FACTORS AFFECTING THE ELECTROFUSION EFFICIENCY OF PORPHYRA PROTOPLASTS

The effects of various factors on the electrofusion efficiencies of Porphyra protoplasts were investigated. These factors were protoplast stabilizing reagents, divalent cations, membrane digestive enzymes and cold storage of the protoplasts. Fusion efficiencies were dependent on the concentrations of reagents used to adjust the osmotic pressure of the medium. With mannitol or sorbitol the maximum fusion efficiency (approximately 16%) was observed at concentrations of 0.6 to 0.7 M; glucose was less effective. Brief treatment of the protoplasts with pronase stimulated electrofusion, whereas treatment with proteinase K, trypsin, phospholipase C or lipase repressed fusion. The addition of Ca2+ at 10(-5) to 10(-4) M in the protoplast medium enhanced the fusion efficiency to approximately four times that of the non-treated control. Sr2+ and Co2+ also stimulated electrofusion, but less effectively than Ca2+. The fusion capacity of the protoplasts remained stable for about 3 h when kept on ice, but decreased gradually when left at room temperate.