STUDIES ON FUNCTION AND MOBILITY OF MITOCHONDRIAL PLASMIDS FROM CLAVICEPS-PURPUREA

Linear mitochondrial plasmids occur in most field isolates of the gras s pathogen Claviceps purpurea; their function is still unknown. Infect ion experiments with plasmid-free strains obtained by curing with ethi dium bromide had indicated that these plasmids might play a role in th e parasitic cycle. Pathogenicity tests with a derivative of C. purpure a strain K, which had lost its endogenous plasmid spontaneously during vegetative growth, did not demonstrate a function of this plasmid in pathogenicity. One of the reasons for the maintenance and widespread d istribution of such 'selfish' plasmids could be their mobility, which is indicated by the presence of identical plasmids in non-related C. p urpurea isolates, and which is proved here by transmission of a plasmi d between two nonrelated strains by protoplast fusion.