Fig. 5. Pa-Dl posterior tip expression during germ band elongation requires Pa-Wnt1 and Pa-cad.

(A,B) Post-blastoderm Pa-Dl segmental expression (*) in wild type (A) is unaffected in Wnt1^RNAi (B), despite the GZ being reduced (GZ outlines in A,B insets). (C) Wild type expression of Pa-Dl during germ band elongation. (D) Loss of Pa-Dl at the posterior tip (arrow) and absence of stripes in the anterior GZ (bracket), but not in neuroblasts (arrowheads) in Pa-Wnt1^RNAi embryo. (E,F) Pa-cad expression (brackets) is similar in post-blastoderm wild type (E) and N^RNAi embryos (F). Wild type expression of Pa-Dl (G) is expanded in Pa-cad^RNAi embryos (H) covering the posterior region and does not form stripes (bracket); neural expressions remain unaffected (arrowheads). (I–K) Inhibition of Wnt-signalling in culture affects Pa-Dl expression. (I) Pa-Dl in the posterior tip (arrow) and in segmental stripes (A4) in a 0-hour control embryo. (J) After 16 hours in DMSO control culture Pa-Dl is expressed in the posterior tip (arrow) and two additional stripes have been added in the anterior GZ (arrowheads). (K) Embryos cultured for 16 hours in the IWP-3 Wnt-inhibitor show greatly reduced Pa-Dl expression in the posterior tip (arrow) and only one new stripe (arrowhead) has formed. T1: first thoracic segment; A4: fourth abdominal segment.