Fig. 6. Both nrv2.1 and nrv2.2, but not nrv1 and nrv3, are required for and possess tube-size control activity. (A) Organization of the nrv2 locus. Exons common to both nrv2 isoforms are shown as red boxes, while exons specific for the nrv2.1 and nrv2.2 isoforms are shown in blue and green, respectively. (B-G) Tracheal tube diameter and length defects are caused by the injection of dsRNA corresponding to coracle (C), nrv2 common exons (D), nrv2.1 and nrv2.2 specific exons (E,F) into otherwise wild-type animals with tracheal GFP expression. Injection of these dsRNAs also causes septate junction barrier defects (data not shown). Injection of buffer (B) or nrv3 dsRNA (G) did not cause tracheal tube-size defects. (H,I) Expression of nrv2.1 in nrv2 homozygotes using the e22C-Gal4 driver rescued all tracheal morphology defects (H), but expression of nrv1 (I) or nrv3 (J) did not detectably rescue the nrv2 defects. Rescue by nrv2.2 is shown in Fig. 1H. Genotypes: (B-G) btl-Gal4 UAS-GFP; (H) nrv2^k13315e22C-Gal4/nrv2^k04223 UAS-nrv2.1; (I) nrv2^k13315e22C-Gal4/nrv2^k04223UAS-nrv1; (J) nrv2^k13315e22C-Gal4/nrv2^23BUAS-nrv3. Scale bar: 5 µm.