IMMUNOLOCALIZATION OF ARABINOGALACTAN PROTEINS IN AMARANTHUS-HYPOCHONDRIACUS L. OVULES

Amaranthus hypochondriacus ovules are of the crassinucellate type, hav ing several layers of nucellus cells between the micropyle and the emb ryo sac through which pollen tubes have to penetrate. The ultrastructu ral features of the micropylar nucellus cells appear to reflect cells with high metabolic activity. With the monoclonal antibodies MAC207 an d JIM8 (against arabinogalactan proteins) we have shown that the prese nce of the two epitopes was different in the gametophytic tissues and embryo sac. The young embryo and suspensor cells are reactive only to Mab JIM8. The selective presence and localization of these two epitope s was also demonstrated in the micropylar nucellus cells. The expressi on of these arabinogalactan proteins in this ovule seems to be closely aligned with the pathway of the pollen tube, possibly providing direc tional guides for tube growth inside the ovule.