Transcriptional regulation of breathless FGF receptor gene by binding of TRACHEALESS/dARNT heterodimers to three central midline elements in Drosophila developing trachea

The development of Drosophila trachea is under the control of spatially and/or quantitatively regulated activity of BREATHLESS FGF receptor, which is also essential for midline glial migration. Here, we identified the minimum enhancer region of breathless, cloned the Drosophila ARNT gene (dARNT), and showed biochemical and genetic evidence that breathless expression in developing trachea is regulated by direct interactions between TRACHEA-LESS/dARNT heterodimers and three central midline elements (TACGTGs) situated in the minimum enhancer region. Our results also showed that SINGLEMINDED/dARNT heterodimers, which are essential for breathless expression in midline precursor cells, share DIVA targets in common with TRACHEA-LESS/dARNT, indicating that two different basic helix-loop-helix-PAS protein complexes act through the same target sites in vivo.