. cerevisiae mitochondrial mRNA 5'-UTLs that is a potential rRNA binding site.     

Transpositional bursts and chromosome rearrangements in unstable lines of Drosophila

The phenomenon of transpositional bursts-massive simultaneous transpositions of mobile elements belonging to different structural classes and accompanied by multiple mutagenesis were earlier described. Although the mechanisms of this phenomenon are still unclear, it is obvious now that it embraces total genome and includes not only transpositions of different mobile elements but also recombination processes--homologous recombination for LTR's and gene conversion. It is shown in this work that transpositional bursts may be accompanied by appearance of grass chromosomal rearrangements. The chain of closely related mutations which is characterized, as well as pedigrees described earlier, by coordinated mutational transitions and multiple transpositions of mdg1, mdg2 and retrotransposon jokey was analyzed. Spontaneous appearance of mutations in the loci yellow, white (deficiency for 462 kb) and cut (insertion of mdg4, together with jokey) correlates with appearance of inversion In(I), 14A-20B, and the reversions of these mutations to the wild type (y+w+ct+) or to other alleles (ctMR2--insertion of mdg4 without jokey) are accompanied by reversions of inversion. The relationship of all lines analyzed in this work as well as the lines from other pedigrees was proved using analysis of polymorphic restriction sites at the scute and cut loci (5 probes were used). All "y w ctpN"--type mutants are shown to have insertion of about 7 kb at the scute locus which causes no alteration of phenotype. This once again proves multiple and coordinated character of changes taking place during hybrid dysgenesis.     

Cause for maintaining high instability at the yellow gene in Drosophila melanogaster lines, isolated during the "mode for mutation" period in Uman populations

Mobile genetic elements are responsible for most spontaneous mutations in Drosophila melenogaster. The discovered in the 1980s phenomenon of frequent change of the wild-type yellow phenotype for a mutant one, and vice-versa, in strains of Drosophila melanogaster isolated from the Uman' natural population can be, according to our data, explained by repeated inversions and reinversions of the gene regulatory region located between the two copies of the hobo transport. However, most molecular genetic events accompanying the process can occur without the phenotype change. After several generations, the strains, remaining phenotypically unchanged, can possess different molecular genetic properties with respect to yellow. Using genetically homogenous or isogenic strains for the genetic analysis or for production of the new plant cultivars or animal breeds, geneticists and breeders often face the problem of stability of the strains. In the present study, the mechanism underlying the generation of instability at the yellow locus of D. melanogaster determined by the hobo-induced genome instability is described.     

Behavior of hobo and P transposons in yellow2-717 unstable line of Drosophila melanogaster and its derivatives after crossing with a laboratory strain

Using fluorescent in situ hybridization technique (FISH), the frequency of hobo and P mobile elements transpositions on X chromosomes from the y2-717, isolated from the Uman' population of Drosophila melanogaster, as well as from its phenotypically normal and mutant derivatives, obtained as a result of crosses the males examined with the C(I)DX, ywf/Y females, was evaluated. It was demonstrated that the maximum frequency of hobo transpositions on X chromosomes of the males from derivative strains, subjected to repeated hobo-dysgenic crosses reached a value of 1.2 x 10(-2) per site per X chromosome per generation. The number of hobo copies in male X chromosomes from derivative strains was 3 times higher than in the original initial strain. Furthermore, the "old" hobo sites remained unchanged. In derivative strains, the frequency of hobo insertions was higher than that of excisions. One of the derivative strains, y1t-717alk3-2, was characterized by high intra-strain instability of hobo element localization. In the y2-717a1k3 and y1t-717alk3-2 strains a large inversion, In(1)1B; 13CD, was described. At the absence of the full-sized P element in the strains involved in crosses, maximum frequency of P element transpositions in the derivative strains reached a value of 1.2 x 10(-2) per site per X chromosome per generation.     

The effect of gamma-radiation on induction of the hobo element transposition in Drosophila melanogaster

The transposition frequency of the hobo mobile element in four successive generations of Drosophila melanogaster strain y2-717 after an acute gamma-irradiation with a dose of 30 Gr amounted to 7.5 x 10(-4) per site per genome per generation. Under the same conditions, PCR analysis of the genomic DNA of y2-717 flies detected new variants of defective hobo sequence. No changes in the hobo localization and PCR products compared with the control were detected in the case of single irradiation with doses of 3 and 30 Gr. The localizations of hobo element on polytene chromosomes of y2-717 strain did not change during 11 generations after five exposures of flies to 30 Gr. Irradiation of a highly unstable D. melanogaster strain y+743 did not increase the number of families with mutant progeny, yet increased the total number of mutant descendants almost twofold, from 5 to 9%.     

Hoxb2 and hoxb4 act together to specify ventral body wall formation

Three different alleles of the Hoxb4 locus were generated by gene targeting in mice. Two alleles contain insertions of a selectable marker in the first exon in either orientation, and, in the third, the selectable marker was removed, resulting in premature termination of the protein. Presence and orientation of the selectable marker correlated with the severity of the phenotype, indicating that the selectable marker induces cis effects on neighboring genes that influence the phenotype. Homozygous mutants of all alleles had cervical skeletal defects similar to those previously reported for Hoxb4 mutant mice. In the most severe allele, Hoxb4(PolII), homozygous mutants died either in utero at approximately E15.5 or immediately after birth, with a severe defect in ventral body wall formation. Analysis of embryos showed thinning of the primary ventral body wall in mutants relative to control animals at E11.5, before secondary body wall formation. Prior to this defect, both Alx3 and Alx4 were specifically down regulated in the most ventral part of the primary body wall in Hoxb4(PolII) mutants. Hoxb4(loxp) mutants in which the neo gene has been removed did not have body wall or sternum defects. In contrast, both the Hoxb4(PolII) and the previously described Hoxb2(PolII) alleles that have body wall defects have been shown to disrupt the expression of both Hoxb2 and Hoxb4 in cell types that contribute to body wall formation. Our results are consistent with a model in which defects in ventral body wall formation require the simultaneous loss of at least Hoxb2 and Hoxb4, and may involve Alx3 and Alx4.     

Patterns of hobo elements and their effects in natural populations of Drosophila melanogaster in Japan

We studied the dynamics of hobo elements of Drosophila melanogaster in Japan with the goal of better understanding the invasion and evolution of transposons in natural populations. One hundred and twenty-six isofemale lines and 11 older stocks were tested for the presence and genetic phenotype of hobo elements. The oldest H strain, containing complete and deleted hobo elements, is Hikone-H (1957), but Hikone-R (1952) has no hobo-homologous sequences. The findings suggest that the hobo element invaded Japanese populations in the mid-1950s, at about the same time as the P element invasion in Japan. This chronology is consistent with the hypothesis of a recent worldwide hobo element invasion into D. melanogaster in the mid-1950s. In recently collected populations, H degrees strains (low hobo activity and high repression potency) are predominant, whereas H+ strains (high hobo activity and high repression potency) are predominant in the Sakishima Islands, the most southwestern islands of the Japanese archipelago. H' strains (high hobo activity and low repression potency) were first found in limited island populations. Japanese populations have not only full-size hobo elements and 1.5 kb Th elements but also characteristic deletion derivatives (1.6 and 1.8 kb XhoI fragments) that we have named Jh elements. These results are consistent with transgenic experiments with complete hobo elements, in which populations evolved to H+ or H degrees via H', and in which 1.8 kb fragments appeared. We conclude that hobo elements invaded the central region of Japan, spread to the far islands, and that the invasion is currently at an intermediate, nonequilibrium stage.