Culture and development of electrically fused protoplasts from red marine algae, Porphyra yezoensis and P. suborbiculata

Abstract

The electrically fused products of protoplasts from a wild type and a mutant strain of Porphyra yezoensis were cultured in a modified agar medium, named “soft agarose two-layer medium” for 40 days, and then transferred and cultured subsequently in a liquid medium. In the soft agarose two-layer medium, fused products could be distinguished easily from unfused protoplasts. The survival rate of fused products in the soft agarose two-layer medium was considerably higher than that of those in the liquid medium. However, growth rate of multi-cellular bodies which developed from fused protoplasts was higher when protoplasts were moved from the two-layer medium to liquid medium. The fused products repeated cell divisions and formed irregular-shaped multi-cellular bodies. After 2 months of culture, a large number of cells in these cellular bodies differentiated into monospores which then germinated and grew to young thalli. Eventually, four out of approximately 180 fused protoplasts developed to young thalli. Morphologically hybrid-like thalli were obtained in an electrofusion experiment with protoplasts from Porphyra suborbiculata and a mutant strain of P. yezoensis, which suggested that genetic recombination would be possible between these two species.