Abstract:HrpN gene was placed under the control of AOX1 promoter in a Pichia expression vector pPIC6αA. Through electroporation transformation of X-33 Pichia and Blasticidin selection, a strain of Pichiapastoris capable of secreting harpinEa into the medium at high level was obtained. After initially purified, SDS-PAGE analysis of the expression products indicated that harpinEa was secreted at high level when the Pichiapastoris expression clone had been induced for 96 hours. The results of bioassay showed that the recombinant harpinEa had the ability of eliciting hypersensitive response in tobacco. The activity of this harpinEa is higher than that of harpinEa expressed in Escherichia coli.