Previous work identified a gamma tubulin gene, gTub23C, in Drosophila (Zheng et al., 1991). We now report identification of a second gamma tubulin gene, gTub37CD. Immunoblot analysis and immunolocalization show that gTub37CD and gTub23C are differentially expressed during gametogenesis and development. During oogenesis, gTub23C was detected at centrosomes and in the cytoplasm of mitotic germ cells, but was not detected in germ cells following completion of mitosis. Conversely, gTub37CD was not detected in proliferating germ cells, but appeared to accumulate in germ cells during egg chamber development. Neither gamma tubulin isoform was detected at the anterior or posterior poles of developing oocytes. During spermatogenesis, only gTub23C was detected at centrosomes where it showed cell cycle- and differentiation-dependent organization. During the transition into the first meiotic division, gTub23C became organized as a corpuscular focus at centrioles until completion of meiosis II. During post meiotic spermatid differentiation, gTub23C was detected first as a rod and then as a collar like structure near the juncture of the nucleus and the elongating flagellum, but was not detected in bundles of mature sperm. The germline-specific CDC25 encoded by twine is required for organization of gTub23C into corpuscular focus in spermatocytes, but not for separation of centriole pairs in M-phase or post-meiotic organization of gTub23C at centrioles. Following reconstitution of a canonical centrosome at fertilization, only gTub37CD was detected at centrosomes in syncytial embryos, but both gTub37CD and gTub23C were detected at centrosomes in cellularized embryos. Colocalization of these two isoforms suggests that gTub23C and gTub37CD both contain structural features of gamma tubulins essential for localization to centrosomes.
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Figure 1 - Amino acid sequence comparison of two Drosophila g-tubulin isoforms.
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Figure 2 (33k) -
Differential expression of gTub37CD and gTub23C in males and females.
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Figure 3 (39k) - Immunoblot analysis of gTub23C and gTub37CD expression during embryonic and larval development.
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Figure 4 (72k)
- Immunolocalization of gTub23C in ovaries.
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Figure 5 (99k) - Immunolocalization of gTub37CD in ovaries.
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Figure 6 (77k) - Immunolocalization of gTub23C during spermatogenesis.
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Figure 7
(66k) -Immunolocalization of gTub23C during the G2/M transition in twine mutants.
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Figure 8
(83k) - Immunolocalization of gTub23C in twine mutant spermatids.
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Figure 9 (50k)
- Immunolocalization of gTub23C and gTub37CD during embryogenesis.
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