Electron microscopic study of plant-animal cell fusion.

Abstract

Avian erythrocytes and protoplasts isolated from mesophyll cells of tobacco plants were suspended in 1% protease, agglutinated with polyethylene glycol (PEG) and subsequently fused upon elution of the PEG. The fusion reaction was monitored by scanning (SEM) and transmission (TEM) electron microscopy. SEM studies showed a marked difference in the topography of agglutinated cells. During, and subsequent to fusion, the markedly different surfaces of the two cell types became homogeneous and lines of demarcation between the cells were no longer visible. TEM revealed that adhesion occurred over the entire membrane area between agglutinated cells. Incipient fusion was evidenced by the appearance of vacuoles at the intermembrane surfaces. During initial elution of the PEG, cytoplasmic channels between erythrocytes and protoplasts were evident. With continued elution of the PEG, starch-containing plant chloroplasts and starch grains were seen within erythrocytes and homogenous erythrocyte cytoplasm was present inside plant protoplasts. Cytoplasmic mixing between the two cell types occurred within 3 hours of elution. The frequency of interkingdom fusion was estimated to be 0.5–1%.