A RACE-SPECIFIC INSERTION OF TRANSPOSABLE ELEMENT IS801 IN PSEUDOMONAS-SYRINGAE PV. PHASEOLICOLA

The isolation and cloning of a random amplified polymorphic DNA-polyme rase chain reaction (RAPD-PCR) band specific for Pseudomonas syringae pv, phaseolicola race 1 allowed us to design a pair of primers that am plify 1.2-kb race 1-specific and 2.7-kb race 2-specific fragments, pro viding a rapid method for the identification of races by standard PCR methods. Restriction analysis revealed identical endonuclease sites in both fragments but the race 2 fragment contains a 1.5-kb insertion, i dentified as transposable element IS801 by sequence comparison. One co mplete and one partial open reading frame (ORF), each with a high prob ability of encoding a protein, have been identified in the 1.2-kb frag ment common to both race 1 and race 2 sequences. As IS801 disrupts the partial ORF in the race 2 fragment, the complete sequence of this ORF has been obtained as well as its promoter region. The possibility tha t it may encode an avirulence gene is discussed as well as the role of transposable elements in pathogen evolution.