Fig. 5. Septate junctions control tracheal tube size through multiple pathways. Null mutations in the known septate junction genes coracle and neurexin cause the identical tracheal tube size phenotypes as null nrv2 mutations (C-E). Double null mutant combinations of nrv2 and coracle have the same phenotype as either single mutant (compare F with D and E), suggesting nrv2 and coracle act in the same pathway. Similarly, double null mutant combinations of nrv2 and gli are not more severe than the nrv2-null mutants (compare H with D). By contrast, varicose, convoluted and cystic mutations exacerbate the tracheal phenotypes of null nrv2 mutations (compare J with D,F,H,I; L with D,F,H,K; N with D,F,H,M), suggesting that varicose, convoluted and cystic do not function only in a single linear pathway with nrv2. Dotted lines indicate tracheal lumens. Genotypes: (A) Oregon R; (B) nrg¹⁷; (C) nrx⁴⁸⁶⁵; (D) nrv2^23B; (E) cor⁵; (F) nrv2^nwu3cor⁵; (G) gli^AE2-45; (H) nrv2^nwu3gli^J29-7b; (I) conv^k6507b; (J) nrv2^nwu3conv^k6507b; (K) vari^3953b; (L) nrv2^k04223vari^3953b; (M) cys^k13717b; (N) nrv2^nwu3cys^k13717b. Scale bar: 5 µm.

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