Isolation And Functional Identification Of PR4b Promoter In Potato

Potato late blight,caused by Phytophthora infestans(Mont.)de Bary,is the first disease threaten to potato production.Breeding the resistant varieties to late blight is one of the major goals for potato.Previously,we cloned the StPR4b and identified that it was significantly up-regulated expression by P.infestans.Transiently expressed the StPR4b could positively regulated the potato immunity and inhabited the colonization of the P.infestans.Also,it was found to directly interact with several secreted proteins encoded RXLR effectors,implying that it is candidated to a key target armed race between pathogen effectors and host resistance proteins.In this study,we focused on the pathogen-inducible characteristics of the promoter of StPR4b,cloned the DNA sequence with PCR,and identified and functional analyzed the key cis-elemen responded for pathogen-inducible.After promoter deletion assay,it showed that deletion of-839 bp to-1203 bp significantly affected the pathogen-inducible activity of the promoter of StPR4b,indicating existence of positive regulatory elements in this region.However,deletion of -814bp to-925 bp nearly abolished the pathogen-inducible activity,implying existence of key cis-element in this region.Plantcare analysis was indicated that there was no known pathogen responsive elements and has a ABRE elements in-837 bp to-843 bp.Therefore,we validated that the ABRE element could respond to Phytophtora infestans inducibility and actived the downstream gene expression.Meanwhile,the StPR4b promoter lacking ABRE element was nearly attenuated the pathogen-inducible activity.In summary,we have identified that the promoter of StPR4b is highly induced by P.infestans,and clarified its core cis-acting element of ABRE.These results provided opportunityfor analyzing resistance network of potato late blight and R gene engineering.