High impact information on pb

• Nevertheless, pb protein is detected during embryogenesis in nuclei of the labial and maxillary lobes and in part of the mandibular segment [1].
• The proboscipedia locus of the Antennapedia complex: a molecular and genetic analysis [1].
• We also describe a transcription unit very close to pb, which is expressed dorsally during embryogenesis in a pattern resembling that of the nearby zygotic lethal zerknüllt (zen) locus [1].
• Surprisingly, we find that individuals deleted for both the pb and z2 transcription units survive to adulthood and produce normal larval cuticular structures [1].
• Unlike the other homeotic genes of the ANT-C, pb has no obvious role in embryonic development [1].

Biological context of pb

• At the same time, expression from the transgene also rescues recessive pb mutations [2].
• However, the phenotypes of proboscipedia (pb) mutants, which transform the proboscis into leg or antenna, indicate a basic homology among these limbs [3].
• At the earliest stages of embryogenesis, only the expression of pb was found to differ dramatically between Oncopeltus and the other insects examined, although significant differences were observed later in development [4].
• Levels of homeotic protein function can determine developmental identity: evidence from low-level expression of the Drosophila homeotic gene proboscipedia under Hsp70 control [2].
• Gene dosage experiments varying the number of HSPB elements indicate that the extent of the dominant transformation depends on the level of PB protein [2].

Anatomical context of pb

• Accumulation of pb protein is also detected in mesodermal cells and in a unique subset of nuclei throughout the central nervous system [1].
• This is shown to be a consequence of ectopic pb expression in the thorax [5].
• HOXA-2 activity expressed from the Tubulin alpha 1 promoter modified the pb null phenotype resulting in a proboscis-to-arista transformation, indicating that HOXA-2 was able to suppress SCR activity required for tarsus formation [6].

Regulatory relationships of pb

• Tribolium pb therefore positively regulates distal Scr expression, a role that it has in common with Drosophila pb [7].
• We conclude that the Hox genes Sex combs reduced and proboscipedia control an appendage organizer and cell autonomous fate determination during embryonic labial palp development in Tribolium [7].
• However, HOXA-2 expressed from a Tubulin alpha 1 promoter was unable to direct maxillary palp determination when either ectopically expressed in the antenna or in the maxillary palp primordia of a pb null mutant [6].

Other interactions of pb

• The Drosophila proboscis is specified by two Hox genes, proboscipedia and Sex combs reduced, via repression of leg and antennal appendage genes [3].
• Evidence for a direct functional antagonism of the selector genes proboscipedia and eyeless in Drosophila head development [8].
• The gene proboscipedia (pb) is a member of the Antennapedia complex in Drosophila and is required for the proper specification of the adult mouthparts [9].
• Repression of wg by pb has not been reported in the labial imaginal discs of Drosophila [7].
• Drosophila proboscipedia (pb; HoxA2/B2 homolog) mutants develop distal legs in place of their adult labial mouthparts [10].

References