The generation of periodic pattern during early Drosophila embryogenesis

Development ◽  
1988 ◽  
Vol 104 (Supplement) ◽  
pp. 35-50 ◽  
Author(s):  
Ken Howard
Keyword(s):  
De Novo ◽  
Relevant Literature ◽  
Positional Information ◽  
Periodic Pattern ◽  
Gene Interactions ◽  
Segment Polarity Genes ◽  
Segment Polarity ◽  
Pair Rule Gene ◽  
Unique Domain ◽  
Pair Rule

The first indication of the formation of segment primordia in Drosophila is expression of the segment-polarity genes in particular parts of each primordium. These patterns are controlled by another class of genes, the pair-rule genes, which show characteristic two-segment periodic expression. Each pair-rule gene has a unique domain of activity and in one view different combinations of pair-rule gene products directly control the expression of the segment-polarity genes. There is a hierarchy within the pair-rule class revealed by pair-rule gene interactions. It is unlikely that these interactions generate the periodicity de novo. Instead, pair-rule genes respond to positional information generated by a system involving zygotic gap and maternal coordinate genes. In this paper, I will concentrate on the problem of the mechanism that generates these pair-rule patterns, the first periodic ones seen during segmentation. I will review and discuss some of the relevant literature, illustrating certain points with data from my recent work.

scholarly journals Successive specification of Drosophila neuroblasts NB 6-4 and NB 7-3 depends on interaction of the segment polarity genes wingless, gooseberry and naked cuticle

Development ◽  
2001 ◽  
Vol 128 (17) ◽  
pp. 3253-3261 ◽  
Author(s):  
Nirupama Deshpande ◽  
Rainer Dittrich ◽  
Gerhard M. Technau ◽  
Joachim Urban
Keyword(s):  
Cell Fate ◽  
Cell Lineage ◽  
Positional Information ◽  
Dorsoventral Patterning ◽  
Expression Domain ◽  
Direct Role ◽  
Segment Polarity Genes ◽  
Segment Polarity ◽  
Unique Identity

The Drosophila central nervous system derives from neural precursor cells, the neuroblasts (NBs), which are born from the neuroectoderm by the process of delamination. Each NB has a unique identity, which is revealed by the production of a characteristic cell lineage and a specific set of molecular markers it expresses. These NBs delaminate at different but reproducible time points during neurogenesis (S1-S5) and it has been shown for early delaminating NBs (S1/S2) that their identities depend on positional information conferred by segment polarity genes and dorsoventral patterning genes. We have studied mechanisms leading to the fate specification of a set of late delaminating neuroblasts, NB 6-4 and NB 7-3, both of which arise from the engrailed (en) expression domain, with NB 6-4 delaminating first. In contrast to former reports, we did not find any evidence for a direct role of hedgehog in the process of NB 7-3 specification. Instead, we present evidence to show that the interplay of the segmentation genes naked cuticle (nkd) and gooseberry (gsb), both of which are targets of wingless (wg) activity, leads to differential commitment to NB 6-4 and NB 7-3 cell fate. In the absence of either nkd or gsb, one NB fate is replaced by the other. However, the temporal sequence of delamination is maintained, suggesting that formation and specification of these two NBs are under independent control.

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.

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.

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.

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.

Decoding positional information: regulation of the pair-rule gene hairy

Development ◽  
1990 ◽  
Vol 110 (4) ◽  
pp. 1223-1231 ◽  
Author(s):  
K.R. Howard ◽  
G. Struhl
Keyword(s):  
Transcriptional Activation ◽  
Transcriptional Repression ◽  
Expression Patterns ◽  
Positional Information ◽  
Regulatory Elements ◽  
Regulatory Factors ◽  
Cis Acting ◽  
Pair Rule Gene ◽  
Necessary And Sufficient ◽  
Pair Rule

In the series of local gene activations that occur during early Drosophila development, the striped expression patterns of the pair-rule genes provide the first indication of segmental periodicity. The experiments that we report here address the question of how these patterns arise, by studying the regulation of one of these genes, hairy. We show that each of the seven stripes of hairy expression is controlled by a distinct subset of cis-acting regulatory elements, some mediating transcriptional activation and others transcriptional repression. In general, elements necessary and sufficient for triggering a particular stripe response are clustered on the DNA and appear to overlap or be interspersed with elements involved in at least one other stripe response. Our results extend previous findings suggesting that periodic hairy expression arises by a decoding process in which each stripe is triggered by particular combinations or concentrations of regulatory factors. These regulatory factors are likely to include the products of the gap class of segmentation genes that are required for activating or positioning particular subsets of hairy stripes and are expressed with overlapping distributions during early embryogenesis.

scholarly journals Growth zone segmentation in the milkweed bug Oncopeltus fasciatus sheds light on the evolution of insect segmentation

2018 ◽  
Author(s):  
Tzach Auman ◽  
Ariel D. Chipman
Keyword(s):  
Gene Expression ◽  
Growth Zone ◽  
Oncopeltus Fasciatus ◽  
Milkweed Bug ◽  
Segment Polarity Genes ◽  
Temporal Relationships ◽  
Segment Polarity ◽  
Spatio Temporal ◽  
Segment Pattern ◽  
Pair Rule

AbstractOne of the best studied developmental processes is the Drosophila segmentation cascade. However, this cascade is generally considered to be highly derived and unusual. We present a detailed analysis of the sequential segmentation cascade of the milkweed bug Oncopletus fasciatus, as a comparison to Drosophila, with the aim of reconstructing the evolution of insect segmentation. We analyzed the expression of 12 genes, representing different phases during segmentation. We reconstruct the spatio-temporal relationships among these genes And their roles and position in the cascade. We conclude that sequential segmentation in the Oncopeltus germband includes three phases: Primary pair-rule genes generate segmental gene expression in the anterior growth zone, followed by secondary pair-rule genes, expressed in the transition between the growth zone and the segmented germband. Segment polarity genes are expressed in the segmented germband. This process generates a single-segment periodicity, and does not have a double-segment pattern at any stage.

Anterior repression of a Drosophila stripe enhancer requires three position-specific mechanisms

Development ◽  
2002 ◽  
Vol 129 (21) ◽  
pp. 4931-4940 ◽  
Author(s):  
Luiz Paulo Moura Andrioli ◽  
Vikram Vasisht ◽  
Ekaterina Theodosopoulou ◽  
Adam Oberstein ◽  
Stephen Small
Keyword(s):  
Binding Sites ◽  
Positional Information ◽  
Common Mechanism ◽  
Sequence Repeat ◽  
Conserved Sequence ◽  
Gap Gene ◽  
Embryo Formation ◽  
Pair Rule Gene ◽  
Specific Position ◽  
Pair Rule

The striped expression pattern of the pair-rule gene even skipped(eve) is established by five stripe-specific enhancers, each of which responds in a unique way to gradients of positional information in the earlyDrosophila embryo. The enhancer for eve stripe 2(eve 2) is directly activated by the morphogens Bicoid (Bcd) and Hunchback (Hb). As these proteins are distributed throughout the anterior half of the embryo, formation of a single stripe requires that enhancer activation is prevented in all nuclei anterior to the stripe 2 position. The gap genegiant (gt) is involved in a repression mechanism that sets the anterior stripe border, but genetic removal of gt (or deletion of Gt-binding sites) causes stripe expansion only in the anterior subregion that lies adjacent to the stripe border. We identify a well-conserved sequence repeat, (GTTT)4, which is required for repression in a more anterior subregion. This site is bound specifically by Sloppy-paired 1 (Slp1),which is expressed in a gap gene-like anterior domain. Ectopic Slp1 activity is sufficient for repression of stripe 2 of the endogenous eve gene,but is not required, suggesting that it is redundant with other anterior factors. Further genetic analysis suggests that the(GTTT)4-mediated mechanism is independent of the Gt-mediated mechanism that sets the anterior stripe border, and suggests that a third mechanism, downregulation of Bcd activity by Torso, prevents activation near the anterior tip. Thus, three distinct mechanisms are required for anterior repression of a single eve enhancer, each in a specific position. Ectopic Slp1 also represses eve stripes 1 and 3 to varying degrees,and the eve 1 and eve 3+7 enhancers each contain GTTT repeats similar to the site in the eve 2 enhancer. These results suggest a common mechanism for preventing anterior activation of three different eve enhancers.

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.

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