Head versus trunk patterning in the Drosophila embryo; collier requirement for formation of the intercalary segment

Development ◽  
1999 ◽  
Vol 126 (19) ◽  
pp. 4385-4394 ◽  
Author(s):  
M. Crozatier ◽  
D. Valle ◽  
L. Dubois ◽  
S. Ibnsouda ◽  
A. Vincent
Keyword(s):  
Molecular Mechanisms ◽  
Drosophila Embryo ◽  
Phenotypic Analysis ◽  
Gap Genes ◽  
Segment Polarity ◽  
Pair Rule Gene ◽  
Combinatorial Model ◽  
Hlh Transcription Factors ◽  
Head Skeleton ◽  
Pair Rule

Whereas the segmental nature of the insect head is well established, relatively little is known about the genetic and molecular mechanisms governing this process. In this paper, we report the phenotypic analysis of mutations in collier (col), which encodes the Drosophila member of the COE family of HLH transcription factors and is activated at the blastoderm stage in a region overlapping a parasegment (PS0: posterior intercalary and anterior mandibular segments) and a mitotic domain, MD2. col mutant embryos specifically lack intercalary ectodermal structures. col activity is required for intercalary-segment expression both of the segment polarity genes hedgehog, engrailed, and wingless, and of the segment identity gene cap and collar. The parasegmental register of col activation is controlled by the combined activities of the head-gap genes buttonhead and empty spiracles and the pair-rule gene even skipped; it therefore integrates inputs from both the head and trunk segmentation systems, which were previously considered as being essentially independent. After gastrulation, positive autoregulation of col is limited to cells of anterior PS0. Conversely, heat-pulse induced ubiquitous expression of Col leads to disruption of the head skeleton. Together, these results indicate that col is required for establishment of the PS(−1)/PS0 parasegmental border and formation of the intercalary segment. Our data support neither a simple combinatorial model for segmental patterning of the head nor a direct activation of segment polarity gene expression by head-gap genes, but rather argue for the existence of parasegment-specific second order regulators acting in the head, at a level similar to that of pair-rule genes in the trunk.

Dynamic changes in the functions of Odd-skipped during early Drosophila embryogenesis

Development ◽  
1998 ◽  
Vol 125 (23) ◽  
pp. 4851-4861 ◽  
Author(s):  
B. Saulier-Le Drean ◽  
A. Nasiadka ◽  
J. Dong ◽  
H.M. Krause
Keyword(s):  
Target Gene ◽  
Target Genes ◽  
Drosophila Embryo ◽  
Gene Products ◽  
Dynamic Changes ◽  
Stage Of Development ◽  
Segment Polarity ◽  
Pair Rule Gene ◽  
Candidate Target ◽  
Pair Rule

Although many of the genes that pattern the segmented body plan of the Drosophila embryo are known, there remains much to learn in terms of how these genes and their products interact with one another. Like many of these gene products, the protein encoded by the pair-rule gene odd-skipped (Odd) is a DNA-binding transcription factor. Genetic experiments have suggested several candidate target genes for Odd, all of which appear to be negatively regulated. Here we use pulses of ectopic Odd expression to test the response of these and other segmentation genes. The results are complex, indicating that Odd is capable of repressing some genes wherever and whenever Odd is expressed, while the ability to repress others is temporally or spatially restricted. Moreover, one target gene, fushi tarazu, is both repressed and activated by Odd, the outcome depending upon the stage of development. These results indicate that the activity of Odd is highly dependent upon the presence of cofactors and/or overriding inhibitors. Based on these results, and the segmental phenotypes generated by ectopic Odd, we suggest a number of new roles for Odd in the patterning of embryonic segments. These include gap-, pair-rule- and segment polarity-type functions.

Two distinct mechanisms for differential positioning of gene expression borders involving the Drosophila gap protein giant

Development ◽  
1998 ◽  
Vol 125 (19) ◽  
pp. 3765-3774 ◽  
Author(s):  
X. Wu ◽  
R. Vakani ◽  
S. Small
Keyword(s):  
Target Genes ◽  
Early Embryo ◽  
Drosophila Embryo ◽  
Anterior Border ◽  
Gap Gene ◽  
Gap Genes ◽  
Pair Rule Gene ◽  
Differential Positioning ◽  
Pair Rule

We have combined genetic experiments and a targeted misexpression approach to examine the role of the gap gene giant (gt) in patterning anterior regions of the Drosophila embryo. Our results suggest that gt functions in the repression of three target genes, the gap genes Kruppel (Kr) and hunchback (hb), and the pair-rule gene even-skipped (eve). The anterior border of Kr, which lies 4–5 nucleus diameters posterior to nuclei that express gt mRNA, is set by a threshold repression mechanism involving very low levels of gt protein. In contrast, gt activity is required, but not sufficient for formation of the anterior border of eve stripe 2, which lies adjacent to nuclei that express gt mRNA. We propose that gt's role in forming this border is to potentiate repressive interaction(s) mediated by other factor(s) that are also localized to anterior regions of the early embryo. Finally, gt is required for repression of zygotic hb expression in more anterior regions of the embryo. The differential responses of these target genes to gt repression are critical for the correct positioning and maintenance of segmentation stripes, and normal anterior development.

Segmentation gene expression in the housefly Musca domestica

Development ◽  
1991 ◽  
Vol 113 (2) ◽  
pp. 419-430 ◽  
Author(s):  
R. Sommer ◽  
D. Tautz
Keyword(s):  
Gene Expression ◽  
Musca Domestica ◽  
Segmentation Gene ◽  
Gap Genes ◽  
Segment Polarity ◽  
Pair Rule Gene ◽  
Segmentation Gene Expression ◽  
Early Expression ◽  
Early Developmental ◽  
Pair Rule

Drosophila and Musca both belong to the group of higher dipteran flies and show morphologically a very similar early development. However, these two species are evolutionary separated by at least 100 million years. This presents the opportunity for a comparative analysis of segmentation gene expression across a large evolutionary distance in a very similar embryonic background. We have analysed in detail the early expression of the maternal gene bicoid, the gap genes hunchback, Kruppel, knirps and tailless, the pair-rule gene hairy, the segment-polarity gene engrailed and the homoeotic gene Ultrabithorax. We show that the primary expression domains of these genes are conserved, while some secondary expression aspects have diverged. Most notable is the finding of hunchback expression in 11–13 stripes shortly before gastrulation, as well as a delayed expression of terminal domains of various genes. We conclude that the early developmental gene hierarchy, as it has been defined in Drosophila, is evolutionary conserved in Musca domestica.

scholarly journals Dosage-Sensitive Maternal Modifiers of the Drosophila Segmentation Gene runt

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 839-852
Author(s):  
Joseph B Duffy ◽  
James Wells ◽  
J Peter Gergen
Keyword(s):  
Transcriptional Regulation ◽  
Transcriptional Regulator ◽  
Drosophila Embryo ◽  
Over Expression ◽  
Spatial Regulation ◽  
Gap Genes ◽  
Pair Rule Gene ◽  
Pair Rule ◽  
Anterior Posterior

Abstract The protein encoded by the pair-rule gene runt functions as a transcriptional regulator during anterior-posterior patterning of the Drosophila embryo. Results of over-expression experiments as well as parallels drawn from the recent characterization of vertebrate homologues indicate that interactions with other proteins are likely to be central to the function of the Runt protein. To identify factors important for runt activity, we took advantage of an adult visible phenotype observed in animals heterozygous for runt mutations. Using a set of 126 different deficiency chromosomes we screened ~65% of the genome for genes that act as dose-sensitive maternal modifiers of runt. Eighteen deficiencies representing 12 putative loci were identified as maternally acting enhancers of runt haplo-insufficiency. Further characterization of two of these regions led to the identification of the interacting loci. Both of these loci affect the spatial regulation of runt transcription and appear genetically complex. Furthermore, the effects of one of these loci, M(1)1B, is indirect and mediated through effects on the transcriptional regulation of posterior gap genes.

scholarly journals Odd-paired controls frequency doubling in Drosophila segmentation by altering the pair-rule gene regulatory network

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Erik Clark ◽  
Michael Akam
Keyword(s):  
Gene Expression ◽  
Gene Regulatory Network ◽  
Regulatory Network ◽  
Frequency Doubling ◽  
Drosophila Embryo ◽  
Anteroposterior Patterning ◽  
Regulatory Interactions ◽  
Pair Rule Gene ◽  
Gene Regulatory ◽  
Pair Rule

The Drosophila embryo transiently exhibits a double-segment periodicity, defined by the expression of seven 'pair-rule' genes, each in a pattern of seven stripes. At gastrulation, interactions between the pair-rule genes lead to frequency doubling and the patterning of 14 parasegment boundaries. In contrast to earlier stages of Drosophila anteroposterior patterning, this transition is not well understood. By carefully analysing the spatiotemporal dynamics of pair-rule gene expression, we demonstrate that frequency-doubling is precipitated by multiple coordinated changes to the network of regulatory interactions between the pair-rule genes. We identify the broadly expressed but temporally patterned transcription factor, Odd-paired (Opa/Zic), as the cause of these changes, and show that the patterning of the even-numbered parasegment boundaries relies on Opa-dependent regulatory interactions. Our findings indicate that the pair-rule gene regulatory network has a temporally modulated topology, permitting the pair-rule genes to play stage-specific patterning roles.

Quantitative Analysis of Gene Function in the Drosophila Embryo

Genetics ◽  
2000 ◽  
Vol 154 (1) ◽  
pp. 273-284
Author(s):  
William D Tracey ◽  
Xiangqun Ning ◽  
Martin Klingler ◽  
Sunita G Kramer ◽  
J Peter Gergen
Keyword(s):  
Gene Function ◽  
Model Systems ◽  
Drosophila Embryo ◽  
Direct Role ◽  
Developmental Context ◽  
Maternal Mrna ◽  
Early Drosophila Embryo ◽  
Segment Polarity ◽  
Pair Rule

Abstract The specific functions of gene products frequently depend on the developmental context in which they are expressed. Thus, studies on gene function will benefit from systems that allow for manipulation of gene expression within model systems where the developmental context is well defined. Here we describe a system that allows for genetically controlled overexpression of any gene of interest under normal physiological conditions in the early Drosophila embryo. This regulated expression is achieved through the use of Drosophila lines that express a maternal mRNA for the yeast transcription factor GAL4. Embryos derived from females that express GAL4 maternally activate GAL4-dependent UAS transgenes at uniform levels throughout the embryo during the blastoderm stage of embryogenesis. The expression levels can be quantitatively manipulated through the use of lines that have different levels of maternal GAL4 activity. Specific phenotypes are produced by expression of a number of different developmental regulators with this system, including genes that normally do not function during Drosophila embryogenesis. Analysis of the response to overexpression of runt provides evidence that this pair-rule segmentation gene has a direct role in repressing transcription of the segment-polarity gene engrailed. The maternal GAL4 system will have applications both for the measurement of gene activity in reverse genetic experiments as well as for the identification of genetic factors that have quantitative effects on gene function in vivo.

Dose-dependent regulation of pair-rule stripes by gap proteins and the initiation of segment polarity

Development ◽  
1990 ◽  
Vol 110 (3) ◽  
pp. 759-767 ◽  
Author(s):  
R. Warrior ◽  
M. Levine
Keyword(s):  
Expression Patterns ◽  
Gene Products ◽  
Embryonic Cells ◽  
Periodic Patterns ◽  
Threshold Response ◽  
Gap Gene ◽  
Relative Placement ◽  
Segment Polarity ◽  
Pair Rule Gene ◽  
Pair Rule

A key step in Drosophila segmentation is the establishment of periodic patterns of pair-rule gene expression in response to gap gene products. From an examination of the distribution of gap and pair-rule proteins in various mutants, we conclude that the on/off periodicity of pair-rule stripes depends on both the exact concentrations and combinations of gap proteins expressed in different embryonic cells. It has been suggested that the distribution of gap gene products depends on cross-regulatory interactions among these genes. Here we provide evidence that autoregulation also plays an important role in this process since there is a reduction in the levels of Kruppel (Kr) RNA and protein in a Kr null mutant. Once initiated by the gap genes each pair-rule stripe is bell shaped and has ill-defined margins. By the end of the fourteenth nuclear division cycle, the stripes of the pair-rule gene even-skipped (eve) sharpen and polarize, a process that is essential for the precisely localized expression of segment polarity genes. This sharpening process appears to depend on a threshold response of the eve promoter to the combinatorial action of eve and a second pair-rule gene hairy. The eve and hairy expression patterns overlap but are out of register and the cells of maximal overlap form the anterior margin of the polarized eve stripe. We propose that the relative placement of the eve and hairy stripes may be an important factor in the initiation of segment polarity.

The molecular basis for metameric pattern in the Drosophila embryo

Development ◽  
1987 ◽  
Vol 101 (1) ◽  
pp. 1-22 ◽  
Author(s):  
M. Akam
Keyword(s):  
Molecular Basis ◽  
Subsequent Development ◽  
The Body ◽  
Drosophila Embryo ◽  
Homeotic Genes ◽  
Simple Pattern ◽  
Segment Polarity ◽  
Maternal Determinants ◽  
Segment Pattern ◽  
Pair Rule

The metameric organization of the Drosophila embryo is generated in the first 5 h after fertilization. An initially rather simple pattern provides the foundation for subsequent development and diversification of the segmented part of the body. Many of the genes that control the formation of this pattern have been identified and at least twenty have been cloned. By combining the techniques of genetics, molecular biology and experimental embryology, it is becoming possible to unravel the role played by each of these genes. The repeating segment pattern is defined by the persistent expression of engrailed and of other genes of the ‘segment polarity’ class. The establishment of this pattern is directed by a transient molecular prepattern that is generated in the blastoderm by the activity of the ‘pair-rule’ genes. Maternal determinants at the poles of the egg coordinate this prepattern and define the anteroposterior sequence of pattern elements. The primary effect of these determinants is not known, but genes required for their production have been identified and the product of one of these, bicoid is known to be localized at the anterior of the egg. One early consequence of their activity is to define domains along the A-P axis within which a series of ‘cardinal’ genes are transcribed. The activity of the cardinal genes is required both to coordinate the process of segmentation and to define the early domains of homeotic gene expression. Further interactions between the homeotic genes and other classes of segmentation genes refine the initial establishment of segment identities.

scholarly journals Annotation of segmentation pathway genes in the Asian citrus psyllid, Diaphorina citri

Gigabyte ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Sherry Miller ◽  
Teresa D. Shippy ◽  
Prashant S. Hosmani ◽  
Mirella Flores-Gonzalez ◽  
Lukas A. Mueller ◽  
...  
Keyword(s):  
Asian Citrus Psyllid ◽  
Control Methods ◽  
Diaphorina Citri ◽  
Segment Polarity Genes ◽  
Gap Genes ◽  
Segment Polarity ◽  
Protein Gradients ◽  
Pest Control Methods ◽  
Pair Rule ◽  
Anterior Posterior

Insects have a segmented body plan that is established during embryogenesis when the anterior–posterior (A–P) axis is divided into repeated units by a cascade of gene expression. The cascade is initiated by protein gradients created by translation of maternally provided mRNAs, localized at the anterior and posterior poles of the embryo. Combinations of these proteins activate specific gap genes to divide the embryo into distinct regions along the anterior–posterior axis. Gap genes then activate pair-rule genes, which are usually expressed in parts of every other segment. The pair-rule genes, in turn, activate expression of segment polarity genes in a portion of each segment. The segmentation genes are generally conserved among insects, although there is considerable variation in how they are deployed. We annotated 25 segmentation gene homologs in the Asian citrus psyllid, Diaphorina citri. Most of the genes expected to be present in D. citri based on their phylogenetic distribution in other insects were identified and annotated. Two exceptions were eagle and invected, which are present in at least some hemipterans, but were not found in D. citri. Many of the segmentation pathway genes are likely to be essential for D. citri development, and thus they may be useful targets for gene-based pest control methods.

Grasshopper hunchback expression reveals conserved and novel aspects of axis formation and segmentation

Development ◽  
2001 ◽  
Vol 128 (18) ◽  
pp. 3459-3472 ◽  
Author(s):  
Nipam H. Patel ◽  
David C. Hayward ◽  
Sabbi Lall ◽  
Nicole R. Pirkl ◽  
Daniel DiPietro ◽  
...  
Keyword(s):  
Expression Patterns ◽  
Axis Formation ◽  
Embryonic Cells ◽  
Embryonic Patterning ◽  
Axial Patterning ◽  
Gap Gene ◽  
Segment Polarity ◽  
Pair Rule Gene ◽  
Set Up ◽  
Pair Rule

While the expression patterns of segment polarity genes such as engrailed have been shown to be similar in Drosophila melanogaster and Schistocerca americana (grasshopper), the expression patterns of pair-rule genes such as even-skipped are not conserved between these species. This might suggest that the factors upstream of pair-rule gene expression are not conserved across insect species. We find that, despite this, many aspects of the expression of the Drosophila gap gene hunchback are shared with its orthologs in the grasshoppers S. americana and L. migratoria. We have analyzed both mRNA and protein expression during development, and find that the grasshopper hunchback orthologs appear to have a conserved role in early axial patterning of the germ anlagen and in the specification of gnathal and thoracic primordia. In addition, distinct stepped expression levels of hunchback in the gnathal/thoracic domains suggest that grasshopper hunchback may act in a concentration-dependent fashion (as in Drosophila), although morphogenetic activity is not set up by diffusion to form a smooth gradient. Axial patterning functions appear to be performed entirely by zygotic hunchback, a fundamental difference from Drosophila in which maternal and zygotic hunchback play redundant roles. In grasshoppers, maternal hunchback activity is provided uniformly to the embryo as protein and, we suggest, serves a distinct role in distinguishing embryonic from extra-embryonic cells along the anteroposterior axis from the outset of development – a distinction made in Drosophila along the dorsoventral axis later in development. Later hunchback expression in the abdominal segments is conserved, as are patterns in the nervous system, and in both Drosophila and grasshopper, hunchback is expressed in a subset of extra-embryonic cells. Thus, while the expected domains of hunchback expression are conserved in Schistocerca, we have found surprising and fundamental differences in axial patterning, and have identified a previously unreported domain of expression in Drosophila that suggests conservation of a function in extra-embryonic patterning.

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