Fig. 1

Tgfβ-f is a TGF-β family member expressed by follicle cells surrounding the developing gonads of B. schlosseri. a Alignment of the TGF-β domain of Botryllus (Bsc) Tgfβ-f with the TGF-β domains of human (Hsa) Bmp2, Nodal, and TGFβ1. Sites where amino acids are conserved in at least 75 % of the sequences are highlighted black, and sites with at least 75 % amino acid similarity are highlighted gray. Conserved cysteine residues are highlighted red. b Schematic of a Botryllus colony. The adult zooid (z) is connected to a developing primary bud (pb) that contains maturing gonads including oocytes (o) and testes (t). Secondary buds (sb) are present anterior to the maturing gonads and the primary bud niche (pn) that contains germ cells. The bodies and buds of a colony are interconnected by an extracorporeal vasculature (v). c–e Confocal images of tgfβ-f expression in fertile adult colonies. Expression of tgfβ-f is present in follicle cells surrounding the maturing oocytes (c), primitive follicle cell-derived support cells around maturing testes (d), and circulating cells in the vasculature (e; dotted lines outline the vasculature). Scale bars indicate 50 µm. Nuclei are shown by DAPI staining (blue)