Transcriptional activator. Plays a role in ventral mesoderm specification and acts together with nog during muscle differentiation. Mediates posterior pattern formation of the embryo, including specification of posterior mesoderm, via activation of the Wnt and Fgf signaling pathways. Interacts with ripply2.2/bowline. Associates with tle4 in the presence of ripply2.2/bowline. At gastrulation, expressed in the lateral and ventral mesoderm. Expressed around the blastopore except at the dorsal midline. As gastrulation proceeds, expression extends anteriorly and ventrally. At the tailbud stage, expression then retracts caudally becoming restricted to the tip of the tailbud. Expression begins in early gastrula embryos, reaches a peak in late gastrula to early neurula embryos (stages 13-16) and then declines until stage 30. By activin and vegt signaling, both acting via nodal. By bmp signaling in a dose-dependent manner. Fgf is necessary but not sufficient for induction.