ISOLATION OF ARABIDOPSIS GENES THAT DIFFERENTIATE BETWEEN RESISTANCE RESPONSES MEDIATED BY THE RPS2 AND RPM1 DISEASE RESISTANCE GENES

The Arabidopsis disease resistance gene RPS2 is involved in recognitio n of bacterial pathogens carrying the avirulence gene avrRpt2, and the RPM1 resistance gene is involved in recognition of pathogens carrying avrRpm1 or avrB. We identified and cloned two Arabidopsis genes, AIG1 and AIG2 (for avrRpt2-induced gene), that exhibit RPS2- and avrRpt2-d ependent induction early after infection with Pseodomonas syringae pv maculicola strain ES4326 carrying avrRpt2. However, ES4326 carrying av rRpm1 or avrB did not induce early expression of AIG1 and AIG2. Conver sely, ES4326 carrying avrRpm1 or avrB induced early expression of the previously isolated defense-related gene ELI3, whereas ES4326 carrying avrRpt2 did not, The induction patterns of the AIG genes and ELI3 dem onstrate that different resistance gene-avr gene combinations can elic it distinct defense responses. Furthermore, by examining the expressio n of AIG1 and ELI3 in plants infiltrated with a mixed inoculum of ES43 26 carrying avrRpt2 and ES4326 carrying avrRpm1, we found that there i s interference between the RPS2- and RPM1-mediated resistance response s.