Generation of body plan phenotypes in early embryogenesis.

We have presented a number of simple methods that can be used to interfere in the normal establishment and subsequent development of dorsal axial structures in Xenopus. It should be emphasized that, despite the striking similarity in phenotypes which result from these treatments, different developmental processes are being affected at the different windows of sensitivity. For example, UV light, known to damage RNA (for review, see Kalthoff, 1979), also disrupts microtubule polymerization. These activities may be important at different developmental times, relating to the distribution of maternal determinants (in the oocyte) or to the coordinated assembly of cortical microtubules (in the just-fertilized egg). The ventralizing and dorsalizing effects of the various late-acting agents (e.g., TB, suramin, RA, GV sap) undoubtedly stem from their interference with cellular behaviors during the critical morphogenetic period of gastrulation.