Inhibition of harpinPss-mediated hypersensitive response in tobacco and petunia by AP1, an amphipathic protein isolated from tomato leaves

Abstract

Harpin_Pss, encoded by hrpZ in the hrp gene cluster from Pseudomonas syringae pv. syringae, is a glycine-rich, cysteine-lacking protein. It acts as an hypersensitive response (HR) elicitor in certain plants like tobacco, tomato and petunia. We isolated a 20 kDa protein, AP1, from tomato leaves, that could inhibit the activation of the HR by harpin_Pss. The interaction between AP1 and harpin_Pss resulted in an increase in the molecular weight of AP1.The inhibition of harpin_Pss elicitor activity or interference may be due to the competition between these two proteins for a putative receptor site in the plant cell plasma membrane. The C-terminal portion of harpin_Pss interacts more strongly with AP1 than the N-terminal portion.