Fig. 6. Tudor domains are required for protein localization and for proper architecture of polar granules. (A-D'') Preblastoderm embryos from wild-type (wt), Tud domain mutants tud^A36 and tud^B42, and tud^B45 were co-stained with rabbit anti-Tud (A-D, green channel) and rat anti-Vas antibody (A '-D', red channel). Overlay images are shown in A ''-D ''. (A-A'') Wild type; (B-B'') tud^A36; (C-C'') tud^B42; (D-D'') tud^B45. Anterior is to the left and dorsal is up. (E,F,F',H-K) Electron micrographs of germ plasm. Polar granules are indicated with arrows; m, mitochondria; MVB, multivesicular body, frequently observed at the egg cortex (Mahowald et al., 1981). (E) Germ plasm of the wild-type embryos shows distinct round or barrellike electron-dense polar granules. (F,F') Different ultra-thin sections across the same wild-type polar granule demonstrating hollow sphere morphology. (G,G') A simplified diagram of a polar granule. (H) Polar granules of tud^A36 mutant frequently show a string- or rod-like architecture. Polar granule remnants of tud^B42 (I) and tud^B45 (K) are extremely rare. Scale bars: in E, 500 nm for E,H-K; in F, 500 nm for F,F '.