Role of the proneural gene, atonal, in formation of Drosophila chordotonal organs and photoreceptors

Development ◽  
1995 ◽  
Vol 121 (7) ◽  
pp. 2019-2030 ◽  
Author(s):  
A.P. Jarman ◽  
Y. Sun ◽  
L.Y. Jan ◽  
Y.N. Jan
Keyword(s):  
Sense Organ ◽  
Proneural Gene ◽  
Morphogenetic Furrow ◽  
Helix Loop Helix ◽  
Eye Disc ◽  
In The Wild ◽  
Almost All ◽  
Selection Of ◽  
Stimulation Of Division

The Drosophila gene atonal encodes a basic helix-loop-helix protein similar to those encoded by the proneural genes of the achaete-scute complex (AS-C). The AS-C are required in the Drosophila PNS for the selection of neural precursors of external sense organs. We have isolated mutants of atonal, which reveal that this gene encodes the proneural gene for chordotonal organs and photoreceptors. In atonal mutants, all observable adult chordotonal organs, and almost all embryonic chordotonal organs fail to form; all adult photoreceptors are missing. For both types of sense organ, this defect is already apparent at the level of precursor formation. Therefore it is a failure in the epidermal-neural decision process i.e. a proneural defect. The failure to form photoreceptors results in atrophy of the atonal mutant imaginal disc, due to apoptosis and lack of stimulation of division. Lack of photoreceptors should also eliminate signalling that arises from differentiating photoreceptors and is required for morphogenetic furrow movement in the wild-type eye disc. Nevertheless, a remnant morphogenetic furrow is still observed in the atonal mutant disc. This presumably reflects the process of furrow initiation, which would not depend on signals from developing photoreceptors.

Wingless blocks bristle formation and morphogenetic furrow progression in the eye through repression of Daughterless

Development ◽  
2002 ◽  
Vol 129 (14) ◽  
pp. 3393-3402 ◽  
Author(s):  
Kenneth M. Cadigan ◽  
Austin D. Jou ◽  
Roel Nusse
Keyword(s):  
Gene Expression ◽  
Ectopic Expression ◽  
Dominant Negative ◽  
Proneural Gene ◽  
Morphogenetic Furrow ◽  
Heterologous Promoter ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Dominant Negative Form ◽  
Negative Form

In the developing eye, wingless activity represses proneural gene expression (and thus interommatidial bristle formation) and positions the morphogenetic furrow by blocking its initiation in the dorsal and ventral regions of the presumptive eye. We provide evidence that wingless mediates both effects, at least in part, through repression of the basic helix-loop-helix protein Daughterless. daughterless is required for high proneural gene expression and furrow progression. Ectopic expression of wingless blocks Daughterless expression in the proneural clusters. This repression, and that of furrow progression, can be mimicked by an activated form of armadillo and blocked by a dominant negative form of pangolin/TCF. Placing daughterless under the control of a heterologous promoter blocks the ability of ectopic wingless to inhibit bristle formation and furrow progression. hedgehog and decapentapleigic could not rescue the wingless furrow progression block, indicating that wingless acts downstream of these genes. In contrast, Atonal and Scute, which are thought to heterodimerize with Daughterless to promote furrow progression and bristle formation, respectively, can block ectopic wingless action. These results are summarized in a model where daughterless is a major, but probably not the only, target of wingless action in the eye.

asense is a Drosophila neural precursor gene and is capable of initiating sense organ formation

Development ◽  
1993 ◽  
Vol 119 (1) ◽  
pp. 1-17 ◽  
Author(s):  
M. Brand ◽  
A.P. Jarman ◽  
L.Y. Jan ◽  
Y.N. Jan
Keyword(s):  
Ectopic Expression ◽  
Sense Organ ◽  
Neural Precursor Cells ◽  
Neural Precursor ◽  
Gene Products ◽  
Proneural Gene ◽  
Proneural Genes ◽  
Helix Loop Helix ◽  
Normal Gene ◽  
Proneural Cluster

Neural precursor cells in Drosophila arise from the ectoderm in the embryo and from imaginal disc epithelia in the larva. In both cases, this process requires daughterless and the proneural genes achaete, scute and lethal-of-scute of the achaete-scute complex. These genes encode basic helix-loop-helix proteins, which are nuclear transcription factors, as does the asense gene of the achaete-scute complex. Our studies suggest that asense is a neural precursor gene, rather than a proneural gene. Unlike the proneural achaete-scute gene products, the asense RNA and protein are found in the neural precursor during its formation, but not in the proneural cluster of cells that gives rise to the neural precursor cell. Also, asense expression persists longer during neural precursor development than the proneural gene products; it is still expressed after the first division of the neural precursor. Moreover, asense is likely to be downstream of the proneural genes, because (1) asense expression is affected in proneural and neurogenic mutant backgrounds, (2) ectopic expression of asense protein with an intact DNA-binding domain bypasses the requirement for achaete and scute in the formation of imaginal sense organs. We further note that asense ectopic expression is capable of initiating the sense organ fate in cells that do not normally require the action of asense. Our studies therefore serve as a cautionary note for the inference of normal gene function based on the gain-of-function phenotype after ectopic expression.

Role of the morphogenetic furrow in establishing polarity in the Drosophila eye

Development ◽  
1995 ◽  
Vol 121 (12) ◽  
pp. 4085-4094 ◽  
Author(s):  
F. Chanut ◽  
U. Heberlein
Keyword(s):  
Ectopic Expression ◽  
Morphogenetic Furrow ◽  
Eye Disc ◽  
Drosophila Eye ◽  
Retinal Epithelium ◽  
Anteroposterior Polarity ◽  
Crystalline Array

The Drosophila retina is a crystalline array of 800 ommatidia whose organization and assembly suggest polarization of the retinal epithelium along anteroposterior and dorsoventral axes. The retina develops by a stepwise process following the posterior-to-anterior progression of the morphogenetic furrow across the eye disc. Ectopic expression of hedgehog or local removal of patched function generates ectopic furrows that can progress in any direction across the disc leaving in their wake differentiating fields of ectopic ommatidia. We have studied the effect of these ectopic furrows on the polarity of ommatidial assembly and rotation. We find that the anteroposterior asymmetry of ommatidial assembly parallels the progression of ectopic furrows, regardless of their direction. In addition, ommatidia developing behind ectopic furrows rotate coordinately, forming equators in various regions of the disc. Interestingly, the expression of a marker normally restricted to the equator is induced in ectopic ommatidial fields. Ectopic equators are stable as they persist to adulthood, where they can coexist with the normal equator. Our results suggest that ectopic furrows can impart polarity to the disc epithelium, regarding the direction of both assembly and rotation of ommatidia. We propose that these processes are polarized as a consequence of furrow propagation, while more global determinants of dorsoventral and anteroposterior polarity may act less directly by determining the site of furrow initiation.

Decommissioning – a path forward for Australia

2019 ◽  
Vol 59 (1) ◽  
pp. 25
Author(s):  
Stuart J. Barrymore ◽  
Jane Ballard
Keyword(s):  
Review Process ◽  
Australian Government ◽  
Discussion Paper ◽  
Adequate Funding ◽  
Sea Bed ◽  
Fit For Purpose ◽  
Almost All ◽  
The Cost ◽  
Selection Of

Australia has embarked on a review of its decommissioning law and practice with a comprehensive discussion paper being issued by the Department of Industry, Innovation and Science. Initial stakeholder comments and submissions have been made, and the Department is now considering those submissions with a view to issuing recommendations to the Minister. The discussion paper ultimately proposes that new laws will be implemented to ensure that Australia has a 21st century fit-for-purpose decommissioning regime to apply to its offshore petroleum installations. After an overview of the review process and the selected issues that the Department regards of significance, this article considers a selection of the issues that emerge. It is evident that diverse views exist on almost all topics, and it will not be an easy task to find a balance that both meets the goals and aspirations of industry and community sectors. This challenge is compounded by the scale of decommissioning operations and the cost that will be incurred to remediate wells and remove associated facilities. The balance sought is one that does not stifle industry’s capacity to further invest nor impose onerous or uncompetitive imposts or controls, but also assures that adequate funding is available to carry out decommissioning works. Everyone seemingly accepts that it is not the role of the Australian Government to remove the facilities and restore the sea bed. Globally, techniques that are being increasingly utilised to manage this risk involve the imposition of securities or other assurance and enhanced statutory liability mechanisms. These legal and commercial considerations are given particular focus in the article.

Hedgehog is an indirect regulator of morphogenetic furrow progression in the Drosophila eye disc

Development ◽  
1997 ◽  
Vol 124 (17) ◽  
pp. 3233-3240 ◽  
Author(s):  
D.I. Strutt ◽  
M. Mlodzik
Keyword(s):  
Pattern Formation ◽  
Imaginal Disc ◽  
Morphogenetic Furrow ◽  
Anterior Edge ◽  
Eye Disc ◽  
Drosophila Eye ◽  
Eye Imaginal Disc ◽  
Inductive Signal ◽  
Rate Of Movement

Pattern formation in the eye imaginal disc of Drosophila occurs in a wave that moves from posterior to anterior. The anterior edge of this wave is marked by a contracted band of cells known as the morphogenetic furrow, behind which photoreceptors differentiate. The movement of the furrow is dependent upon the secretion of the signalling protein Hedgehog (Hh) by more posterior cells, and it has been suggested that Hh acts as an inductive signal to induce cells to enter a furrow fate and begin differentiation. To further define the role of Hh in this process, we have analysed clones of cells lacking the function of the smoothened (smo) gene, which is required for transduction of the Hh signal and allows the investigation of the autonomous requirement for hh signalling. These experiments demonstrate that the function of hh in furrow progression is indirect. Cells that cannot receive/transduce the Hh signal are still capable of entering a furrow fate and differentiating normally. However, hh is required to promote furrow progression and regulate its rate of movement across the disc, since the furrow is significantly delayed in smo clones.

Transcriptional regulation of atonal during development of the Drosophila peripheral nervous system

Development ◽  
1998 ◽  
Vol 125 (18) ◽  
pp. 3731-3740 ◽  
Author(s):  
Y. Sun ◽  
L.Y. Jan ◽  
Y.N. Jan
Keyword(s):  
Nervous System ◽  
Photoreceptor Cells ◽  
Chordotonal Organ ◽  
Proneural Gene ◽  
Morphogenetic Furrow ◽  
Specific Expression ◽  
Coding Sequences ◽  
Eye Disc ◽  
Photoreceptor Development ◽  
Eye Morphogenesis

atonal is a proneural gene for the development of Drosophila chordotonal organs and photoreceptor cells. We show here that atonal expression is controlled by modular enhancer elements located 5′ or 3′ to the atonal-coding sequences. During chordotonal organ development, the 3′ enhancer directs expression in proneural clusters; whereas successive modular enhancers located in the 5′ region drive tissue-specific expression in chordotonal organ precursors in the embryo and larval leg, wing and antennal imaginal discs. Similarly, in the eye disc, the 3′ enhancer directs initial expression in a stripe anterior to the morphogenetic furrow. These atonal-expressing cells are then patterned through a Notch-dependent process into initial clusters, representing the earliest patterning event yet identified during eye morphogenesis. A distinct 5′ enhancer drives expression in intermediate groups and R8 cells within and posterior to the morphogenetic furrow. Both enhancers are required for normal atonal function in the eye. The 5′ enhancer, but not the 3′ enhancer, depends on endogenous atonal function, suggesting a switch from regulation directed by other upstream genes to atonal autoregulation during the process of lateral inhibition. The regulatory regions identified in this study can thus account for atonal expression in every tissue and essentially in every stage of its expression during chordotonal organ and photoreceptor development.

The role of Wingless signaling in establishing the anteroposterior and dorsoventral axes of the eye disc

Development ◽  
2001 ◽  
Vol 128 (9) ◽  
pp. 1519-1529 ◽  
Author(s):  
J.D. Lee ◽  
J.E. Treisman
Keyword(s):  
Signaling Molecules ◽  
Morphogenetic Furrow ◽  
Wild Type ◽  
Dorsoventral Axis ◽  
Eye Disc ◽  
Wingless Signaling ◽  
Drosophila Eye ◽  
Ectopic Activation ◽  
Lateral Margins

The posteriorly expressed signaling molecules Hedgehog and Decapentaplegic drive photoreceptor differentiation in the Drosophila eye disc, while at the anterior lateral margins Wingless expression blocks ectopic differentiation. We show here that mutations in axin prevent photoreceptor differentiation and lead to tissue overgrowth and that both these effects are due to ectopic activation of the Wingless pathway. In addition, ectopic Wingless signaling causes posterior cells to take on an anterior identity, reorienting the direction of morphogenetic furrow progression in neighboring wild-type cells. We also show that signaling by Decapentaplegic and Hedgehog normally blocks the posterior expression of anterior markers such as Eyeless. Wingless signaling is not required to maintain anterior Eyeless expression and in combination with Decapentaplegic signaling can promote its downregulation, suggesting that additional molecules contribute to anterior identity. Along the dorsoventral axis of the eye disc, Wingless signaling is sufficient to promote dorsal expression of the Iroquois gene mirror, even in the absence of the upstream factor pannier. However, Wingless signaling does not lead to ventral mirror expression, implying the existence of ventral repressors.

scholarly journals The Nicotiana tabacum Mediator subunit MED25 regulates nicotine biosynthesis through interacting with the basic helix-loop-helix (bHLH) transcription factor NtMYC2s

2021 ◽  
Author(s):  
Ge Bai ◽  
Yong Li ◽  
Da-Hai Yang ◽  
Tao Pang ◽  
Zhi-Yong Fan ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Acid Treatment ◽  
Plant Secondary Metabolites ◽  
Bhlh Transcription Factor ◽  
Wild Type ◽  
Helix Loop Helix ◽  
Transgenic Lines ◽  
In The Wild ◽  
Nicotine Biosynthesis

Nicotine is one of the most important secondary metabolites in tobacco, and its biosynthesis can be induced by topping and jasmonic acid treatment. NtMYC2s play pivotal roles in the regulation of nicotine. The mediator server as a bridge betwen the transcription factors and RNA polymerase in order to facilitates transcription and functions in plants. However, the role of mediator in the regulation of nicotine biosynthesis remains unknown. In this study, we firstly identify the NtMED25 through homologous analysis. NtMED25 interacts with NtMYC2s through the MD region. Interestingly, the nicotine content is decreased in the the knock-down transgenic lines of NtMED25, and the expression levels of two nicotine biosynthesis genes, NtQPT2 and NtPMT2, are also reduced when compared with that in the wild-type plants. Furthermore, NtMED25 enhances the binding of NtMYC2a/ NtMYC2b to the promoter of NtPMT2 and NtQPT2, and then facilitates the nicotine biosynthesis. Therefore, our study revealed the function of mediator in the regulation of nicotine, and provide the insight role on the transcriptional regulation of plant secondary metabolites.

Women’s disadvantage in holding supervisory positions. Variations among European countries and the role of horizontal gender segregation

2016 ◽  
Vol 60 (3) ◽  
pp. 262-282 ◽  
Author(s):  
Johanna Dämmrich ◽  
Hans-Peter Blossfeld
Keyword(s):  
Labour Force ◽  
Gender Segregation ◽  
Work And Family ◽  
European Countries ◽  
Labour Force Survey ◽  
Welfare Regimes ◽  
Male Dominated ◽  
Almost All ◽  
Selection Of

Using the Labour Force Survey 2013, this paper examines gender differences in holding supervisory positions in 26 European countries and relates these differences to horizontal gender segregation, i.e. women and men working in different jobs. First, we confirm the findings of previous studies that women are still disadvantaged in holding supervisory positions in almost all countries. Second, by examining how women’s disadvantage varies when working in male-dominated, gender-mixed, and female-dominated occupations, we observe women’s lowest disadvantage in male-dominated occupations in most countries. Third, applying a two-stage multilevel analysis, we explore at the macro level how the country variation in women’s disadvantage in holding supervisory positions is related to horizontal gender segregation, selection of women in the labour market, and conditions facilitating the combination of work and family, and whether women’s disadvantage significantly differs among welfare regimes. We provide evidence that differences among welfare regimes capture much better country variation than single macro indicators.

Role of decapentaplegic in initiation and progression of the morphogenetic furrow in the developing Drosophila retina

Development ◽  
1997 ◽  
Vol 124 (2) ◽  
pp. 559-567 ◽  
Author(s):  
F. Chanut ◽  
U. Heberlein
Keyword(s):  
Posterior Margin ◽  
Imaginal Disc ◽  
Photoreceptor Cells ◽  
Morphogenetic Furrow ◽  
Retinal Differentiation ◽  
Eye Disc ◽  
Forward Edge ◽  
Eye Imaginal Disc ◽  
Precise Role

Morphogenesis in the Drosophila retina initiates at the posterior margin of the eye imaginal disc by an unknown mechanism. Upon initiation, a wave of differentiation, its forward edge marked by the morphogenetic furrow (MF), proceeds anteriorly across the disc. Progression of the MF is driven by hedgehog (hh), expressed by differentiating photoreceptor cells. The TGF-beta homolog encoded by decapentaplegic (dpp) is expressed at the disc's posterior margin prior to initiation and in the furrow, under the control of hh, during MF progression. While dpp has been implicated in eye disc growth and morphogenesis, its precise role in retinal differentiation has not been determined. To address the role of dpp in initiation and progression of retinal differentiation we analyzed the consequences of reduced and increased dpp function during eye development. We find that dpp is not only required for normal MF initiation, but is sufficient to induce ectopic initiation of differentiation. Inappropriate initiation is normally inhibited by wingless (wg). Loss of dpp function is accompanied by expansion of wg expression, while increased dpp function leads to loss of wg transcription. In addition, dpp is required to maintain, and sufficient to induce, its own expression along the disc's margins. We postulate that dpp autoregulation and dpp-mediated inhibition of wg expression are required for the coordinated regulation of furrow initiation and progression. Finally, we show that in the later stages of retinal differentiation, reduction of dpp function leads to an arrest in MF progression.

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