Sequence analysis of the small cryptic Xanthomonas campestris pv. vesicatoria plasmid pXV64 encoding a Rep protein similar to gene II protein of phage 12-2.

The complete nucleotide sequence (1,851 bp) was determined for the Xanthomonas campestris pv. vesicatoria plasmid pXV64. Sequence analysis revealed an intergenic region (IG) of 355 bp and two oppositely running open reading frames, ORF1 and ORF2, encoding polypeptides of 39 and 16 kDa, respectively. While the function of ORF2 is not known, ORF1 is suggested to be the gene encoding Rep protein based on (i) similarity in amino acid sequence to that of the gene II protein (gIIP) of filamentous phage 12-2, (ii) presence of a sequence in the ori-containing region which is similar to the sequence around the Rep nicking site in some rolling circle-replicating replicons, and (iii) ability to support replication in trans of the region containing pXV64 ori (392 bp) which is located within the region including IG and a short stretch in the N-terminus of ORF2.