INITIATION OF PLANT-DISEASE RESISTANCE BY PHYSICAL INTERACTION OF AVRPTO AND PTO KINASE

Resistance to bacterial speck disease in tomato occurs when the Pto ki nase in the plant responds to expression of the avirulence gene avrPto in the Pseudomonas pathogen. Transient expression of an avrPto transg ene in plant cells containing Pto elicited a defense response. In the yeast two-hybrid system, the Pto kinase physically interacted with Avr Pto. Alterations of AvrPto or Pto that disrupted the interaction in ye ast also abolished disease resistance in plants. The physical interact ion of AvrPto and Pto provides an explanation of gene-for-gene specifi city in bacterial speck disease resistance.