Fig. 7. orb and spn-E are required for the organisation of the microtubule cytoskeleton at stage 9. (A-D) -tubulin staining. (E-H) Merge of eight consecutive frames of a time-lapse movie of autofluorescent particles. A static particle shows as a dot, whereas a moving particle forms a line. Wild-type oocytes (A,E) show a characteristic anterior to posterior gradient of microtubules and very little cytoplasmic movement. By contrast, spn-E^4E2-14/spn-E^hls157 (B,F) and orb^7E4-5 (C,G) oocytes display thick microtubule bundles and rapid circular cytoplasmic movements. Similar observations were made in spn-E^2A9-14 and spn-E^8D4-11, and in all orb alleles described in panel I. (D,H) Wild-type patterns of microtubule distribution and cytoplasmic streaming are restored in half of orb yps double-mutant oocytes (yps^JM2 orb^mel/yps^JM2 orb^F303). (I) Allelic series of orb alleles. The alleles mentioned in the table were crossed to orb^F343 and classified according to the phenotype of transheterozygous females. The ventralised eggs laid by these females were unfertilised. `early arrest' indicates that egg chambers in these females arrested development during early oogenesis and failed to reach vitellogenic stages. (J) Western blot analysis of Oskar and ORB in orb, orb yps and spn-E ovaries. -Tubulin (TUB) was used as a loading control. Longer exposure (on the right) shows the presence of low levels of ORB in spn-E mutant ovaries. Similar observations were made with spn-E^2A9-14, spn-E^4E2-14 and spn-E^8D4-11 alleles. Exact genotypes are as follows: TM3, yps^JM2 orb^F303/TM3; yps, yps^JM2/yps^JM2 orb^F303; orb, orb^mel/yps^JM2 orb^F303; orb yps, yps^JM2 orb^mel/yps^JM2 orb^F303; spn-E/TM3, spn- E^hls157/TM3; spn-E, spn-E^4E2-14/spn-E^hls157.