SYNTHESIS AND ASSEMBLY OF FLAGELLAR SURFACE-ANTIGENS DURING ZOOSPOROGENESIS IN PHYTOPHTHORA-CINNAMOMI

Cryomicrotomy and immunofluorescence microscopy employing three differ ent categories of monoclonal antibody (MAb) that label antigens on the surface of one or both flagella of Phytophthora cinnamomi have been u sed to follow the synthesis and assembly of flagellar surface componen ts. MAb Zf1 binds to the surface of both the anterior tinsel and poste rior whiplash flagella, as well as to a nuclear component. The labelin g of the flagella is punctate in nature, is brighter at the flagellar base, and does not always extend to the distal tip of the flagella. MA bs in the Zt group recognise an antigen that is located along the side s of the tinsel flagellum and may be associated with the base of the m astigonemes. Immunodot-blot analysis has shown that binding of Zt MAbs is abolished by pretreatment with either pronase or periodate oxidati on indicating that the antigen is a glycoprotein. MAbs in the Zg group bind to the mastigonemes on the tinsel flagellum and to packets of ma stigonemes in the cytoplasm of zoospores. Zt and Zg antigens increase in abundance during zoosporogenesis and are present throughout the lif e cycle of the fungus, whereas the non-nuclear localisation of the Zf antigen appears only during sporulation. Prior to association with the flagellar surface, all three components become clustered in the groov e region of zoospores. They do not become associated with the flagella r surface until at least 15 min after the flagellar axoneme has formed .