Genome-wide identification of the Sec-dependent secretory protease genes in Erwinia amylovora and analysis of their expression during infection of immature pear fruit

The general secretory(Sec)pathway represents a common mechanism by which bacteria secrete proteins,including virulence factors,into the extracytoplasmic milieu.However,there is little information about this system,as well as its associated secretory proteins,in relation to the fire blight pathogen Erwinia amylovora.In this study,data mining revealed that E.amylovora harbors all of the essential components of the Sec system.Based on this information,we identified putative Sec-dependent secretory proteases in E.amylovora on a genome-wide scale.Using the programs SignalP,LipoP,and Phobius,a total of 15 putative proteases were predicted to contain the N-terminal signal peptides(SPs)that might link them to the Sec-dependent pathway.The activities of the predicted SPs were further ttvreaaalicsdyeta otgepelda nsuesmsi inicng cprarenoa psEeesrtdcy h.s eiTrgirncaihfniicsa carcniotplltiyi-obwnahasle enad nEaa.ll kyaaslmiensye lo spvhohorowas epwdh atasht aaust sete h(deP theoo xipAnr)o ecgsueslinaotene f iuofms i1 om1 na tosufyr steth epe em1 a t5 rh s,ae txs tcuroagcngfyeitrsomtipnelagd s ttmhhieecii rr pperoox---xL?tential roles in plant infection.The results of this study support the suggestion that E.amylovora might employ the Sec system to secrete a suite of proteases to enable successful infection of plants,and shed new light on the interaction of E.amylovora with host plants.