CENTRIOLE AND CENTROSOME DYNAMICS DURING THE EMBRYONIC-CELL CYCLES THAT FOLLOW THE FORMATION OF THE CELLULAR BLASTODERM IN DROSOPHILA

We have used immunofluorescence and electron microscopy to examine cen trosome dynamics during the first postblastodermic mitoses in the Dros ophila embryo. The centrosomal material, as recognized by antibodies a gainst CP190 and gamma-tubulin, does not show the typical shape change s observed in syncytial embryos, but remains compact throughout mitosi s. Centrioles, however, behave as during the syncytial mitoses, with e ach daughter cell inheriting two separated centrioles at the end of te lophase. During interphase in epithelial cells that have a distinct G1 phase, two isolated centrioles are found, suggesting that the separat ion of sister centrioles is tightly coupled to a mitotic oscillator in both the ''abbreviated'' and the ''complete'' embryonic division cycl es. The centrioles of the Drosophila embryo sharply differed from the sperm basal body, having a cartwheel structure with nine microtubular doublets and a central tubule. This ''immature'' centriolar morphology was shown to persist throughout embryonic development, clearly demons trating that these centrioles are able to replicate despite their appa rently neotenic structure. (C) 1997 Academic Press.