Immunocytochemical Reactions to Intact Protein Bodies in Rice (Oryza sativaL.): Using Antibodies to Purified Fractions of Some Rice Polypeptides

Rice flour and commercial rice protein concentrate (enzymatically destarched rice flour) from mature rice grains (Oryza sativaL., cv. Lemont) were embedded and sectioned for use in electron-microscopical immunocytochemistry. Polyclonal antibodies were raised in rabbits against the following purified rice protein fractions: 10 and 13 kDa prolamins, 23–25 and 38 kDa glutelins, ‘total prolamins’, ‘total glutelins’, and two insoluble particulate waste products derived from protein concentrate. Western blot procedures showed that the antibodies produced were specific for their particular fractions, and that antibodies to particulate waste fractions reacted with bands at positions of approximately 12 and 28 kDa, normally not evident as strong bands in SDS-PAGE gel preparations of rice. Immunogold procedures, using Protein A and electron microscopy, significantly labelled both types of rice protein body (PB-I and PB-II) in the embedded substrates for each antibody. This varies from other reported research when rice proteins have been fractionated on gels, or when antibodies to total glutelins or total prolamins have been tested on developing rice grains. Estimates of labelling efficiencies show that each protein body type contains a substantial number of antigenic determinants for all the species of polypeptide studied.