Fig. 1. Map of the Poxn gene and its enhancers with associated functions identified by Poxn rescue constructs and Poxn-Gal4 reporter genes. (A) Map of chromosomal region at 52D1, including the Poxn gene. Transcribed regions of Poxn (red bar), and annotated genes CG8249 and CG8253 (gray bars) are shown with arrows indicating their directions of transcription below a scale that indicates distances in kb from the `upstream' transcriptional start site of Poxn. The insertion P{Lac-W}M22 and the Poxn deficiency Df(2R)Poxn<sup>M22-B5</sup> (open bar) are mapped. The deficiency deletes about 17 kb and extends from 131 bp upstream of the Poxn start codon in exon 2 to 730 bp proximal of the duplicated insertion site of the excised P element. In addition, the location of a genomic fragment is indicated that was used as transgene Resdistal (blue bar) to rescue the annotated genes affected by the Poxn deficiency. (B) Map of the Poxn gene, Poxn rescue constructs and Poxn-Gal4 constructs driving the GFP reporter gene. Below a restriction map (only selected restriction sites are indicated; numbers in parentheses refer to distances in base pairs from the `upstream' transcriptional start site marked 0) of the region including the Poxn gene, the composition of Poxn rescue constructs and of Poxn-Gal4 driver constructs, as listed on the right, is illustrated with respect to the Poxn upstream region (green), 5' leader and 3' trailer (orange), coding region (black), introns (yellow) and downstream region (light blue). In Poxn-Gal4 constructs, the position of the Gal4-coding region is shown as open box. (C) Map of Poxn enhancers and their functions. Double-headed arrows indicate location of Poxn enhancers, which regulate Poxn expression in specific spatiotemporal patterns and the associated functions listed on the right. Enhancers regulating expression during embryonic and larval stages not mapped in this study (W. B. and M. N., unpublished), some of which overlap with, or even contribute to, adult functions, are also shown. In few cases, enhancers delimited by arrows have only been tested to be essential, not necessarily also sufficient, for the control of a specific Poxn function (see text).