Gene expression of the Ia form of Ubx is driven by an Hsp70 promoter.
chordotonal organ & axon | conditional ts
peripheral nervous system & mesothoracic segment | conditional ts
peripheral nervous system & metathoracic segment | conditional ts
peripheral nervous system & prothoracic segment | conditional ts
trichome & mesothoracic femur | posterior
Ubiquitous expression of UbxIa.hs causes a specific transformation of the shape of the proximal femur of T2, and to a lesser extent T1, toward the shape of T3. The effect is strongest approximately 8 to 20 hours after pupariation, after which time the effect becomes progressively less strong. Expression after pupation does not increase the length or width of the T2 femur or basitarsus.
Sternopleural precursor development on the T2 leg can be suppressed by expression of UbxIa.hs using heat shock from 24-22 hours before puparium formation and also from 22-20 hours before puparium formation (although at lower efficiency). Heat shocks from 7-5 hours before puparium formation do not inhibit sternopleural precursor development.
Ubiquitous expression of UbxIa.hs transforms anterior segments into extra A1 segments.
Expression of uniform high levels of Ubx protein during pupal development repressed trichomes on most of the posterior second femur. Maximal repression occurs between 20 and 28 hours after puparium formation. Trichomes are repressed in a proximal to distal direction.
Uniform expression of UbxIa.hs in wild-type embryos transforms all three thoracic segments and 2-3 head segments into A1-like segments.
Parasegments 1 to 5 are transformed into parasegment 6 like metameres.
Pattern of sensory neurons and support cells within the anterior compartments of T1-T3 was transformed homeotically toward that normally observed in the anterior compartment of A1. The dorsal ch3 organs of the posterior compartments of PS5 and PS6 were sometimes replaced by lateral ch3 organs. The new lateral ch3 organs in T2 and T3 and the new dorsal ch3 in T1 always extend their axons within the segment of origin indicating a transformation to a more posterior fate. UbxIa.hs and UbxIVa.hs are equally effective at promoting changes in cuticular features such as denticle belts.
Overexpression of Ubx via a heat shock promoter represses Ubx expression.
Heat induction causes failure of head involution. Prothoracic segment identity is transformed toward mesothoracic, with no parallel defects in the PNS. lch5 organs in abdominal segments 1 and 2 are transformed to triscolopidial and tetrascolopidial. Thoracic segment 2 and 3 dch3 organs are occasionally in an abnormal position and severe defects are seen in thoracic segment 1 es organs.
Ectopic expression of Ubx at early embryonic stages transforms the identity of abdominal segments.
Heat induction greater than ten minutes results in transformation of parasegments 1 through 5 into five additional copies of parasegment 6 with parasegment 6 like denticle belts. Head involution is completely blocked, formation of head specific structures is suppressed. Formation of both the Keilin's organs and ventral pits is suppresses in all three thoracic parasegments. The PNS of thoracic parasegments 3, 4 and 5 is transformed into a parasegment with abdominal characteristics. Very short heat shocks 72 hours after egg laying produce viable adult flies with transformation of antennae into legs, rare transformations of eye into thoracic cuticle causing a rough eye phenotype and few transformations of haltere to wing material.
UbxIa.hs, hthC1 has embryonic head phenotype
UbxIa.hs, hthC1 has embryonic mesothoracic segment phenotype
UbxIa.hs, hthC1 has embryonic metathoracic segment phenotype
UbxIa.hs, hthC1 has embryonic prothoracic segment phenotype
Mann.
Mann and Hogness.
Carried in plasmid "pPhsUBX Ia". Expressed in Drosophila S2 cells.
Heat induced ectopic expression of Ubx represses Dfd expression.
Ectopic expression of Scr and Ubx demonstrates suppression of salivary gland formation is due to repression of the endogenous Scr gene.
Many changes in the embryonic PNS promoted by UbxIVa.hs are promoted more strongly by UbxIa.hs.
The binding sites of the Ubx Ia protein isoform (expressed using UbxIa.hs) and the Ubx IVa protein isoform (expressed using UbxIVa.hs) on polytene chromosomes have been mapped. Most sites are the same for both isoforms. The sites are all euchromatic, include both bands and interbands, and are reproducible from chromosome to chromosome.