Polytene chromosomes normal.
When mitotic clones induced in the labial disc are double mutant for both pb5 and hhAC, the labial-to-leg transformation is modified. Overall tissue size is reduced compared to pb5 single mutants and distinct leg tarsi can no longer be seen, although remaining tissue still has prothoracic leg identity, as evidenced by the presence of sex comb teeth. When mitotic clones induced in the labial disc are double mutant for pb5 and hhts2 and larvae are raised at the restrictive temperature for the hhts2 mutation throughout the L3 stage, no labial-to-leg transformation occurs. Expression of ciScer\UAS.cAa under the control of Scer\GAL4pb.PJ in pb5/+ heterozygotes enhances the reduced pseudotracheal row phenotype of ciScer\UAS.cAa single mutants.
pb1 Scr5/pb5 Scr4 flies show transformation of the proboscis into the antenna. The transformation varies from thick and shortened aristae with claws and pulvillae to apparently complete antennae with aristae, third and second antennal segments bearing characteristic bristles.
The addition of a combination of skdpap-1 and MED17s2956 enhances the transformation phenotype seen in the labium of pb4/pb5 flies. Instead of transformation to antennal structures, a transformation to T1 leg structures (including sex comb teeth and claws) is seen. The addition of skdpap-1 enhances the transformation phenotype seen in the labium of pb4/pb5 flies. Instead of transformation to antennal structures, a transformation to T1 leg structures (including claws) is seen.
Mutant leg transformation is incompletely rescued by pbhs.PB, often resulting in a weak transformation of labium to antenna rather than to prothoracic leg. Alternatively, partially rescued flies may show small patches of labial tissue transformed to distal leg tissue.