IDENTIFICATION OF A NEW ARABIDOPSIS DISEASE RESISTANCE LOCUS, RPS4, AND CLONING OF THE CORRESPONDING AVIRULENCE GENE, AVRRPS4, FROM PSEUDOMONAS-SYRINGAE PV PISI

A molecular genetic approach was used to study the interaction between Arabidopsis and an avirulence gene from Pseudomonas syringae pv, pisi , P. syringae pv, ptsi strain 151 induces a hypersensitive response (H R) when inoculated on the Arabidopsis accession Po-1, A genomic cosmid library was constructed from DNA from P. syringae pv, pisi strain 151 and a cosmid was identified that causes the normally virulent P. syri ngae pv. tomato strain DC3000 to induce an HR on Po-1, The cosmid was subcloned and a 1.2-kb DNA fragment conferring avirulence activity was sequenced, The single significant open reading frame within the 1.2-k b fragment was designated avrRps4. An avrRps4-specific probe hybridize s to DNA from all P. syringae pv, pisi strains tested, P. syringae str ains carrying avrRps4 induces an HR on specific accessions of both Ara bidopsis and soybean, Arabidopsis accession Ws-0 is resistant to DC300 0(avrRps4), whereas accession RLD is susceptible, Resistance segregate s as a single dominant locus in a genetic cross between Ws-0 and RLD. This disease resistance locus, RPS4, was mapped to chromosome 5 betwee n the molecular markers sAT2105 and KG-8.