Fusion studies of pollen protoplasts and generative cell protoplasts in Lilium longiflorum

Abstract

Cell fusion of pollen protoplasts and generative cell protoplasts, which were isolated from angiosperm pollen grains, was studied for the first time in Lilium longiflorum. Using an electric pulse, a high frequency of cell fusion was induced between pollen protoplasts, between generative cell protoplasts, and between pollen protoplasts and generative cell photoplasts. Each fusion product could be cultured for a prolonged period. In the cell resulting from fusion of two pollen protoplasts, the two generative cells divided after 8–10 days of culture resulting in the formation of four sperm cells, or male gametes. The cell resulting from fusion of two generative cell protoplasts survived for about 10 days, but no nuclear fusions or divisions were observed during the culture period. When a pollen protoplast and a generative cell protoplast were fused, the original generative cell from the pollen protoplast divided into two sperm cells within 10 days, as when two pollen protoplasts were fused. However, the generative nucleus transferred into the vegetative cell cytoplasm of the pollen protoplast by the fusion never divided and the chromatin became dispersed as in the vegetative nucleus. These results are discussed in relation to pollen ontogeny, in particular to the differentiation of generative and vegetative nuclei, which must be regulated by the cytoplasm of each cell after unequal microspore cell division.