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Pat Simpson - One of the best experts on this subject based on the ideXlab platform.

  • how to pattern an epithelium lessons from achaete scute regulation on the notum of drosophila
    Gene, 2002
    Co-Authors: Manuel Calleja, Olivier Renaud, Kazuya Usui, Daniela Pistillo, Gines Morata, Pat Simpson
    Abstract:

    The notum of Drosophila is a good model system for the study of two-dimensional pattern formation. Attention has mainly focused on the regulation of the spatial expression of the genes of the achaete-scute complex (AS-C) that results in a stereotyped bristle pattern. Expression of AS-C genes has traditionally been viewed as a consequence of the activity of a group of factors that constitute a Prepattern [Stern, 1954. Am. Sci. 42, 213]. The Prepattern is thought to be composed of a mosaic of transcription factors that act in combination, through discrete cis-regulatory sequences, to activate expression of genes of the AS-C in small clusters of cells at the sites of each future bristle. Recent results challenge this view and suggest a hierarchy of activity amongst Prepattern genes. It is suggested that in the medial notum, the selector-like gene pannier regulates the entire pattern, and is the only factor to directly activate AS-C genes. Other factors may play subsidiary roles. On the lateral notum genes of the iroquois complex appear to regulate the lateral pattern. Regulation of pannier and iroquois depends upon the signalling molecule Decapentaplegic. The majority of genes are expressed in either longitudinal or transverse domains on the notum and we discuss the possibility that pattern formation may rely on these two axial coordinates. We also discuss preliminary results suggesting that Prepattern factors also regulate genes required for other, little studied, aspects of notal morphology, such as the muscle attachment sites and pigment distribution. Thus there may be a common Prepattern for the entire structure.

  • genetic analysis of bristle loss in hybrids between drosophila melanogaster and d simulans provides evidence for divergence of cis regulatory sequences in the achaete scute gene complex
    Developmental Biology, 2000
    Co-Authors: Nick Skaer, Pat Simpson
    Abstract:

    The two closely related species of Drosophila, D. melanogaster and D. simulans, display an identical bristle pattern on the notum, but hybrids between the two are lacking a variable number of bristles. We show that the loss is temperaturedependent and provide evidence for two periods of temperature sensitivity. A first period of heat sensitivity occurs during larval development and corresponds to the time when the Prepattern of expression of genes whose products activate achaete‐scute in the proneural clusters preceding bristle precursor formation is established. A second period of cold sensitivity corresponds to the time of emergence of the bristle precursor cells and the maintenance of their neural fate, a process requiring high levels of Achaete‐Scute. Expression of achaete‐scute at these two critical periods depends on cis-regulatory elements of the achaete‐scute complex (AS-C). The differences between males, which have only one copy of the X-linked AS-C from D. simulans, and females, which have copies from both parental species, are compared, together with the effects of crossing in different rearrangements of the D. melanogaster AS-C that delete regulatory and/or coding sequences. We provide evidence that bristle loss in the hybrids may result from a decrease in the level of transcription at the AS-C and argue that interaction between trans-acting factors and cis-regulatory elements within the AS-C has diverged between the two species. © 2000 Academic Press

  • drosophila development a Prepattern for sensory organs
    Current Biology, 1996
    Co-Authors: Pat Simpson
    Abstract:

    Abstract The sensory bristles of Drosophila arise in stereotyped positions from small clusters of cells that express achaete–scute genes. A set of genes has now been identified that regulate achaete–scute expression and form a Prepattern for sensory bristle development.

Gerd Jurgens - One of the best experts on this subject based on the ideXlab platform.

  • different auxin response machineries control distinct cell fates in the early plant embryo
    Developmental Cell, 2012
    Co-Authors: Eike H Rademacher, Annemarie S Lokerse, Alexandra Schlereth, Cristina I Llavataperis, Martin Bayer, Marika Kientz, Alejandra Freire Rios, Jan Willem Borst, Wolfgang Lukowitz, Gerd Jurgens
    Abstract:

    The cell types of the plant root are first specified early during embryogenesis and are maintained throughout plant life. Auxin plays an essential role in embryonic root initiation, in part through the action of the ARF5/MP transcription factor and its auxin-labile inhibitor IAA12/BDL. MP and BDL function in embryonic cells but promote auxin transport to adjacent extraembryonic suspensor cells, including the quiescent center precursor (hypophysis). Here we show that a cell-autonomous auxin response within this cell is required for root meristem initiation. ARF9 and redundant ARFs, and their inhibitor IAA10, act in suspensor cells to mediate hypophysis specification and, surprisingly, also to prevent transformation to embryo identity. ARF misexpression, and analysis of the short suspensor mutant, demonstrates that lineage-specific expression of these ARFs is required for normal embryo development. These results imply the existence of a Prepattern for a cell-type-specific auxin response that underlies the auxin-dependent specification of embryonic cell types.

  • pattern formation in the flowering plant embryo
    Current Opinion in Genetics & Development, 1992
    Co-Authors: Gerd Jurgens
    Abstract:

    Recent mutation studies in Arabidopsis suggest rules by which the primary organization of the plant body is established in the early embryo. The main types of plant tissue arise independently of pattern formation along the axis of polarity. The axis is initially partitioned into three regions. This Prepattern is later refined, possibly by position-specific cell activities, as indicated by morphological features as well as the distribution of molecular markers.

Kaoru Saigo - One of the best experts on this subject based on the ideXlab platform.

  • diversification of cell types in the drosophila eye by differential expression of Prepattern genes
    Mechanisms of Development, 2001
    Co-Authors: Takashi Hayashi, Kaoru Saigo
    Abstract:

    According to Freeman (Development, 124 (1997) 261), reiterative use of Spitz signals emanating from already differentiated ommatidial cells triggers the differentiation of around ten different types of cells. Here we show evidence that the choice of cell fate by newly recruited ommatidial cells strictly depends on their developmental potential. Using forced expression of a constitutively active form of Ras1, three developmental potentials (rough, seven-up, and prospero expression) were visualized as relatively narrow bands corresponding to regions where rough-, seven-up- or prospero-expressing ommatidial cells would normally form. Ras1-dependent expression of ommatidial marker genes was regulated by a combinatorial expression of eye Prepattern genes such as lozenge, dachshund, eyes absent, and cubitus interruptus, indicating that developmental potential formation is governed by region-specific Prepattern gene expression.

  • bar homeobox genes are latitudinal Prepattern genes in the developing drosophila notum whose expression is regulated by the concerted functions of decapentaplegic and wingless
    Development, 1999
    Co-Authors: Makoto Sato, Tetsuya Kojima, Tatsuo Michiue, Kaoru Saigo
    Abstract:

    In Drosophila notum, the expression of achaete-scute proneural genes and bristle formation have been shown to be regulated by putative Prepattern genes expressed longitudinally. Here, we show that two homeobox genes at the Bar locus (BarH1 and BarH2) may belong to a different class of Prepattern genes expressed latitudinally, and suggest that the developing notum consists of checker-square-like subdomains, each governed by a different combination of Prepattern genes. BarH1 and BarH2 are coexpressed in the anterior-most notal region and regulate the formation of microchaetae within the region of BarH1/BarH2 expression through activating achaete-scute. Presutural macrochaetae formation also requires Bar homeobox gene activity. Bar homeobox gene expression is restricted dorsally and posteriorly by Decapentaplegic signaling, while the ventral limit of the expression domain of Bar homeobox genes is determined by wingless whose expression is under the control of Decapentaplegic signaling.

Juan Modolell - One of the best experts on this subject based on the ideXlab platform.

  • tailup, a LIM-HD gene, and Iro-C cooperate in Drosophila dorsal mesothorax specification
    Development (Cambridge England), 2007
    Co-Authors: Joaquín De Navascués, Juan Modolell
    Abstract:

    The LIM-HD gene tailup (tup; also known as islet) has been categorised as a Prepattern gene that antagonises the formation of sensory bristles on the notum of Drosophila by downregulating the expression of the proneural achaete-scute genes. Here we show that tup has an earlier function in the development of the imaginal wing disc; namely, the specification of the notum territory. Absence of tup function causes cells of this anlage to upregulate different wing-hinge genes and to lose expression of some notum genes. Consistently, these cells differentiate hinge structures or modified notum cuticle. The LIM-HD co-factors Chip and Ssdp are also necessary for notum specification. This suggests that Tup acts in this process in a complex with Chip and Ssdp. Overexpression of tup, together with araucan, a 'pronotum' gene of the iroquois complex (Iro-C), synergistically reinforces the weak capacity of either gene, when overexpressed singly, to induce ectopic notum-like development. Whereas the Iro-C genes are activated in the notum anlage by EGFR signalling, tup is positively regulated by Dpp signalling. Our data support a model in which the EGFR and Dpp signalling pathways, with their respective downstream Iro-C and tup genes, converge and cooperate to commit cells to the notum developmental fate.

  • The achaete-scute complex as an integrating device.
    The International journal of developmental biology, 1998
    Co-Authors: Juan Modolell, Sonsoles Campuzano
    Abstract:

    A classical model to study pattern formation is provided by the epidermal sensory organs (bristles and other sensilla) that cover the body of Drosophila. Many of these sensory organs (SOs) arise in very constant positions. How are these positions specified? To a large extent, they are defined by the highly resolved sites of expression of the proneural genes of the achaete-scute complex (AS-C). These genes, which confer to cells the capacity to become SO precursors, attain their resolved patterns of expression by means of many position-specific enhancers located within the non-transcribed AS-C DNA. Each enhancer drives expression at one or very few sites. Evidence is growing that the enhancers interact with combinations of activators and repressors (Prepattern) distributed in partially overlapping domains which are larger than the AS-C expressing sites. AS-C transcription is activated only at sites with appropriate combinations of factors. Thus, the AS-C integrates the positional information embodied in the relatively broad distributions of Prepattern factors and creates a sharper and topographically more precise pattern.

  • cis regulation of achaete and scute shared enhancer like elements drive their coexpression in proneural clusters of the imaginal discs
    Genes & Development, 1995
    Co-Authors: Jose Luis Gomezskarmeta, Isabel Rodriguez, Carmen Martinez, Joaquim Culi, Dolores Ferresmarco, Diego Beamonte, Juan Modolell
    Abstract:

    The pattern of bristles and other sensory organs on the adult cuticle of Drosophila is prefigured in the imaginal discs by the pattern of expression of the proneural achaete (ac) and scute (sc) genes, two members of the ac-sc complex (AS-C). These genes are simultaneously expressed by groups of cells (the proneural clusters) located at constant positions in discs. Their products (transcription factors of the basic-helix-loop-helix family) allow cells to become sensory organ mother cells (SMCs), a fate normally realized by only one or a few cells per cluster. Here we show that the highly complex pattern of proneural clusters is constructed piecemeal, by the action on ac and sc of site-specific, enhancer-like elements distributed along most of the AS-C (approximately 90 kb). Fragments of AS-C DNA containing these enhancers drive reporter lacZ genes in only one or a few proneural clusters. This expression is independent of the ac and sc endogenous genes, indicating that the enhancers respond to local combinations of factors (Prepattern). We show further that the cross-activation between ac and sc, discovered by means of transgenes containing either ac or sc promoter fragments linked to lacZ and thought to explain the almost identical patterns of ac and sc expression, does not occur detectably between the endogenous ac and sc genes in most proneural clusters. Our data indicate that coexpression is accomplished by activation of both ac and sc by the same set of position-specific enhancers.

Reed, Robert D. - One of the best experts on this subject based on the ideXlab platform.

  • Data from: Transcriptome analysis reveals novel patterning and pigmentation genes underlying Heliconius butterfly wing pattern variation
    2013
    Co-Authors: Hines, Heather M., Mcmillan W Owen, Papa Riccardo, Ruiz Mayte, Papanicolaou Alexie, Wang Charles, Nijhout H. Frederik, Reed, Robert D.
    Abstract:

    BACKGROUND: Heliconius butterfly wing pattern diversity offers a unique opportunity to investigate how natural genetic variation can drive the evolution of complex adaptive phenotypes. Positional cloning and candidate gene studies have identified a handful of regulatory and pigmentation genes implicated in Heliconius wing pattern variation, but little is known about the greater developmental networks within which these genes interact to pattern a wing. Here we took a large-scale transcriptomic approach to identify the network of genes involved in Heliconius wing pattern development and variation. This included applying over 140 transcriptome microarrays to assay gene expression in dissected wing pattern elements across a range of developmental stages and wing pattern morphs of Heliconius erato. RESULTS: We identified a number of putative early Prepattern genes with color-pattern related expression domains. We also identified 51 genes differentially expressed in association with natural color pattern variation. Of these, the previously identified color pattern “switch gene” optix was recovered as the first transcript to show color-specific differential expression. Most differentially expressed genes were transcribed late in pupal development and have roles in cuticle formation or pigment synthesis. These include previously undescribed transporter genes associated with ommochrome pigmentation. Furthermore, we observed upregulation of melanin-repressing genes such as ebony and Dat1 in non-melanic patterns. CONCLUSIONS: This study identifies many new genes implicated in butterfly wing pattern development and provides a glimpse into the number and types of genes affected by variation in genes that drive color pattern evolution

  • Transcriptome analysis reveals novel patterning and pigmentation genes underlying Heliconius butterfly wing pattern variation
    BMC, 2012
    Co-Authors: Hines, Heather M., Papa Riccardo, Ruiz Mayte, Papanicolaou Alexie, Wang Charles, Nijhout H, Mcmillan W, Reed, Robert D.
    Abstract:

    Abstract Background Heliconius butterfly wing pattern diversity offers a unique opportunity to investigate how natural genetic variation can drive the evolution of complex adaptive phenotypes. Positional cloning and candidate gene studies have identified a handful of regulatory and pigmentation genes implicated in Heliconius wing pattern variation, but little is known about the greater developmental networks within which these genes interact to pattern a wing. Here we took a large-scale transcriptomic approach to identify the network of genes involved in Heliconius wing pattern development and variation. This included applying over 140 transcriptome microarrays to assay gene expression in dissected wing pattern elements across a range of developmental stages and wing pattern morphs of Heliconius erato. Results We identified a number of putative early Prepattern genes with color-pattern related expression domains. We also identified 51 genes differentially expressed in association with natural color pattern variation. Of these, the previously identified color pattern “switch gene” optix was recovered as the first transcript to show color-specific differential expression. Most differentially expressed genes were transcribed late in pupal development and have roles in cuticle formation or pigment synthesis. These include previously undescribed transporter genes associated with ommochrome pigmentation. Furthermore, we observed upregulation of melanin-repressing genes such as ebony and Dat1 in non-melanic patterns. Conclusions This study identifies many new genes implicated in butterfly wing pattern development and provides a glimpse into the number and types of genes affected by variation in genes that drive color pattern evolution.