FIG. 4.

Scenario of duplication-insertion of strain 5632 vpma genes from locus I to locus II via a circular intermediate. Schematics illustrate a putative scenario in which the vpma cluster of 5632 at locus II originates from locus I by a mechanism of duplication-insertion involving a circular intermediate and IS elements. Small bars with a letter below represent 14-nt sequences (a, b, and c) flanking the ISMag1 element either after an insertion event (a and b) or after a homologous recombination event (c). The dotted arrow indicates the clustering process for seven vpma genes at one end of locus I, starting from the current configuration. It represents a series of an unknown number of possible DNA rearrangements. Asterisks indicate duplicated vpma genes. The gel picture shows PCR amplification of the circular intermediate obtained using primers xerF and pv1R, with strain 5632 crude DNA extract as the template.