ISSN:0192-253X    

DOI:10.1002/dvg.1020100302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe pair‐rule geneshairy,runt,even‐skipped, andfushi tarazuexpress their mRNAs and proteins in striped patterns in theDrosophilaembryo at the blastoderm stage. Previous studies have shown that the generation of these patterns depends upon products of the gap genes and upon interactions between the pair‐rule genes themselves. Here we show that blocking protein synthesis induces expression of each of the pair‐rule mRNAs in virtually all regions of the embryo. Our observations together with genetic studies carried out in other laboratories suggest that negative feedback between the pair‐rule genes plays a key role in striped expression of pair‐rule genes. We propose that stable proteins, present in all regions of the embryo, first activate transcription ofthese pair‐rule genes constitutively. Then, various combinations of unstable proteins repress their transcription in a patterned fashion; each stripe of accumulated products of a given pair‐rule gene marks a region where it was not repressed. We develop this idea in mathematical form and demonstrate that a network of mutual repression by pair‐rule genes can make each blastoderm nucleus into a genetic switch with two stable states. If preexisting gap gene patterns provide initial bias to the blastoderm nuclei, then the “bistable switch behavior” of the nuclei can refine an initially weak spatial bias into a final pat

ISSN:0192-253X    

DOI:10.1002/dvg.1020100303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThetransformergene is one of a set of regulatory genes that form the hierarchy controlling all aspects of somatic sexual differentiation inDrosophila melanogaster.The genetransformeroccupies an intermediate position in this hierarchy. Analysis of this gene has allowed us to determine the mechanism by which it is regulated in a sex‐specific manner and to examine the way in which the regulatory hierarchy is organized. The female‐specific expression of thetragene, previously inferred from genetic observations, is bused on sex‐specific alternative splicing oftrapre‐mRNA and is not the result of sex‐specific transcriptional activation. The female‐specific RNA produced by this alternative splicing is the functional mediator oftraactivity. Multiple genetic, molecular, and transformation experiments show that female‐specific activation of genes or gene products occurs in the orderSex lethal>transformer>transformer‐2>doublesex·intersex>female differentiation. The results do not distinguish the level at whichtransformermight regulate the downstream genetransformer‐2.Neithertransformernor any of the downstream genes feedback on, or participate in, alternative splicing oftransformerRNA. The mechanism by whichSex lethalregulatestransformersplicing appears to be a repression of the use of one of a pair of spl

ISSN:0192-253X    

DOI:10.1002/dvg.1020100304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractUsing a heterologous rat cDNA probe, we have identified a 14.7 kbpDrosophila melanogastergenomic clone containing the X‐linked genePgd+, which encodes the enzyme 6‐phosphogluconate dehydrogenase (6PGD). We used in situ hybridization to larval polytene chromosomes, a somatic transient expression assay for enzyme activity, and the rescue of the lethalPgd−phenotype by germline transformation to verify the identity of the gene. A 7.4 kbp fragment including the gene and approximately 1.2 kbp of upstream and 1.8 kbp of downstream sequences was relocated to autosomal ectopic sites by germline transformation; this transduced gene exhibits levels of enhanced activity in males comparable to those of the indigenous gene at its normal X chromosome locus. We conclude that the sequences responsible for dosage compensation ofPgd+are included in this fra

ISSN:0192-253X    

DOI:10.1002/dvg.1020100305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractMost variegating position effects are a consequence of placing a euchromatic gene adjacent to α‐heterochromatin. In such rearrangements, the affected locus is inactivated in some cells, but not others, thereby giving rise to a mosaic tissue of mutant and wild‐type cells. A detailed examination of the molecular structure of three variegatingwhite mottledmutations ofDrosophila melanogaster, all of which are inversions of the X chromosome, reveals that their euchromatic breakpoints are clustered and located approximately 25 kb downstream of thewhitepromoter and that the heterochromatic sequences to which thewhitelocus is adjoined are transposons. An analysis of three revertants of thewm4mutation, created by relocatingwhiteto another euchromatic site, demonstrates that they also carry some heterochromatically derived sequences with them upon restoration of the wild‐type phenotype. This suggests that variegation is not controlled from a heterochromatic sequence immediately adjacent to the variegating gene but rather from some site more internal to the heterochromatic domain itself. As a consequence of this observation we have proposed a boundary model for understanding how heterochromatic domains may be formed.It has been recognized for many years that the phenotype of variegating position effects may be altered by the presence oftrans‐acting dominant mutations that act to either enhance or suppress variegation. Using P‐element mutagenesis, we have induced and examined 12 dominant enhancers of variegation that represent four loci on the second and third chromosomes. Most of these mutations are cytologically visible duplications or deficiencies. They exert their dominant effects through changes in the copy number of wild‐type genes and can be divided into two reciprocally acting classes. Class I modifiers are genes that act as enhancers of variegation when duplicated and as suppressors when mutated or deficient. Conversely, class II modifiers are genes that enhance when mutated or deleted and suppress when duplicated. The available data indicate that, inDrosophila, there are 20‐30 loci capable of dominantly modifying variegation. Of these, most appear to be of the class I type whereas only two class II modifiers have been identified so far.But how does a change in the dosage of only one of a large number of modifier loci act to enhance or suppress, in an antipodal manner, the variegating phenotype? If each of the class I genes is involved in the formation of heterochromatin, then changing the dosage of a single member of the group might not be expected to modify variegation since the dosage of any of the remaining members of that group should still be rate limiting. These remaining members appear to be rate limiting because each has a dose‐dependent effect on the phenotype as indicated by the fact that decreasing any one of them causes suppression of variegation. To explain this paradoxical behavior we propose a model, based on the law of mass action, for understanding how these suppressor‐enhancer loci function. The model assumes that each class I gene codes for a protein involved in the assembly of heterochromatic domains. From a consideration of this assembly reaction we show that, at equilibrium, the final concentration of assembled product varies as an exponential function of the concentration of each component of the reaction. The mass action model provides some insight into the dynamics and control of a repressed (heterochromatic) state as well as assembly‐driven reactions in general. Our results also have broader implications for a variety of antipodal dosage‐dependent effects, particularly as they relate to developmentally significant loci and the elaboration of

ISSN:0192-253X    

DOI:10.1002/dvg.1020100306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractDrosophilaKc cells are ecdysone‐responsive: hormone treatment leads rapidly to increased synthesis of several ecdysone‐inducible polypeptides (EIPs) and to commitment to eventual proliferative arrest. Later, the treated cells undergo morphological transformation, cease to proliferate, and develop new enzymatic activities, notably, acetylcholineslerase (AChE) activity. These responses have proven useful as models for studying ecdysone action. Here we report the sensitivity of Kc cells to another important insect developmental regulator—juvenile hormone (JH). We find that JH inhibits some, but not all, aspects of the ecdysone response. When Kc cells are treated with ecdysone in the presence of either natural JHs or synthetic analogues, the morphological and proliferative responses are inhibited and AChE induction is blocked. Most striking is that JHs protect the cells from the rapid proliferative commitment induced by ecdysone alone. The JH effects exhibit reasonable dose‐response curves with half‐maximal responses occurring at very low JH concentrations. Nonetheless, even at high JH concentrations the inhibitory effects are incomplete. It is interesting that EIP induction appears to be refractory to JH. It seems clear that JH is not simply a generalized inhibitor of ecdysone‐induce

ISSN:0192-253X    

DOI:10.1002/dvg.1020100307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWe reviewed studies on the developmental regulation of the 68C glue gene cluster ofDrosophila melanogaster.Extensive transformation analyses ofSgs‐3have shown that four regions necessary for normal expression can be distinguished. The first ( + 10 to ‐50) contains the transcription start site and TATA motif. This region can be replaced functionally by corresponding sequences from thehsp70gene, but it is sensitive to point mutations in the TATA sequence. The second region (‐50 to ‐98) contains more than one upstream sequence that, in combination with the other elements, leads to stage and tissue‐specific expression. The third region (centered at ‐600) contains an element that enhances transcript levels some 20‐fold. The final region (between ‐1.65 and ‐2.35 kb) contains elements having modest (twofold to threefold) effects on expression, one of which is contained in the coding sequences ofSgs‐7, a second me

ISSN:0192-253X    

DOI:10.1002/dvg.1020100308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractGenes that encode 3rd instar larval cuticle proteins (LCP's) ofDrosophila melanogasterare located in at least two chromosomal sites. The genes encoding four of the five predominant LCP's are located in a cluster at the chromosomal region 44D. They are organized in pairs that are transcribed divergently, and expressed with different timing during the third larval instar. Towards understanding the basis of gene regulation within the 44D cluster, we have analyzed genetic variants, including the2‐3variant, which has an insertion of a copia‐like transposable element, H.M.S. Beagle, within the 44D cluster. The Beagle element appears to inactivate theLCP‐3gene by inserting into its TATA box, but also may cause the precocious expression of two otherLCPgenes,LCP‐1andLCP‐f2, in the cluster. The long terminal repeat (LTR) of the Beagle element apparently contains a sequence, perhaps an enhancer‐like element, which causes altered expression of these genes. We have also investigated thecis‐regulatory elements involved in expression of theLCP‐2gene in wild‐type larvae. We have identified two upstream regions that may contain separate cisregulatory elements. The region between ‐252 bp and ‐515 bp may be essential for any expression of LCP‐2. Additionally, the region between ‐515 bp and ‐795 bp appears to be required for the normal level of

ISSN:0192-253X    

DOI:10.1002/dvg.1020100309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWe have used in vitro mutagenesis and somatic transformation [Sofer and Martin, 1987a; Martinet al., 1986] to investigate the role ofcis‐acting sequences in the control of alcohol dehydrogenase gene expression in larvae ofDrosophila melanogaster.Two sets of experiments were carried out. In the first, a series of aeletions were constructed in the region upstream of the proximal transcriptional start site. In the second, one or both introns were removed from within the structural gene. These constructs (on circular plasmids) were injected into Adh‐null embryos and ADH activity was assayed in third instar larvae of the injected generation. The first set of experiments indicated that there are at least three distinct regulatory regions essential for larval activity located in the 5′ flanking region of the gene. One, in an area that includes the TATA box, was found to be necessary but not sufficient for larval ADH activity. Two others, further upstream, seemed to have enhancer‐like properties because their absence could be compensated by a second copy of theAdhgene on the same plasmid molecule. The second set of experiments showed that neither the tis‐sue distribution nor amount of ADH activity was affected by the removal of one or both introns from t

ISSN:0192-253X    

DOI:10.1002/dvg.1020100310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractTheP1gene, together with theLSP‐1a,‐1β, and‐ly,LSP‐2, andP6genes, is expressed exclusively in the larval fat body ofD.melanogaster during the third instar. In vivo mapping of the cis‐acting regulatory sequences of theP1gene was carried out using hybrid constructs with three different reporter genes and a combination of transient and germline transformation assays. This revealed that regulatory elements involved in the setting up of the temporal and spatial specificities of transcription of theP1gene are located in a short DNA region immediately upstream of the mRNA transcription start. This region includes on element that behaves as a fat‐body transcriptional enhancer and element(s) required for ecdysone inducibility of transcription

ISSN:0192-253X    

DOI:10.1002/dvg.1020100311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY