Fate of a Mutant Macrochloroplast in Somatic Hybrids

Protoplast isolation from a moss, Physcomitrella patens (Hedw.)B.S.G., was optimized regarding preculture of plants, digestion procedure and isolation protocol. PEG-mediated protoplast fusion in batch experiments resulted in at least 29% fusion products. All of these appeared to be one-to-one fusions. In about 50% of the fusants nuclei fused within 90 minutes as well. Protoplast fusion with wild-type and chloroplast mutant PC22 was performed. Fusion products harbouring wild-type plastids as well as a giant mutant chloroplast were transferred to feeder-cultures in millicells and fate of the macrochloroplast was observed. Analysis of regenerants revealed that deficiencies in plastid division and in cellular differentiation are two uncoupled genetic traits in moss mutant PC22.