Detection by Protein A-Gold of Antigens toBotrytis cinereain Cytoplasm of InfectedVicia faba

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Abstract
Thin sections of leaves of Vicia faba, uninfected and infected with Botrytis cinerea were treated with two antisera, one prepared against the surface components of B. cinerea and the other prepared against the fimbriae of the smut fungus, Ustilago violacea. Then a suspension containing protein A-gold complexes was applied to the sections. A full range of serological control treatments included use of preimmune serum. Treatment with either antiserum resulted in heavy gold labeling of host cells in infected tissue but not of cells in healthy tissue. In many cases the labeled host cells were not penetrated by the fungus and were some distance from the nearest hypha. Treatment of infected host cells with preimmune serum did not result in gold labeling. Two hypotheses are proposed for these results. First, fimbrial protein, either as intact fibrils or as dissociated subunits, enters host cells well ahead of the hyphae. Second, infection by the fungus may stimulate a response by the host that includes synthesis of host proteins with antigenic regions similar to those of surface proteins of B. cinerea and those of fimbriae of U. violacea.