title: Localization and behavior of putative blastopore determinants in the uncleaved Xenopus egg.
abstract: The present study examines putative blastopore determinants in uncleaved Xenopus eggs. Deletion of marginal and lower portions of Xenopus eggs when between 30 and 50% of the first cell cycle has been completed (0.3-0.5 normalized time (NT)) results in the complete absence of the blastopore, while deletion of the vegetal hemisphere during the same period leads to the formation of a smaller blastopore. Extrusion of only yolk and deep cytoplasm of the vegetal hemisphere during 0.3-0.5 NT does not affect the formation or size of the blastopore. Consistently, transplantation of cortical and subcortical cytoplasm from marginal, but not other, sites of eggs at 0.3-0.5 NT to an animal blastomere from 16-cell stage embryos induces an ectopic blastopore and bottle cell-like cells. This does not occur in the same transplantation from eggs at 0.2 NT. These results suggest that the blastopore determinants become localized to the marginal cortical and/or subcortical cytoplasm during 0.2-0.3 NT. Other results suggest the involvement of a hexyleneglycol-sensitive system in the process of localization of the blastopore determinants to the marginal region during 0.2-0.3 NT. The properties and behavior of the putative blastopore determinants are discussed in relation to those of VegT, which previously has been shown to induce ectopic blastopores.
authors.affiliation: Department of Biology, Faculty of Science, Yamagata University, Japan. shinagaw@sci.kj.yamagata-u.ac.jp
authors.forename: A
authors.initials: A
authors.lastname: Shinagawa
authors.forename: S
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000166:cytology*; D004626:Embryology; D005260:Female; D010063:Ovum / Q000166:cytology*; D014982:Xenopus laevis