Pseudomonas syringae pv tomato induces the expression of tomato EREBP-likegenes Pti4 and Pti5 independent of ethylene, salicylate and jasmonate

The tomato genes Pti4 and Pti5 encode ethylene-responsive element binding p rotein-like transcription factors that bind to the GCC box, a conserved cis -element in many defense-related genes. The Pti proteins have previously be en shown to interact with the tomato disease resistance protein Pto. Here w e report that the expression of both Pti4 and Pti5 are induced by a virulen t strain of Pseudomonas syringae pv tomato. The expression of Pti5 is furth er enhanced by the interaction of the Pto gene in tomato and the correspond ing avrPto gene in the bacterium. The enhancement of Pti5 expression by Pto -avrPto interaction requires a functional Prf gene in the plant. Pti5 appea rs to be expressed specifically during biotic stresses, suggesting a specif ic role in plant defense. Pti4 and several EREBP-like genes are induced by ethylene, salicylate and wounding. However, the Pseudomonas bacterium induc ed a wild-type level of Pti4 and Pti5 transcripts in tomato plants carrying the nahG transgene, the Nr mutation, or the def1 mutation. In addition, th e ethylene action inhibitor norbornadiene did not inhibit the induction of Pti4 and Pti5 either in the compatible or incompatible interactions. The re sults suggest that the Pseudomonas bacterium induces Pti4 and Pti5 expressi on through a pathway independent of salicylic acid, ethylene and jasmonic a cid.