Figure 1. Putative structure of Tc1–2_Xt transposable element and expression during development. (A) The sequence analysis of the 116 copies of the Tc1–2_Xt transposable element in the X. tropicalis genome showed the typical structure of Tc1-like elements. The length of this element is 1,581 bases. It is flanked by two inverted repeats (IR) containing two direct repeats (white triangles) for the binding of the transposase. The transposase ORF (green) contains a putative DNA binding domain (blue) and the catalytic triad (red, aspartic-aspartic-glutamic residues (DDE)). Five copies in the genome could code for an intact transposase. (B) Schematic representation of the expression of Tc1–2_Xt during X. tropicalis early development. The expression of Tc1–2_Xt is shown in blue for early stages of X. tropicalis development. No expression is detected before the beggining of the zygotic transcription (st.6 is shown as an example, lateral view). Expression is clearly detected from gastrula stage (st.10) in the Spemann’s organizer and then in anterior and neural tissues. Views are indicated in brackets. CNS, central nervous system. Figures were downloaded from http://www.xenbase.org/anatomy/static/NF/NF-all.jsp and modified according to the expression pattern obtained by in situ hybridization.