A genomic fragment containing the ppk25 gene, including 5kb from upstream of the ppk25 start codon and approximately 2kb of non-coding downstream sequence. The GAL4 open reading frame has been inserted immediately after the ppk25 start codon. A mutation has been introduced in the start codon of the ppk25 reading frame, to prevent expression of the ppk25 protein, but to allow any potential regulatory sequences that may be present in the intron to be included in the construct.
Scer\GAL4ppk25.PS transcript is detected by RLM-RACE in male prothoracic legs, but not in adult heads from which the antennae had been removed. Scer\GAL4ppk25.PS drives expression in a small subset of gustatory and olfactory receptor neurons, some of which have been implicated in male courtship behavior, and which coexpress fru. Expression is observed in a subset of neurons innervating the taste hairs of both male and female legs and wings, but in no other body parts. Scer\GAL4ppk25.PS is limited to one gustatory neuron per leg taste bristle. Expression is also observed in olfactory neurons that project from antennal segment three to antennal lobes VA1v or VL2a. Expression does not overlap with that of CheB42a protein.
Scer\GAL4ppk25.PS drives expression in one of four gustatory receptor neurons of many of the taste bristles in the male legs; expression is consistantly observed in 43 gustatory receptor neurons on the tibia and five tarsal segments. All of the prothoracic gustatory receptor neurons labelled by Scer\GAL4ppk25.PS co-express Ecol\lexAfru.P1. For the pairs of prothoracic neurons labelled by Ecol\lexAfru.P1, expression of Scer\GAL4ppk25.PS can be detected in both, or only one of the neurons. Expression of Scer\GAL4ppk25.PS and Scer\GAL4ppk25.PS is very similar: all but 11 Scer\GAL4ppk29.3.020 positive neurons, are also labelled by Scer\GAL4ppk29.3.020. In most cases, these 11 Scer\GAL4ppk29.3.020-expressing neurons are paired within a single taste hair with a neuron that expresses both Scer\GAL4ppk25.PS and Scer\GAL4ppk29.3.020. Gustatory receptor neurons in the wing margin, but not in the labellum, also express Scer\GAL4ppk25.PS. The leg and wing neurons project to each of the thoracic ganglia. The prothoracic neurons that are labelled by Scer\GAL4ppk25.PS send sexually dimorphic projections to the first thoracic ganglion: projections from males cross the midline more often than female ones.