scholarly journals Organogenesis in Drosophila melanogaster: embryonic salivary gland determination is controlled by homeotic and dorsoventral patterning genes

Development ◽  
1992 ◽  
Vol 114 (1) ◽  
pp. 49-57 ◽  
Author(s):  
S. Panzer ◽  
D. Weigel ◽  
S.K. Beckendorf
Keyword(s):  
Drosophila Melanogaster ◽  
Salivary Gland ◽  
Homeotic Gene ◽  
Dorsoventral Patterning ◽  
Sex Combs Reduced ◽  
Sex Combs ◽  
Positive Action ◽  
Gland Morphogenesis ◽  
Pattern Forming ◽  
Anterior Posterior

We have investigated Drosophila salivary gland determination by examining the effects of mutations in pattern forming genes on the salivary gland primordium. We find that the anterior-posterior extent of the primordium, a placode of columnar epithelial cells derived from parasegment 2, is established by the positive action of the homeotic gene Sex combs reduced (Scr). Embryos mutant for Scr lack a detectable placode, while ectopic Scr expression leads to the formation of ectopic salivary glands. In contrast, the dorsal-ventral extent of the placode is regulated negatively. Functions dependent on the decapentaplegic product place a dorsal limit on the placode, while dorsal-dependent genes act to limit the placode ventrally. We propose a model in which these pattern forming genes act early to determine the salivary gland anlage by regulating the expression of salivary gland determining genes, which in turn control genes that are involved in salivary gland morphogenesis.

Transvection and Silencing of the Scr Homeotic Gene of Drosophila melanogaster

Genetics ◽  
2002 ◽  
Vol 161 (2) ◽  
pp. 733-746
Author(s):  
Jeffrey W Southworth ◽  
James A Kennison
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosomal Aberrations ◽  
Regulatory Element ◽  
Regulatory Elements ◽  
Anomalous Behavior ◽  
Polycomb Group ◽  
Homeotic Gene ◽  
Polycomb Group Proteins ◽  
Sex Combs Reduced ◽  
In Cis

Abstract The Sex combs reduced (Scr) gene specifies the identities of the labial and first thoracic segments in Drosophila melanogaster. In imaginal cells, some Scr mutations allow cis-regulatory elements on one chromosome to stimulate expression of the promoter on the homolog, a phenomenon that was named transvection by Ed Lewis in 1954. Transvection at the Scr gene is blocked by rearrangements that disrupt pairing, but is zeste independent. Silencing of the Scr gene in the second and third thoracic segments, which requires the Polycomb group proteins, is disrupted by most chromosomal aberrations within the Scr gene. Some chromosomal aberrations completely derepress Scr even in the presence of normal levels of all Polycomb group proteins. On the basis of the pattern of chromosomal aberrations that disrupt Scr gene silencing, we propose a model in which two cis-regulatory elements interact to stabilize silencing of any promoter or cis-regulatory element physically between them. This model also explains the anomalous behavior of the Scx allele of the flanking homeotic gene, Antennapedia. This allele, which is associated with an insertion near the Antennapedia P1 promoter, inactivates the Antennapedia P1 and P2 promoters in cis and derepresses the Scr promoters both in cis and on the homologous chromosome.

scholarly journals The ash-1, ash-2 and trithorax genes of Drosophila melanogaster are functionally related.

Genetics ◽  
1989 ◽  
Vol 121 (3) ◽  
pp. 517-525 ◽  
Author(s):  
A Shearn
Keyword(s):  
Drosophila Melanogaster ◽  
Null Allele ◽  
Homeotic Gene ◽  
Bithorax Complex ◽  
Substantial Evidence ◽  
Genetic Tests ◽  
Recessive Lethal ◽  
The Third ◽  
Sex Combs

Abstract Mutations in the ash-1 and ash-2 genes of Drosophila melanogaster cause a wide variety of homeotic transformations that are similar to the transformations caused by mutations in the trithorax gene. Based on this similar variety of transformations, it was hypothesized that these genes are members of a functionally related set. Three genetic tests were employed here to evaluate that hypothesis. The first test was to examine interactions of ash-1, ash-2 and trithorax mutations with each other. Double and triple heterozygotes of recessive lethal alleles express characteristic homeotic transformations. For example, double heterozygotes of a null allele of ash-1 and a deletion of trithorax have partial transformations of their first and third legs to second legs and of their halteres to wings. The penetrance of these transformations is reduced by a duplication of the bithorax complex. The second test was to examine interactions with a mutation in the female sterile (1) homeotic gene. The penetrance of the homeotic phenotype in progeny from mutant mothers is increased by heterozygosis for alleles of ash-1 or ash-2 as well as for trithorax alleles. The third test was to examine the interaction with a mutation of the Polycomb gene. The extra sex combs phenotype caused by heterozygosis for a deletion of Polycomb is suppressed by heterozygosis for ash-1, ash-2 or trithorax alleles. The fact that mutations in each of the three genes gave rise to similar results in all three tests represents substantial evidence that ash-1, ash-2 and trithorax are members of a functionally related set of genes.

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

Development ◽  
1997 ◽  
Vol 124 (1) ◽  
pp. 149-157 ◽  
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.

scholarly journals Novel regulation of the homeotic gene Scr associated with a crustacean leg-to-maxilliped appendage transformation

Development ◽  
1999 ◽  
Vol 126 (6) ◽  
pp. 1121-1128 ◽  
Author(s):  
A. Abzhanov ◽  
T.C. Kaufman
Keyword(s):  
Expression Patterns ◽  
Homeotic Gene ◽  
Homeotic Genes ◽  
Porcellio Scaber ◽  
Sex Combs Reduced ◽  
Early Embryos ◽  
Sex Combs ◽  
Thoracic Legs ◽  
Post Transcriptional Regulation ◽  
Late Stages

Homeotic genes are known to be involved in patterning morphological structures along the antero-posterior axis of insects and vertebrates. Because of their important roles in development, changes in the function and expression patterns of homeotic genes may have played a major role in the evolution of different body plans. For example, it has been proposed that during the evolution of several crustacean lineages, changes in the expression patterns of the homeotic genes Ultrabithorax and abdominal-A have played a role in transformation of the anterior thoracic appendages into mouthparts termed maxillipeds. This homeotic-like transformation is recapitulated at the late stages of the direct embryonic development of the crustacean Porcellio scaber (Oniscidea, Isopoda). Interestingly, this morphological change is associated with apparent novelties both in the transcriptional and post-transcriptional regulation of the Porcellio scaber ortholog of the Drosophila homeotic gene, Sex combs reduced (Scr). Specifically, we find that Scr mRNA is present in the second maxillary segment and the first pair of thoracic legs (T1) in early embryos, whereas protein accumulates only in the second maxillae. In later stages, however, high levels of SCR appear in the T1 legs, which correlates temporally with the transformation of these appendages into maxillipeds. Our observations provide further insight into the process of the homeotic leg-to-maxilliped transformation in the evolution of crustaceans and suggest a novel regulatory mechanism for this process in this group of arthropods.

scholarly journals REVERTANTS OF DOMINANT MUTATIONS ASSOCIATED WITH THE ANTENNAPEDIA GENE COMPLEX OF DROSOPHILA MELANOGASTER: CYTOLOGY AND GENETICS

Genetics ◽  
1983 ◽  
Vol 105 (3) ◽  
pp. 581-600
Author(s):  
T Hazelrigg ◽  
T C Kaufman
Keyword(s):  
Drosophila Melanogaster ◽  
Gene Complex ◽  
Dominant Mutation ◽  
Sex Combs Reduced ◽  
X Ray ◽  
Lethal Mutations ◽  
Sex Combs ◽  
Chromosomal Loci ◽  
Chromosome Bands

ABSTRACT Using X-ray mutagenesis we have induced and recovered phenotypic revertants of four dominant mutations thought to be associated with the Antennapedia complex of Drosophila melanogaster. These include seven revertants of Antennapedia-73b (Antp73b), six of Extra Sex Combs of Wakimoto (Scxw), three of Deformed (Dfd) and one of Humeral (Hu). Fifteen of the 17 revertants are associated with chromosomal aberrations and localize Antp73b, Scxw and Hu to polytene chromosome bands 84B1,2. The Dfd lesion is apparently located in or adjacent to bands 84A4,5. Since all of the dominants are reverted by events that delete their respective chromosomal loci, we conclude that all four are the result of a gain-of-function lesions. Complementation analysis of the various revertant chromosomes has shown that Scxw and Hu are dominant allelic variants of the Antp locus. The Dfd lesion represents a dominant mutation at a locus just proximal to Antp and previously only occupied by recessive lethal mutations. Characterization of the revertants of Scxw and a comparison with the properties of the original mutation has revealed that the original lesion has effects on both the Antp and Sex Combs Reduced (Scr) loci and that these defects are in some cases separable by the reverting event.

scholarly journals A functional and structural analysis of the Sex combs reduced locus of Drosophila melanogaster.

Genetics ◽  
1991 ◽  
Vol 129 (2) ◽  
pp. 423-441 ◽  
Author(s):  
A M Pattatucci ◽  
D C Otteson ◽  
T C Kaufman
Keyword(s):  
Drosophila Melanogaster ◽  
Gene Function ◽  
Molecular Mapping ◽  
Genetic Locus ◽  
Regulatory Region ◽  
Genomic Rearrangements ◽  
Fushi Tarazu ◽  
Sex Combs Reduced ◽  
Sex Combs ◽  
Normal Head

Abstract We have undertaken a developmental genetic analysis of the homeotic gene Sex combs reduced (Scr) of Drosophila melanogaster by examining embryonic and adult phenotypes of mutations affecting Scr gene function. Molecular mapping of Scr breakpoint lesions has defined a segment of greater than 70 kb of DNA necessary for proper Scr gene function. This region is split by the fushi tarazu (ftz) gene, with lesions affecting embryonic Scr function molecularly mapping to the region proximal (5') to ftz and those exhibiting polyphasic semilethality predominantly mapping distal (3') to ftz. Gain-of-function mutations are associated with genomic rearrangements and map throughout the Scr locus. Our analysis has revealed that the Scr locus encompasses genetic elements that are responsible for functions in both the embryonic and larval to adult periods of development. From these studies, we conclude that Scr is a complex genetic locus with an extensive regulatory region that directs functions required for normal head and thoracic development in both the embryo and the adult and that the regulation of Scr during these two periods is distinct.

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