Fig. 1. MAPK activation in swimming larvae of Ciona intestinalis. (A) Comparative western blot analysis of Ciona-tissue homogenates with antibodies against dual-phosphorylated ERK, JNK and p38, and non-phosphorylated ERK, JNK and p38. Top: Coomassie Blue-stained gel showing the total protein. Bottom: western blotting was performed at various stages of the swimming larval phase and during metamorphosis. ERK- and JNK-proteins were expressed and activated during the acquisition of metamorphosis competence. (B) The CNS and papillae in swimming larvae of C. intestinalis. OC, ocellus; OT, otolith. (C) Ci-JNK activation was localized in the CNS. Ci-JNK phosphorylation (green) was detected in the sensory vesicles, the neck region, the visceral ganglion and along the nerve cord. (D) Ci-ERK activation was localized in the papillae of C. intestinalis larvae. Ci-ERK phosphorylation (green) was detected in the three posterior palps of the papillae of the tadpole. Scale bars: 120 µm.