Overexpression of Pti5 in tomato potentiates pathogen-induced defense geneexpression and enhances disease resistance to Pseudomonas syringae pv. tomato

The tomato Pti5 gene encodes a pathogen-inducible ethylene response element -binding protein-like transcription factor that interacts with the disease resistance gene product Pto. Overexpression of Pti5 or Pti5-VP16, a transla tional fusion with a constitutive transcriptional activation domain, in tom ato enhanced resistance to Pseudomonas syringae pv. tomato. Constitutive ex pression of Pti5 or Pti5-VP16 did not affect the basal level of pathogenesi s-related gene expression, but it accelerated pathogen-induced expression o f GluB and Catalase. The results demonstrate a positive role of Pti5 in def ense gene regulation and disease resistance and suggest that a pathogen-act ivated posttranscriptional regulatory step is necessary for the pathogen in duction of the defense gene expression.