Figure 2.

Distal components of the dorso-ventral, Toll, and Imd signaling pathways. (A) The distal part of the embryonic dorso-ventral patterning pathway, showing the end of the proteolytic cascade that leads to the cleavage of Spaetzle and intracellular signaling. (B) Established elements of the distal part of the Toll pathway, where a serpin, nec, regulated a proteolytic cascade leading to the cleavage of Spaetzle. This pathway reuses many of the components seen in embryonic dorso-ventral patterning, and it is induced by infection with Gram-positive bacteria and fungi. (C) Established elements of the Imd pathway, which is induced by Gram-negative bacteria. At present, none of components in the extracellular cascades are known for this pathway.