Apoptosis-like cell death of Brassica napus leaf protoplasts.

•   The cleavage of nuclear DNA into oligonucleosomal fragments that is the hallmark of apoptosis in animal cells occurs during the culture of Brassica napus leaf protoplasts. •   The changes in nuclei of cultured Brassica napus leaf protoplasts were studied by propidium iodide (PI) and 4', 6-diamino-2-phenylindole, dihydrochloride (DAPI) staining, transmission electron microscopy, flow cytometry analysis, and DNA laddering staining with ethidium bromide and Southern hybridization. •   Free 3'-OH termini of nuclear DNA fragments were labelled with DIG-dUTP, catalyzed by terminal deoxynucleotidyl transferase (TdT), and used as probes for Southern hybridization. This method (TUNEL on membrane) allowed visualization of DNA fragments with 3'-OH termini on a nylon membrane. •   These results suggest that loss of viability of protoplast with culture time is accompanied by apoptosis-like cell death. However, the forms or processes undergoing to apoptotic cell death in B. napus leaf protoplasts appears to be different in some details to those in animal cells.