transcription factor - homeodomain - Antp class - required for the formation of labial and maxillary palps - represses leg development in proboscis there is a non-cell autonomous requirement of Proboscipedia for growth and differentiation of the distal maxillary palp during metamorphosis
Gene model reviewed during 5.50
4.3 (northern blot)
None of the polypeptides share 100% sequence identity.
798, 793, 788 (aa)
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\pb using the Feature Mapper tool.
bp transcripts are first detected in 2-4hr embryos, peak 6-8hr embryos, and diminish toward the end of embryogenesis. In larvae, they are most abundant at the second instar stage. They are detected throughout the pupal period with peak in the second 12 hours of pupal development. They are not detected in adults.
Antp P1 control causes ectopic expression of pb in the ventral nerve cord of the posterior prothorax, mesothorax and metathorax in a pattern that closely resembles that of wild type Antp protein. Spatially correct but reduced pb protein expression is also observed.
pb protein expression was assayed with antibodies to a pb/lacZ fusion protein. pb protein is first detected between 5.5 and 6hrs in a group of nuclei in the presumptive mesoderm behind the stomodeum. pb protein expression in the mesoderm is dynamic and the expressing cells migrate away from the ventral midline, separating into two groups. After hour 7, expression is observed in 6-8 cells internal to each manidibular lobe. Subsequently, staining is observed in a group of cells that become positioned along the walls of the foregut. Staining is also observed in the labial and maxillary lobes. By the end of germ band retraction, staining in the labial lobes and sternal region is quite intense. Staining in the maxillary and mandibular lobes has also become intense. By about 10hrs, staining is also observed in a group of cells in the vicinity of the posterior foregut which are later found around the esophagus and proventriculus. Expression in the gnathal segments remains strong during head involution. pb protein begins to be expressed in the CNS in a pattern that becomes increasingly complex. It is expressed in a subset of cells in the supraesophageal ganglion, the subesophageal ganglion, and in the ventral nerve cord. Distinct patterns of pb expression are observed in the CNS of the thoracic segments, the first six abdominal segments, and the more posterior abdominal segments.
GBrowse - Visual display of RNA-Seq signalsView Dmel\pb in GBrowse 2
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Please Note This section lists cDNAs and ESTs that fall within the genomic extent of the gene model, which may include cDNAs and ESTs of genes within introns, or of overlapping genes. Please see GBrowse for alignment of the cDNAs and ESTs to the gene model.
For each fully sequenced cDNA the DGRC maintains various forms of the cDNA (e.g tagged or untagged) in several different host vectors for subsequent cloning and expression in Drosophila and Drosophila cell lines.
Source for merge of: pb l(3)04498
Annotation CG17880 renamed CG31481 in release 3 of the genome annotation.
Ectopic expression of pb can alter the developmental program of adult legs into maxillary or labial palps. These homeotic transformations have equal effect on all three sets of legs. Molecular events occurring downstream of the establishment of compartment boundary are affected by ectopic pb expression in imaginal discs.
Eye loss can be induced by pb protein that no longer effectively bind to DNA. The dose-sensitive eye loss thus appears to be mediated by specific, context-dependent protein-protein interactions.
Effects of overexpression of ANTP-C genes on tarsal segmentation in ss mutants is studied.
Simultaneous removal of pb and Scr activity results in a proboscis-to-antenna transformation. Dominant negative pb molecules inhibit the activity of Scr indicating that pb and Scr interact in a multimeric protein complex in determination of proboscis identity. The absence of pb and Scr expression leads to antennal identity, expression of pb only leads to maxillary palp identity, expression of Scr only leads to tarsus identity and the expression of both pb and Scr leads to proboscis identity.
A phylogenetic analysis of the Antp-class of homeodomains in nematode, Drosophila, amphioxus, mouse and human indicates that the 13 cognate group genes of this family can be divided into two major groups. Genes that are phylogenetically close are also closely located on the chromosome, suggesting that the colinearity between gene expression and gene arrangement was generated by successive tandem gene duplications and that the gene arrangement has been maintained by some sort of selection.
pb is required for the formation of the adult mouthparts, labial and maxillary palps.
Quantitative aspects of pb function are important in determining segmental identity, including cross regulatory events involved in this determination.
A conserved region located in the second intron of pb is essential for proper formation of the adult mouthparts. The upstream DNA of pb appears to contain negative regulatory DNA required for silencing pb product accumulation in inappropriate domains of third instar imaginal discs.
Sequences contained in a pb minigene are capable of suppressing a w marker located in a P-element vector. Regions of pb have been identified that are able to repress w gene in a manner that is sensitive to homolog pairing, pairing sensitive (PS) regions. These PS regions are important for the developmental regulation of pb.
The homologs of Antp, ftz, Scr, Dfd, Ama, bcd, zen, pb and lab, but not zen2 are all present in D.pseudoobscura.pseudoobscura, in the same linear order and similarly spaced along the chromosome as in D.melanogaster.
Comparative analysis of the homeobox sequences reveals the subdivision of the Antp-type homeobox genes into three classes early in metazoan evolution, one includes Abd-B, the second includes abd-A, Ubx, Antp, Scr, Dfd and ftz, and the third includes zen, zen2, pb and lab.
The pb protein is capable of participating in negative regulation of the more posteriorly expressed Antp, as well as serving a homeotic selector function in the head.
Null alleles transform the labial palps of the adult into portions of the prothoracic leg. The distal tarsal segments are present, including claws and pulvilli. The distal portion of the first tarsal segment including the sex comb in males is fused directly to the proximal portion of the femur. Thus proximal first tarsus, tibia and distal femur are absent. Leg segments proximal to femur are not present. Hypomorphic alleles produce a labial-palp-to-antenna transformation. Generally only more distal (arista) antennal structures are seen. Extremely weak hypomorphic alleles exist which produce no ostensible phenotype as homozygotes but do reveal a weak antennal transformation in combination with a deletion or null allele. Both null and hypomorphic alleles also show an alteration in maxillary palp morphology which has been interpreted as a transformation toward an antennal identity.