Fig. 1. Xnr3 MO-injected embryos have gastrulation and convergent extension defects. (A) Uninjected animal caps and caps injected with Xnr3 morpholino (MO) were dissected at the late blastula stage and photographed at the late neurula stage (stage 20). The MO blocks elongation movements caused by ectopic expression of full-length Xnr3 mRNA in the range 100-300 pg (second panel), but not those caused by Xnr3 ORF (fourth panel). Xnr3 ORF mRNA consists of the open reading frame only, and lacks the binding site. (B) Sibling, control (top row) and Xnr3 MO-injected (bottom row) embryos at late gastrula (stage 12), neurula (stage 17), and tailbud (stage 30). A total of 20 ng of MO was injected into two dorsal marginal cells at the 4-cell stage. (C) MO injection (0-20 ng) caused a range of defects, scored as five classes of phenotype at stage 38. Numbers on right side of embryos indicate five classes. Class 1: normal embryo. Class 2: embryo has slightly shortened axis. Class 3: closed blastopore and neural fold, normal head and a slightly dorsally curved trunk and shortened axis. Class 4: slightly opened neural folds, dorsally curved trunk and shortened axis. Class 5: open neural folds, dorsally curved trunk and shortened axis. (D) The morphology of Keller explants of uninjected, and 20 ng of Xnr3 MO-injected embryos dissected at sibling stage 10.5 and cultured until sibling stage 24. (E) Xnr3 ORF mRNA rescues elongation of MO-injected Keller explants. Left column is uninjected explant, middle is MO-injected, and right column is MO + ORF mRNA-injected explant. 20 ng of Xnr3 MO and/or 200 pg of Xnr3ORF mRNA were injected into the dorsal marginal two cells of the 4-cell-stage embryo and explants were dissected at stage 10.5.

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