Biochemical differentiation in the tobacco flower probed with monoclonal antibodies

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Abstract
We have isolated a series of monoclonal antibodies that react to antigens in flowers of Nicotiana tabacum L. (tobacco) displaying specificity or preferentiality in their cell and tissue distributions. We immunized mice with extracts from tobacco flowers and then screened the hybridomas by enzyme-linked immunosorbent assay (ELISA) against extracts from leaves, sepals, petals, stamens and pistils; twenty five were chosen from the total screened. The antigens detected by about half of the antibodies were periodate-sensitive, implying that the epitopes were carbohydrate. Competition ELISA assays were used to determine if any antibodies were reacting to the same epitopes. Western blot analysis showed that while some antibodies reacted to specific bands, the bulk either failed to react or reacted to multiple bands, consistent with a glyco-conjugate nature for many of the antigens. Analysis of the spatial pattern of antigen distribution within tobacco flowers by immunolocalization showed that some antibodies recognized epitopes that were limited to very specific cells and tissues. We used the immunolocalization technique to analyze a mutant with stigmoid anthers: an antibody recognizing a pistil transmitting-tract antigen also reacted to cells in stigmoid anthers. Our results with this antibody set imply that biochemical differentiation within the tobacco flower includes cell-and tissue-specific glyco-moeities, and also that similarities, at the biochemical level, exist between a normal floral organ and the abnormal organ in a phenotype with a developmental switch.