Xenbase Image ID: 79952

Fig. 2. Time-window of competence to respond to Siamois. (A) Schematic representation of the GR-Sia expression construct. (B) Embryos were injected ventrally with 50 pg/bl GR-Sia mRNA at the four-cell stage, and DEX (10 mM) was added at stage 6 (32-cell) or stage 9.25, and embryos allowed to develop to tadpoles (left). Note that induction of Siamois activity from stage 9.25 was not sufficient to allow for head formation. Hematoxylin–eosin staining on cross-sections revealed the formation of a full set of duplicated dorsal structures including a notochord in embryos treated with DEX at stage 6 (6/6), while embryos treated at stage 9.25 typically lacked a notochord in the secondary axis (11/12) (right). (C) Bar graph showing a compilation of three independent experiments where the activity of GR-Sia is represented as a function of time of addition of DEX. Duplicated axes were scored complete when they showed a cement gland and at least one eye. Note that head induction did not occur past stage 9 of the blastula, while trunk duplication was still pronounced 2-h later, at the onset of gastrulation (stage 10). n = total number of injected embryos. Image published in: Kodjabachian L and Lemaire P (2001) Copyright © 2001. Image reproduced with permission of the Publisher, Elsevier B. V. Larger Image Printer Friendly View

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