Posterior-ventralizing factor in Xenopus mesoderm induction. Induces posteroventral mesoderm and counteracts dorsalizing signals such as activin. Homodimer; disulfide-linked (By similarity). Forms heterodimers with the TGF-beta family member derriere. Part of a complex consisting of twsg1 and chrd. Interacts with tsku (PubMed:16319115). Expressed both maternally and zygotically. Expressed at a low level maternally with expression levels increasing rapidly after stage 9. Expression is maintained throughout development and in a range of adult tissues including the ovary and testis. Belongs to the TGF-beta family.