The Hpal (harpin) and Ssbx (harpin-like protein,highly conserved single-stranded DNA-binding protein in Xanthomonas species) of X.oryzae pv.oryzicola (the causal agent of bacterial leaf streak in rice) triggers hypersensitive response (HR) in nonhost tobacco.Accompanied with HR caused by Hpal and Ssbx was the activated expression of HR marker genes (HIN1,HSR203J),the deposition of callose deposition and reactive oxygen species (ROS) burst.However,like Hpal this defense was inhibited by AvrAc from X.camprtris pv.campetris.