Fig. 7. Genetic interaction with Rho-family GTPases. (A-B') Stage 16 embryos stained with an antibody against Cut (dark brown) or ß-galactosidase (light brown). (A) Rho1^72R/CyOwg-LacZ; cv-c^M62/cv-c^M62 embryo exhibiting the typical cv-c^M62 MpT phenotype. (A') Higher magnification of MpTs shown in A. (B) A much less severe MpT phenotype is seen in Rho1^72R/Rho1^72R; cv-c^M62/cv-c^M62 embryos (n=48), in which normal tubulogenesis often takes place. Arrowheads in B indicate elongated anterior MpTs. (B') Higher magnification of MpTs shown in B. (C-F) Cuticle preparations of late embryos. (C) Rac1^J11,Rac2 mutant embryos show abnormal head involution (black arrowhead), germband retraction and strong dorsal closure phenotypes in 82% of the embryos (n=46). (D) In Rac1^J11,Rac2,cv-c^M62 mutant embryos, head involution (arrowhead), germband retraction and dorsal closure phenotypes are less severe; the dorsal closure phenotype is rescued in 37% of embryos (n=44). (E,F) cv-c^M62 posterior spiracle phenotypes are enhanced in a Rac1^J11,Rac2 background. (E) cv-c^M62 homozygote showing variable penetrance of the posterior spiracle phenotype (arrowheads). (F) Rac1^J11,Rac2,cv-c^M62 showing complete penetrance of the posterior spiracle phenotype (arrowheads). In 71% of Rac1,Rac2,cv-c^M62 embryos, posterior spiracle invagination fails and the spiracles remain on the exterior (compared with 28% in cv-c^M62 embryos).