Ultrastructural characteristics of intergeneric protoplast fusion

Abstract

Protoplasts from mesophyll cells of pea plants and from cultured cells of Vicia were agglutinated with polyethylene glycol (PEG) and subsequently fused upon elution of PEG to form heterokaryons. Ultrastructural studies have shown that during agglutination, localized areas of tight adhesion occurred between plasmalemmae; the membranes remained separated by a narrow gap. The plasmalemmae of adhering protoplasts were relatively smooth. Agglutination and subsequent fusion of protoplasts did not appear to be dependent on a minimum depth of cytoplasm in either partner. Fusion was first observed at the margins of the adhering surfaces. As the areas of cytoplasmic continuity enlarged, the agglutinated plasmalemmae dispersed in the cytoplasm. Cytoplasmic mixing in heterokaryons occurred within 3 h.