Fig. 4.
The gene tbr is regulated by other endomesodermal transcription factors in the starfish A. miniata, but not in the sea urchin S. purpuratus. (A) Comparison of the effects on tbr transcript abundance caused by perturbations of otx or gatae expression in sea urchins and starfish. Transcript levels consequent on perturbations are represented as in Fig. 2. Light gray and solid bars represent ΔCT (left ordinate) or fold change (right ordinate) in tbr expression after the indicated perturbation in sea urchins and starfish, respectively. The significance of the difference in ΔCT between sea urchin and starfish was determined by using a t test, and the resultant P values are provided. Error bars, ±SE. Sea urchin data can be accessed at http://sugp.caltech.edu/endomes. (B and C) Expression of tbr is required for endomesodermal specification in starfish. A. miniata (48 h) zygotes were injected with either 1 mM of a random sequence (control) MASO (B) or 600 μM αTbr MASO (C). The archenteron forms correctly in B but fails to develop when levels of Tbr are diminished in C.