THRUST REVERSAL BY TUBULAR MASTIGONEMES - IMMUNOLOGICAL EVIDENCE FOR A ROLE OF MASTIGONEMES IN FORWARD MOTION OF ZOOSPORES OF PHYTOPHTHORA-CINNAMOMI

The role of tubular mastigonemes in the reversal of thrust of the ante rior flagellum of Phytophthora cinnamomi was analysed using mastigonem e-specific monoclonal antibodies and immunofluorescence and video micr oscopy. Exposure of live zoospores of P. cinnamomi to the mastigoneme- specific Zg antibodies caused alterations in the arrangement of mastig onemes on the flagellar surface and at Zg concentrations above 0.3 mu g/ml, mastigonemes became detached from the flagellum. As a consequenc e of antibody binding to the mastigonemes there were concentration-dep endent perturbations in zoospore swimming behaviour and anterior flage llum beat pattern. With increasing antibody concentration zoospores sw am more slowly and other parameters of their swimming pattern, such as the wavelength of the swimming helix and the frequency of rotation, w ere also reduced. The effects of Zg antibodies were specific at two le vels: control immunoglobulins or antibodies that bound to other flagel lar surface components did not have an effect on motility, and Zg anti bodies did not interfere with the motility of zoospores of oomycete sp ecies to which they did not bind. The effects of antibody-induced disr uption of mastigoneme arrangement strongly support previous hypotheses that tubular mastigonemes are responsible for thrust reversal by the anterior flagellum, enabling it to pull the cell through the surroundi ng medium.