Immunolocalization of arabinogalactan proteins inAmaranthus hypochondriacus L. ovules

Abstract

Amaranthus hypochondriacus ovules are of the crassinucellate type, having several layers of nucellus cells between the micropyle and the embryo sac through which pollen tubes have to penetrate. The ultrastructural features of the micropylar nucellus cells appear to reflect cells with high metabolic activity. With the monoclonal antibodies MAC207 and JIM8 (against arabinogalactan proteins) we have shown that the presence 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 epitopes was also demonstrated in the micropylar nucellus cells. The expression of these arabinogalactan proteins in this ovule seems to be closely aligned with the pathway of the pollen tube, possibly providing directional guides for tube growth inside the ovule.