Localization of calmodulin in flagella of zoospores ofPhytophthora cinnamomi

Summary Calmodulin distribution in the tinsel and whiplash flagella of zoospores ofPhytophthora cinnamomi has been studied by immunofluorescence microscopy and immunogold labelling. In whole zoospores labelled with a monoclonal antibody raised against pea calmodulin, followed by a second antibody-FITC, both flagella appear to be weakly stained except for a region at the base of the tinsel flagellum which was stained intensely. A similar staining pattern was also detected in isolated flagella labelled with anti-calmodulin. To identify the calmodulin rich region of the tinsel flagellum, we labelled sections of zoospores embedded in Lowicryl K4M with anti-calmodulin followed by a second antibody gold probe. In the tinsel flagellum, the gold labelling was restricted to a paraxonemal swelling close to the base. Very little gold labelling was detected elsewhere. The swelling extends for 1.5–2.0 n from the base of the tinsel flagellum and is hook shaped in cross section. Immunoblot analysis confirmed that the staining was specific for calmodulin.