The Drosophila centriole: conversion of doublets to triplets within the stem cell niche

Abstract

We report here that two distinct centriole lineages exist in Drosophila: somatic centrioles usually composed by microtubule doublets and germ line centrioles characterized by triplets. Remarkably, the transition from doublets to triplets in the testis occurs within the stem cell niche with the formation of the C-tubule. We demonstrated that the old mother centriole that stays in the apical cytoplasm of the male germline stem cells (GSCs) is invariably composed by triplets, whereas its daughter is always built by mixed doublets and triplets. This difference represents the first documentation of a structural asymmetry between mother and daughter centrioles in Drosophila GSCs and may reflect a correlation between the architecture of parent centrioles and their ability to recruit centrosomal proteins. We also found that the old mother centriole is linked to the cell membrane by distinct projections that may play an important role in keeping its apical position during centrosome separation.

Coupling Form and Function: How the Oligomerisation Symmetry of the SAS-6 Protein Contributes to the Architecture of Centriole Organelles

“…Alternatively, different SAS-6 and Bld10/Cep135 isoforms could be accommodated in centrioles without varying symmetry by changing the size of microtubule blades at the outer organelle wall in a compensatory manner. We note, for example, that D. melanogaster germ line centrioles possess a triplet of microtubules in each organelle blade, while centrioles in somatic cells have microtubule doublets [43].…”

Centrioles without microtubules - a new morphological type of centriole

“…However, it was shown that MT doublets were present in Drosophila centriolar cylinders in somatic cells, and MT triplets were present in generative cells (Tates, 1971; Gottardo et al, 2015). …”

“…Another observation concerning the structural diversity of centrioles was that somatic cell centrioles in Drosophila consist of doublets and germ cell line centrioles consist of MT triplets (Gottardo et al, 2015). In the cell cycle of vertebrates there is also a stage when young procentrioles consist of MT doublets, but this stage is very short and occurs near the beginning of procentriole formation (Guichard et al, 2010).…”

Cell polarity: having and making sense of direction—on the evolutionary significance of the primary cilium/centrosome organ in Metazoa

“…The genetic analysis of early development in these two models, which may not be representative of the most common development of Ecdysozoa, has yet been of invaluable importance for identifying the conserved core complex of gene products necessary for centriole duplication [203], as well as key regulatory activities controlling the centrosome maturation and activity at G2–M–G1 transition [207,209,213]. Yet, somatic centrioles—the situation is apparently different for basal bodies from the sperm cells in flies [243]—are not canonical in these two species, and look as simplified versions of the highly conserved centriolar structure, lacking the distal part where appendages are anchored on the mother centriole. As a matter of fact, they lack from one-third in the fly to half in the worm of gene products that are conserved in both unicellular organisms and mammalians [223].…”