Little is known about the mechanism of fusion of plant gametes during reproduction. Studies on reproduction in animals suggest that fusion of sperm and egg includes protein recognition. We raised monoclonal antibodies against purified Brassica rapa sperm cells to visualize membrane proteins. Three antibodies (BRSP1, 2, 3) bound to B. rapa protoplasts isolated from stem, root, and leaf tissues indicating that the epitopes to these monoclonals were not specific to sperm cells. The molecular weight of the epitope to BRSP1 was 54 kDa, and it was not glycosylated. Antibodies also recognized gametes of other angiosperm species (Arabidopsis, Eruca, Lilium, Plumbago, Nicotiana) and a fern (Ceratopteris), and gametes of a green alga (Acetabularia). However, the molecular weight of these epitopes varied. None of the antibodies to B. rapa sperm prevented fertilization in assays with Ceratopteris richardii or with Acetabularia acetabulum indicating that these particular protein epitopes may not be associated with gamete fusion. Funded by NSF-RUI grant IBN-9816945.

Key words: antibodies, Brassica, fertilization, gametes, sperm