Surface-related Changes of Fusing Phytophthora Zoospores

Zoospores of Phytophthora spp. were fused and then regenerated using a technique previously described. At various points in the fusion and regeneration processes, components of spore surfaces were immunolabelled with specific monoclonal antibodies. Changes in the antigenic properties of spore surfaces during these events were monitored by fluorescence microscopy. Additional, surface- related processes of the phenomena were monitored by electron microscopy, in the presence of lithium ions and polyethylene glycol, zoospores aggregated into clumps and began to fuse. During this time, zoospores retained their reniform shape and antibodies reacted only with plasma membrane-bound antigenic components that are characteristic of the zoosporic state. Immunolabelling of cell wall occurred only after the fusion solution was replaced with a regeneration solution. As expected, the fusion and the asynchronous regeneration process resulted in the formation of enlarged cells with enlarged or multiple nuclei.