Fig. 1

Ciona robusta cardiopharyngeal gene regulatory network and tunicate phylogeny. a–c Regulatory network diagrams for cardiopharyngeal founder lineage cells during three embryonic stages. Schematics on the left indicate stage and cell lineage. Background colors delineate discrete regulatory modules. Solid lines indicate regulatory connections supported by functional enhancer analysis, while dashed lines indicate regulatory connections supported by expression data. Circles represent signal dependent activation and double slanted lines represent signal transduction. a Initial specification of the cardiopharyngeal founder cells (pink) through exclusive up-regulation of Mesp and subsequent expression of Ets1/2. b Signal-dependent regulation of early trunk ventral cell genes by Ets1/2 and an unknown ATTA-binding co-factor. Ets1/2 activation in the TVCs is dependent on FGF9/16/20 signaling transduced by the MapK pathway. c Presumptive modules differentially regulated by FoxF, Hand-like, or GATAa. FoxF is portrayed as the primary regulator of TVC migration, while GATAa regulates a highly conserved heart “kernel” in conjunction with BMP2/4 signaling. F1, H1, H2, and K1 represent hypothetical target genes. Figure is based on Woznica et al. and Cota et al. [41, 42]. d Simplified tunicate phylogeny based on DeBiasse et al. (in prep), that is congruent with Delsuc et al. [43]. Background colors represent sub-clades, Phlebobranchia (yellow), Stolidobranchia (red), or Appendicularia (blue)