IMMUNOLOCALIZATION OF CENTRIN IN THE FLAGELLAR APPARATUS OF MALE GAMETES OF ECTOCARPUS-SILICULOSUS (PHAEOPHYCEAE) AND OTHER BROWN ALGAL MOTILE CELLS

Centrin or a centrin homologue was localized using immunofluorescence in the flagellar basal body region in zoids of five brown algal species: Ectocarpus siliculosus (Dillw.) Lyngb., Scytosiphon lomentaria (Lyngb.) Link, Laminaria digitata (Huds.) Lamour., Sphacelaria rigidula (Kutz.) Prud'homme van Reine, and Fucus serratus L. The antigen is restricted to short rods extending along the basal body(ies) and toward the nucleus, which always remains firmly linked to the flagellar apparatus in isolated cytoskeletons. To identify these antigenic sites, pre- and postembedding immunogold electron microscopy was applied to male gametes of E. siliculosus. At least three different structures associated with the basal bodies were antigenic: a fibrous structure connecting the proximal end of the posterior basal body to the nucleus (nucleus-basal body connector), a striated band that links the two basal bodies to each other and is located in the angle formed by them, and amorphous material interconnecting the basal bodies in their most proximal regions. In addition, specific labeling occurs along the external surface and within the lumen of both basal bodies and in the flagellar transitional region. The possible function of these centrin-containing structures is discussed.