Proboscipedia and Sex combs reduced are essential for embryonic labial palpus specification in Bombyx mori

Mutations of the Drosophila homeotic proboscipedia gene (pb; the Hox-A2/B2 homologue) provoke dose-sensitive defects. These were used to search for dose-sensitive dominant modifiers of pb function. Two identified interacting genes were the proto-oncogene Ras1 and its functional antagonist Gap1, prominent intermediaries in known signal transduction pathways. Ras1+ is a positive modifier of pb activity both in normal and ectopic cell contexts, while the Ras1-antagonist Gap1 has an opposite effect. A general role for Ras1 in homeotic function is likely, since Ras1+ activity also modulates functions of the homeotic loci Sex combs reduced and Ultrabithorax. Our data suggest that the modulation occurs by a mechanism independent of transcriptional control of the homeotic loci themselves, or of the Ras1/Gap1 genes. Taken together our data support a role for Ras1-mediated cell signaling in the homeotic control of segmental differentiation.

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Sequence of the Tribolium castaneum Homeotic Complex: The Region Corresponding to the Drosophila melanogaster Antennapedia Complex

Genetics ◽

10.1093/genetics/160.3.1067 ◽

2002 ◽

Vol 160 (3) ◽

pp. 1067-1074

Author(s):

Susan J Brown ◽

John P Fellers ◽

Teresa D Shippy ◽

Elizabeth A Richardson ◽

Mark Maxwell ◽

...

Keyword(s):

Tribolium Castaneum ◽

Hox Genes ◽

Transcription Unit ◽

Sex Combs Reduced ◽

Sex Combs ◽

Selector Genes ◽

Homeotic Selector Genes ◽

Encoding Genes ◽

Single Cluster ◽

Homeotic Selector

Abstract The homeotic selector genes of the red flour beetle, Tribolium castaneum, are located in a single cluster. We have sequenced the region containing the homeotic selector genes required for proper development of the head and anterior thorax, which is the counterpart of the ANTC in Drosophila. This 280-kb interval contains eight homeodomain-encoding genes, including single orthologs of the Drosophila genes labial, proboscipedia, Deformed, Sex combs reduced, fushi tarazu, and Antennapedia, as well as two orthologs of zerknüllt. These genes are all oriented in the same direction, as are the Hox genes of amphioxus, mice, and humans. Although each transcription unit is similar to its Drosophila counterpart in size, the Tribolium genes contain fewer introns (with the exception of the two zerknüllt genes), produce shorter mRNAs, and encode smaller proteins. Unlike the ANTC, this region of the Tribolium HOMC contains no additional genes.

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Homeotic complex and teashirt genes co-operate to establish trunk segmental identities in Drosophila

Development ◽

10.1242/dev.120.8.2287 ◽

1994 ◽

Vol 120 (8) ◽

pp. 2287-2296 ◽

Cited By ~ 12

Author(s):

P. de Zulueta ◽

E. Alexandre ◽

B. Jacq ◽

S. Kerridge

Keyword(s):

Heat Shock ◽

Target Genes ◽

Homeotic Genes ◽

Sex Combs Reduced ◽

Downstream Target ◽

Functional Aspects ◽

Sex Combs ◽

Head Segment ◽

Posterior Trunk ◽

Segmental Identity

Homeotic genes determine the identities of metameres in Drosophila. We have examined functional aspects of the homeotic gene teashirt by ectopically expressing its product under the control of a heat-shock promoter during embryogenesis. Our results confirm that the gene is critical for segmental identity of the larva. Under mild heat-shock conditions, the Teashirt protein induces an almost complete transformation of the labial to prothoracic segmental identity, when expressed before 8 hours of development. Positive autoregulation of the endogenous teashirt gene and the presence of Sex combs reduced protein in the labium explain this homeosis. Patterns in the maxillary and a more anterior head segment are partly replaced with trunk ones. Additional Teashirt protein has no effect on the identity of the trunk segments where the gene is normally expressed; teashirt function is overridden by some homeotic complex acting in the posterior trunk. Strong heat-shock regimes provoke novel defects: ectopic sense organs differentiate in posterior abdominal segments and trunk pattern elements differentiate in the ninth abdominal segment. Teashirt acts in a partially redundant way with certain homeotic complex proteins but co-operates with them for the establishment of specific segment types. We suggest that Teashirt and HOM-C proteins regulate common sets of downstream target genes.

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Ectopic expression of homeotic genes caused by the elimination of the Polycomb gene in Drosophila imaginal epidermis

Development ◽

10.1242/dev.104.4.713 ◽

1988 ◽

Vol 104 (4) ◽

pp. 713-720 ◽

Cited By ~ 19

Author(s):

A. Busturia ◽

G. Morata

Keyword(s):

Ectopic Expression ◽

Homeotic Genes ◽

Sex Combs Reduced ◽

Hierarchical Order ◽

Sex Combs ◽

Morphological Patterns

The morphological patterns in the adult cuticle of Drosophila are determined principally by the homeotic genes of the bithorax and Antennapedia complexes. We find that many of these genes become indiscriminately active in the adult epidermis when the Pc gene is eliminated. By using the Pc3 mutation and various BX-C mutant combinations, we have generated clones of imaginal cells possessing different combinations of active homeotic genes. We find that, in the absence of BX-C genes, Pc- clones develop prothoracic patterns; this is probably due to the activity of Sex combs reduced which overrules Antennapedia. Adding contributions of Ultrabithorax, abdominal-A and Abdominal-B results in thoracic or abdominal patterns. We have established a hierarchical order among these genes: Antp less than Scr less than Ubx less than abd-A less than Abd-B. In addition, we show that the engrailed gene is ectopically active in Pc- imaginal cells.

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Novel patterns of homeotic protein accumulation in the head of the Drosophila embryo

Development ◽

10.1242/dev.105.1.167 ◽

1989 ◽

Vol 105 (1) ◽

pp. 167-174 ◽

Cited By ~ 8

Author(s):

J.W. Mahaffey ◽

R.J. Diederich ◽

T.C. Kaufman

Keyword(s):

Nerve Cord ◽

Protein Product ◽

Drosophila Embryo ◽

Protein Accumulation ◽

Homeotic Genes ◽

Gene Products ◽

Ventral Region ◽

Sex Combs Reduced ◽

Sex Combs ◽

Dorsal Epidermis

Antibodies that specifically recognize proteins encoded by the homeotic genes: Sex combs reduced, Deformed, labial and proboscipedia, were used to follow the distribution of these gene products during embryogenesis. The position of engrailed-expressing cells was used as a reference and staining conditions were established that could distinguish, among cells expressing engrailed, one of the homeotic proteins or both. Our observations demonstrate two important facts about establishing identity in the head segments. First, in contrast to the overlapping pattern of homeotic gene expression in the trunk segments, we observe a non-overlapping pattern in the head for those homeotic proteins required during embryogenesis. In contrast, the spatial accumulation of the protein product of the non-vital proboscipedia locus overlaps partially with the distribution of the Deformed and Sex combs reduced proteins in the maxillary and labial segments, respectively. Second, two of the proteins, Sex combs reduced and Deformed, have different dorsal and ventral patterns of accumulation. Dorsally, these proteins are expressed in segmental domains while, within the ventral region, a parasegmental register is observed. The boundary where this change in pattern occurs coincides with the junction between the ventral neurogenic region and the dorsal epidermis. After contraction of the germ band, when the nerve cord has completely separated from the epidermis, the parasegmental pattern is observed only within the ventral nerve cord while a segmental register is maintained throughout the epidermis.

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Evolution of the insect body plan as revealed by the Sex combs reduced expression pattern

Development ◽

10.1242/dev.124.1.149 ◽

1997 ◽

Vol 124 (1) ◽

pp. 149-157 ◽

Cited By ~ 5

Author(s):

B.T. Rogers ◽

M.D. Peterson ◽

T.C. Kaufman

Keyword(s):

Morphological Evolution ◽

Expression Patterns ◽

Morphological Characters ◽

Homeotic Gene ◽

Homeotic Genes ◽

Cell Fates ◽

Sex Combs Reduced ◽

Sex Combs ◽

Evolutionarily Conserved ◽

Epidermal Expression

The products of the HOM/Hox homeotic genes form a set of evolutionarily conserved transcription factors that control elaborate developmental processes and specify cell fates in many metazoans. We examined the expression of the ortholog of the homeotic gene Sex combs reduced (Scr) of Drosophila melanogaster in insects of three divergent orders: Hemiptera, Orthoptera and Thysanura. Our data reflect how the conservation and variation of Scr expression has affected the morphological evolution of insects. Whereas the anterior epidermal expression of Scr, in a small part of the posterior maxillary and all of the labial segment, is found to be in common among all four insect orders, the posterior (thoracic) expression domains vary. Unlike what is observed in flies, the Scr orthologs of other insects are not expressed broadly over the first thoracic segment, but are restricted to small patches. We show here that Scr is required for suppression of wings on the prothorax of Drosophila. Moreover, Scr expression at the dorsal base of the prothoracic limb in two other winged insects, crickets (Orthoptera) and milkweed bugs (Hemiptera), is consistent with Scr acting as a suppressor of prothoracic wings in these insects. Scr is also expressed in a small patch of cells near the basitarsal-tibial junction of milkweed bugs, precisely where a leg comb develops, suggesting that Scr promotes comb formation, as it does in Drosophila. Surprisingly, the dorsal prothoracic expression of Scr is also present in the primitively wingless firebrat (Thysanura) and the leg patch is seen in crickets, which have no comb. Mapping both gene expression patterns and morphological characters onto the insect phylogenetic tree demonstrates that in the cases of wing suppression and comb formation the appearance of expression of Scr in the prothorax apparently precedes these specific functions.

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Tissue- and stage-specific control of homeotic and segmentation gene expression in Drosophila embryos by the polyhomeotic gene

Development ◽

10.1242/dev.103.4.733 ◽

1988 ◽

Vol 103 (4) ◽

pp. 733-741 ◽

Cited By ~ 10

Author(s):

J.M. Dura ◽

P. Ingham

Keyword(s):

Negative Regulator ◽

Homeotic Genes ◽

Sex Combs Reduced ◽

Sex Combs ◽

Segmentation Gene Expression ◽

The Central Nervous System ◽

C Complex ◽

Specific Control ◽

Blastoderm Stage ◽

Drosophila Embryos

The distributions of the products of the homeotic genes Sex combs reduced (Scr) and Ultrabithorax (Ubx) and of the segmentation genes, fushi tarazu (ftz), even skipped (eve) and engrailed (en) have been monitored in polyhomeotic (ph) mutant embryos. None of the genes monitored show abnormal expression at the blastoderm stage in the absence of zygotic ph expression. Both Scr and Ubx are ectopically expressed in the epidermis of ph embryos, confirming the earlier proposal, based on genetic analysis, that ph+ acts as a negative regulator of Antennapedia (ANT-C) and bithorax (BX-C) complex genes. At the shortened germ band stage, en is also ectopically expressed, mainly in the anterior region of each segment. In contrast to these effects in the epidermis, the expression of en, Ubx, Scr and ftz is largely or completely suppressed in the central nervous system, whereas eve becomes ectopically expressed in most neurones.

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