PLASMID MAINTENANCE FUNCTIONS ENCODED ON DICTYOSTELIUM-DISCOIDEUM NUCLEAR PLASMID DDP1

All of the plasmid-carried genes expressed during vegetative growth ar e essential for long-term maintenance of plasmid Ddp1 in the nucleus o f Dictyostelium discoideum. Deletion of Ddp1 genes expressed only duri ng development had no detectable effect on plasmid maintenance. Deleti on of vegetatively expressed genes, either singly or in pairs, resulte d in (i) a rapid loss of plasmid from cells grown in the absence of se lection for plasmid retention, (ii) variation in the proportion of mon omer to multimer forms of the plasmid molecules, and/or (iii) abnormal ities in plasmid copy number. At least two plasmid-encoded gene produc ts influence patterns of expression of plasmid genes.