Fig. 1. Cytokinesis fails in the embryonic epithelium of tum mutant embryos. (A) Diagram of the Tum protein showing the location of the two premature stop codon mutations in the tum^DH15 and tum^AR2 alleles, the Pbl- and Pav-interacting regions deleted in the tum^Pav and tum^Pbl deletions, and the amino acids deleted in the tum^EIE and tum^YRL deletions. Numbers indicate the amino acids deleted in the transgenes or altered to stop codons in the mutants. (B-D) Binucleate cells accumulate in the tum^DH15 mutant epithelium. DNA (B, and blue in D) and F-actin (C and green in D). Examples of binucleate cells in a stage 11 mutant embryo are indicated with asterisks in D. (E-G) Expression of UAS-tum rescues the cytokinetic defect of tum^DH15 embryos. DNA (E and blue in G), Tum (F and red in G) and F-actin (green in G). Tum was expressed in mutant embryos using the prdGal4 driver. The bracket below panels F and G indicates the approximate position of the prd stripe. Tum is located in midbody remnants and at the cytokinetic furrow of a telophase cell (F and G, arrow). Binucleate cells are abundant in non-expressing stripes of cells (some marked by asterisks in G). Bar, 5 µm.