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 specie s: Ectocarpus siliculosus (Dillw.) Lyngb., Scytosiphon lomentaria (Lyn gb.) Link, Laminaria digitata (Huds.) Lamour., Sphacelaria rigidula (K utz.) Prud'homme van Reine, and Fucus serratus L. The antigen is restr icted to short rods extending along the basal body(ies) and toward the nucleus, which always remains firmly linked to the flagellar apparatu s in isolated cytoskeletons. To identify these antigenic sites, pre- a nd postembedding immunogold electron microscopy was applied to male ga metes of E. siliculosus. At least three different structures associate d 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 amorpho us material interconnecting the basal bodies in their most proximal re gions. In addition, specific labeling occurs along the external surfac e and within the lumen of both basal bodies and in the flagellar trans itional region. The possible function of these centrin-containing stru ctures is discussed.