Fig. 4. Genes controlled by the MAPK pathways. (A) mRNA expression of ERK target genes at 25 hpf. mRNA was extracted from untreated embryos or embryos treated with 6 µM U0126, reverse transcribed and semi-quantitative specific PCR was performed (see Materials and methods). (B) mRNA expression of JNK target genes at 25 hpf. mRNA was extracted from untreated embryos or embryos treated with 10 µM SP600125, reverse transcribed and semi-quantitative specific PCR was performed (see Materials and methods). (C) Whole-mount in situ hybridization of genes controlled by ERK and JNK displaying, respectively, specific expression in papillae and in the nervous system (arrows) of Ciona intestinalis larvae. Ci-Vwa1 and Ci-GNRH were detected in sensory vesicle (arrows); Ci-endogl was observed in visceral ganglion and Ci-oatp in the neck region (arrows).