Centriole maturation in the amoebae ofPhysarum polycephalum

Summary The precise geometry of pro-centriole formation has been studied inPhysarum polycephalum amoebae. The spatial references used were the posterior and the anterior kinetosomes which are unequivocally defined by the presence of the posterior para-kinetosomal structure, the microtubular array 4 and the microtubular arrays 1, 2, and 3. The observations made suggest that pro-centrioles follow a maturation process. A pro-centriole formed during the n^th cell cycle becomes the posterior kinetosome during the (n + 1)^th cell cycle and the anterior one during all the following cell cycles. Pro-centriole formation occurs late in the cell cycle. This observation disagrees with a role of pro-centriole formation in the regulation of S phase in contrast to what has been suggested in other eucaryotic cells.