Fig. 5. Mutations in the Drosophila PKA catalytic subunit DC0 suppress the Pka-R1¹⁸³⁰⁴ maternal-effect bicaudal phenotype. The patterning defects of embryos derived from CyO/+; Pka-R1¹⁸³⁰⁴/Pka-R1^E1 (Pka-R1 single mutant) and DC0^E95/+; Pka-R1¹⁸³⁰⁴/Pka-R1^E1 (Pka-R1¹⁸³⁰⁴ mutant lacking one wild-type copy of DC0) mothers were evaluated by cuticle analysis. In the Pka-R1 single mutant, only 18% of the embryos appear wild type, and 65% of the embryos display a phenotype reflecting ectopic posterior patterning activity (29% head deletion, 36% bicaudal). Removal of one wild-type copy of DC0 completely suppresses this phenotype, and 88% percent of the embryos display a wild-type cuticle pattern. A similar suppression was observed when the DCO^H2 allele was tested.