Fig. 2. Malpighian tubules do not express epithelial Na⁺ channels (ENaCs). (A) Phylogenetic tree of all Drosophila ENaCs identified by BLASTP search using human amiloride-sensitive cation channel 2, neuronal hBNaC2 (GenBank accession number NP 064423) protein sequence as a probe. (B) RT-PCR for putative EnaCs (left-hand panels) and corresponding Southern blots with probes specific to each gene (right-hand panels). Labels refer to known genes or to Gadfly-predicted genes. Size markers denote expected sizes from genomic (black arrows) and cDNA (white arrows) templates. The ladder is a Gibco BRL 1 kb ladder. The templates are as follows: Genomic, genomic DNA; Whole fly, whole-fly cDNA; Head, head cDNA; Tubule, Malpighian tubule cDNA; No template, no template (negative control).