MONOCLONAL-ANTIBODIES AGAINST PHLOEM P-PROTEIN FROM PLANT-TISSUE CULTURES .2. TAXONOMIC DISTRIBUTION OF CROSS-REACTIVITY

P-protein, a filamentous protein found in the sieve elements of most a ngiosperms, is believed to function in the sealing of phloem wound sit es. We report here on the use of a highly sensitive immunomicroscopy a ssay to study the ability of P-protein specific monoclonal antibodies RS21, RS22, and RS23, made against the P-protein from Streptanthus tor tuosus (Brassicaceae), to recognize the native P-protein in a number o f different plant genera. RS21, RS22, and RS23 all recognized the P-pr otein in other genera within the Brassicaceae including Arabidopsis an d in the closely related family, Capparaceae. RS21 and RS22 also were able to bind to the P-protein in plants more distantly related to S. t ortuosus. The labeling of P-protein was also observed in the monocots Iris and Narcissus probed with RS21. No label was seen with members of the Poaceae that are reported to lack P-protein. None of the monoclon al antibodies was able to bind to the P-protein in members of the Cucu rbitaceae.