Abstract
Sperm elongation and nuclear shaping in Drosophila largely depends on the microtubule cytoskeleton that in early spermatids has centrosomal and non-centrosomal origins. We report here an additional γ-tubulin focus localized on the anterior pole of the nucleus in correspondence of the apical end of the perinuclear microtubules that run within the dense complex. The perinuclear microtubules are nucleated by the pericentriolar material, or centriole adjunct, that surrounds the basal body and are retained to play a major role in nuclear shaping. However, we found that both the perinuclear microtubules and the dense complex are present in spermatids lacking centrioles. Therefore, the basal body or the centriole adjunct seem to be dispensable for the organization and assembly of these structures. These observations shed light on a novel localization of γ-tubulin and open a new scenario on the distribution of the microtubules and the organization of the dense complex during early Drosophila spermiogenesis.
Highlights
Microtubules (MTs) play a central role during Drosophila spermiogenesis and are mainly involved in the elongation of the spermatids and the assembly of the motile sperm axoneme
We report here an additional γ-tubulin focus localized on the anterior pole of the nucleus in correspondence of the apical end of the perinuclear microtubules that run within the dense complex
MT Distribution Significantly Changes during Early Drosophila Spermiogenesis
Summary
Microtubules (MTs) play a central role during Drosophila spermiogenesis and are mainly involved in the elongation of the spermatids and the assembly of the motile sperm axoneme. MTs of the sperm axoneme growth from the cilium-like regions are inherited at the end of spermatogenesis [1] and their elongation does not require the intraflagellar transport (IFT) machinery, which uses microtubule motors to transport cargo from the cell body to the ciliary tip and back [2]. The sperm axoneme of the Drosophila spermatids requires a cytoplasmic mode of assembly [3,4]. The assembly and further elongation of the axonemal MTs would require tubulin translocation by diffusion through the ciliary cap. The observation of ribosomes within the apical region of the ciliary cap [6] suggests that protein synthesis in this region could assist in sustaining MT elongation
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