Fig. 7

Cardiomyocyte/smooth muscle-like core regulatory complex (CoRC) factors in the ACCs. a Larva electroporated with Foxc > H2B::mCherry (Cirobu.REG.KhL57. 96,067-98,197, red), recapitulating expression of Foxc in the cell lineage giving rise to both the oral siphon primordium and the papillae. b In situ hybridization for Mef2, showing broad, possibly maternal expression throughout the embryo at 9 hpf, but also upregulation in the papilla territory (arrow). c In situ hybridization for Myocardin, which is expressed ubiquitously at 9.5 hpf, including in papilla territory (arrow). d–f Two-color in situ hybridization at 7 hpf for dNk4 and eFoxg. Presumptive protuberances of the papillae (which include the ACCs) are marked by Foxg expression at this stage, surrounding a territory of Foxg-negative cells. f Merged image shows Nk4 (green) expressed broadly in both Foxg +(magenta) and Foxg-negative cells within the whole papilla territory. g In situ hybridization for Nk4 at 9 hpf, showing gradual restriction to three presumptive papilla protuberances, two of which are visible at this focal plane (arrows). h Electroporation of Nk4 (Cirobu.REG 4,056,723-4,057,773, green) and Foxc (magenta) reporter plasmids confirms expression of Nk4 throughout papilla territory but not the oral siphon primordium (osp), viewed at 11 hpf and 17 hpf. Oral siphon primordium not visible in 17 hpf image. Nk4 reporter mosaicism resulted in one unlabeled papilla. i Diagram comparing CoRCs for gut smooth muscles, cardiomyocytes, and myoepithelia to Ciona ACCs, suggesting deep homology according to the model proposed by Brunet et al. [8]. Dashed outline around solid color indicate expression data only, no functional data yet obtained. Dashed outline around white indicate no expression or functional data so far. All scale bars = 25 µm