Fig. 7.

A model for the potential CEH-14/CEH-63/MBR-1 transcription factor network in DVC. Regulatory interactions occur successively, as represented from early to mid to late time points, as the embryo is elongating. First CEH-14 activates mbr-1. Subsequently ceh-63 is activated by CEH-14 (not necessarily directly) and another unknown pathway (denoted by ?), either being partially sufficient. Finally CEH-14 and CEH-63 activate mbr-1 co-operatively. In the ceh-63 mutant, CEH-63 is not produced and so the activation of mbr-1 is not sustained. In the ceh-14 mutant, there is no initial activation or sustained activation of mbr-1, but CEH-63 can be activated weakly/unreliably by the alternative pathway. Upon ceh-14 RNAi, the early expression of CEH-14 and the initial activation of mbr-1 fail. Although the later expression of CEH-14 remains and is sufficient to activate CEH-63, this is not sufficient to initiate mbr-1 expression.