IMMUNOCYTOCHEMICAL LOCALIZATION OF DELTA-ZEIN IN THE PROTEIN BODIES OF MAIZE ENDOSPERM CELLS

The delta-zein, a minor component of the maize prolamin. shows extensi ve immunological cross-reactivity with alpha- and beta-zeins. The adso rption of an anti-delta-zein serum sequentially with cross-reacting an tigens revealed that only about 18% of the reactivity of the antiserum was directed to epitopes unique to delta-zein. The localization of th e various zein classes within the protein bodies of endosperm cells is important to understanding the synthesis, sequestering, and utilizati on of these storage proteins. Sections of 28 days after pollination (D AP) isolated protein bodies and 18 and 40 DAP whole endosperms were re acted sequentially with whole anti-delta-zein serum and gold-conjugate d protein A. The results showed intense gold labeling in the core (ins ide the peripheral zone) and weak labeling in the periphery of the sec tions. This localization was not definitive in view of the above-menti oned cross-reactivities. To obtain an unequivocal localization, the wh ole antiserum was adsorbed with alpha-, beta-, and gamma-zeins and ren dered monospecific for delta-zein. Immunostaining of protein body sect ions with monospecific antiserum showed that gold label was exclusivel y in the core region of the protein body and appeared to be in discret e lines and zones especially in 18 DAP protein bodies. The data from l ocalizations using the monospecific antiserum indicated that delta-zei n occurs throughout the core region of the protein body. probably inte rspersed with alpha- and beta-zeins. The location of delta-zein is con sistent with that predicted from its order of degradation during seed germination.