Centrin in the groove: immunolocalisation of centrin and microtubules in the putatively primitive protistChilomastix cuspidata (Retortamonadida)

Abstract

Immunochemical techniques were used to identify and localise centrin and α-tubulin inChilomastix cuspidata, an amitochondriate “excavate flagellate”. Immunoblotting showed that the molecular mass of centrin is 20 kDa and α-tubulin is 55 kDa. Immunofluorescence microscopy localises centrin to the basal-body region of the flagellar apparatus and in a centrin-containing root which runs along the groove towards the posterior of the cell. Confocal microscopy of cells double-labelled with anticentrin and antitubulin antibodies suggests that centrin is also associated with a group of microtubules called the hook band. Centrin labelling extends for two thirds of the length of the hook band, ending in a pill-like structure. In all we distinguish five major components of the centrin root. The distribution of these proteins is discussed in terms of the functions centrin and tubulin may play in this putatively primitive protist and its relatives.