Ventral cell rearrangements contribute to anterior-posterior axis lengthening between neurula and tailbud stages in Xenopus laevis

Studies of morphogenesis in early Xenopus embryos have focused primarily on gastrulation and neurulation. Immediately following these stages is anothe r period of intense morphogenetic activity, the neurula-to-tailbud transiti on. During this period the embryo is transformed from the spherical shape o f the early stages into the long, thin shape of the tailbud stages. While g astrulation and neurulation depend largely on active cell rearrangement and cell shape changes in dorsal tissues, we find that the neurula-to-tailbud transition depends in part on activities of ventral cells. Ventral explants of neurulae lengthen automously as much as the ventral sides of intact emb ryos, while dorsal explants lengthen less than the dorsal sides of intact e mbryos. Analyses of cell division, cell shapes, and cell rearrangement by t ransplantation of labeled cells and by time lapse recordings in live intact embryos concur that cell rearrangements in ventral mesoderm and ectoderm c ontribute to the autonomous anterior-posterior axis lengthening of ventral explants between neurula and tailbud stages. (C) 1999 Academic Press.