Basal body duplication in Paramecium requires gamma-tubulin

First discovered in the fungus Aspergillus nidulans [1], gamma-tubulin is a ubiquitous component of microtubule organizing centres [2], In centrosomes , gamma-tubulin has been immunolocalized at the pericentriolar material, su ggesting a role in cytoplasmic microtubule nucleation [3], as well as withi n the centriole core itself [4], Although its function in the nucleation of the mitotic spindle and of cytoplasmic interphasic microtubules has been d emonstrated in vitro [5,6] and in vivo [7-9], the hypothesis that gamma-tub ulin could intervene in centriole assembly has never been experimentally ad dressed because the mitotic arrest caused by the inactivation of gamma-tubu lin in vivo precludes any further phenotypic analysis of putative centriole defects. The issue can be addressed in the ciliate Paramecium, which is ch aracterized by numerous basal bodies that are similar to centrioles but the biogenesis of which is not tightly coupled to the nuclear division cycle. We demonstrate that the inactivation of the Paramecium gamma-tubulin genes leads to inhibition of basal body duplication.