A method for the efficient transfer of isolated mitochondria into yeast protoplasts

When protoplasts isolated from non-respiring rho0 strains of S. cerevisiae are incubated with mitochondria from respiring rho+ strains in the presence of polyethylene glycol, a small fraction of the acceptor protoplasts acquires respiratory capacity. Pretreatment of the isolated mitochondria and protoplasts with Ca2+ ions enhanced the frequency of ensuing respiration-competent colonies by almost three orders of magnitude. When mitochondria were isolated from a strain exhibiting killer capacity as a cytoplasmic marker, in addition to the appropriate nuclear and mitochondrial markers, about one-third of the ensuing rho+ colonies were not killers. Possible mechanisms for the transfer of mitochondria into acceptor protoplasts were studied.