CONSERVED SPATZLE TOLL SIGNALING IN DORSOVENTRAL PATTERNING OF XENOPUS EMBRYOS/

The Spatzle/Toll signaling pathway controls ventral axis formation in Drosophila by generating a gradient of nuclear Dorsal protein. Dorsal controls the downstream regulators dpp and sog, whose patterning funct ions are conserved between insects and vertebrates. Although there is no experimental evidence that the upstream events are conserved as wel l, we set out to ask if a vertebrate embryo can respond to maternal co mponents of the fly Dorsal pathway. Here we demonstrate a dorsalizing activity for the heterologous Easter, Spatzle and Toll proteins in UV- ventralized Xenopus embryos, which is inhibited by a co-injected domin ant Cactus variant. We conclude that the Dorsal signaling pathway is a component of the conserved dorsoventral (d/v) patterning system in bi lateria. (C) 1998 Elsevier Science Ireland Ltd.