THE REPLICATOR REGION OF THE RHIZOBIUM-LEGUMINOSARUM CRYPTIC PLASMID PRL8JI

The replicator region of the cryptic plasmid pRL8JI from Rhizobium leg uminosarum strain 3841 was cloned and sequenced. The recombinant plasm id (pYK3) was selected by function from a partial EcoRI library of tot al DNA cloned in pSUP202 and shows incompatibility with plasmid pRL8JI when conjugated into R. leguminosarum strains 3841 and its derivative 1062. The cloned insert(approximate to 10.5 kb) comprises five EcoRI fragments none of which confers replicative stability when cloned indi vidually. A single 5.0-kb BamHI fragment, that spans all five EcoRI fr agments and confers replicative stability on pSUP202 in R. leguminosar um, has been sequenced. This replicator region shows organisational an d sequence similarity to the replicator regions of the Agrobacterium p lasmids pTiB6S3 and pRiA4b. It has three open reading frames (repA, re pB, repC) and a conserved intergenic sequence.