CG17009 encodes aust, a paralogue of borr. (A) RT-PCR of aust candidate genes using cDNA from wild-type or aust testes. (B) Representation of CG17009 and its neighboring gene CG4454 (borr). Regions corresponding to the proximal and distal exons of borr show homology with the two CG17009 exons (broken lines). Sequencing from two independent aust alleles identified point mutations in CG17009. (C) Alignment of Aust and Borr protein sequences using ClustalW (Thompson et al., 1994). Arrows denote amino acids. Black asterisks, conserved residues; red asterisks, point mutations present in the aust alleles. (D) Phylogenetic tree of aust and borr for Drosophila species using the XP_309424 gene from Anopheles gambiae as the outgroup. Significance was assessed via bootstrapping with 1,000 replicates. Bootstrap values are shown.