DIFFERENTIAL EXPRESSION OF 2 GAMMA-TUBULIN ISOFORMS DURING GAMETOGENESIS AND DEVELOPMENT IN DROSOPHILA

Previous work identified a gamma-tubulin gene, gamma Tub23C, in Drosop hila (Zheng et al., 1991). We now report identification of a second ga mma-tubulin gene, gamma Tub37CD. Immunoblot analysis and immunolocaliz ation show that gamma Tub37CD and gamma Tub23C are differentially expr essed during gametogenesis and development. During oogenesis, gamma Tu b23C was detected at centrosomes and in the cytoplasm of mitotic germ cells, but was not detected in germ cells following completion of mito sis. Conversely, gamma Tub37CD was not detected in proliferating germ cells, but appeared to accumulate in germ cells during egg chamber dev elopment. Neither gamma-tubulin isoform was detected at the anterior o r posterior poles of developing oocytes. During spermatogenesis, only gamma Tub23C was detected at centrosomes, where it showed cell cycle- and differentiation-dependent organization. During the transition into the first meiotic division, gamma Tub23C became organized as a corpus cular focus at centrioles until completion of meiosis II. During postm eiotic spermatid differentiation, gamma Tub23C was detected first as a rod and then as a collar-like structure near the juncture of the nucl eus and the elongating flagellum, but was not detected in bundles of m ature sperm. The germline-specific CDC25 encoded by twine is required for organization of gamma Tub23C into corpuscular focus in spermatocyt es, but not for separation of centriole pairs in M-phase or postmeioti c organization of gamma Tub23C at centrioles. Following reconstitution of a canonical centrosome at fertilization, only gamma Tub37CD was de tected at centrosomes in syncytial embryos, but both gamma Tub37CD and gamma Tub23C were detected at centrosomes in cellularized embryos. Co localization of these two isoforms suggests that gamma Tub23C and gamm a Tub37CD both contain structural features of gamma-tubulins essential for localization to centrosomes. (C) 1997 Academic Press.